discipline specific core course fundamentals of nutrition

Graduate Course

UNIT 1 : BASIC CONCEPTS IN FOOD AND NUTRITION

Lesson 1 : Concept of Food, Nutrition and Health Lesson 2 : Introduction to Food, Food Groups and Balanced Diet

UNIT 2 : NUTRIENTS

Lesson 3 : Macronutrients Lesson 4 : Micronutrients-I Lesson 5 : Micronutrients-II

UNIT-3 : CULINARY SCIENCE

Lesson 6 : Introduction to Cooking Lesson 7 : Methods of Cooking Lesson 8 : Role of Food Groups in Cookery Lesson 9 : Effect of Cooking on Food Components Lesson 10 : Ways of Conserving and Enhancing Nutrients

Written by: Ms. Anjali Assistant Professor Department of Food and Nutrition, Lady Irwin College, University of Delhi Delhi-110001

SCHOOL OF OPEN LEARNING University of Delhi

5, Cavalry Lane, Delhi-110007

1

UNIT 1

BASIC CONCEPTS IN FOOD AND NUTRITION

Lesson 1 : Concept of Food, Nutrition and Health

Lesson 2 : Introduction to Food, Food Groups and Balanced Diet

3

Ingestion

Digestion

Absorption

Transportation

Utilisation

Excretion

LESSON 1

CONCEPT OF FOOD, NUTRITION AND HEALTH INTRODUCTION

Food and nutrition are considered as the foundation for health and development. The relation between foods, its nutrients and health are complex and have a significant effect on individuals and society. The nutrients present in the food are essential for body’s growth, protection from disease and maintenance. Therefore the complete understanding of the food and its effect on the long term health is crucial. OBJECTIVES To interpret the basic relationship between food, nutrition and health. To familiarize about the types of malnutrition. To understand the concept of health, its dimensions and determinants.

Food can be defined as anything edible that can be solid, semisolid or liquid which when swallowed, digested and assimilated in the body, proves useful to it. These substances not only keep the person alive but also provide energy used for growth and development, regulate the body processes and protect the body from diseases. Nutrition is the science of looking at how the body uses nutrients and at how and why people eat. It deals with digestion, absorption and metabolism of food. It can be defined as

‘The science of foods, the nutrients and other substances therein; their action, interaction and balance in relation to health and disease’

(Robinson 1966)

The process of nutrition involves different steps (Figure 1.1). Nutrients are defined as substances in food that the body needs to function properly. They provide energy for activity, growth, and all functions of the body such as breathing, digesting food and keeping warm; and materials for the growth and repair of the body, and for keeping the immune system healthy.

Figure 1.1: Steps in the process of nutrition

4

‘Nutrients are the nourishing substances in food that are essential for the growth, development and maintenance of body functions. When the intake does not regularly meet the nutrient needs dictated by the cell activity, the metabolic

processes slow down or even stop.’- (Wardlaw and Insel)

The main classes of nutrients that the body needs are carbohydrates, proteins, fats, vitamins, minerals, dietary fibre and water.

Our body needs all the nutrients in the right quantities and if these nutrients are not taken adequately in the diet, it leads to ill health. When the essential nutrients are consumed in adequate amount and proportion as per body needs it is called optimum nutrition or adequate nutrition.

Malnutrition refers to deficiencies, excesses or imbalance in a person’s intake of energy and nutrients. Malnutrition includes both Undernutrition and Overnutrition(Figure 1.2). 1. Undernutrition refers to the deficiency of one or more nutrients. It can be Protein

Energy deficiency.eg. Kwashiorkor or marasmus or can be any micronutrient deficiency eg Vitamin or minerals deficiency

2. Overnutrition results from the imbalance of energy consumed (excess) and energy expended (less). For example, overweight or obesity results from the overconsumption of energy than body energy expenditure.

Figure 1.2: Types of malnutrition

Food is the necessity for the survival of life and the amount and type of food one eat can have far-reaching consequences on health. In simpler words, one can say that you are what you eat. The food choice doesn’t solely depend on physiological needs but rather also governed by several other factors like biological (taste and hunger), economic (cost and income), physical (education and time) social (culture and family) and psychological (mood and stress) along with attitude, beliefs and knowledge about food.

Malnutrition

Undernutrition

Protein, Energy Deficiency

Micronutrient related

Overnutrition Overweight or obesity

5

LET’S CHECK THE PROGRESS

1. Briefly explain the term nutrition?

-------------------------------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------------

2. Briefly explain malnutrition and its types.

-------------------------------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------------

CONCEPT OF HEALTH

‘Every human being is the author of his own health or disease’ - Buddha

The concepts of health vary both individual and community wise. Conventionally health is considered a mere ‘absence of disease.’ Although there is a common saying that health is wealth but often it is taken for granted and not valued until lost. It is our good health that stays with us for long rather than any relationships or any other things like wealth, power, fame etc.

Health can be defined as physical, mental, and social wellbeing, and as a resource for living a full life. It refers not only to the absence of disease but the ability to recover and bounce back from illness and other problems.

Health is very subjective and carries a different meaning for each individual. Therefore, there are several definitions of health that have been offered from time to time. Some are as follows:

a. “The condition of being sound in body, in mind and spirit, especially freedom from physical disease or pain.” (Webster)

b. “The condition of the body and the degree to which it is free from illness, or the state of being well:” (Cambridge English Dictionary)

c. “A person’s health is the condition of their body and the extent to which it is free from illness or is able to resist illness.” (Collins Dictionary)

WHO definition

The absence of disease alone does not indicate good health. A healthy person should have a sound body and mind. According to the World Health Organisation (WHO), health is:

6

“A state of complete physical, mental and social well-being, and not merely the

absence of disease and infirmity.”

In 1986, the WHO further elucidated that health is:

"A resource for everyday life, not the objective of living. Health is a positive concept emphasizing social and personal resources, as well as physical capacities."

This means that health is a resource to support an individual's function in wider society. A healthful lifestyle provides the means to lead a full life.

Health is multidimensional, WHO definition envisages three specific dimensions: physical, mental and social, though there are several dimensions (Figure 1.3) which are interrelated and provide a full picture of health.

Figure 1.3: Different dimensions of health

i. Physical Dimension

It refers to the bodily aspect of health and indicates the ‘perfect functioning’ of the body. It is the state in which every body organ function to the full capacity in perfect coordination with the entire body. It ranges from the state of diseases to the state of optimum physical condition.

Dimensions of health

PhysicalBodily aspect

MentalCognitive

aspect

SocialSocial aspect

EmotionalPersons mood

or general emotional

state.

VocationalLife

successes

SpiritualSense of overall

purpose in life.

7

The other health dimensions are also affected if there is a deterioration in physical condition. e.g. a person with a common cold is often isolated to prevent others from infection. He/she may not be able to focus and may feel depressed.

ii. Mental Dimension

It focuses on the cognitive facet of health. It is the individual’s ability to use their reasoning power to solve problems or to recall information. Often this dimension is connected to emotional health. However, there is a difference. Mental health relates to brain functioning, while a person’s mood depends on one’s emotional health. Some of the issues associated with this dimension are Alzheimer’s and dementia.

According to WHO,

“Mental health is defined as a state of well-being in which every individual realises his/her potential, can cope with the normal stresses of life, can work

productively and fruitfully, and is able to make a contribution to her/his community.”

Mental dimension is inter-related to other dimensions of health as well.

Poor mental health Poor physical well-being

Good mental health Greater self-esteem Confidence in social situations Improved spiritual health.

iii. Social Dimension

The social dimension of health includes the social relationship. It refers to the ability to create and maintain meaningful social relationships within socially acceptable standards and behaving properly with them.

Family is the basic social unit of relationship, and these relationships impact a person’s life the most. Other key relationships are close friends, social networks, teachers and Professional networks etc. A socially integrated person is said to suffer less from physical and mental problems and thus, may be healthier. The community’s social health is governed by its development, tolerance, consideration and generosity towards others. It also depends upon the education level, productivity, and societal security of its members.

The interrelatedness of social dimension with other dimensions of health can be seen below:

Bad social life Feeling isolated and unwanted Demotivation Depression.

iv. Emotional Dimension

The emotional state or mood of a person tells about his/here motional health. It is the ability to empathize and express one’s own feelings like anger, happiness,

8

sadness, inappropriate manner. It also involves coping the stress effectively and appropriately. It relates to self-esteem as well as the ability to control emotions to maintain a realistic perspective on situations. It is how one reacts when something happens unexpectedly (highs and lows) in life.

Emotional health affects the other dimensions of health as a person with good self-esteem is more confident in social settings, makes friends quickly and often perform better in physical activity.

v. Spiritual Dimension

The word spiritual refers to “one’s innermost self”. It is also called “Psychic dimension”. Spiritual health relates to the sense of overall purpose in life. It is the commitment to one’s value system and strongly determined by the belief and faith system. Modern-day hectic schedule and stresses make this dimension very vital as peace with oneself are important to achieve world peace. A person having an integrated self is said to be healthier than those who don’t see a purpose to live. Emotional and mental health are highly affected by this dimension. Having a goal may help people to have positive outlook/ perspective in life and over coming hardship. Following yoga, pranayama and meditation are some of the ways of improving spiritual health.

vi. Vocational Dimension This is a considerably a new dimension of health. It is subjective in nature and depends on one’s opinions about their life goals and achievements. Each person wants to take their own path to achieve vocational goals. Professional development in terms of getting a job or occupation of one’s interest is one of the aspects of this dimension.

Hence, one can define health as “a state of complete physical, mental, social, emotional spiritual and vocational well-being, and not merely the absence of disease or infirmity.”

SPECTRUM OF HEALTH

The spectrum of health states that health is a dynamic phenomenon which undergoes continuous changes on a regular basis. It is not static. It ranges from the state of optimum health to the lowest point on the health-disease spectrum is death and the highest point corresponds to optimum health (Figure 1.4). Health fluctuates within a range of optimal wellbeing to various levels of dysfunction, including death. The

Optimum health Seemingly HealthyFreedom from sickness

Chronic diseasesSickDeath

Figure 1.4: Spectrum of health

transianothbe mi

DETE

Healtto affTheseTheseand arAccorwhichand P

1. P

o B -

lin

Gsa

ition from oher state beginimum tom

ERMINAN

h does not fect the perse factors use factors mre interrelatrding to WHh include Pe

Physical env

Person's ch

Biological d-Age, sex aifespan andndividual’s

Genetic facsusceptibilitanaemia, ha

• Biologi• Behavi

Person's

• Social-• Econom

Social an

• Water q• Air qua• Climate• Built en• Food sa• Land an

Physical

optimum hegins. A pers

morrow. It im

NTS OF HE

exist in isolson’s healthsually start

may be bioloting and maHO, the deterson’s charvironment (F

F

haracteristi

determinannd genetic f

d probability control.

ctors -Herety to certainemophilia,

ical- Gendeoural- Alco

s characteri

Social clasmic- Educat

nd economi

qualityalitye and geogrnvironmentafetynd soil qual

l environme

ealth to ill son may funmplies that h

EALTH

lation. It deh. These comat the indiv

ogical, behaay impact onterminants racteristics Figure 1.5).

Figure 1.5: D

cs and beh

nts of healthfactors- They of develo

dity plays an ailments. etc.

er, Genetics,ohol use, Die

istics and b

ss, social netion, Emplo

ic environm

raphy- Tempt- Transport

lity

ent

9

health is onction at mahealth is a s

epends on mmponents arvidual leveavioural, sone’s state ofof health caand behavi

Determina

aviours: It

h- ese inborn foping certai

a vital role eg. Genetic

, Ageet, Physical

behaviours

tworks etcoyment etc

ment

perature, Ra, Housing q

often graduaaximum levstate not to b

many compore known al and move

ocio-culturaf health. an be divideours, Social

ants of healt

consists of

factors playin illnesses.

in determinc disorders

l activity, To

ainfallquality, Road

al and whervels of healtbe attained

onents whics the determe through thal, economic

ed into threl and econo

th

both:

y a decisive . It is comp

ning one’s e.g. disease

obacco use

ds etc

re one stateth today anonce.

ch merge tominants of hhe wider soc, and ecol

ee core cateomic enviro

role in predpletely beyo

lifespan, anes like sick

e ends d may

gether health. ociety. logical

egories nment

dicting ond an

nd the kle cell

10

Age- Older adults are biologically prone to be in poorer health than adolescents due to the physical and cognitive effects of ageing.

Gender- Although men and women are equal in several ways but the probability of occurrence of few diseases vary gender-wise due to the anatomy and hormones. eg. Heart diseases are more common in men while most of the women suffer from osteoporosis.

o Behavioural determinants of health

--Lifestyle factors -These factors include diet, physical exercise, smoking, and alcohol use, etc. Individuals may have more control over these factors by making the choice to adopt a healthy lifestyle practice that enhances health. These factors are also called as modifiable factors.

2. Social and economic environment Human health is also influenced by the social-economic conditions of the person

or the community. These factors are multiple, interactive and very often go beyond the extent of an individual’s control.

o Social determinants of health

--Social and community support- Greater support from families, friends and communities are linked with better health. The caring and respect occur in such social relationships help people to cope with challenges and act as a buffer against health problems.

--Culture- One’s family and community’s customs, traditions and beliefs also affect health.

o Economic determinants of health

--Income- Money is also said to influence health as health status improves at every rise in the income level and social hierarchy. Higher-income and status generally results in more control and discretion. Income determines living conditions such as safe housing and ability to buy sufficient good food.

The Gross National Product (GNP) per capita is the commonly used measure economic performance. The economic status affects purchasing power, the standard of living, quality of life (QoL), family size and the pattern of disease in the community. Paradoxically, wealth may also be a contributing factor to several Non-Communicable Diseases (NCDs) as high rates of coronary heart disease, diabetes and obesity are often seen in the upper socio-economic groups.

11

--Education- Health status improves with the level of education. Education is closely tied to socio-economic status. It increases opportunities for job and income security, improves people’s ability to access and understand information to help them keep healthy. Illiteracy is often linked with poor health, more stress levels and lower self-confidence.

--Employment and working conditions-the health and work shares a dynamic relationship. The social organisation of work, management styles and social relationships in the workplace all affect health. The people who are employed are healthier and happier as it helps them build confidence, improves self-esteem, keeps busy, socialise, and provides monetary support. Joblessness has several negative effects on health like psychological and social damage. People who are out of the work suffers from both physical and mental problems and thus, have a shorter life expectancy.

--Health services- The health services aim to improve the health of community or population via. prevention, diagnosis and treatment of disease. These services cover a range of personal and community services like provision of Primary Health Care, provision of sanitation and hygiene which includes safe drinking water. It consists of medical professionals and auxiliary health care workers. A person’s income is also a key factor in seeking health care services.

3. Physical environment Environmental factors play an important role. Sometimes the environment alone

is enough to impact health or may cause illness in a person who is genetically susceptible. Hippocrates, a Greek physician revolutionised medicine and first related disease to the environment. He argued that diseases do not occur due to god’s punishment rather illness happens due to environmental factors e.g., temperature, water, food, air, etc.

In the 19th century, Max von Pettenkofer, also known as the father of hygiene, gave a dogma that environmental factors are responsible for the occurrence of diseases and thus, revived the concepts of disease-environment association. The environmental factors that are said to impact the overall good health include: o Water quality o Air quality o Climate and geography- Temperature, Rainfall o Built environment- Transportation, Housing quality, Roads etc o Food safety o Land and soil quality

12


1. Define health.

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

2. Briefly explain the relationship between different dimensions of health.

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------

3. Explain how socio-economic determinant impact health?

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

SUMMARY

The effective management of food intake and nutrition are both keys to good health. Eating the right foods can help your body cope more successfully with an ongoing illness. Understanding good nutrition and paying attention to what to eat can help to maintain or improve health. Health is a state of complete physical, mental and social well-being, and not just the absence of disease and illness. Human happiness and well-being depend on the better health of an individual. The physical, mental and social, spiritual, emotional, and vocational dimension are some of the dimensions of health. Biological, behavioural, socio-economic and environmental factors are the determinants of health. In short, numerous factors contribute to the health and well-being of populations.

KEYWORDS Kwashiorkor- a form of malnutrition that occurs when there is not enough protein in the diet. Marasmus- a form of severe malnutrition characterized by energy deficiency. Infirmity- physical or mental weakness. Dimension- an aspect or feature of a situation. Alzheimer's disease- a progressive disorder that causes brain cells to degenerate and die, due to which there are a continuous decline in thinking, behavioural and social skills that disrupts a person's ability to function independently

13

GNP- Gross national product (GNP) measures the nation’s total economic activity and shows the average income of a country's citizens Morbidity- the condition of being diseased. Mortality- the state of being mortal/dead. Sickle cell anaemia- an inherited form of anaemia in which there aren't enough healthy red blood cells (RBCs) to carry adequate oxygen throughout your body. Haemophilia- Genetic disorder that impairs the body's ability to make blood clots, a process needed to stop bleeding. Primary health care (PHC)- refers to "essential health care". It is an approach to health and wellbeing centred on the needs and circumstances of individuals, families and communities. Working conditions – conditions relating to a worker’s job environment, such as hours of work, safety, paid holidays and vacations, rest periods possibilities of advancement, etc. REFERENCES

Robinson, W.D., ‘Nutrition in medical education’, Proceedings, Western Hemisphere Nutrition Congress 1965, American Medical Association, Chicago, 1966.

Wardlaw, G. M., & Insel, P. M. (2011). Perspectives in nutrition. 11th Ed. McGraw-Hill Education.

Websites: https://www.who.int/hia/evidence/doh/en/

14

LESSON 2

INTRODUCTION TO FOOD, FOOD GROUPS AND BALANCED DIET INTRODUCTION

Human life needs few things for survival food being one of them as life cannot exist without food. It is what matters to people most of the time more than anything else in this world. There is a direct impact of foods that we chose to eat on our ability to enjoy life. The most obvious positive effect of food is the pleasurable feeling one gets from eating a good-tasting meal. Over centuries, food has acted as a vehicle for the expression of affection, and companionship. It provides our bodies with nutrients to build new body cells and tissues and prevent and fight the infections. Apart from satisfying hunger, food performs many other vital functions in the body. OBJECTIVES

To know various functions of food. To familiarise the concept of food groups. To understand the importance of a balanced diet in achieving good health.

Food is any solid, semi-solid or liquid substance which is consumed to provide nutritional support for an organism and keep it healthy. Food can be obtained from plant or animal source. It contains certain nutrients like carbohydrates, proteins etc. In simpler words, food is what humans and animals eat to survive. One of the properties of the food is that one should be able to ingest, digest and absorb it in ode to utilise it for body functions. Food should be chewable, palatable and should be able to enter the gastrointestinal (GI) tract. Ingestion stats with the intake of food. It refers to the entry of food in the alimentary canal through the mouth. After this, food undertakes the process of breakdown of complex substances into simple ones by the process of digestion. Some of these complex forms of nutrients such as carbohydrates, proteins and fats undergo breakdown. For e.g.

Carbohydrates monosaccharides (glucose, galactose and fructose) Proteins amino acids (alanine, glycine) Fats fatty acids (oleic acid, stearic acid)

After the process of digestion, the process of absorption takes places in which the simple form of nutrients (end products of digestion) are absorbed by the inner membrane of the

15

small intestine called villi. Then it enters into the bloodstream. This movement of nutrients from the intestinal wall to the bloodstream is called as absorption of food. Figure 2.1 depicts the digestive processes.

Figure 2.1: The Digestive processes

Food supplies nutrients to the body, and help us to maintain the nutritional status and health. For example, we can say banana, a food as our body can ingest, digested, and finally absorb it. These nutrients released from the food help the body in carrying out the day-to-day activities and thus maintain health. The nutrients provided by the food are carbohydrates, fats, proteins, vitamins, minerals, dietary fibre and water perform several tasks in the body for maintaining our health. Apart from providing nutrients to the body, food has other functions also. FUNCTIONS OF FOOD

To make diet planning simple, the food groups have been divided according to their functions. Foods are classified according to the functions (Figure 2.2), namely:

16

1) Physiological functions 2) Psychological functions 3) Social functions

Figure 2.2: Functions of food

1) Physiological functions of food

The physiological functions of food can be further sub-divided as follows:

1 Energy giving 2 Body-building 3 Protection and Regulation

a) Energy giving

The human body is never at rest. There is a number of voluntary processes like professional and recreational activities and involuntary processes like respiration, blood circulation that occurs in the body. These processes are important for the body and thus needs fuel. Some amount of energy is also essential to main body temperature.

Carbohydrate and fat-rich foods are the main sources that provide energy to the body. Although proteins also provide energy but their most important function is to build and

Functions of food

Physiological Psychological Social

Body building (Proteins)

Protection and regulation (Vitamins and minerals)

Energy giving (Carbohydrate, Fats)

o Whole grain cereals o Vegetable oils &

butter o Nuts & oils seeds o Sugar

o Pulses o Nuts and oilseeds o Milk and milk

products o Meat, fish, poultry

o Green leafy vegetables

o Other vegetables o Fruits o Eggs o Milk and milk

products o Flesh foods

17

repair body tissues. Therefore, we will not include them in this group. Carbohydrate is starch, sugars and cellulose. Fat sources are vanaspati, butter, ghee, nuts and oilseeds. Energy-rich foods constitute a major faction of Indian traditional diet. The amount of energy released by the nutrients are as follows:

o 1 gram of carbohydrate yields 4 kilocalories, o 1 gram of fat yields 9 kilocalories o 1 gram of protein yields 4 kilocalories.

b) Body-building

Our body undergoes regular wear and tear on a regular basis. There are around 300 billion new cells like nerve cells, brain cells etc. which are generated every day by the body. All these cells, tissues, and different organs of human body like muscles, bone and organs are built upon and maintained by the proteins. Thus, building the body is an important function of the food. The body building foods provides proteins to the human body.

Foods like milk and milk products, pulses, cereals, meat, fish, poultry, nuts, etc. are some of the sources that provides protein to the human body. There are multiple ways by which these foods can be incorporated in the daily diet. For e.g. in parathas, stuffed chapati, raita/curd with sprouts etc.

Since Indian diet is prominently vegetarian in nature and we largely depends upon cereal – pulse for our energy and protein needs. This increases the importance of cereals and pulses in our diets. To ensure good quality protein in vegetarian diet one can also opt for cereal pulse combination e.g. khichdi, roti, dal and subji; sambar–idli. The cereal and pulse diet complement each other as cereals lacks in lysine which is abundant in the pulses.

The building of new tissues is very important particularly for growing children and pregnant women. There is also a continuous breakdown of old tissues and building up of new tissues going on in our body at all ages irrespective of the apparent growth, thus maintaining a need for bodybuilding nutrients.

c) Regulatory and protective function

Food also perform regulatory and protective function. It regulates several involuntary and voluntary activities like homeostasis, muscle contraction, blood clotting, heat bating, and removal of waste products. To perform these processes certain nutrients like minerals and vitamins are responsible. Although the nutrients amount required for these function is very small but it is vital that it should be present in the sufficient amount in the diets on the daily basis. For example, Vitamins K is responsible for the clotting of blood. B group vitamins also play. Apart from regulation of body processes, food also prevents us from

18

various infections, and diseases. For example Vitamin A helps in building immunity and enhances the body resistance to fight against invading pathogens.

The important food sources which helps in performing these functions includes green leafy vegetables (GLVs), milk, fresh fruits and vegetables, fish etc.

2) Psychological functions of food

Another function that food performs is the psychological function. Different foods help to satisfy different kinds of emotional needs like stress, happiness etc. among humans. eg. Foods like chocolates are often associated with relieving stress, mother feeding her child with breast milk develops a sense of security among her new-born child. Preparing food for family members creates love and affection. Food is used to express feelings of special attention, friendship, recognition or punishment. The person begins to associate the food habits and foods commonly consumed by him, as it gives him a sense of security and satiety. The foods daily eaten by us, gives us more mental satisfaction, even a nutritionally balanced meal may not be satisfying to the individual if it is unfamiliar or distasteful to him/her. In a friendly gathering, one may try unfamiliar foods and thus enlarge our food experiences. During the course of time and repeated experience, strange foods become familiar and new tastes are formed. These new tastes that are developed should again be satisfying to the mind. For example, a person accustomed to traditional Indian cuisine takes time to adjust to Chinese or western dishes but feels mentally satisfied at the sight of familiar foods. 3) Social functions of food Human is a social animal and food helps him being social. Meal times are not merely the occasion for the intake of food but they also have some other social function for the people (Seymour 1983). The social functions that food performs are: Social groupings Social relationships Socialization Symbolism Role performance

Food is said to be the central ingredient of all the celebrations, meetings, and special occasions like marriage, birthday parties etc. and thus, act as a vehicle to get together and social gatherings and exchange of ideas. Indian society is a food-centric society and our culture is so obsessed with eating that we incorporate eating at every occasion. Every stage of life is usually marked by the feasts associated with it. For e.g. childbirth

19

ceremony, mundans, birthdays, marriages etc. The food menu should bring the people together, rather than creating difference among them e.g. vegetarian vs non-vegetarian food eaters. Meals served at the social functions bring people close and builds social relationships with friends, family, neighbour etc. and thus creates social acceptance among people. Sharing food/ meals with any person indicates that one is accepting friendship. Due to prevailing patriarchy in Indian scenario, males are given more food both quality and quantity-wise. Sweets are also distributed and exchanged to mark certain auspicious occasion like festivals. Food represents our social life and help express our happiness. Food is also linked with social prestige and status. Some foods are considered as foods for rich people as the number of dishes served per meals depicts one’s social status. Food also carries a specific significance in the religious context. In the religious places like temples, gurudwar as food is served to all sections of the society irrespective of the class and creed. This brings people close, produces social cohesion and thus bridges the communal or social divide among the people. Specific foods like or Prasad is served to the devotees at these places as a deity benediction. Earlier people with the same social status used to eat together. A person with inferior status was not allowed to share a meal with higher status people. Different religious communities have different eating pattern because of religious texts and practices. Some foods are strongly recommend while some are rejected. Food thus becomes an integral part of the social and religious life of people. For e.g. Jains are vegetarians and avoid eating any underground vegetables like garlic, ginger etc. Thus, it can be concluded that food functions ranges from satisfying the hunger to building mutual understanding and above all helps to maintain the nutritional status and health. FOOD GROUPS

Consumption of diet having all the nutrients in the appropriate quantity is essential. In order to acquire the goodness of all the food groups in a diet, one must choose food items from each food group depending upon the functions they perform like energy giving foods etc.

The ICMR has grouped the foodstuffs according to the similarity in the nutrients content as it is not possible to consume all the food items in the diet at one time. Moreover, since the food items varied in their nutrient quantity (more or less), the grouping of food was required. Therefore, to overcome this problem, food items providing the similar nutrients have been grouped together, termed as a ‘Food Group’.

Indian Council of Medical Research (ICMR) has classified the different food items into five food groups, based on their nutritional content and for the ease of meal planning.

20

1. Cereals, grains and products

2. Pulses and legumes

3. Milk and meat products

4. Fruits and vegetables

5. Fats and sugars

1. Cereals, grains and products

The foodstuffs included in this group are rice, maize, maida, bajra, jowar, bread, etc. These food items are rich incarbohydrates and energy. Being the cheapest sources of energy this food group is an important part of the diet of all groups.

Along with energy and carbohydrates, this food group also have some quantities of proteins. As cereal is staple food in our daily diet, plenty amount of proteins are derived from them. However, cereals are poor in lysine and rich in methionine, pulses are poor in methionine and rich in lysine, when cereals are mixed with pulses in the same meal then the quality of protein improves through mutual supplementation.

The cereals are also abundant in B complex vitamins, provided one consumes whole grain cereals. These B complex vitamins are absent in refined cereals such as maida etc. as the outer layer of the cereal is removed in refined cereals. Whole-grain cereals are also rich in minerals like iron calcium etc. For e.g. bajra is rich in iron, ragi is rich in calcium. Cereals lacks vitamin C, but its content can be enhanced by the processes of germination and fermentation. 2. Pulses and legumes

This food group include various pulses and legumes, like green gram, black gram beans, etc. Nuts and oilseeds like groundnuts, sesame is included in this group. This food group provides good portion of protein in the vegetarian diet as pulses and legumes are the good source of proteins. The proteins provided by this food group is the second class proteins.

Pulses and legumes are generally consumed with cereals to ensure the quality of protein in the diet as pulses and legumes lacks methionine which is abundant in the cereals. This method of improving protein quality though pulse-cereal combination is called mutual supplementation. Some of the examples of mutual supplementation found in Indian kitchens are dal-roti, dal-chawal etc.

This food group also provides good amount of B group vitamins and minerals especially thiamine. It does not contain Vitamin C, though, its content can be improved by the

21

process of germination and fermentation. Germination is also said to enhance the ion content of the pulses. Another good source of proteins are nuts and oil seeds which is also a good source of energy as it is rich in fats. Oilseeds like sesame seeds are also abundant in calcium. The oil cake left after the extraction of oils is rather a very good source of proteins which is commonly used as an animal feed.

3. Milk and meat products

This food group is further subdivided into two groups:

i. Milk and milk products. ii. Eggs, meat, fish, poultry etc.

The food items in these food groups provide us with the first-class proteins. First-class proteins are the proteins which contain all the Essential Amino Acids (EAA). Essential amino acids are the amino acids which cannot be synthesized in the body on its own and thus one needs to take it in diet. There are nine amino acids namely: Histidine, Methionine, Isoleucine, Leucine, Lysine, Phenylalanine, Tryptophan, Threonine, and Valine.

i) Milk and its products

Milk and its products like curd, cheese are the good source of good quality proteins. It also provides us with calcium and phosphorous, vitamin A and riboflavin. It is considered as a very important food for growing children, as it provides them with good quality proteins and they are also able to digest it. For small infants’ upto 6 months, mother’s breast milk is the only food given to them.

ii) Eggs, meat, fish and chicken These are excellent sources of first-class protein, which can be totally utilized in our body for building the body. They also contain B-group vitamins in good amounts. Among, this liver is a very good source of vitamin A and vitamin B12. Eggs contain nearly all the nutrients but are particularly good source of protein, fats, vitamin A, iron, calcium and phosphorus.

4. Fruits and Vegetables

This food groups add taste, flavour, and varied colours to the diet. It can be sub-divided into two groups. This food items in this food group provide vitamins and minerals which gives protection from infections. a. Vegetables

i. Green leafy vegetables ii. Other vegetables

22

b. Fruits

Green leafy vegetables like mustard leaves (sarso), radish leaves, amaranth leaves (cholai), fenugreek leaves (methi), and spinach etc. are included in this food group. These leafy vegetables are a good source of vitamins and minerals like carotene (precursor of vitamin A), folic acid and iron.

For e.g., 100 mg amaranth leaves contain 8553±1813 β- carotene.

The green leafy vegetables also provide a good amount of calcium, if consumed in the diet.

Other vegetables include orange and yellow coloured vegetables which provide us mainly with carotenes and antioxidants. This group provides vitamins and minerals. Nutrients are not destroyed as fruits are mostly consumed in the raw state. It also has lots of fibre content which prevent constipation. Vitamin C is found in citrus fresh fruits.

Fruits also provide a good amount of vitamins and minerals along with dietary fibre to our meals. The fibrous tissues, which are not digested, help to move the food through the digestive tract and regulate the excretion of body wastes.

5. Fats and Sugars Fats and oils like vegetable oils, vanaspati and ghee are dense sources of energy. One gram of fat provides 9 Kcal. It is mostly used as the cooking medium and hence form a necessary part of the diet of all section of the society. It helps to increase the palatability of our food. Sugar, jaggery and honey supplies energy in the form of carbohydrates. Apart, from providing carbohydrates, jaggery is also a good source of iron.

There are still number of food items that are still not covered in these food groups and are used in our diets on regular basis for e.g. spices and condiments. The spices makes the food palatable tasty, colourful and appealing do not contribute much to the nutritive value of the diet.

The five food groups with their nutrients contribution is given in Table 2.1.

23

Table 2.1: Five Food Groups and their major nutrients.

Food Group Food items Main Nutrients

I. Cereal, grains and products

Rice, Wheat, Ragi, Bajra, Maize, Jowar, Barley, Rice Flakes, Wheat Flour

Energy, Protein, Invisible Fat, Thiamine (Vitamin B1), Riboflavin (Vitamin B2), Folic Acid (Vitamin B9), Iron, Fibre.

II. Pulses and legumes

Bengal Gram, Red Gram, Lentil, Black Gram Green Gram, Rajma, Soybean, And Beans.

Energy, Protein, Invisible Fats, Thiamine (Vitamin B1), Riboflavin (Vitamin B2), Folic Acid (Vitamin B9), Calcium, Iron, Fibre.

III. Milk and meat products

Milk, Cheese Curd, Chicken, Liver, Fish, Egg, Meat

Protein, Fat, Riboflavin (Vitamin B2), Calcium.

IV. Fruits and vegetables

Fruits: Mango, Papaya, Orange, Sweet, Guava, Lime, Melon etc. Vegetables: (Green

Leafy): Amaranth, Coriander, Spinach, Mint, and Fenugreek Leaves Etc. Other Vegetables: Carrots, Ladyfinger, Beans, Brinjal, Onions Etc.

Vitamin A, Vitamin C, Riboflavin (Vitamin B2), Iron, Fibre. Vitamin A, Riboflavin (Vitamin B2), Folic Acid (Vitamin B9), Calcium, Dietary Fibre, Iron. Vitamin A, Folic Acid (Vitamin B2), Calcium, Dietary Fibre.

V. Fats and Sugar

Fats: Butter, Ghee, Cooking Oil Etc. Sugars: Honey, Sugar, Jaggery

Energy, Fats, Essential Fatty Acids (EFA) Energy

24

BALANCED DIET

No food is complete in itself. In order to have all the nutrients in adequate proportion, we must include different type of foods in our diet. A diet balanced for one may not be balanced for the other person because nutritional requirements vary from person to person. For e.g. an adult balanced diet cannot be given to a child as they both have different nutritional requirements. The nutritional requirements are affected by different factors like age, gender, climate, occupation, the composition of the body etc.

In order to provide the nutrients, good nutrition or adequate food consumption according to the dietary needs of the human body is necessary. A well-balanced diet combined with the regular physical activity is the foundation of good health. Poor nutrition can lead to reduced immunity, increased susceptibility to disease, impaired physical and mental development, and reduced productivity. Since a healthy diet consists of different kinds of foods, therefore the food-based approach has been largely followed.

A healthy diet consumed throughout the life-course helps in preventing malnutrition in all its forms as well as a wide range of non-communicable diseases (NCDs) and conditions. But rapid urbanization/globalization increased consumption of processed foods and changing lifestyles has led to a shift in dietary patterns. Eating a nutritious and balanced diet is one of the best ways to protect and promote good health.

Food items from all the five food groups given by ICMR are included to make a diet balanced to fulfil the nutritional needs of a person. A balanced diet is one which provides all the nutrients in required amounts and proper proportions in a person’s diet without increasing its calorie intake from the Recommended Dietary Allowance (RDA). In addition, a balanced diet should provide other non-nutrients such as dietary fibre, antioxidants and phytochemicals which bestow positive health benefits. Antioxidants such as vitamins C and E, beta-carotene, riboflavin and selenium protect the human body from free radical damage. Other phytochemicals such as polyphenols, flavones, etc., also afford protection against oxidant damage. Spices like turmeric, ginger, garlic, cumin and cloves are rich in antioxidants. A balanced diet is the one which contains different types of food in adequate quantity and right proportion so as to meet the nutritional requirements of our body. It can easily be achieved through a blend of the five basic food groups. The quantities of foods needed to meet the nutrient requirements vary with age, gender, physiological status and physical activity. Around 50-60% of total calories should come from carbohydrates in a balanced diet, preferably from complex carbohydrates, about 10-15% from proteins and 20-30% from both visible and invisible fat. Apart from providing adequate nutrients for growth and maintenance, there is an extra provision for nutrients as a margin of safety in the balanced diet. The margin of

safetyconsu

Balanin Tab

Ta

FO

CereaproduPulseMilk produRootsGreenOtherFruitSugarFats To calcu

An exgiven

y is used in ume the nutr

nced Diet foble 2.2.

able 2.2: Ba

OOD GROU

al, grains &ucts es & legume& milk

ucts s& tuber n vegetabler vegetablets r

ulate the day's req

xample of an below.

Figure 2.3

stress condrients in the

or Adults(m

alanced die

UPS g/p

&

es 1

es es

quirement of abov

an adult ma

3: Sample m

ditions like e required am

an and wom

et for adultportio

portion M

30 1

30 100 ml

100 100 100 100

5 5

ve-mentioned foo

an day’s die

meal plan f

25

during fastimount.

man) - Seden

ts-sedentaryons) (ICMR

SedentarMan Wom12.5 9

2.5 23 3

2 21 2 21 4 45 4

od groups for an i

et belonging

for an adult

ing, fevers

ntary/Mode

y/ moderatR, 2011)

Type of wry Mman Man9 15

2 3 3 3

2 2 1 1 2 2 1 1 4 6 4 6 individual, multip

g to the mid

t man (sede

etc. where o

erate/Heavy

te/ heavy ac

work Moderate n Woman

11

2.5 3

2 1 2 1 6 5

ply grams per por

ddle-income

entary) (IC

one is not a

y Activity is

ctivity (No.

Hen Man

20

4 3

2 1 2 1

11 8

rtion with no of p

e group (M

CMR, 2011)

able to

s given

. of

eavy Woman

16

3 3

2 1 2 1 9 6

ortions.

MIG) is

26


1. Explain the following briefly:

a) RDA

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

b) Food group

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

c) Social functions of food

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

2. ‘A balanced diet for a person may not be balanced one for the other’. Justify.

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

3. Explain the concept of mutual supplementation.

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

SUMMARY All the nutrients in the diet are provided by right amount and proportion of the all the food groups. The quantity of the food group vary based on one’s gender, age, occupation and the physiological condition. Along with supplying nutrients to the body food also contains different flavouring compounds However food serves several other functions such as physiological, psychological and social. There are several ways of categorising foods into food groups like on the basis of type of food or the nutrients supplied by foods. A balanced diet includes foods from all the food groups.

27

KEYWORDS Digestion- a process by which complex substance in the food is broken down into simpler substances Ingestion- intake of food Satiety- the feeling of fullness Symbolism- expressing the invisible/intangible (social status) by means of visible representation (food) REFERENCES ICMR. Nutrient requirements and recommended dietary allowances for Indians. A report of the expert group of Indian Council of Medical Research (ICMR), National Institute of Nutrition, Hyderabad. 2010.

Indian Council of Medical Research (ICMR). Dietary Guidelines for Indians- A Manual. National Institute of Nutrition, Hyderabad, 2011.

Seymour, D 1983, ‘The social functions of the meal’, International Journal of Hospitality Management.

29

UNIT 2

NUTRIENTS Lesson 3 : Macronutrients

Lesson 4 : Micronutrients-I

Lesson 5 : Micronutrients-II

31

LESSON 3

MACRONUTRIENTS

INTRODUCTION "Macro means big." These nutrients are needed in larger quantities (in gram range). They normally include water, carbohydrates, fat and protein. Macronutrients (except water) are also called energy-providing nutrients. Energy is measured in calories and is essential for the body to grow, repair and develop new tissues, conduct nerve impulses and regulate life process. Good nutrition is a basic component of health. It is of prime importance in the attainment of normal growth and development and in the maintenance of health throughout life. Since last century several advances have been made in the field of Nutrition. Between the two world wars, research was mainly centred on vitamins. After the Second World War, research on protein gained momentum. During 1970’s a great deal of interest had been focused on the role of dietary fats in the pathogenesis of atherosclerosis and its complications, particularly coronary artery disease. In the last decades of past century, the role of trace elements and dietary fibre in the human health and disease has attracted considerable attention. Since all foods are not of the same quality from the nutritional point of view, individual’s ability to meet his nutritional needs and maintain good health depends on the type and quantity of foodstuffs he is able to include in his diet. OBJECTIVES Describe the functions of energy, protein, carbohydrate and fats in our body. Identify the dietary sources of these nutrients. Understand the clinical manifestations of their deficiencies/excesses.

ENERGY

Energy is defined as a capacity for doing work. It is the heat produced in the body which is utilised for performing the involuntary and voluntary activities, to maintain body temperature and to synthesise new body constituents.

Basal Metabolic Rate (BMR): The minimal rate of energy expenditure compatible with life. It is measured in the supine position under standard conditions of rest, fasting, immobility, and mental relaxation. Depending on its use, the rate is usually expressed per minute, per hour or per 24 hours.

32

Energy Requirement (ER) is defined as the amount of food energy needed to balance energy expenditure in order to maintain body size, body composition and a level of necessary and desirable physical activity, and also to allow optimal growth and development of children, deposition of tissues during pregnancy, and secretion of milk during lactation, consistent with long-ten1 good health.

Total Energy Expenditure (TEE): The energy spent, on average, in a 24-hour period by an individual or a group of individuals. By definition, it reflects the average amount of energy spent in a typical day, but it is not the exact amount of energy spent each and every day (Figure 3.1).

Unit of energy: The energy value of food is expressed in terms of Kilocalories (Kcal). A Kilocalorie is defined as the amount of heat required to raise the temperature of one kilogram of water by 1ºC.

In the metric system, the international unit, which is Kilojoules, is used instead of kilocalories. 1 kilojoule is energy expended when one kilogram of mass is moved by 1 meter using a force of a newton.

1 calorie = 4.184 joule 1 Kcal = 4.184 K joule 1000 Kcal = 4.184 M joule 1 K joule = 0.239 Kcal 1 M joule = 239 Kcal

Components of energy requirements

1. Basal metabolism- This comprises a series of functions that are essential for life, such as cell function and replacement; the synthesis, secretion and metabolism of enzymes and hormones to transport proteins and other substances and molecules; the maintenance of body temperature; uninterrupted work of cardiac and respiratory muscles; and brain function. The amount of energy used for basal metabolism in a period of time is called the basal metabolic rate (BMR), and is measured under standard conditions that include being awake in the supine position after ten to 12 hours of fasting and eight hours of physical rest, and being in a state of mental relaxation in an ambient environmental temperature that does not elicit heat-generating or heat-dissipating processes. Depending on age and lifestyle, BMR represents 45 to 70 percent of daily total energy expenditure, and it is determined mainly by the individual’s age, gender, and body size and body composition.

2. Metabolic response to food- Eating requires energy for the ingestion and digestion

of food, and for the absorption, transport, interconversion, oxidation and deposition of

33

nutrients. These metabolic processes increase heat production and oxygen consumption, and are known by terms such as Dietary-Induced Thermogenes (DIT), Specific Dynamic Action (SDA) of food and thermic effect of feeding. The metabolic response to food increases total energy expenditure by about 10 percent of the BMR over a 24-hour period in individuals eating a mixed diet.

3. Physical activity- This is the most variable and, after BMR, the second largest

component of daily energy expenditure. Humans perform obligatory and discretionary physical activities. Obligatory activities can seldom be avoided within a given setting, and they are imposed on the individual by economic, cultural or societal demands. The term "obligatory" is more comprehensive than the term "occupational" that was used in the 1985 report (WHO, 1985) because, in addition to occupational work, obligatory activities include daily activities such as going to school, tending to the home and family and other demands made on children and adults by their economic, social and cultural environment.

Discretionary activities, although not socially or economically essential, are important for health, well-being and a good quality of life in general. They include the regular practice of physical activity for fitness and health; the performance of optional household tasks that may contribute to family comfort and well-being; and the engagement in individually and socially desirable activities for personal enjoyment, social interaction and community development. Physical Activity Level (PAL)- TEE for 24 hours expressed as a multiple of BMR, and calculated as TEE/BMR for 24 hours. In adult men and non-pregnant, non-lactating women, BMR times PAL is equal to TEE or the daily energy requirement.

Physical Activity Ratio (PAR)- The energy cost of an activity per unit of time (usually a minute or an hour) expressed as a multiple of BMR. It is calculated as energy spent in an activity/BMR, for the selected time unit.

Figure3.1: Components of total energy expenditure (TEE)

Factors affecting components of energy expenditure

Among factors which influences energy needs are age, sex, body size, climate, secretion of endocrine glands, status of health, altered physiological activity.

Basal Metabolic

RatePhysical Activity

Dietary-Induced

Thermogenesis

Total Energy

Expenditure (TEE)

34

i. Age- During the growth period, the BMR is high, therefore during infancy the energy need per kg of body weight are highest than at any phase in life. Energy requirement also decline progressively after early adulthood due to steady decline in the BMR thereafter. The basal metabolism during rapid growth is at a high level. The younger the individuals, the higher the basal metabolism, since much energy is stored for growth. The period at which the basal metabolism reaches its highest level is between the ages of 1-2 years. A gradual decline occurs between the age of 2-5 years, with a more rapid decline until adult age is reached.

ii. Sex- The BMR is higher in adolescent boys and adult males as compared to adolescent girls and adult females. It is not due to direct influence of sex differences, but is due to the differences in body composition. Males have a greater amount of muscles and glandular tissues, which is metabolically more active whereas, females have greater adipose tissues, which is metabolically less active. Hence energy requirement of males is higher than of females.

iii. Body size- It will have an important effect on energy needs because a larger body has a greater amount of muscles and glandular tissue to maintain, thus requiring higher energy allowances. Heat is continuously lost through the skin by radiation. Since the heat loss is proportional to the skin surface, the basal heat production is directly proportional to the surface area. A tall thin individual has a greater surface area than an individual of the same weight who is short and fat and the former will therefore, have a higher basal metabolic rate.

iv. Climate- It is known that the BMR is lower in tropics than in temperate zones. Hence the energy cost of work is slightly higher when the temperature falls below 14ºC. However it is felt that there is no need to make any adjustment for temperature in India.

v. Secretion of endocrine glands- The thyroid gland in particular exerts a marked influence on the energy requirement. If it is over active (hyperthyroidism), the BMR will increase. If the activity of the gland decreases (hypothyroidism), the BMR will be reduced. Thereby increasing or decreasing energy requirements accordingly.

vi. Status of health- During the periods of fever as well as malnutrition, the BMR of an individual is affected. Illness involving an elevation of body temperature markedly increases the basal heat production thus increasing the BMR, hence increased energy requirement.

vii. Altered physiological states- During pregnancy, extra energy is needed for the growth of the foetus, placenta and various maternal tissues, such as in the uterus, breasts and fat stores, as well as for changes in maternal metabolism and the increase in maternal effort at rest and during physical activity during Lactation. The energy cost of lactation has two components: 1) the energy content of the milk secreted; and 2) the energy required to produce that milk. Well-nourished

35

lactating women can derive part of this additional requirement from body fat stores accumulated during pregnancy. In pregnancy, this additional energy is needed to support the growth of foetus and maternal tissue. During lactation energy is required for synthesis of milk.

viii. Effect of food- A certain amount of work is expended in the digestion of food, its absorption, transfer to the tissues and utilisation. The increased heat production as a result of the ingestion of food is known as the specific dynamic action of the food. Protein when eaten alone has been shown to increase the metabolic rate by 30%. On the basis of the mixed diets, which are usually consumed, the specific dynamic action of food is approximately 10% of the energy requirement.

ix. Extent of physical activity- Any kind of physical activity increases the energy expenditure above the basal energy need. Energy for the performance of all types of physical activities ranks next to basal metabolism in amount of energy expended. Sleep causes a reduction of about 10% in the BMR depending on the number of hours spent in sleeping and its manner i.e. restless/ peaceful. The energy need is determined by the nature and duration of physical activity. Sedentary work, which includes office work, bookkeeping, typing, teaching, etc., calls for lesser energy than moderate work (more active and strenuous occupations) such as nursing, home making or gardening. A still greater amount of energy is required by those individuals who are involved in heavy work (hard manual labourer) such as ditch digging, shifting freight etc. Energy needs vary with age, occupation and physiological state.

Recommended Dietary Allowances:

The Indian Council of Medical Research (ICMR, 2010)has recommended the following standards in respect of energy requirements in India (Table 3.1)

Table 3.1: Recommended Energy Requirement/day Group Category/Age Net Energy (kcal/d) Men Sedentary work 2320

Moderate work 2730 Heavy work 3490

Women Sedentary work 1900 Moderate work 2230 Heavy work 2850 Pregnant +350 Lactating 0-6 m +600

6-12 m +520 Infants 0-6 months 92 kcal/kg/d

6-12 months 80 kcal/kg/d Children 1-3 years 1060

Source LET’1.

2.

3.

Carbocompto clorganmetriccellul

Group

Boys Girls Boys Girls Boys Girls

e: Nutrient R

’S CHECK Briefly exa. SD---------------------------------b. B--------------------------------- Enlist the--------------------------------- ‘The ener

---------------------------------

ohydrates aposed of carblass of ornisms on eac tons of lose and

Requirements

THE PROGxplain the foDA ------------------------------------------MR ------------------------------------------

e factors inf------------------------------------------

rgy need is

------------------------------------------

are the mobon, hydrogrganic comarth. Each y

CO2 and other p

Cate4-6 y7-9 y10-1210-1213-1513-1516-1716-17

s and Recom

GRESS following:

------------------------------------------

------------------------------------------

fluencing th------------------------------------------

determined

------------------------------------------

CAR

ost abundangen, and oxy

mpounds foyear, more t

H2O are plant prod

36

gory/Age years years 2 years 2 years 5 years 5 years 7 years 7 years

mmended Die

---------------------------------------------

---------------------------------------------

e total energ---------------------------------------------

d by the natu

---------------------------------------------

BOHYDRA

nt biomolecygen. It belound in lithan 100 biconverted

ducts due

Net135169219201275233302244

etary Allowa

------------------------------------------

------------------------------------------

gy requirem------------------------------------------

ure of physi

------------------------------------------

ATES

cules longs iving illion

into to

Figur

t Energy (k50 90 90 10 50 30 20 40 ances for Indi

---------------------------------------------

---------------------------------------------

ment of an in---------------------------------------------

ical activity

---------------------------------------------

re 3.2: Stru

kcal/d)

ians(ICMR,

------------------------------------------

------------------------------------------

ndividual. ------------------------------------------

’. Explain.

------------------------------------------

C6

ucture of gl

2010).

------------------------

------------------------

------------------------

------------------------

6H12O6

lucose

37

photosynthesis. Hence, carbohydrates are abundant in most plant foods, especially fruits and grains. Regardless of the size of the carbohydrate, once it has been ingested, it is metabolized in the mouth, stomach, and intestines to the smallest structural unit (Figure 3.2),which is usually glucose. The general formula is CnH2nOn.

Classification of carbohydrates

The building blocks of all carbohydrates are sugars and they can be classified according to how many sugar units are combined in one molecule. Glucose, fructose and galactose are prominent examples among the single unit sugars, also known as monosaccharides. Double units are called disaccharides, with sucrose (table sugar) and lactose (milk sugar) being the most widely known. Carbohydrates are classified on the basis of chemical and physiological classification (Figure 3.3). On the basis of chemical classification they can be classified as monosaccharides, disaccharides and polysaccharides. On the basis of physiological classification it can be classified as simple and complex. The term ‘Saccharide’ means sugar or sweetness is related to the characteristics taste of many of the simple carbohydrates. Monosaccharides are simple sugars which serve as the building blocks of complex sugars and polysaccharides. Carbohydrates were first named according to the sources from which they were obtained e.g. grape sugar, cane sugar, malt sugar, milk sugar, etc. Then they were named from a prefix related to the sources followed by the suffix ‘ose’ e.g. Fructose (fruit sugar), Lactose (milk sugar) these names are still used.

Figure 3.3: Classification of carbohydrates

Classification of carbohydrates

Chemical classification (Basis of the number of forming units)

Monosaccharides Oligosaccharides Polysaccharides

Physiological classification (Basis of the degree of polymerization)

Simple-monosaccharides,disaccharides,

oligosaccharidesComplex-

polysaccharides

38

The table below shows the different examples of dietary carbohydrates.

Table 3.2:Examples of dietary carbohydrates

CLASS EXAMPLES Monosaccharides Glucose, fructose, galactose Disaccharides Sucrose, lactose, maltose Polyols Isomalt, maltitol, sorbitol, xylitol, erythritol Oligosaccharides Fructo-oligosaccharides, malto-oligosaccharides Starch polysaccharides Amylose, amylopectin, maltodextrins Non-starch polysaccharides (dietary fibre)

Cellulose, pectins, hemicelluloses, gums, inulin

Functions

The functions of carbohydrates are: i. Source of energy- The main function of carbohydrate is to provide fuel for the body

carbohydrates burn in the body at the rate of 4 kcal/g. Glucose is the main source of energy. So all types of carbohydrates are converted to glucose in body and then used for immediate tissue energy need. A small amount is stored as glycogen in the liver and muscles, and some is stored as fat in the adipose tissue.

ii. Protein sparing Action- The body uses carbohydrates preferentially as a source of energy when it is adequately supplied in the diet, thus sparing protein for tissue building.

iii. Provide taste to the food- As most of the carbohydrates are sweet in nature, they improve the palatability of the diets.

iv. For complete oxidation of fats- A certain amount of carbohydrate is necessary in the diet so that the oxidation of fats can proceed normally. If carbohydrates are severely restricted in the diet, fats are metabolized resulting in ketosis.

v. Lactose- been less soluble than other sugars, it remains in the intestine long enough to encourage the growth of desirable bacteria, which help in synthesis of B-complex vitamins. it also helps in better absorption and utilisation of calcium.

vi. Contribution of dietary fibre- Cellulose, hemicellulose and pectin gives no nutrients to the body, but these fibres are very useful in providing bulk to the diet. These indigestible substances facilitate the elimination of intestinal wastes by stimulating the peristaltic movements of gastrointestinal tract. They also have the property of absorbing water thus giving bulk to the intestinal contents. Lack of adequate dietary fibre in diets containing refined foods, leads to constipation and colon cancer, also some of the dietary fibres like gum and mucilage in our diet have been shown to lower blood cholesterol in hypercholesteraemic subjects and blood sugar in diabetes. Vegetables, especially the leafy ones, fruits and unrefined cereals are rich in fibre and a generous inclusion of these provides a diet rich in fibre.

39

vii. Conversion to fat- Excess glucose can be stored as fat in adipose tissue for later use. This stored form of glucose is called glycogen and is primarily found in the liver and muscle.

Sources

There are three main sources of carbohydrates; these are starch, sugar and cellulose.

a. Starches are present in cereals(e.g. rice, wheat, maize, sago and all bakery products), pulses, potatoes, sweet potatoes and dry fruits.

b. Sugars are present in cane sugar, jiggery, honey, jam, jellies, dry fruits, sweets and fresh fruits, e.g. banana, sapota, grapes, mango.

c. Cellulose is the fibrous substance present in whole grains, whole pulses, whole fruits etc.

Recommended Dietary Allowances

Carbohydrates are a vital component of a healthy and balanced diet as they usually supply the largest proportion of energy to the body. They can help to control body weight, especially when combined with exercise, are vital for proper gut function and are an important fuel for the brain and active muscles. Neither starch nor sugar has been found to have any special role in the development of serious diseases such as Type 2 diabetes, and the role of sugar in the development of tooth decay is less important in today's fluoride and oral hygiene aware populations. The WHO/FAO report on carbohydrates in human nutrition and the scientific opinion on dietary reference values for carbohydrates and dietary fibre from EFSA hold key information for health professionals and research scientists.

ICMR has not given any specific recommendations for carbohydrates. However, in a balanced diet 50-60% of the total calories should come from carbohydrates. Only 10 per cent should come from sugar and the rest should come from the complex carbohydrates.

For example in a 2000 kcal diet, 250- 300g of carbohydrate is recommended.

Deficiency

The energy needs are not met if the diets are deficient in carbohydrates. The work efficiency is lowered. Also person become underweight. Growth will be slow in the case of children. Symptoms of ketosis may also develop. Lack of dietary fibre in the diet leads to constipation and colon cancer.

If carbohydrates are consumed in excess they get accumulated as fat in the body leading to obesity and predisposes an individual with diabetes and heart ailments.

40

DIETARY FIBRE

Dietary fibre also known as roughageis defined as that indigestible parts of plants. It is the portion of food derived from plant, which is resistant to hydrolysis/ digestion in the human system. It consists of both insoluble and soluble fibre. Table 3.3 gives details about types of fibre and its sources.

Table 3.3: Fibre: its sources and functions Fibre Source Functions Insoluble fibre

Cellulose Whole wheat flour, bran, root vegetables, legumes

o Prevents constipation o Lowers the risk of diverticular

disease

Hemi cellulose Bran, whole grains Lignin Root vegetables

Soluble fibre

Pectins Apple, guava, carrots, strawberries

o Lowers fat absorption helps in weight management

o Lowers cholesterol o Stabilizes blood glucose levels o Reduces risk of cardiovascular

disease o Maintain healthy gut bacteria

Gums Oatmeal, barley, legumes


There have been no studies on evaluating the dietary fibre requirements in Indians. However, WHO committee on chronic degenerative disease recommended a daily intake of 30g dietary fibre. Hence, based on energy intake a level of about 40g/2000 kcal in a diet is considered safe. Excess fibre intake can lead to the reduced absorption of nutrients as it can bind minerals such ascalcium, magnesium, iron and zinc. It may also cause abdominal discomfort and diarrhoea or even intestinal blockage if enough fluid is not consumed. CONCEPT OF GLYCEMIC INDEX AND GLYCEMIC LOAD

Watter Willet of Harvard University pioneered the concept of glycemic load. It is defined as the product of dietary glycemic index and total dietary carbohydrate.

The glycemic load (GL) is an equation that takes into account the planned portion size of a food as well as the glycemic index of that food. It combines both the quantity and quality of carbohydrates. It is also the best way to compare blood glucose values of different types and amounts of foods.

41

Glycemic Load = GI/100 multiplied by the net grams of planned carbohydrate

(Net carbohydrate is the total grams of carbohydrate minus the dietary fiber).

For example, a single apple has a GI of 38 and contains 13 grams of carbohydrates.

GL= 38 x 13/100 = 5

The glycemic index (GI) is a tool to measure how individual foods are expected to impact blood sugar levels. The glycemic index (GI) is a ranking of foods based on their measured blood glucose response compared with a reference food, either white bread or glucose. The GI is calculated by measuring the incremental area under the blood glucose. The number is a comparison between individual foods and a sugar called glucose. Glucose is given a value of 100. If the test food is assigned a value below 100, that food is expected to impact your blood sugar less than glucose. If the test food is assigned a value over 100, that food is expected impact your blood sugar more than glucose. In theory, a large amount of a low GI food may increase your blood sugar as much as a small amount of a high GI food. The glycaemic index of some common foods (using glucose as standard)

Low GI (≤ 40)

Foods with a low GI (41 – 55)

Intermediate GI (56 – 70)

High GI (> 70)

Raw apple Lentils Soy beans Kidney beans Cow’s milk Carrots (boiled) Barley Fructose

Noodles and pasta Apple juice Raw orange juice Dates Raw banana Yoghurt (fruit) Sweet corn Chocolate

Brown rice Rolled oats Soft drinks Pineapple Sucrose (table sugar) Honey

Bread (white/wholemeal) Boiled potato Cornflakes French Fries Mashed potatoes White rice (low amylose or "sticky rice") Rice crackers

LET’S CHECK THE PROGRESS 1. Briefly explain the following :

a. Carbohydrates as a source of energy

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------

42

b. Protein sparing action of carbohydrates

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. What are the various sources of carbohydrates? ---------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

PROTEINS The word protein means to ‘take the first place’. In 1938 a Dutch chemist Mulder, described that all living plants and animalscontain certain substance without which life was not possible and this was identified as proteins. In constitution of body they stand next to the water. Indeed proteins are of the greatest importance in human nutrition. They are complex organic compounds containing the carbon, hydrogen, oxygen, nitrogen and usually sulphur Some proteins also contain phosphorus, iron, iodine, copper and other inorganic elements. The proteins differ from carbohydrates and fats as they contain nitrogen. Proteins are made up of much smaller units known as amino acids. FUNCTION Proteins are very essential for life processes, as there is hardly any important physiological function in which proteins to not participate. The important functions of proteins are:

1. Source of energy 2. Growth and maintenance of tissue 3. Formation of essential body compounds 4. Transport of nutrients 5. Regulation of water balance 6. Maintenance of appropriate pH 7. Defense and detoxification

1) Body building- It is the most important function of protein. These are the major structural components of body tissues. In fact every living cell contains protein. The first need for proteins therefore is to supply the materials for growth and development and the continuous replacement of the cell protein.

43

2) Body regulatory- Many proteins have highly specialised functions in the regulation of body processes. All chemical reactions in the body are carried out by enzymes, which are protein in nature. Proteins are also a constituent of haemoglobin, which is necessary to carry oxygen from lungs to tissues and bring back carbon dioxide. Governing the body reaction are hormones, which are also proteins. Plasma protein has a fundamental role in the maintenance of water balance. Blood proteins also help in maintaining acid base balance of the body. 3) Body protection- There is a protein called gamma globulin, which has a capacity to fight against invading organism. The body’s resistance to disease is maintained in part by antibodies which are protein in nature. 4) Energy yielding- The energy needs of the body take priority over other needs. If diet does not furnished sufficient energy from carbohydrates and fats, the proteins of the diet as well as tissue protein will be used up for giving energy. One gram of protein gives 4 calories. 5) Maintenance of body temperature- During the metabolism of proteins extra heat is liberated, which is used for maintaining the body temperature. FOOD SOURCES There are two main dietary sources of proteins 1. Animal sources- Milk and milk products (excluding butter and ghee), eggs, meat,

fish and poultry. 2. Plant sources- Pulses e.g. soyabean, bengal gram, red gram dal, green gram, black

gram dal; Cereals e.g. wheat, maize, rice, barley, jowar, bajra; and nuts e.g. peanuts, almond, cashew nuts. Fruits and vegetables are poor sources of protein.

PROTEIN QUALITY It is not only the quantity of protein which is important, but also the quality. This depends mainly on the type and amount of amino acids present in the particular protein. There are twenty-two amino acids which are needed by the human body, out of which eight are called ‘essential’. It is because body cannot synthesise them, therefore they must be obtained from the diet. Rest of the amino acids are termed as 'non-essential’ as they can be synthesised in our body. Essential amino acids are isoleucine, leucine, lysine, methionine phenyl alanine, threonine, tryptophan and valine. In addition to these, infants require histidine for growth. Based on the quality of proteins, they can be classified into three classes. a. Complete protein (first class)

44

b. Partially complete protein (second class) c. Incomplete proteins (third class) o Complete proteins- These contain all the essential amino acids in sufficient quantities

so that a normal rate of growth can be maintained by the body. Mainly proteins from animal source belong to this class i.e. milk, meat, eggs, fish and poultry. Wheat germ and dried yeast have a biologic value approaching that of animal sources.

o Partially complete proteins- They can maintain life but they lack sufficient amount of some of the amino acids necessary for growth. Proteins from plant source like pulses, wheat and nuts belong to this class.

o Incomplete proteins- They can neither promote growth nor maintain life because they lack many of the amino acids or even if they contain, it is in very small amounts. Gelatin and zein which is found in corn are the examples which belongs to this class.

Supplementary value of proteins is the capacity of one protein to make good the deficiency of another protein. This is also known as the ‘mutual supplementation effect’.

The chief source of protein in diets for most of the world’s people is from plants. Just because plant foods, when fed alone, do not provide necessary quota of essential amino acids is no reason to condemn them as protein sources. However four possibilities exist for improving the protein quality.

o To feed some amount of animal or complete protein with second and third class protein e.g. to include little amount of animal protein at each meal.

o To use a combination of various vegetable proteins so that they would make up the deficiency of each other e.g. mixture of cereals and pulses.

o To add the lacking essential amino acids synthetically.

o By germination and fermentation e.g. sprouting of pulses, cereals etc. Recommended Dietary Allowances The protein requirements vary from individual to individual. Apart from age and physiological conditions, factors like emotional disturbances, infection and stress can affect a person's protein requirement. For proper utilisation of protein, energy intakes should be adequate. Maximum amount of protein per kg of body weight is required during infancy i.e. till one year of age. The requirement per kg of body weight slowly decreases as one reaches the adulthood and then it is stable i.e. 1 gram per kg of desirable body weight. During pregnancy and lactation the protein allowances for woman are increased over the basic level. The Indian Council of Medical Research (ICMR, 2010) has recommended the following standards in respect of protein requirement in India (Table 3.4)

45

Table 3.4:Recommended Protein Requirement / day

Group Particulars Proteins (g/d) Men Sedentary work

60 Moderate work Heavy work

Women Sedentary work 55 Moderate work

Heavy work Pregnant 78

Lactating 0-6 m 74 6-12 m 68

Infants 0-6 months 1.16 kcal/kg/d 6-12 months 1.69 kcal/kg/d

Children 1-3 years 16.7 4-6 years 20.1 7-9 years 29.5

Boys 10-12 years 39.9 Girls 10-12 years 40.4 Boys 13-15 years 54.3 Girls 13-15 years 51.9 Boys 16-17 years 61.5 Girls 16-17 years 55.5

Source: Nutrient Requirements and Recommended Dietary Allowances for Indians (ICMR, 2010).

Deficiency

A reduced protein intake or constant consumption of poor quality proteins oven an extended period of time leads to depletion of tissue reserves and lowering of blood protein levels. The protein deficiency occurs mostly during infancy, early childhood, pregnancy and lactation.

In children protein deficiency leads to occurrence of marasmus and kwashiorkor (Figure3.2 and 3.3). They show retarded growth, oedema and diarrhoea. In adults usually protein deficiency causes loss of weight, weakness and lowered resistance to diseases.

46

LET’S CHECK THE PROGRESS 1. What are the various functions of protein in our body?

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. Briefly explain the following: a) Protein quality --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- b) Supplementary value of proteins ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3. Discuss the RDA of protein of lactating mothers and infants. ---------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

LIPIDS OR FATS

Fat is an important component of our diet and serve a number of functions. These are also organic compound of carbon, hydrogen and oxygen. These differ from carbohydrates in

Figure 3.2: Clinical photograph of a child suffering from marasmus Source: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSiXAPLu8yPLkoeuPbJOHlES_h14QY_CusNwxRBrepY3aBbX658

Figure 3.3:Clinical photograph of a child suffering from kwashiorkor Source:https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRrC72u042F9nrSaPgG3hTzjfLqZFQAutBku14yzGbvLeAXY_m5

47

that they have much smaller proportion of oxygen and much greater proportion of carbon and hydrogen. Lipids are broadly classified into two groups: simple lipids and compound lipids. Simple lipids include fatty acids and waxes. All other lipids are included under compound lipids e.g. carotenoids and phosphoglycerides. The term fat is generally applied to all triglycerides regardless of whether they are solid or liquid at room temperature. Triglycerides from animal sources contain a higher percentage of saturated fatty acids and are normally solids at room temperature and known as fats. The plant triglycerides are rich in unsaturated fatty acids and are generally liquids at room temperature and called oils. Fats in the diet can be of two kinds, the visible and invisible fat. The visible fats are those which are derived from animal fats like butter, ghee and those derived from vegetable sources like mustard oil, groundnut oil, sunflower oil etc. Apart from the added/visible fat, some amount of fat is present in other foods like cereals, pulses, oilseeds, milk, eggs and meats. The invisible fat is believed to contribute significantly to the total fat and essential fatty acid content of the diet depending upon the foodstuffs present in the diet. Essential Fatty Acids Certain fatty acids should be provided essentially in the diets, as they are not synthesized in the body. These are polyunsaturated fatty acids, namely linoleic, linolenic and arachidonic acids and are grouped as ‘essential’ fatty acids. They are required for metabolism and for maintenance of normal health of the skin. Therefore, proper type of fats which are rich in essential fatty acids e.g. peanut, cottonseed, corn and sunflower oils, must be present in the diet. Animal fats are poor sources of essential fatty acids. However, it is only the linoleic acid which we really need as the other two can be synthesized in the body from the same i.e. linoleic acid. Functions The functions of fats are:

1. Energy yielding- Fats are concentrated source of energy. One gram of fat gives 9 calories. Compared to carbohydrate it not only gives more amount of energy but at a faster rate.

2. Fats also perform the protein sparing action in the same way as carbohydrate does.

3. Storehouse of energy for the body’s needs- In fact not only amount of fats as such are stored in adipose tissue, but any amount of glucose, amino

48

acids, not promptly utilised are also stored in the body, thereby energy is continuously available from the stores in adipose tissues.

4. Insulation and padding- The subcutaneous layer of fat is an effective insulator and reduces loss of body heat in cold weather, thus regulating the body temperature. The vital organs such as the kidneys are protected against physical injury by a padding of fat around the organs.

5. Fat help in absorption and transportation of fat-soluble vitamins in the body.

6. Provides essential fatty acids: Fat is also the source of certain essential fatty acids (the ones that cannot be synthesised in the body) which are essential for metabolism and for maintaining a normal skin.

7. Fat act as a lubricant for various body organs specially the organs of the gastrointestinal tract.

8. Gives satiety value: Fat decreases the secretion of hydrochloric acid (HCL) in the stomach. Thus, the food stays in the gastrointestinal (GI) tract for a longer time and feeling of hunger is delayed.

9. Fat also increases the palatability of the diet by adding flavour to many cooked food preparations.

Food sources Dietary fats are derived from two main sources (1) Animal sources- It includes butter, ghee, curd, whole milk and its products, meat,

fish, poultry, and eggs. (2) Plant sources- They include all vegetable oils e.g. groundnut, gingelly, mustard,

cottonseed, sunflower, and coconut oil. It also includes hydrogenated fats, margarine, nuts and oilseeds like cashew nuts, peanuts, almonds and mustard seeds.

Recommended Dietary Allowances The fat requirement mainly depends upon the energy needs of the individual. From physiological point of view there can be wide variation in fat intake and still good health can be maintained. On an average about 15 to 20% of the total energy should be supplied from fats. The dietary fats should be a good source of essential fatty acids and hence at least 50% of the dietary fat should be from vegetable oils rich in essential fatty acids. Deficiency Just like carbohydrates deficiency, the energy needs will not be met if the diet is deficient in fat content. Hence leading to underweight, weakness and lowered work efficiency. In

49

addition to this the deficiency of the essential fatty acids may affect several metabolic reactions. A deficiency of these fatty acids is believed to lead to a skin condition known as ‘phyrnoderma’ (toad skin) in which the skin becomes rough and thick horny papules of the size of a pinhead erupt in certain areas of the body, notably, thighs, buttock and trunk. In addition to this, the deficiency of fat-soluble vitamins and essential fatty acids will also result. This will cause the ailments related to skin, eyes, bones etc. Excess If excessive fat is consumed it will result in obesity, gastrointestinal disturbances and predisposes to many other diseases like diabetes and cardiovascular ailments. In recent years there has been a revival of interest in the nutritional aspect of excessive intake of the fat in the diet in increasing the chances of cardiovascular diseases. Excessive lipids in blood, gradually causes it to deposit under the lining of blood vessels, resulting in atherosclerosis wherein the blood vessels are narrowed and hardened leading to heart diseases.

LET’S CHECK THE PROGRESS 1. ‘Fat is an important component of our diet and serves a number of functions.’

Justify this statement. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. Explain the following briefly: a. Essential fatty acids --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- b. Consequences of excessive fat intake ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

SUMMARY

Health of an individual depends on the type and quantity of foodstuffs included in the diet. Nutrients are the constituents in food that must be supplied to the body in suitable amounts. These include proteins, fats, carbohydrates, minerals, water and vitamins. We need energy to perform various involuntary and voluntary activities, to maintain body temperature and to synthesise new body constituents. Energy needs vary with age,

50

occupation and physiological state. Carbohydrates and fats are the main source of energy in our diet, whereas protein is primarily concerned with tissue building. It is not only the quantity of protein which is important, but also the quality. This depends mainly on the type and amount of amino acids present in the particular protein. Protein deficiency is associated with loss of weight, weakness and lowered resistance to diseases. Carbohydrates are the cheapest source of energy whereas fats are concentrated source of energy.

KEY WORDS

Cardiovascular diseases- These are a group of disorders of the heart and blood vessels. It generally refers to conditions that involve narrowed or blocked blood vessels that can lead to a heart attack, chest pain (angina) or stroke. Fermentation- Fermentation is the process in which a substance breaks down into a simpler substance. Microorganisms like yeast and bacteria usually play a role in the fermentation process as in beer, wine, bread, yogurt and other foods. Germination- Germination is the process by which an organism grows from a seed or similar structure. Involuntary activities- An involuntary action is one which occurs without the conscious choice of an organism like a blink, a sneeze, a yawn and those other actions which one cannot control. Voluntary activities- Voluntary actions are those actions on which you have control. These actions can be controlled by you wilfully e.g. snapping of fingers, walking, punching etc.

REFERENCES

ICMR. Nutrient requirements and recommended dietary allowances for Indians. A report of the expert group of the Indian Council of Medical Research, National Institute of Nutrition, Hyderabad. 2010. I.T. Johnson. Functional Foods. Wood head Publishing Series in Food Science, Technology and Nutrition2011(Second edition), Pages 202-233 B. Srilakshmi. Nutrition Science. New Age International (P) Ltd Publishers 2016 (Fifth Edition) Websites: https://upload.wikimedia.org/wikipedia/commons https://www.google.co.in/imghp?hl=en http://www.emro.who.int/health-topics/macronutrients

51

LESSON 4

MICRONUTRIENTS-I

INTRODUCTION

These nutrients include minerals and vitamins. Unlike macronutrients, these are required in very minute amounts. Together, they are extremely important for the normal functioning of the body. Their main function is to enable the many chemical reactions to occur in the body. Micronutrients do not function for the provision of energy

The term ‘vitamine’ derives from the word ‘vital amine’ which means essential nitrogenous compounds. The term was coined by Polish scientist Funk, who gave the name ‘vitamine’ to anti beri-beri substance. Later on ‘e’ was dropped and thus the term ‘vitamin’ was coined. However with the discovery of more vitamins, it was soon realise that all the vitamins are not nitrogenous compounds; but all vitamins are essential for health.

OBJECTIVES

Describe the role of various vitamins in our body. Enumerate foods rich in specific vitamin. Discuss the adverse consequences of their deficiency.

VITAMIN

Vitamins are complex chemical substances, required by the body in very small amounts. They do not yield energy, but act as catalyst in various body processes. Since vitamins cannot be manufactured in the body (at least insufficient amount) they have to be supplied through the diet. Vitamins are broadly classified into two groups:

(1) Fat soluble vitamins e.g. Vitamin A, D, E and K

(2) Water soluble vitamins e.g. B group vitamins and Vitamin C.

VITAMIN A

Vitamin A was discovered in the early 19th Century by Dr. McCollum and Davis. Dr McCollum carried out experiments on rats and found that when butter and egg yolk were added to the diet of groups of rat, they were healthier, stronger as compared to the other group which were fed on lard and vegetables only. He came to the conclusion that butter and egg yolk contains some vital elements that were absent in lard and vegetables. In 1913, he isolated vitamin A from butter and egg yolk.

Chemistry

Vitamin A occurs in several forms; as retinal (aldehyde form), as retinol (alcohol form) and as retinoic acid (acid form). These several forms may be referred to as Vitamin A. In

52

its pure form, vitamin A is a pale yellow crystalline compound and occurs naturally in animals. It is soluble in fat solvents but insoluble in water, and is relatively stable to heat, acids and alkalis. It is easily oxidised and rapidly destroyed by ultraviolet radiation. The ultimate source of all vitamin A is in the carotenes which are synthesized by plants. Animals, as well as man in turn convert a considerable portion of carotene of the food they eat into vitamin A. Carotenes are dark red crystalline compounds also known as ‘pro-vitamin A’ or ‘precursors of vitamin A’. Alpha, beta, gamma molecules of carotene are of significance in nutrition. The form that shows maximum vitamin A activity is beta-carotene (β carotene).

Functions

1. Vitamin A is required for normal vision in dim light. The retina has two kinds of cells-rods and cones. Rods are sensitive to dim light, the cones respond to bright light. The rods contain a pigment called rhodopsin. Rhodopsin is formed by the combination of a specific form of vitamin A with a protein. Rhodopsin in the presence of bright light breaks down into its components. In the dark these components, vitamin A and protein again combine to regenerate rhodopsin. This rhodopsin helps us to see in dim light. This is called a visual cycle.

2. Vitamin A is required to maintain the integrity of epithelium, especially the membranes that line eyes, the mouth and the gastrointestinal, respiratory and genitourinary tract. These membranes offer resistance to bacterial invasion.

3. Vitamin A is essential for normal skeletal and tooth development. 4. It has a probable role in the immunological defence mechanism of the body.

Food sources

Only animal foods contain vitamin A as such; fish-liver oil being the outstanding. Milk, butter, whole milk, cheese, liver and egg yolk contain good quantities of vitamin A. Vitamin A as such is not present in plant foods, but its precursor, carotene is present which is converted into vitamin A in the body. Carotene is present in plant foods with green and yellow colourings. There is a direct correlation between the greenness of a leaf and its carotene content.

Green leafy vegetables- spinach, turnip tops, beet greens, coriander leaves, curry leaves. Yellow vegetables- carrot, sweet potatoes, pumpkin. Yellow fruits- papaya, mango, apricot, peaches.


Recommended allowance for Indians as given by the ICMR expert committee (2010) is shown in Table 4.1. Vitamin A is measured in microgram (mcg or μg) but values are also sometimes reported as International Units (IU).

53

1 IU of vitamin A activity = 0.3 mcg of retinol or 0.6mcg β carotene The value of vitamin A is expressed as retinol equivalents (RE) According to FNB, USA (2002), 1 RE = 1 mcg retinol = 12 mcg β carotene According to ICMR (2010), following formula is used to interconvert retinol and β carotene 1 mcgβ carotene = 0.125 mcg Retinol When the diet contains sources of both β carotene and retinol, Vitamin A is calculated by the following method: Retinol Equivalents (mcg) = Retinol (mcg) +β carotene (mcg)/8

Table 4.1:Recommended Dietary Allowance of Vitamin A for Indians

Group Vitamin A (mcg/d) Retinol β-carotene

Men 600 4800 Women 600 4800 Pregnancy 800 6400 Lactation 950 7600 Infants 0-6 months

350 -

6-12 months 2800 Children 1-3 years 400 3200 4-6 years 400 3200 7-9 years 600 4800 Boys (10-17) years 600 4800 Girls (10-17) years 600 4800


Deficiency

a. Xerophthalmia is an eye manifestation arising due to Vitamin A deficiency. Blindness, as a result of xerophthalmia, is an important public health problem in India. One of the earliest manifestations of xerophthalmia is night blindness (XN). Individual suffering from night blindness cannot see in dim light or around dusk. This is followed by conjunctivalxerosis (X1A), which means dryness of the conjunctiva (this transparent membrane that covers the cornea and lines the inside of the eyelid)(Figure4.1). In addition to xerosis, dry, foamy, triangular spots may appear on the conjunctiva. These are called Bitot’s spot (X1B)(Figure4.2). As in case of conjunctiva, the normal

54

cornea (the anterior, transparent portion of the outermost layer of the eye) is moist and shining. When vitamin A deficiency become severe, the cornea becomes dry and dull and appear like ground glass. This condition is called corneal xerosis (X2)which means dryness of the cornea (Figure 4.3). The most dangerous form of xerophthalmia is known as keratomalacia (X3B). In this condition the cornea becomes very soft and raw and easily infected. It leads to destruction of the eye. The eyes get completely melted and destroyed (Figure4.4). This condition leads to irreversible blindness.

b. The deficiency of vitamin A leads to the degeneration and keratinization of the epithelium. This increase the susceptibility to infection of the eye, nasal passages, middle ear, pharynx, mouth, respiratory tract, lungs and genitourinary tract.

c. Dry and scaly skin is an important symptom of deficiency of this vitamin. This patched skin is an important symptom of Vitamin A deficiency which is known as toad’s skin.

Major changes in the eyes due to Vitamin A deficiency

Figure 4.1: ConjunctivalXerosis Source:https://encryptedtbn0.gstatic.com/images?q=tbn:ANd9GcSTN7CdZotk_cE4nvNeqr8IcZcq0TZm3TNvoHrI7z7bTpFl9gltA

Figure 4.4: Keratomalacia Source:https://encryptedtbn0.gstatic.com/images?q=tbn:ANd9GcQVMsLD1UifUk4HVTPgYrTLt87OuMfXnCB400WbUnW8wAuzHahp6A

Figure 4.3: Corneal Xerosis Source:https://encryptedtbn0.gstatic.com/images?q=tbn:ANd9GcQA8dAEJjf8vugEIgeDvPagmC-aq0_7eMuLrrj4-ghfqbb1udwDAw

Figure 4.2: Bitot’s spot Source:https://encryptedtbn0.gstatic.com/images?q=tbn:ANd9GcQhVGdCLTr_TPalJRDQWTME54CzGtc0D9XPa8NAYDzwDZS678nRVg

Pure Valso k Chem Vitamtwo ai. ii.

Pure but in

Sunlig(Figuexpreexerccardio

Vitamin D known as an

mistry and C

min D is a gare of nutriti

Vitamin Vitamin skin on e

vitamin D insoluble in w

ght convertre 4.5), Vit

ession, impaise-inducedovascular he

Fi

was isolatentirachitic v

Characterist

group of stional interesD2 or ErgoD3 or chol

exposure to is white, crwater. They

ts an inactitamin D3.O

acting a widd inflammealth, gluco

igure 4.5: M

V

d in crystalvitamin.

tics

terol compost. calciferol folecalciferol ultraviolet

rystalline coy are stable t

ive form oOnce converde variety ofation, tum

ose metaboli

Metabolism

55

VITAMIN D

line form in

ounds posse

ound in planwhich occulight.

ompound wto heat, alka

f Vitamin rted to the f health and

mor suppreism, bone h

m of Vitami

D

n 1930 and

essing anti-

nts and urs in anim

which is solualis, and ox

D in our sD3 form, t

d performanessor gene

health and sk

in D3 in live

was called

rachitic pro

mal cells and

uble in fats idation.

skin into a this Vitami

nce-related ves, neurolkeletal mus

er and kidn

calciferol.

operties, bu

d activates

and fat sol

circulatingin regulatesvariables, suogical funcle perform

ney

It was

ut only

in the

lvents,

g form s gene uch as nction,

mance.

56

Functions

1. Vitamin D regulates the absorption of calcium and phosphorus from the intestinal tract and also calcification of bones and teeth. It believed that vitamin D renders the intestinal mucosa more permeable to calcium and phosphorus. Thus vitamin D is required for normal bone and teeth development.

2. Vitamin D regulates the enzyme ‘alkaline phosphatase’ which regulates the release of phosphate organic compounds.

Food sources Vitamin D occurs only in foods of animal origin. Fish liver oils are the richest natural source. Liver, eggs and butter contain useful amount. Small amounts are present in fresh milk and milk products. Another cheap source of vitamin D is sunlight. Exposure to ultraviolet rays of the sunlight converts the precursor of Vitamin D (7dehydro-cholesterol) present in the skin, to its active form. Recommended Dietary Allowances The recommended daily allowance of vitamin D is not given by ICMR. If the exposure to sunlight is sufficient, deficiency symptoms are not seen. In case of inadequate exposure to sunlight, a daily supplement of 400 IU is recommended for adults. Deficiency Deficiency of vitamin D leads to rickets in children, a condition in which the level of calcium and phosphorus is always low. Bone growth cease and in more severe cases the bone which has already formed maybe demineralized. The long bones increase at the ends and they may become curved instead of remaining straight. This results in clinical changes which are observed by Swelling or bending of ribs leading to the condition known as ‘rachitic rosary’

(Figure 4.6). Knock-knees (Figure 4.7) Bowed legs (Figure 4.8) Curvature of vertebral column Deformities of the pelvic bones Softening of the skull The delayed closing of fontanels in infants Delayed dentition. Malformation of teeth and tooth decay.

57

Deficiency in adults leads to Osteomalacia, a condition characterised by Softening and bending of bones Pain in bones of legs and lower back Difficulty in walking Bones become fragile so that they are susceptible to frequent fractures In old age a deficiency of both Vitamin D and Calcium leads to osteoporosis a condition in which bones become porous, fragile and breaks easily leading to multiple fractures.

VITAMIN E

Evans and Bishop in 1922 established that the fact that a fat soluble factor was necessary for reproduction in rats. They showed that the absence of this factor, or vitamin E, as it was designated, leads to infertility in rats. Chemistry and characteristics Vitamin E consists of a group of chemical substances called ‘tocopherols’. Alpha to copherol is the compound possessing the greatest Vitamin E activity. High temperature and acids do not affect the stability of this vitamin, but oxidation takes place in the presence of rancid fats or lead and ironsalts. Decomposition occurs in ultraviolet light, alkalis and oxygen. Functions

i. The primary role of Vitamin E is to act as an antioxidant. By accepting the oxygen, it helps to prevent the oxidation of Vitamin A in the intestine, thereby sparing vitamin A.

Figure 4.6: Rachitic Rosary Source: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSPAypjFdsZQaShI6sep09mDOsTSXYmzD-_xYxG0fQOSzTSaP0sA

Figure 4.7: Knock knees Source: https://encryptedtbn0. gstatic.com/images?q=tbn:ANd9GcSQsJxiB6Nff17AmPtly7z1V1D3IsOSva6mTvnJIVec3vHkL-RZ

Figure 4.8: Bow legs Source:https://encryptedtbn0.gstatic.com/images?q=tbn:ANd9GcSoBUaxMxPgiOuHxhtWXgAJVaKKNQqEBJeYeKrvpRBjOwqDmcseMw

58

ii. Vitamin E reduces the oxidation of polyunsaturated fatty acids, thereby helping to maintain the integrity of cell membranes.

iii. Vitamin E plays a role in the formation of RBC’s in the bone marrow. iv. It helps in releasing the energy from carbohydrates and fats, through the synthesis

of a coenzyme Q. v. In some animals Vitamin E is required to prevent the sterility.

Food sources

Many vegetable oils such as wheat germ oil and cottonseed oils are good sources of vitamin E. Good concentration of Vitamin E is present in dark-green leafy vegetables, nuts, legumes, as well as whole grain cereals. Although foods of animal origin are low in vitamin E, liver, heart, kidney, milk and eggs are the animal sources of this vitamin. Human milk provides an adequate amount of Vitamin E to infants; cow's milk is low in this vitamin.


The vitamin E requirement is linked to that of polyunsaturated fatty acids (PUFA)content of the diet, as it protects the oxidation of PUFA. The requirement of Vitamin E suggested is 0.8mg/gof dietary essential fatty acids.

Deficiency

Vitamin E deficiency results in increased haemolysis (breakdown) of the red blood cells leading to anaemia. Premature infants also shows a low level of tocopherol. In some species of animals, vitamin E deficiency is also known to cause reproductive failure .In human beings vitamin E deficiency is not frequently reported.

VITAMIN K

A Danish scientist Dam (1934) found that a ‘Koagulation vitamin’ (coagulation or clotting) was necessary to prevent fatal haemorrhages in chicks by promoting normal blood clotting.

Chemistry and Characteristics

Vitamin K is found in nature in two forms: K1or phylloquinone, is found in plant source (e.g. alpha –alpha) and K2 or menaquinoneis produced by bacterial synthesis (in human and animals). These are soluble in fat. They are not destroyed by heat but are unstable to alkalis, strong acids, oxidation and light.

Functions

1. Vitamin K is essential for the formation of prothrombin and other clotting proteins by the liver.

2. Vitamin K probably also participates in oxidative phosphorylation in the tissues.

59

3. Heart health: Vitamin K may help keep blood pressure lower by preventing mineralization, where minerals build up in the arteries. This enables the heart to pump blood freely through the body.

Food sources

Vitamin K1 occurs in high amounts in leafy green vegetables, such as spinach, cabbage, cauliflower. Other sources include vegetable oils and some fruits.

Sources of menanoquines, or K2, include meat, dairy products, pork liver, eggs, fermented soy beans. Cereals, fruits and other vegetables are poor sources.


The variations in intestinal synthesis and in the diet have made it impossible to establish a daily allowance. Dietary deficiency is not believed to be a problem.

Deficiency

Deficiency usually occurs due to faulty absorption or due to liver disorders that affect the synthesis of prothrombin. Dietary deficiency is rather unusual. A low level of prothromb in and other clotting factors leads to increased tendency to haemorrhages. Premature infants, anoxic infants and those whose mothers have been taking anticoagulants are most susceptible to deficiency.


1. Name various fat soluble and water soluble vitamins. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. What are the various functions of vitamin D in our body? ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3. Briefly explain the following : a. Visual cycle ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

60

b. Dietary sources of vitamin A ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

c. Xerophthalmia --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- d. Rickets --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- e. Vitamin E as an antioxidant ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

VITAMIN B COMPLEX In 1911, Funk coined the term ‘vitamin’ for the substance which he found effective in preventing beri-beri. McCullum and Davis applied the term water-soluble B to the concentrates which curedberi-beri. It was soon discovered that vitamin B was not a single substance but a group of compounds, to which we now designate as the B complex. Some of these are discussed here:

THIAMINE OR VITAMIN B1 Chemistry and Characteristics

Thiamine hydrochloride is a white crystalline substance. It has a faint yeast-like odour and a salty, nut like taste. It is readily soluble in water but not in fat solvents or fats. It is readily destroyed by heat in neutral or alkaline solution; in acidic medium it is resistant to heat up to 120oC.

Functions

Thiamine teams up with an enzyme to form a coenzyme. The latter act as a catalyst with the oxidation processes.

1. It is essential for the utilisation of carbohydrates in the body; in deficiency there is accumulation of pyruvic acid and lactic acid in the tissues and body fluids.

61

2. Thiamine is also essential for the maintenance of good appetite and normal digestion.

3. It has a role in brain metabolism as the deficiency causes neurological and nervous disorder.

Food Sources

All the natural foods contain thiamine, even if in very small amounts. Important sources are dried yeast, whole grain cereals and pulses, oilseeds and nuts especially groundnuts. Meat, fish, egg, vegetables and fruits are relatively poor sources.

Recommended Dietary Allowances Thiamine requirements are expressed on the basis of energy intake. The recommended dietary allowances is 0.5 milligram/1000kcal.

Deficiency

The clinical manifestations of thiamine deficiency are beri-beri and Wernicke’ encephalopathy. The Philippino word beriberi means “I can’t I can’t”. Beri-beri exists in three forms- dry, wet and infantile beri-beri. Manifestations of minor thiamine deficiency are loss of appetite, absence of ankle jerks, knee jerks and presence of calf tenderness.

o Dry beriberi- Thiamine deficiency with nervous system involvement is termed dry beriberi. This presentation usually occurs when poor caloric intake and relative physical inactivity are present. The neurologic findings can be peripheral neuropathy characterized by symmetrical impairment of sensory, motor, and reflex functions of the extremities, especially in the distal lower limbs. Histologic analysis has shown that the lesions arise from a degeneration of the myelin in the muscular sheaths without inflammation

o Wet beriberi- a more acute form, there is oedema (overabundance of fluid in the tissues) resulting largely from cardiac failure and poor circulation.

o Infantile beri-beri- Disease in infants due to deficiency of thiamine. This disease is well-known in undeveloped countries among malnourished infants but it is very rare in developed countries. It can occur if a breastfeeding mother has an inadequate intake of thiamine.

RIBOFLAVIN OR VITAMIN B2

Chemistry and Characteristics

In its pure form this vitamin is bitter tasting, orange yellow, odourless compound in which crystals are needle shaped. It dissolves sparingly in water to give a typical greenish

62

yellow fluorescence. It is stable to boiling in acid, but in alkaline solutions it is readily decomposed by heat. It is also destroyed by exposure to light. Function Riboflavin, like thiamine unites with the enzymes and helps in the tissue oxidation with the release of energy, thus helping in protein, fat and carbohydrate metabolism. Food sources

The richest source is dried yeast. Among the good sources are milk, liver, meat, eggs, kidney and green leafy vegetables. Cereals and fruits are not rich sources, but due to the large quantity consumed, they supply much of vitamin in the Indian diets.


The recommended dietary allowance is 0.6 mg/ 1000 kcal.

Deficiency Ariboflavinosis is one of the most common of the deficiency diseases. Signs suggestive but not specific include:

i) Angular stomatitis: the patients develop cracks on both the sides (angles of upper and lower lips) of the mouth (Figure 4.9).

ii) Cheilosis: The lips develop cracks and become red (Figure 4.10). iii) Soreness of tongue. iv) Redness and burning sensation in the eyes and vascularization of the cornea. v) Scrotal or vulvar dermatitis

Figure 4.9: Angular stomatitis

Source:https://encryptedtbn0.gstatic.com/images?q=tbn:ANd9GcRRG3VdSkS0yhKXMph7igZjJO2h5FJz1gwMW8wS-e7JzBfkeC8

Figure 4.10: Cheilosis

Source:https://encryptedtbn0.gstatic.com/images?q=tbn:9GcTg8FOoj5eaNFwWz5E6bTkK8ia3GAtbTdl3re7ECrAjfxwU7dEz

63

NIACIN OR NICOTINIC ACID

Chemistry and Characteristics It occurs in white needle-like bitter tasting crystals. It is moderately soluble in hot water, but only slightly soluble in cold water. It is stable to heat, alkalis, acids, light and oxidation and unstable to reduction. In fact, it is one of the most stable of the vitamins. Niacin occurs in two forms: niacin and proniacin form i.e. tryptophan. Human body can make 1 mg of this vitamin from 60 mg of tryptophan. Thus if a diet contains large amount of tryptophan, it will provide enough niacin, even though the diet might be low and its niacin content.

Functions

1. Niacin is rapidly converted in the body to nicotinamide, which is a component of coenzymes which are essential for the metabolism of carbohydrates, fats and proteins.

2. It is also essential for the normal functioning of skin, intestinal tract and nervous system.

Food sources

Poultry, meat, fish and peanuts are the good sources. Whole grains are fair sources of niacin. Potatoes, legumes and some green leafy vegetables contains fair amount of niacin but most fruits and vegetables are poor sources. Germination and fermentation enhances the value of niacin in the food.


The recommended daily allowance is 6.6 mg/ 1000 kcal for adults.

Deficiency

Niacin deficiency results in pellagra. Pellagra involves the gastrointestinal tract, the skin and nervous system. Early signs include fatigue, headache, and backache, loss of weight and loss of appetite. Nausea and vomiting are followed by diarrhoea (i.e. loose motion is present).A characteristic symmetrical dermatitis especially on the exposed surface of the body- hands, forearms, elbows, leg, knees, and neck appear. Neurological symptoms include dizziness, confusion, poor memory and irritability. The classic ‘D’ are the final stages i.e. dermatitis, diarrhoea, dementia and death.

64

PYRIDOXINE OR VITAMIN B6 Chemistry and Characteristics Vitamin B6 consists of a group of related compounds: pyridoxine, pyridoxal and pyridoxamine. Vitamin B6 is soluble in water and relatively unstable to heat and to acids. It is destroyed in alkaline solutions and is also sensitive to light. Functions Vitamin B6 is the coenzyme for a large number of enzyme systems, most of which are involved in amino acid metabolism. It plays a role in the conversion of (a) tryptophan to niacin (b) linoleic to arachidonic acid and in the (c) inter conversion of amino acids. Food sources Foods rich in pyridoxine are meat, poultry and fish. Potatoes, sweet potatoes are fair sources. Whole grain cereals are also good sources. Recommended Dietary Allowances The recommended allowance of vitamin B6 for adults is 2 mg/d. Deficiency The deficiency of this vitamin causes impaired protein synthesis and microcytic hypochromic anaemia (smaller sized RBCs pale in colour due to low concentration of haemoglobin). The symptoms include convulsions, dizziness, vomiting, cheilos is, glossit is and abdominal pain.

FOLIC ACID OR VITAMIN B9 Characteristics

Folacin is a generic term for folic acid and other compounds having the activity of folic acid. It consists of three linked components (Figure 4.11): a pteridine group, para amino benzoic acid (PABA) and glutamic acid (an amino acid).Pure folic acid occurs as a bright yellow crystalline compound, only slightly soluble in water. It is easily oxidised in an acidic medium and is sensitive to light. Folate and folic acid are forms of a water-soluble B vitamin. Folate occurs naturally in food, and folic acid is the synthetic form of this vitamin.

65

Figure 4.11 : Folic acid and its component molecules

Functions 1. It is a key ingredient in the making of the nucleic acid that forms part of all

genetic material i.e. DNA. 2. It is also required for normal production of red blood cells (RBCs) in the bone

marrow. 3. It is also required for oxidation of amino acid phenylalanine to tyrosine.

Food sources

It is present in both free and conjugated form. Liver, kidney, deep green leafy vegetables are good sources of this vitamin. Cereals provide a fair amount. Vegetables, dairy foods, pork and light green vegetables are poor sources.


The ICMR expert committee (2010) has recommended the dietary allowance of free Folic acid per day as shown in Table 4.2.

Table 4.2: Recommended Dietary Allowances of Folic Acid Age Group Folic acid (mcg/d)

Adults Pregnancy Lactation Infants

Children 1-3 years 4-6 years 7-9 years

Adolescents 10-12 years 13-15 years 16-17 years

200 500 300 25

80 100 120

140 150 200


66

Deficiency Folic acid deficiency results in megaloblastic anaemia, glossitis and gastrointestinal disturbances. Severe deficiency results in infertility or even complete sterility. This anaemia is the second most common cause of nutritional anaemia in India. Deficiency of folic acid during pregnancy leads to Neural tube defects (NTDs) in the foetus.

CYANOCOBALAMIN OR VITAMIN B12

Characteristics

Cobalam in is another name for vitamin B12.This vitamin is the only cobalt containing substance essential for health. It occurs as deep red needle like crystal which is slightly soluble in water. This vitamin is absorbed from the ileum only. Its absorption depends on the presence of an intrinsic factor (a muco-protein produced by the parietal cells of gastric mucosa).

Functions

1. It helps in the synthesis of nucleic acid and nucleoproteins. 2. It is essential for the maturation of red blood cells in bone marrow. 3. It is also required for the maintenance of nervous tissues.

Food sources

It is present only in the foods of animal origin. Liver, meat, egg and milk are good sources. It is not found in the foods of vegetable origin.


The ICMR expert committee (2010) has recommended the intakes of vitamin B12 as shown in Table 4.3.

Table 4.3: Recommended Dietary Allowances of Vitamin B12 Age Group Vitamin B12 (mcg/d)


Children and Adolescents

1.0 1.2 1.5 0.2

0.2-1.0 Source: Nutrient Requirements and Recommended Dietary Allowances for Indians (ICMR, 2010). Deficiency

Deficiency of this vitamin occurs due to inability to absorb sufficient B12(due to lack of intrinsic factor) leading to Perniciousanaemia. Macrocytic anaemia and degenerative

67

changes of the nervous system may results from deficiency of this vitamin. Other deficiency symptoms includes: weakness, weight loss, anorexia, indigestion, diarrhoea, memory loss and lack of concentration.

ASCORBIC ACID OR VITAMIN C Chemistry and Characteristics Vitamin C, also called ascorbic acid is a white crystalline compound of relatively simple structure and closely related to monosaccharide sugars. It can be prepared synthetically at low cost from glucose. Of all the vitamins, Vitamin C is the most easily destroyed. It is highly soluble in water. It is very unstable when it comes in contact with heat, light, alkalis, oxidative enzymes and trace elements. Functions

Vitamin C plays a pivotal role in body-building process and in disease prevention. The various functions of vitamin C, including the antioxidant activity, formation of protein, tendons, ligaments and blood vessels, for healing wounds and form scar tissue, for repairing and maintaining cartilage, bone, and teeth, and aiding in the absorption of iron.

1. Collagen formation- It is required for the formation and maintenance of collagen, a protein widely distributed in the body. Collagen is the cementing material that holds the cell of the body together.

2. Vitamin C is necessary for production of tissues and for quick post-operative healing.

3. It plays an important role in the normal metabolism of amino acids. 4. Iron Absorption- It helps in easy absorption of iron from gastrointestinal tract by

the reduction of ferric ion to ferrous ion. It enhances the absorption of iron from plant sources (non-heme iron) and improve the absorbability of fortification iron (nonchelated inorganic iron) added to diets that contain inhibitors of iron absorption (e.g., the phytates and polyphenols)

5. Antioxidant- One of the important properties of vitamin C is its antioxidant activity. Antioxidant activity of vitamin C helps to prevent certain diseases such as cancer, cardiovascular diseases, common cold, age-related muscular degeneration and cataract. Antioxidants neutralize free radicals by donating one

Figure 4.12 : Antioxidant Mechanism

68

of their own electrons, ending the electron-stealing reaction, as shown in Figure 4.12. Food sources Fruits and vegetables are the main sources of this vitamin. Citrus fruits (orange, grapefruit, lemon and lime), berries, melons, pineapples, guava, pears, banana, leafy vegetables, green pepper, amla, tomatoes are good sources of ascorbic acid. Dry legumes contain negligible amount which increase approximately seven times during germination. Eggs, meat and poultry do not have any Vitamin C.Human milk contains four to six times as much ascorbic acid as cow's milk that protects the infant from its deficiency.

Recommended Dietary Allowances The values recommended by ICMR expert committee (2010) is shown in the Table 4.4.

Table 4.4: Recommended Dietary Allowances of Ascorbic Acid Age Group Vitamin C (mg/d)


Children and Adolescents

40 60 80 25 40

Source: Nutrient Requirements and Recommended Dietary Allowances for Indians (ICMR, 2010). Deficiency Deficiency of ascorbic acid results in defective formation of the intercellular cementing substance collagen. Fleeting joints pain, irritability, retardation of growth in infants and children, anaemia, shortness of breath, poor healing of wounds and increased susceptibility to infections are some of the signs of deficiency.

Gross deficiency of ascorbic acid results in Scurvy. Scurvy is a disease characterized by swelling and bleeding of gums, multiple haemorrhages, anaemia and weakness. Today frank scurvy is uncommon but partial deficiency of ascorbic acid maybe frequent.

Let’s check the progress

1. Explain the following briefly: a. Ariboflavinosis ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

69

b. Pellagra --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- c. Pernicious anaemia ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

d. Scurvy ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. Mention some of the main food sources of the following nutrients: a. Thiamine --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- b. Folic acid --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- c. Ascorbic acid ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

SUMMARY

Vitamins are broadly categorised as fat soluble vitamins (e.g. Vitamin A, D, E and K) and water soluble vitamins (e.g. Vitamins of B group and Vitamin C). Vitamin A is present as preformed vitamin in animal food sources and as β carotene in plant sources. Vitamin D can be synthesised in our skin in the presence of sunlight and it is essential for calcium absorption. Vitamin E plays an important role as antioxidant while vitamin K is needed for normal blood clotting. Most of the B group vitamins act as coenzyme in the metabolism of carbohydrates, fats and proteins. Vitamin C is found in good amount in fresh fruits and vegetables particularly citrus fruits. Most of the water soluble vitamins are sensitive to heat, acids and alkalis, therefore readily destroyed during cooking. KEY WORDS Antirachitic - used or tending to prevent or cure rickets the antirachitic activity of vitamin

D.

70

Conjunctiva- the mucous membrane that covers the front of the eye

Cornea- the transparent circular part of the front of the eye ball

Epithelium- the layer of cells covering internal and external surfaces of the body

Fontanel- open spaces on top of the baby’s skull

Genito-urinary- it refers to the genital and urinary organs

Haemorrhage- abnormal and severe bleeding (internal or external)

Megaloblasts- large and immature red blood cells

Neural tube defects- defect in the formation of neural tube in foetus

Night blindness- inability to see in dim light

Rachitic rosary- rows of bead like deformities on the ribs

REFERENCES

FNB. Food and Nutrition Board, Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, Iodine, iron, manganese, molybdenum, nickel, silicon, vanadium and zinc, Washington DC: National Academy Press, 2002. ICMR.Nutrient requirements and recommended dietary allowances for Indians.A report of the expert group of the Indian Council of Medical Research, National Institute of Nutrition, Hyderabad. 2010. B. Srilakshmi. Nutrition Science. New Age International (P) Ltd Publishers 2016 (Fifth Edition) Websites: https://upload.wikimedia.org/wikipedia/commons https://www.google.co.in/imghp?hl=en

71

LESSON 5

MICRONUTRIENTS-II INTRODUCTION

In the previous chapters, nutritional needs of the family for energy, protein, carbohydrates, fats and vitamins were discussed. Let us now study the nutritional needs of other important constituents required by human body viz. Minerals and Water. OBJECTIVES

Understand the importance of minerals and water in our body. Enlist the dietary sources of various mineral elements. Describe the adverse consequences of their deficiency.

MINERALS

Minerals may be defined as those elements which remain largely as ash when plant and animal tissues are burnt. The human body contains more than 19 minerals, all of which must be derived from foods. A total of 4% of the body weight is made up of minerals. Some of the important minerals found in our body include calcium, phosphorus, iron, iodine, sodium, potassium, zinc and chloride. All these minerals are derived from the food we eat. Of these, calcium, phosphorus, sodium, potassium, chloride and magnesium are the minerals required in larger amount by the body. Calcium and phosphorus, accounts for three-fourth of the minerals present in the body, and five other elements account for most of the rest. Many of these elements are present in such minute amounts that they are referred to as a trace elements or micronutrients.

Table 5.1: Minerals Macro minerals

(Required in large amounts) Micro minerals

(Required in smaller amounts) Calcium

Phosphorus Potassium Chloride

Magnesium

Iron Iodine Zinc

Copper

Minerals are important for the body in various ways. They are required to form such organic compounds like phosphoproteins, haemoglobin and thyroxin. Hard skeletal structures are formed with the help of elements like calcium, phosphorus and magnesium,

72

whereas soft tissues contain a relatively high proportion of potassium. Mineral elements are also required in the constitution of enzymes, for maintaining osmotic pressure and water balance between intracellular and extracellular compartment, for proper functioning of the nervous system, for muscular contraction and so on. The body requires different amounts of each mineral because each mineral has a different set of functions. Requirements vary according to age, sex and physiological state (for example pregnancy). They may also be influenced by state of health.

Bioavailability and absorption of minerals The bioavailability of a mineral (i.e. how readily it can be absorbed and used by the body) may be influenced by a variety of factors. Bioavailability will depend upon the chemical form of the mineral, other substances present in the diet and (for nutrients such as iron) the individual person’s needs as determined by how much of the nutrient is already stored in the body. This is because the body has sensitive mechanisms for preventing storage of nutrients that can be damaging in excess (as is the case with iron). For example, the bioavailability of iron from plant sources (non-haem iron) is relatively poor compared with iron from meat (haem iron) but absorption is increased when vitamin C is consumed during the same meal because the vitamin C converts it to a more bioavailable chemical form. Some dietary constituents reduce bioavailability. Phytate, for example, found in products made from wholegrain cereals (especially unleavened breads such as chapattis) can bind and hence reduce the absorption of calcium, iron and zinc. Iodine absorption may be hindered by nitrates. Similarly, oxalate present in spinach binds any calcium present, making it unavailable for absorption. Also an excess of one mineral may hinder the absorption of another by competing for the same transport systems in the gut, e.g. excess iron reduces zinc absorption. This generally only becomes a problem when zinc intakes are already marginal. Unlike some vitamins, minerals are fairly stable in normal food processing and storage conditions.

CALCIUM

Calcium (Ca) is the most abundant mineral in the body and is essential for a number of vital functions. Almost 1 kg of calcium is present in an adult man of 60 kg; out of which 99% of the calcium is in the bones and teeth and remaining 1% is widely distributed in body fluids where it fulfils many functions.

Functions 1) Bone and tooth formation- Calcium together with phosphorus and other

elements give rigidity to bones and teeth. This characteristic makes it possible for the bones to support the body. Bone forms protective cavities for vital organs- the heart and lungs in the chest cavity, the brain in cranial cavity.

2)

3)

4)

Food

Milk such produthe le

Facto

Incorpaffectincrea

) Co factoro B

prof

o Mthce

o Cab

o Alip

) It has a ronerve cel

) It aids in

d sources

and milk pas mustard

ucts in theirast calcium

ors favourin

porating heting the abased absorp

r and regullood clottirothrombin f blood (Fig

Membrane ihe cell memells).

Contractionbsence of ca

Activation opase, adeno

Figure

ole in the trl to another

n the absorp

products aregreen, turn

r calcium com

ng and depr

ealthy foodsorption ofption of p

lator of bioing- Calciuto thrombin

gure 5.1). integrity a

mbrane (reg

n of muscle-alcium, musof enzymesosine triphos

e 5.1: Role

ransmissionr). ption of vita

e excellent snip greens, montent. Citr

ressing abso

s in the dif nutrients particular n

73

ochemical rum acts an, this being

and permeagulating the

- It is directscles lose ths- It activasphate and s

e of calcium

n of nerve

amin B12 fr

sources of cmint, spinacrus fruits, le

orption

et is not enfrom the fo

nutrient wh

reactions as a catalyg one of the

ability- It apassage of

tly related their ability tates the numsome proteo

m in blood c

impulses(c

rom the ileu

calcium. Cech, and carregumes, me

nough. Onefood. Some hereas some

yst for thee several ste

activates thef substance

to muscle cto contract. mber of enolytic enzym

clotting

conveying m

um.

ertain greenrot leaves reats, grains

e should unfactors are

e decreases

e conversieps in the cl

e permeabils into and

contraction.

nzymes inclmes.

message fro

n leafy vegerank next toand nuts pr

nderstand fe responsibs its absor

on of lotting

lity of out of

In the

luding

m one

etables o dairy rovide

factors ble for rption.

74

Calcium is the hardest mineral to get absorbed in the body. 30-80 % of the dietary calcium is not getting absorbed in the adult body.

Factors increasing absorption of calcium:

i. Vitamin D- Vitamin D works in the digestive tract to absorb calcium into the blood stream from the walls of the duodenum. Vitamin d also helps maintain normal blood calcium level.

ii. Parathyroid hormone- It increases calcium transport across the membrane of intestinal cells.

iii. Acid environment- Hydrochloric acid secreted in the stomach during the process of digestion is required for the absorption of calcium in the duodenum. Calcium supplements could be taken with magnesium at bedtime or between meals due to the acid environment needed in the stomach to assimilate the calcium. Always consult a physician before beginning a new supplement regimen.

iv. Milk lactose- It favours absorption in infants. Lactose is acted upon by intestinal microbial flora to form acid which causes lowering of pH which makes calcium more soluble.

v. Amino acids- Supplemental calcium is often chelated, or combined with protein molecules called amino acids, to help the body absorb them during digestion. Lysine and arginine increase calcium absorption.

vi. Exercise- Exercise along with vitamin D intake helps calcium absorption thereby making bones strong.

Factors decreasing absorption of calcium:

i. Oxalic acid & phytic acid- Foods that are high in oxalic acid such as spinach, chard and chocolate, reduce calcium absorption. Oxalic acid binds with the calcium to form a salt crystal, calcium oxalate which cannot be absorbed. Phytic acid, which is found in whole-grain foods and high-fibre foods, effects calcium absorption the same way.

ii. Ageing- Calcium absorption is deceased during old age. It is associated with Vitamin D deficiency and hype parathyridism.

iii. Stress- Stress can have a negative effect on HCL production in the stomach and on normal digestive behaviour in the body, and can therefore have a negative effect on calcium absorption.

iv. Caffeine, drugs like anticoagulants, cortisone and thyroxine reduce calcium absorption.

v. Lack of exercise leads to decrease calcium absorption

75


The ICMR expert committee (2010) has recommended dietary allowances as shown in Table 5.2

Table 5.2: Recommended Dietary Allowances of Calcium and Phosphorus Age Group Calcium/day (mg) Phosphorus/day (mg)

Adults Pregnancy Lactation

Infants (0-12 months) Children (1-9 years)

Adolescents (10-17 years)

600 1200 1200 500 600 800

600 1200 1200 750 600 800

Source: Nutrient Requirements and Recommended Dietary Allowances for Indians (ICMR, 2010). Deficiency

A deficiency of calcium in the diet results in retarded calcification of bones and teeth in the young. Due to the deficiency of calcium bones start bending and there is enlargement of ankle and wrist. In children, the deficiency disease is known as Rickets and in adults, as Osteomalacia. Repeated pregnancies coupled with inadequate dietary intake can also give rise to the deficiency of calcium.

PHOSPHORUS

Phosphorus accounts for about 1% of body weight, or one-fourth of the total mineral elements in the body. About 85% of phosphorus is in combination with calcium in bones and teeth. Soft tissues contain much higher amounts of phosphorus than of calcium and most of it is in organic form.

Functions

Phosphorus is one mineral which performs widely differing functions. These are:

1. Mineralisation of bones and teeth- It combines with calcium to form insoluble compound, calcium phosphate, which gives strength and rigidity to bones.

2. Absorption and transport of nutrients- The Phosphorus containing lipoproteins facilitate the transport of fats in the circulation.

3. Component of essential body compounds- Phosphorus is a constituent of nucleoproteins, the basics genetic material. Phospholipids are constituents of cell membranes, thus regulating the transport of solutes into and out of the cell.

4. Phosphorylation is the key reaction in many metabolic processes.

76

5. Phosphorus captures and store vital energy in the cells of many tissues by forming a high energy compound. Muscle tissue is a prominent example where phosphorus helps in energy store and thus fuel muscle contraction.

6. Regulation of Acid-Base balance- Inorganic phosphorus in the body fluids constitutes an important buffer system in the regulation of body neutrality.

Food Sources

Phosphorus is widely distributed in foods; the milk and meat groups being important contributors. Whole grain cereals and flours contain much more phosphorus than refined cereals and flours. Vegetables and fruits contain only small amount of phosphorus.


The ICMR expert committee has recommended the intake as shown in table 5.2. The requirements have been given based on elemental Calcium: Phosphorus ratio of 1:1 for most age groups, except for infants, where the suggested ratio is 1: 1.5. The ratio of Calcium: Phosphorus is important for the calcification of the bones.

Deficiency

A deficiency of phosphorus is generally not seen in human beings because diets having cereals as major food are seldom inadequate in phosphorus.

LET’S CHECK THE PROGRESS 1. Explain the role of calcium in blood clotting? ---------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. What are the factors affecting the absorption of calcium? ---------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

MAGNESIUM The amount of magnesium in the body is much smaller than that of calcium and phosphorus i.e. about 20-35 g in the adult body. Of this about 60% are carbonates and phosphates at the surface of the bones. Most of the remaining magnesium is within the cells.

77

Functions 1. It is required for numerous biological reactions involving the release of energy 2. It is a constituent of bone. It is involved in bone mineralization. 3. It is also essential for normal metabolism of calcium and phosphorus. 4. Its presence in the extracellular fluids regulates the transmission of nerve

impulses. 5. It activates the enzyme responsible for breakdown of glycogen.

Food Sources Dairy products excluding butter provide enough magnesium. Flour and cereal products, dry beans, soyabean, peas and nuts are good sources of magnesium. Green leafy vegetables are excellent sources because magnesium is a part of chlorophyll.

Effect of imbalances Under normal conditions of health and food intake magnesium deficiency is not likely to occur. A deficiency of it may result from malabsorption syndrome, chronic alcoholism, and toxaemia of pregnancy or after intake of diuretics. Deficiency of magnesium results in neuromuscular irritability, tetanic convulsions, twitching, tremors and convulsions. In excess, it results in extreme thirst, excessive heat in the body, decrease in neuromuscular movements.

POTASSIUM An adult body contains about 250 g of potassium of which about 97% of the potassium in the body is in intracellular fluid intracellular fluid (intracellular fluid refer to fluid inside the cells) while the remainder being in the extracellular fluid compartments (extracellular fluid refers to fluid outside the cell). Functions 1. Within the cell it maintains the osmotic pressure and fluid balance. 2. It is required for the synthesis of proteins. 3. It is required for enzymatic reactions taking place within the cell. Some Potassium is

bound to phosphate and is required for the conversion of glucose to glycogen. 4. It is required for the transmission of nerve impulse and for contraction of muscle

fibres.

78

Food Sources It is widely distributed in foods. Meat, poultry and fish are good sources. Fruits, vegetables and whole grain cereals are especially high in potassium. Banana, potatoes, tomatoes, carrots, orange juice, grapefruit juice are rich sources. Recommended Dietary Allowances The exact amount of potassium required is not known. A normal diet provides this mineral in sufficient amount. Deficiency Primarily the deficiency of potassium is not seen. Impaired appetite, severe malnutrition, chronic alcoholism and burn injuries can disturb the acid base balance and lower osmotic pressure.

SODIUM An adult body contains approximately 120g of sodium of which about 50% of the body’s sodium is present in the extracellular fluid, 40% in bones and 10% or less in intracellular fluid (intracellular fluid refers to fluid inside the cell). Functions

1. It is required for maintenance of normal osmotic pressure and water balance. 2. It is also required for maintaining the permeability of cell membrane. 3. Sodium ‘pump’ helps to maintain the electrolyte difference between intracellular

and extracellular fluid compartments.

Food sources

Common salt or sodium chloride is the chief source of sodium in the diet. One teaspoon of salt provides almost 2000 mg sodium. It is universally used to flavour the food we eat and is also used for preserving food for long periods. Numerous sodium compounds are used in food processing and preparation like baking soda, baking powder, sodium alginate, sodium propionate and sodium citrate. Sodium is a naturally occurring constituent in animal foods, including milk, egg, meat, poultry and fish and in certain vegetables as spinach, celery, beet greens and fenugreek. Most vegetables, fruits, cereals, legumes are naturally low in sodium.

79


5-10 gm of salt (sodium chloride) is sufficient for an average healthy adult. An individual doing hard labour may need more. Sodium Imbalance Osmotic pressure and the pH are seriously affected when there is a disturbance in the concentrations of sodium in the extracellular fluid of the body tissues. When there is retention of sodium in the tissue, oedema occurs. In cardiac and renal failure sodium excretion gets reduced. Excess sodium losses occur during the hot weather causing muscular weakness, cramps, fatigue, vomiting and loss of appetite. In this case a small amount of salt may be added to liquid intake.

CHLORINE Chlorine exists in the body almost entirely as chloride ion. Most of the 100 g or so of chloride ions present in the extracellular fluid, but it also occurs to some extent in the red blood cells and to a lesser degree in other cells. Functions

1. It is important in regulation of osmotic pressure, water balance and acid-base balance.

2. It activates the gastric enzymes thus aids in the digestion in the stomach. 3. It is one of the several activators of salivary amylase.


The requirements of chlorine have not been ascertained, but, if sodium chloride is taken liberally, it ensures the adequate intake of chloride as well. Chloride Imbalance Severe vomiting, drainage or diarrhoea leads to large loses of chloride and an alkalosis, because of the replacement of chloride with bicarbonate.

80


1. What are the various functions of magnesium in our body? ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. Briefly explain the concept of Sodium imbalance.

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

IRON

Iron is chief among the trace elements required for the body and is essential for the formation of haemoglobin in red blood cells; haemoglobin binds oxygen and transports it around the body. Iron is also an essential component in many enzyme reactions and has an important role in the immune system. In addition, it is required for normal energy metabolism and for the metabolism of drugs and foreign substances that need to be removed from the body. Muscle tissues contain about 3% of iron as myoglobin and the rest is stored as ferritin, hemosiderin, and in liver, spleen, kidney and bone marrow. Functions 1. Iron is a major constituent of the red coloured compound called haemoglobin present

in the red blood cells. Haemoglobin (Hb) is necessary for transport of oxygen to various parts of the body. Hb carries oxygen from the lungs to the tissues and in turn helps in carrying carbon dioxide from the tissues to the lungs. From the lungs carbon dioxide is then exhaled out.

2. Iron is also present in the muscles in the form of myoglobin. Myoglobin has the capacity to store oxygen. This oxygen is used for muscle contraction and for other immediate needs of the muscle cells.

3. Iron facilitates the complete oxidation of carbohydrates, fats and proteins within the cells.

4. Iron forms a vital component of certain enzymes and substances that aid in metabolism.

5. Iron has protective function. It helps in preventing infections. Food Sources Dietary iron is found in two basic forms. Either as heme iron (from animal sources) or non-heme iron (from plant sources). Heme iron is the most bioavailable form of iron. However, the predominant form of iron in all diets is non-haem iron, found in cereals,

81

vegetables, pulses, beans, nuts and fruit. Absorption of non-haem iron is affected by various factors in food. Phytates (in cereals and pulses), fibre, tannins (in tea) and calcium can all bind non-haem iron in the intestine, which reduces absorption. However, vitamin C, present in fruit and vegetables, aids the absorption of non-haem iron when eaten at the same time, as does meat. Liver, red meat, pulses, nuts, eggs, dried fruits, poultry, fish, whole grains and dark green leafy vegetables are all sources of iron. Lean meats, deep green leafy vegetables and whole grain cereals are good sources. Egg yolk and organ meats are also among good sources. Liver is an excellent source of iron. Other vegetable and fruits are fair sources. Milk, cheese and ice cream are poor sources. Jaggery contains a good amount of iron. Recommended Dietary Allowances The requirement of iron for the body is a small, but due to poor absorption, much more is needed. From a vegetarian diet only 10% of the dietary iron is observed. For a mixed diet 15-20% absorption takes place. Keeping this in mind ICMR expert committee (2010) has recommended the daily allowances for various age groups as shown in Table 5.3

Table 5.3: Recommended Dietary Allowances of Iron Age Group Iron (mg)/day

Adult Male Adult Female Pregnancy Lactation Infants (0-6m) (6-12m) Children (1-9 years) Adolescents boys (10-17 years) Adolescents boys (10-17 years)

17 21 35 21 46 mcg/kg/d 5 9-16 21-28 26-27

Source: Nutrient Requirements and Recommended Dietary Allowances for Indians (ICMR, 2010). Deficiency Anaemia results due to deficiency of iron. Usual symptoms are fatigue, giddiness, and breathlessness on exertion, sleeplessness and loss of appetite. Paleness of the tongue, conjunctiva (white of eye) and nail bed is observed in anaemic person. In severe anaemia, the nails of the fingers and toes become brittle and spoon shaped (koilonychias). Severe anaemia can even lead to death.

82

IODINE

Iodine is an essential component of the thyroid hormones, thyroxine and triiodothyronine, which are vital regulators of metabolic rate and of physical and mental development. About one third of iodine present in an adult body variously estimated from 15 to 23 mg is found in the thyroid gland. The concentration in thyroid tissue is 2500 times as great as in any other tissue, all of which contain traces. Functions The only known function of iodine is as a constituent of thyroglobulin, a protein complex of several iodine containing compounds. The thyroid hormone regulates the rate of oxidation within the cells and in doing so, regulates the physical and mental growth, the functioning of nervous and muscular tissues, circulatory activity and the metabolism of all nutrients. Food Sources Iodine is supplied by food and water; the variations are wide depending upon the iodine content of the soils from which they come. People living in coastal areas and eating locally grown foods ingests enough iodine for their use. In hilly areas where there is a deficiency of iodine in food and drinking water&Iodization of the salt is the only technique available to make good this deficiency in order to prevent goitre. Recommended Dietary Allowances The daily requirement of iodine is 0.15mg or 150 μg/day for adults. This can be obtained by consuming 10g of iodised salt/day for a healthy adult (non-hypertensive). Growing children, pregnant and lactating women may need more (Table 5.4).

Table 5.4: ICMR Recommended Dietary Allowances of Iodine, 2010 Group μg/day Adults Infant

Children (1-5+years) School age children (6-11+years)

Adolescents ≥12 Pregnancy Lactation

150 90 90 120 150 200 200

83

Deficiency Endemic goitre results in the parts of the world, where soil has low iodine content. Endemic goitre is a public health problem in sub-Himalayan region, Maharashtra and sub-Vindhya region, where 50% have goitre. Goitre is characterized by the swelling of the thyroid gland (Figure 5.2).

FLUORINE

Fluorine occurs normally in the body primarily as a calcium salt in the bones and teeth. It is not essential for life but small amount of fluoride bring about striking reductions in tooth decay.

Functions

The main function of fluoride in the body is in the mineralisation of bones and teeth. Fluoride also protects the teeth from dental caries (tooth decay) and is now routinely added to most toothpastes.

Food Sources

The main source is drinking water. It occurs in traces in many foods and in good amounts in shellfish, cheese etc.

Deficiency and Excess of Fluorine

Fluorine is required for deposition of fluoride on teeth and discourages the solubility of minerals and growth of acid forming bacteria. If there is a deficiency of fluorine during the growing period, it will result in dental caries and tooth decay.

In rare cases, very large amounts of (non-dietary) fluoride can cause fluorosis. Symptoms may be mild such as mottling and crumbling of the teeth. The enamel on the teeth loses its lustre, becomes patchy, chalky white and pits appear on its surface. This condition is known as dental fluorosis. It can also cause severe causing skeletal changes such as calcification of ligaments and tendons which leads to muscle, joint and bone problems.

ZINC

Zinc is an important trace mineral that people need to stay healthy. Of the trace minerals, this element is second only to iron in its concentration in the body. It is found in traces in

Figure 5.2: Goitre

Source:https://upload.wikimedia.org/wikipedia/commons/thumb/4/42/Goitre.jpg/120px-oitre.jpg

84

all body tissues and the body’s content of zinc is 2-3 g. It is a constituent of insulin and of many enzymes in the body. Zinc deficiency has been reported to result in growth failure and sexual infantilism in adolescents and in loss of taste and delayed wound healing. Zinc is widely distributed in foodstuffs both animal and vegetable - but the bioavailability of zinc in vegetable foods is low. Animal foods such as milk, meat and fish are dependable sources. For adult man and non-pregnant and non-lactating woman (NPNL) woman for zinc is set at 12 and 10 mg/dayrespectively recommendations for all physiological groups for zinc. Growing children and pregnant and lactating woman need more i.e. 12 mg/day. Most human diets provide these amounts.

Functions i) Regulating immune function

The human body needs zinc to activate T lymphocytes (T cells). T cells help the body in two ways:

o Controlling and regulating immune responses o Attacking infected or cancerous cells

Zinc deficiency can severely impair immune system function. ii) Treats diarrhoea

According to the World Health Organization, diarrhoea kills an astonishing 1.6 million children under 5 every year. Zinc pills may help reduce diarrhoea.

iii) Effects on learning and memory Zinc has a crucial role in regulating how neurons communicate with one another, affecting how memories are formed and how we learn.

iv) Treat the common cold Zinc is found be beneficial in reducing the duration and severity of the common cold in healthy people, when taken within 24 hours of onset of symptoms."

v) Wound healing Zinc plays a role in maintaining skin integrity and structure. Patients experiencing chronic wounds or ulcers often have deficient zinc metabolism and lower serum zinc levels. Zinc is often used in skin creams for treating diaper rash or other skin irritations.

vi) Decreased risk of age-related chronic disease It has been known for decades that zinc has a significant role in immune function. Deficiency has been linked to increased inflammation in chronic disease and triggering new inflammatory processes.

vii) Preventing Age-related Mascular Degeneration (AMD) Zinc prevents cellular damage in the retina, which helps in delaying the progression of AMD and vision loss.

85

WATER The body's need for water is only second to that of oxygen. One can live for weeks without food, but death is likely to follow a deprivation of water for more than a few days. A 10% loss of body water is a serious hazard and death usually follows at a 20% loss. About 70% of body weight of lean adult is accounted for by water. Variations in the water contents in different individual’s ae mainly due to differences in fat contents. In obese males, water constitutes lower percentage to body weight (45-60%). All body tissues contain water but variations in tissue contents are wide. In our body, water is mainly distributed in two compartments (Figure 5.3):

o Intracellular fluids (ICF) which are present within the cells accounts for about 45% of our body weight

o Extracellular fluids (ECF), which are present outside the cells. Examples plasma, interstitial lymph fluids, and transcellular fluid.

Figure illustrates body fluid components. Functions

Water performs number of functions in the human body:

i. Part of structure- Water is a structural component and a cushion of all the cells. ii. Water is the medium of all body fluids including the digestive juice, the lymph,

the blood, the urine and the perspiration. iii. Acts as solvent- Water is a solvent for the products of digestion, holding them in

solution and permitting to pass through the walls for absorption. iv. Transport of nutrients- It is a carrier of nutrients as well as of waste. v. Body temperature regulation- Water has the capacity to regulate the internal

temperature of the body in response to the external temperature. It helps in maintaining the temperature of the body by distributing the heat in the body. Sweat is the main means by which water prevents the human body overheating when the temperature outside it is very high. The evaporation of sweat brings a loss of calories, in the form of heat. This release of energy enables our internal temperature to remain constant.

Transcellular fluid Extracellular fluids

Interstitial lymph fluids Intercellular fluids

8.5 litres Na: K- 28:1

Intracellular fluids 30 litres

Na: K- 1:10

1 liters Plasma 3 liters

Figure 5.3: Body fluid compartments

86

vi. Metabolic and biochemical reactions- Water is not just a transporter of nutritional elements. It acts as a reactant and plays an active role in our metabolic processes. Through a process called hydrolysis, water molecules are part of the biochemical breakdown of proteins, lipids and carbohydrates, which are structurally complex foods, into units more absorbable by the body.

vii. Acts as lubricant- Water is essential as a body lubricant. It is the main constituent of saliva that makes swallowing possible, the mucus secretion of gastrointestinal, respiratory and genitourinary tract, the fluids that bathe the joints and so on.

Food Sources To meet the body’s need water is supplied by the ingestion of water and beverages, the preformed water in foods and the water resulting from the oxidation of foods. Water Balance Our body loses water due to excretion in urine, faeces and perspiration. Some of the water is also lost with the air that we exhale. To make up these losses it is important to consume liberal amount of water. Table 5.5 illustrates the balance between water intake and water losses.

Table 5.5 Normal Water Balance Available water (g) Excreted water (g)

Water intake 1100 In urine 1000

Water in diet 900 In stool 200

Water of oxidation 200 In vapour (skin and lungs) 1000

Total 2200 2200 Let’s check the progress 1. Discuss the importance of water in the body.

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. Explain the following briefly: a. Haemoglobin ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

87

b. Symptoms of anaemia --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- c. Deficiency of fluorine ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

SUMMARY Minerals are important for our body to function properly. Minerals must be supplied to the body in balanced amounts (neither deficiency nor excess) to remain healthy. Some of the important minerals found in our body include calcium, phosphorus, iron, iodine, sodium, potassium, zinc and chloride. All these minerals are derived from the food we eat. Of these, calcium, phosphorus, sodium, potassium, chloride and magnesium are the minerals required in larger amount by the body. Calcium together with phosphorus and other elements give rigidity to bones and teeth. Iron is present in the haemoglobin. Sodium is required for maintenance of normal osmotic pressure and water balance. Water is the medium of all body fluids and is absolutely essential to sustain life.

KEY WORDS

Extracellular fluid- The fluid present outside the cells. Intracellular fluid- The fluid present inside the cells. Osmosis is the movement of water from an area of low concentration of solute to an area of higher concentration of solute. Osmotic pressure- it is the pressure that would have to be applied to a pure solvent to prevent it from passing into a given solution by osmosis, often used to express the concentration of the solution. Osteomalacia- is a characteristic feature of vitamin D deficiency in adults. Softening of bone, particularly in the sense of bone weakened by demineralization Rickets- a disease of children caused by vitamin D deficiency, characterized by imperfect calcification, softening, and distortion of the bones typically resulting in bow legs.

REFERENCES

ICMR. Nutrient requirements and recommended dietary allowances for Indians. A report of the expert group of the Indian Council of Medical Research, National Institute of Nutrition, Hyderabad. 2010. B. Srilakshmi. Nutrition Science. New Age International (P) Ltd Publishers 2016 (Fifth Edition) Websites: https://upload.wikimedia.org/wikipedia/commons

89

UNIT 3

CULINARY SCIENCE

Lesson 6 : Introduction to Cooking Lesson 7 : Methods of Cooking

Lesson 8 : Role of Food Groups in Cookery Lesson 9 : Effect of Cooking on Food components Lesson 10 : Ways of Conserving and Enhancing Nutrients

91

LESSON 6

INTRODUCTION TO COOKING

Some foods like fruits, vegetables and nuts are eaten raw. It is good to consume food in raw form as they retain most of its nutritional value. However, most of the foods are cooked before they are actually eaten. Cookery is an art or practice of cooking. Cooking is defined as “a chemical process which encompasses the mixing of ingredients; the heat application and withdrawal; decision making, technical knowledge and manipulative skills.” It also involves some amount of creativity and hence is considered as both art and technology. Food preparation denotes preparation and cooking. It follows a flow pattern which begins with the selecting and purchasing materials, their handling, processing and the ultimate presentation of dishes to customers. In the course of food preparation, depending on the recipe, foods are subjected to various processes such as washing, grinding, cutting, fermentation, and germination and cooking. In Indian cuisine, fermentation (idli, dosa, dhokla) and germination (sprouting) are common practices. These methods improve digestibility and increase nutrients such as B-complex vitamins and vitamin C.

OBJECTIVES

To understand the terminologies, concepts and principles required for cooking. To explain the meaning and importance of pre-preparation and preparation of

food

OBJECTIVES OF COOKING

Before going into the details of cooking, we should know why we cook food. Though the main objective is to make the food edible, yet there are other reasons for doing so such as:

1. Improvement of food quality

o Makes the food attractive and palatable- Cooking makes the food look attractive and also renders it more tasteful than the uncooked food. More sight of a well-cooked and pleasant looking food activates our digestive enzymes and makes us feel hungry.

o Improves food digestibility and palatability- Cooking makes the food soft and tender which makes it easy and quick to digest. For example, after cooking carbohydrates present in food become easier to digest to a certain extent. Similarly, proteins coagulate on cooking which makes the digestion simple. It is due to this reason that soft and well-cooked food is recommended for people in diseased conditions, as their digestive system is weak.

92

o Enhances the availability of nutrients- For example, cooking destroys trypsin inhibitor present in protein foods. This makes the trypsin freely available to the body. Similarly starch is more easily available after cooking.

2. Increases variety- Variety can be brought in meals easily by using different methods of cooking. For example, one single foodstuff like potato can be cooked by using different methods into a number of dishes and thus add variety to the meals, i.e. potatoes can be cooked as potato sabzi, potato chips, potato chaat, potato halwa, baked potatoes etc., simply by changing the methods of cooking

3. Destruction of micro-organisms- Cooking of food destroys the micro-organism present in them to a large extent, thus, making it safe for consumption. Many foodstuffs like milk, meat, fish, can harbour certain disease-producing microorganism thus making the person sick on the consumption of such foodstuff. Raw milk may have microorganism responsible for causing tuberculosis and typhoid and such milk if consumed raw can be harmful. Meat especially pork, contain eggs of worms which can cause an infestation in the body. Fortunately, these microorganisms are destroyed by usual cooking procedures, thus making the food safe. Another advantage of destroying microorganisms is that the food can be kept for a longer time i.e. its shelf life is increased e.g. pasteurized milk.

4. Increases consumption of food- Cooking improves the colour, texture and makes the food chewable and appealable. Hence, increases the consumption of food and helps us in meeting our nutritional requirements.

5. Concentrate nutrients- Cooking help to concentrate nutrients in food. This may occur due to elimination of moisture or using different food combinations or due to cooking procedures, e.g. sweets like rabri, khoa burfi.

6. Increases antioxidant value

Thus, the cooking of food is very important, as it increases digestibility, appeals to the palate and destroys microorganisms.

PRINCIPLES OF COOKING

Heat transfer: It is an important feature of the cooking process as heat is applied in order to cook the food. It is defined as “the exchange of thermal energy between the two matters.” When food in solid or liquid form becomes warm, its molecules absorb energy and start vibrating rapidly and hence start to jump. As they strike, heat energy is created and transferred (Figure 6.1), which warms and cooks the food.

MethThereradiahave A. C

inth

Fo

B. Cmrisbo

Fow

Thco

o NNwci

Fowcorew

o MMco

hods of Heae are 3 wayation. Each some crossoONDUCTI

n direct conhe hotter por

or example,

The stoveutensil coHot oil inwith it.

ONVECTImolecules th

se to the topottom of the

or examplewater

here are twonvection.

Natural ConNatural convwarm and riirculating cu

or examplewarms up thonvection ceplaced by c

water via con

Mechanical Mechanical ooking time

Fat Transferys by whicof these meover. ION is a m

ntact with a rtion of foo

,

e will conduonducts heatn the utensil

ION is a mehrough any p and the ce vessel (Fig

e, thawing o

wo main c

nvection vection occise while current that e

, when wathe utensil, causes themcooler molenvection.

Convectionconvection

e and cooks

igure 6.1: P

ch heat is tethods of he

method in whot object d to its cool

uct heat enet to its contl uses condu

ethod in whliquid or ga

cooler (hencgure 6.2).

of frozen fo

convection

urs when mcooler (heavevenly distri

er in a utenwhich the

m to move aecules. This

n occurs whfood more

93

Process of h

transferred eat transfer h

which heat islike a hot pler part thro

ergy to the bents. uction heati

hich the tranas. When wce denser) w

food by roo

heat cooki

molecules avier) molecibutes heat

nsil is placeen heats thaway from continuous

hen outsideevenly. Exa

heat transf

to food -cohas its own

s transferredpan. Thereaough conduc

bottom of th

ng as the fo

nsfer of heawater is boilwater molec

om tempera

ing method

at the bottocules in thethroughout

ed on the sthe water m

the interios current cre

forces cirample stirrin

fer

onduction, distinctive

d to the fooafter heat isction.

he utensil an

ood comes i

t occurs by led, the hotcules at the

ature air or

ds: natural

om of a cooe food sinkthe food be

tove to boilmolecules inor of the uteates heat tr

culate heatng the liqui

convectionfeatures, bu

od when it cs transferred

nd from the

into direct c

the movemt water moltop moves

by running

and mech

oking utensk. This creeing prepare

, conductionside. Thertensil as theransfer with

t, which shd in a pot

n and ut also

comes d from

re, the

contact

ment of ecules to the

g cold

hanical

sil get eates a ed.

n heat eafter, ey are hin the

hortens

94

C. RADIATION is the method by which energy is transferred to food through the waves from an energy source. This wave when striking the food, the molecules start vibrating and heat is produced. The radiation can cook food by two methods: infrared and microwave radiation (Figure 6.2).

o Infrared Radiation It operates on an electric or ceramic heating element that provides electromagnetic energy waves which travel in any direction at the speed of light and heat the food rapidly. These waves are mainly absorbed in the surface of the food. Examples in case of toaster ovens, and broilers.

o Microwave Radiation It utilizes short, high-frequency waves that can pierce through the food, which in turn stirs water molecules present in the food and create friction and transfers the heat. If a solid substance is heated, transfer of heat occurs through conduction, while liquids do so through convection. Microwave radiation usually cooks food faster than infrared radiation, as it is able to penetrate foods several inches deep. Microwave radiation works finest when cooking small batches of food.

Figure 6.2: Different methods of heat transfer

PRE-PREPARATION STEPS IN COOKING

Food is one thing that unites us all despite different cultures and regions. Food preparation is an extensive area and involves numerous actions from obtaining raw ingredients and consuming them as food. It's somewhat simplistic and complex, ubiquitous and artistic, personal and universal.

Transforming the raw food constituents into the required form is called ‘pre-preparation’.

CLEA

Cleanprepaare tTherebeforeinsect

Advan

Disad

PEEL

Peelinvegetscrapesurfac

Advan

Disad

CUTT

Cuttinof a kknife VarioDicinMinc

ANING/W

ning the foaration. Sinctreated witefore, it is ne consumptts or birds c

ntages

It helps uThe warmIt also he

dvantages

Water-soof time orB comple

LING AND

ng and scraables or frued. Peels ofce layers by

ntages

It helps uportions fFruits apeeling.

dvantages

Discardinpeeling frlead to a

TING

ng involvesknife or sci

or an eleous terms unng cing

WASHING

food is thece most footh insecticnecessary totion. Addit

can also be c

us to removem water uselps us in rem

luble vitamr washed afex vitamins

D SCRAPIN

aping help iuits can bef vegetables

y using a cir

us to remofrom food.

and vegeta

ng the outerfruits and vedisproportio

s reducing thissors. Wheectric food nder this are

Cutting inCutting in

e first steod products cides or oo wash off ionally, ducleaned via

e dirt, sprayd in washinmoving blo

mins and minfter cutting. are also los

NG

in removinge removed s like carrotrcular motio

ove inedible

ables appea

r leaves of vegetables suonate loss o

he food to sen food is c

chopper, e: nto even sizento very fine

95

p in any consumed

other chemf these chemst and dirt washing.

ys pesticidesng can help od, and oth

nerals are l

st during wa

g inferior, by peelingts could be

on is known

e or undesi

al better

vegetables such as appleof many vita

smaller partchopped usit is called

e cubes. e pieces

food today

micals. micals

from

s etc. us remove ter impuritie

ost if they a

ashing of ce

muddy and. Vegetableused for m

n as paring e

irable

after

uch as cabbes, peaches,amins and d

ts with the sing a chopd as chopp

the worms. es from flesh

are soaked

ereals like ri

d inedible pes like ging

making stocke.g. in case

bage, spinac, pears, pota

dietary fibre

help ping ping.

h products.

for a long p

ice.

portions. Skger, galangks. Removinof an apple

ch and lettucatoes and c

e.

period

kins of gal are ng the

e.

ce and arrots,

96

Shredding Cutting into fine, long pieces. Slicing Cutting into slightly thicker, flat pieces. Grating Reducing to fine particles by rubbing over a rough, sharp surface. Advantages

It helps us in cooking food faster. It helps in improving the appeal of the food e.g. salads.

Disadvantages

Loss of many heat-labile and water-soluble vitamins.

Figure 6.3:Vegetable cuttings

Other terminologies

Processing

There are various forms of processing techniques to which food may be subjected before reaching to the consumer. All of these processes have some effect on their nutrient content. Although foods are often compared before and after processing, a better comparison is at the stage when the food is eaten. For example, during the frozen peas loses about a 10 per cent of vitamin C. But because they require a shorter cooking time

Flower cuts Cubes Chiffonade

Julienned Diagonal cuts Roll cuts

97

than fresh peas, there is virtually no difference between the vitamin C content of fresh and frozen peas as they appear on our plate. The nutritional changes that occur in the commercial preparation of food do not differ much from those in the same food prepared in the home. Both types of food preparation involve some form of processing. There may be differences in palatability and the food manufacturer may use cheaper ingredients such as emulsifiers, cereal fillers and synthetic flavours. This may be partially offset by the fresher foods usually available to the manufacturer. The effect of the different types of processing on nutrients is discussed below.

Grinding- Crushing into small particles in a mill, a grinding stone. Milling- A grinding process using a mill. Mashing- Process by which soft foods ae beaten to a pulp like cooked potatoes. Blanching- To cook by dipping briefly into boiling water, then directly into cold

water. This is not meant to cook the food but to inactivate substances which may adversely affect the nutrient content, colour, flavour or texture of the food. Varying amounts of nutrients are lost in this process, in particular, the water-soluble vitamins.

Dehydration- or the drying of foods is a method of preservation. With the exceptions of vitamin C and pro vitamin A, the nutrient losses that occur in drying are not large. Further losses can occur depending on how the dried food is further processed. If the food is eaten in the dried form, such as dried apricots, then the food is a concentrated source of many nutrients, including dietary fibre

Canning- involves heating food in a closed container to ensure that the micro-organisms present in the raw food can no longer cause deterioration of the food or be hazardous to health. The amount of heating depends on the type of food. Nutrient losses occur from destruction during heating and storage stages. Some nutrients, such as water-soluble vitamins and minerals, may dissolve in the water of the can, but they are lost only if this liquid is not consumed. We can reduce losses of vitamins during storage by storing the cans in a cool place.

Pasteurization- involves heating food for a short time to kill harmful micro-organisms that are present in the food. Not all micro-organisms are destroyed, and spoilage of the food may still occur on storage, but this can be delayed by refrigeration. Nutrient losses during pasteurization of milk and fruit juices are generally small, and in the case of fruit juices, they must contain not less than a specified minimum amount of vitamin C. This generally means that vitamin C is added by the processor to make up for any losses that occurred during processing. To minimize further nutrient losses, milk and fruit juices should be stored away from light and in a cool place.

Marination- the process of steeping/soaking foods in a flavouring mixture before cooking and may last seconds or days.

Steeping- soaking redients in liquid in order to extract colour or flavour

98

Homogenization- Process of making something same throughout e.g. milk by passing large drops through a small opening under great pressure into smaller ones.

Centrifuging- Separation of a mixture of dense and lighter materials by being spun about a central axis at high speed e.g. separation of cream from milk.

Emulsification- Process by which emulsion is formed. Emulsion- a stable suspension of small droplets of one liquid in another with

which it is immiscible. Evaporation / Reduction – Process of liquid converting to a gaseous state. Sieving- Passing of food material through a mesh/sieve to remove impurities


1. Define the following. a. Canning --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- b. Marination --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- c. Blanching ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. Enlist the objectives of cooking. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3. Explain the principle of heat transfer. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

SUMMARY

Cookery is an art and science of preparing food for consumption by using heat. In order to make food digestible and palatable, we need to cook food. Apart from this basic reason there are many reasons behind cooking food. There are 3 ways by which heat is transferred to food - conduction, convection and radiation. Each of these methods of heat transfer has its own distinctive features. Pre-preparation is one of the most important steps in the process of cooking and involves transforming raw ingredients into the

99

required form. It also involves several processing techniques to which food may be subjected before reaching to the consumer. All of these processes have some effect on their nutrient content.

REFERENCES

B. Srilakshmi. Nutrition Science. New Age International (P) Ltd Publishers 2016 (Fifth Edition)

Websites: https://study.com/academy/lesson/what-is-food-preparation-definition-types.html https://www.google.co.in/search?q=heat+transfer&sxsrf=ACYBGNSg-DlM5rXrC8 https://www.rsph.org.uk/uploads/assets/uploaded/1946fe2a-4e6d-46cb-b673b078ddeb12e4.pdf https://hmhub.me/techniques-used-in-pre-preparation/ http://bieap.gov.in/Pdf/HOPaperI.pdf

100

LESSON 7

METHODS OF COOKING

INTRODUCTION

Food is being cooked, since the times of the early man, when he accidentally discovered that cooked meat tastes much better than raw meat. Thereafter, food has generally been consumed in the cooked form by man. With the advancement in all the fields, the man started cooking his food by different methods; as a result, today we use all these different methods to cook our food. A brief description of these cooking methods, their advantages and disadvantages will help in creating awareness about the correct choice of a method for cooking a particular food item.

OBJECTIVES

To develop an understanding of the basic methods of cooking Describe the merits and demerits of different methods of cooking.

The various methods of cooking can be broadly classified into their categories according to the source of heat i.e. moist heat or dry heat which are further classified as shown below:

Figure 7.1: Various methods of cooking

MOIST HEAT METHOD

These are the methods in which we use the heat generated by water in some form or the other. The methods include boiling, steaming, pressure-cooking, and stewing.

Methods of cooking

Moist heat

BoilingSteaming-

DirectIndirectPressure cookingStewing

SimmeringPoaching

Dry heat

BakingRoasting

Grilling/boiling

Using fat

SauteingShallow fryingDeep fat frying

Combination

Braising

101

1) Boiling In this method, the foodstuffs are cooked in boiling water. Thus, the food comes in direct contact with water. In this, the foodstuffs are immersed in water in a suitable container, covered with a lid and the heat is applied. Once a vigorous boil starts the heat can be reduced and cooking continued till the food is tender. Food may be boiled in any liquid, which is bubbling at the surface such as stock, milk, juices or syrups. Foods that are cooked by boiling are rice, eggs, dals, potatoes, meat, sago and beetroot. Boiling can be done with an excess of water (eggs) or with sufficient water (dal, upma). Food cooked by this method is always recommended for patients. Points to be considered for good results o Put water in just sufficient quantity, so that it is used up by the food completely. If

extra water is used for boiling, then the amount that cannot be used up by the food has to be discarded. When the extra water is discarded it takes away certain water-soluble nutrients and the flavour of the food with it.

o Cover the utensil when the food is being cooked so that cooking is quick and the fuel consumption less.

o Boiling violently does not cook the food faster; In fact, it wastes fuel, breaks the food and spoils its appearance. It is always advisable to simmer the gas, once the boiling starts.

Advantages of boiling 1. It is the simplest method of cooking. It does not require special skill and equipment. 2. Uniform cooking can be done. 3. The food cooked is light and easily digestible. 4. If the amount of water is proportionate to the quantity of food to be cooked and the

food is cooked covered, the nutrients are retained in the food to a large extent. Disadvantages of boiling 1. It is time-consuming. It takes time and fuel may get wasted. 2. Water-soluble pigments, like betalain/betacyanin (red pigment), may be lost. Beetroot

should be cooked along with the skin to prevent the loss of colour. 3. Boiled foods are not considered tasty because flavour compounds are leached into the

water. Over boiling of food make the food mushy. 4. If the food is boiled in excess water, which is later thrown away, then this leads to

draining away of water-soluble nutrients particularly Vitamin C, Vitamin B group and minerals.

However, if sometimes there is extra water after boiling which has to be drained away, then it should be used in some other preparations like cooking of dals, soups, etc. so that the nutrients are not lost.

102

2) Steaming Steaming is also a method of cooking food with water, but in this case, the food does not come in direct contact with water. In this method, the food is cooked by the heat generated by steam and hence takes a slightly longer time, as compared to boiling.

Steaming is done in two ways i.e. direct steaming and indirect steaming.

Direct Steaming – In this method, the food comes in direct contact with the steam. Direct steaming can be done in an ordinary steamer or in an improvised steamer as described below. Take sufficient water in a suitable container and allow it to boil so as to generate steam. The food to be cooked is kept in a metal strainer over this utensil and it is covered tightly with a lid. This way the steam rising from the water below rises up and comes in direct contact with the food kept in the strainer, thus cooking it. The water in the container is maintained at boiling temperature throughout the process of steaming. For example, steaming of cut vegetables, or sprouted pulses, fish, idli, dhokla etc.

Indirect Steaming – In this method, the food does not come in direct contact with the steam, but is cooked by the heat of the steam surrounding the container containing the food material. The water is boiled in a utensil. The food to be steamed is kept in a smaller container, which can be closed from the top and then placed in this utensil containing water. The utensil containing water is also covered with a tight-fitting lid. As the boiling water forms the steam, it surrounds the container containing food, which gets cooked by the heat of this surrounding steam. The process takes a slightly longer time than the direct method of steaming. The heat has to be maintained throughout the process so that the formation of steam continues. Example of indirect steaming is steaming of puddings like custards.

Points to be considered for good results o The water in the lower vessel has to be maintained at boiling temperature throughout

so that the process of steam formation continues. o The container should always be covered with a tight-fitting lid so that the steam does

not escape. o In indirect steaming container containing the food should be closed properly or

covered tightly with a greaseproof paper, so as to prevent condensation of moisture from falling on the food.

o Keep some boiling water handy so that the water in the steamer or the lower vessel can be easily replaced as it boils away.

Advantages 1. Whether cooked by the direct or indirect method the food is soft, easy to digest and

hence ideal for the elderly and sick people particularly those with weak digestion. 2. The food is tasty and full of flavour. 3. The food retains maximum nutritive value particularly in the indirect method of

steaming; there is practically no loss of nutrients. However, some amounts of water-

103

soluble nutrients i.e. vitamins of B group and vitamin C are lost by indirect method of steaming (dripping loss) but the nutrients loss is much less as compared to boiling.

4. The food generally does not get over-heated. 5. It does not require constant attention. 6. The texture of the food is better and becomes light and fluffy. 7. Steamed foods have good flavour. Disadvantages 1. It is a slow process of cooking and only easy to cook foods can be prepared by this

method. 2. If a sufficient amount of water is not there in the lower container, it might evaporate

completely and the container starts burning even before the food is cooked. 3) Pressure Cooking In this method, the food is cooked under pressure and with an increase in pressure the temperature also correspondingly increases. Thus, the food is cooked very fast. Actually, it is a type of steaming only, in which water is boiled under high pressure, thus raising the temperature and reducing the cooking time. The equipment used for this purpose is a pressure cooker, which is common equipment in every household these days. There are two-three containers in a pressure cooker, which allow more than one thing to be cooked at the same time, thus saving fuel, as well at a time. If only one item has to be cooked it can be used without these containers. Practically foods which can be cooked in a pressure cooker are pulses, rice, vegetables, meat etc. Points to be considered for good results o Do not fill the pressure cooker more than two-thirds. o Put the weight on the cooker only after some steam has been formed and it starts

coming out of the vent pipe. This makes sure that there is no blockage in the vent pipe.

o Once the pressure has been built, heat should be reduced and time noted. o Cook for a specific time according to the food being cooked. o Before opening the pressure cooker, make sure that the pressure has dropped

completely, which can be achieved by either allowing it to cool on its own or by cooling it under running water.

Advantages 1. Pressure-cooking saves time and fuel and thus is a very economical method of

cooking. 2. Retention of nutrients is maximum in pressure cooking. 3. By using separate containers, more than one food can be cooked at one time.

104

Disadvantages 1. If proper precautions are not taken, as described earlier, it can be dangerous as it can

burst. 2. Food can be overcooked if cooked for extra time than specified. 4) Stewing This is a very gentle method of cooking, in which the food is cooked in a closed pan using only a small quantity of liquid. Once the liquid reaches the boiling point, the heat is reduced, and it is only allowed to simmer in it, which makes it a slow and long process. The amount of water left after cooking is only marginal i.e. one to two tablespoons which are served along with the food. Thus, the flavour of food is fully retained. The foods which are generally stewed are fruits, vegetables, meat etc. Points to be considered for good results o Use a pan with a tight-fitting lid. o Prepare the food and cut into moderate size pieces, so that it is convenient to serve. o Use liquid only insufficient amount as to half cover the food. o Bring the liquid to boiling point and then simmer very gently until the food is perfectly

tender. o Serve the liquid left with the food only. Advantages 1. Cheap cuts of meat which are tough or under-ripe, fruits and vegetables can be

prepared by this method, as the slow moist method of cooking softens fibres thus making the food tender.

2. Meat and vegetable may be cooked and served together, making an appetizing dish. 3. Food retains most of the nutrients and is full of flavour, thus very appetizing. Disadvantages 1. It is a very slow method of cooking. 2. It requires constant attention. 3. A good amount of vitamin C is destroyed because of the slow process of cooking. 5) Simmering When foods are cooked in a pan with a well-fitting lid at a temperature just below the boiling point (82-99ºC) congregates of the liquid in which they are immersed, the process is known as simmering. It is a useful method when foods have to be cooked for a long time to make it tender as in the case of cheaper cuts of meat, fish cooking, custards, kheer, vegetables, and carrot halwa. This method is also employed in making soups. Advantages 1. Food gets cooked thoroughly.

105

2. Scorching or burning is prevented. 3. Losses due to leaching are minimum. Disadvantages 1. There is loss of heat-sensitive nutrients, due to the long period of cooking. 2. It takes more time and more fuel is required. 6) Poaching This involves cooking in the minimum amount of liquid at a temperature of 80-85ºC that is below the boiling point. Foods generally poached are eggs, fish and fruits. For poaching eggs, the addition of little salt or vinegar to the cooking liquid lowers the temperature of coagulation. Eggs cook quickly by poaching. Advantages 1. It is a very quick method of cooking. 2. Food is easily digestible since no fat is used. Disadvantages 1. Food is bland in taste. 2. Water-soluble nutrients may be leached into the water.

DRY HEAT METHOD

1) Baking It is the cooking of food in hot air in a closed oven. The food to be cooked is kept in a preheated oven, where it is surrounded by hot air in the closed oven, thus getting cook by the dry heat. Usually, the oven is heated to a particular temperature according to the food which is to be baked and this temperature is maintained throughout the cooking procedure. The foods generally prepared by this method are cakes, biscuits, pies, pastries, pudding, vegetables, and potatoes etc. Points to be considered for good results o The food should always be kept in a preheated oven. o The temperature of the oven should be maintained throughout. o The oven should be closed properly and should not be opened too frequently as the air

from the outer atmosphere gets in and disturbs the temperature. o Food should be baked till firm and light brown in colour. Advantages 1. The food cooked by baking is easy to digest. 2. Baked foods add variety to our meals.

Disadvantages 1. It is a slow method of cooking and takes a longer time. 2. Specific equipment i.e. an oven is needed to use this method.

106

2) Roasting It is cooking the food uncovered in hot air i.e. by dry heat. This can be done in a tandoor, in an oven or in a thick heavy pan. Certain foods like chicken, joints of good quality meats, are roasted with occasional basting (i.e. addition of a little fat, so as to prevent the surface from drying, add to the flavour), whereas vegetable likes potatoes, sweet potatoes, and brinjal are roasted on a direct flame or in an oven without addition of any fat. Similarly, cereals like suji, broken wheat, and vermicelli etc. are roasted in a heavy-bottomed pan with or without the addition of a little fat depending on the preparations to be made from them. Some foodstuffs can also be roasted in a suitable medium like sand or salt which gets heated faster and can retain the heat, so as to maintain the right temperature required by this method, they immediately puff up and are ready to eat. Thus the temperature required in roasting is generally higher than baking. Points to be considered for good results o While roasting on the oven, the ventilation of the oven is very important and both the

oven and shelves should be thoroughly clean, otherwise, the flavour is affected. o The temperature should be maintained throughout. o Avoid piercing of food while roasting, as the juices can escape. o While roasting on an open fire, the food should be turned frequently. Advantages 1. Compared to baking, it is a quicker method of cooking. 2. A variety of foodstuffs can be prepared by roasting. 3. It requires less or no fat. 4. Flavour is improved. 5. It reduces the moisture content of food and improves keeping quality e.g. rava. 6. It is easy to powder e.g. cumin seeds after roasting. Disadvantages 1. The foodstuffs being roasted required constant attention. 2. Losses of nutrients like amino acids occur when the food becomes brown

3) Grilling or Broiling It is cooking of food by direct heat over a hot fire or under a grill; this is also a method of cooking by direct heat. Usually, the food is put on grill bars and is cooked over direct heat with the help of little fat. The grill bars are first brushed with oil to prevent food from sticking and can be heated by charcoal, coke gas or, electricity. Since the heat is high, the foods get cooked quickly. The only first-class cut of poultry, certain fish and vegetables like tomato, and mushroom, can be prepared this way. The most common grilled preparation is seekh kababs. Points to be considered for good results o The food should be basted occasionally with melted fat to prevent drying of the

surface and to add flavour. o It should be turned frequently to prevent browning.

107

o Proper care should be taken so that the food is uniformly brown on all the sides. Advantages 1. The food prepared is of delicacy and tasty. 2. It is a quick method of cooking. 3. It requires less or no fat. Disadvantages 1. Only good quality foods can be prepared by this method and hence it is an expensive

method. 2. It needs constant attention.

FRYING

This is a method of cooking in which the food is cooked by the heat of hot fat. Fat or oil can be heated to a much higher temperature, as compared to water and thus, as the food comes in contact with this heated fat, it gets cooked quickly. Fried foods are very tasty and hence popular in our meals. There are three types of frying:

1) Sautéing This means to toss the foodstuff in a little amount of heated fat until it is partially cooked and absorbs the fat. The food is tossed occasionally or turned over with a spatula to enable all the pieces to come in contact with the oil and get cooked evenly. Sometimes the pan is covered till tender in its own steam. The product obtained when cooked by this method is slightly moist, tender but without any liquid or gravy. It is usually done as a pre-preparation step in many dishes e.g., sautéing of vegetable in the preparation of vegetable pulao, or sautéing of noodles, thin pieces of meat etc. 2) Shallow fat Frying In this method, a shallow pan like frying pan or an ordinary griddle is used in which the food is fried in a little amount of fat. During frying it is turned over, so that it may be evenly browned on both the sides. In this case also, the fat used is usually absorbed by the foodstuff. The preparations generally cooked by this method are parantha, omellete, tikkis, pancakes etc. Some food contains sufficient fat in themselves like bacon and sausages. Hence these can be fried without the addition of any fat. 3) Deep fat frying The food is completely immersed in hot fat and therefore a deeper utensil like karahi and a large quantity of fat is required. The fat is heated in the karahi and as it becomes hot, the food to be fried is put in it which gets cooked quickly. Common preparations which

Sautéing Shallow fat frying Deep fat frying

108

are made by this method are poories, pakoras, cutlets, samosas etc. While deep frying care should be taken to see that the fat does not get overheated, as the fat decomposes at high temperature, which not only spoils the taste of the food but is even harmful to our body. At the same time, if the fat is not hot enough, the food can break up and also absorbs extra fat, thus making it very greasy. Therefore, it is important to judge that the fat has been heated to the right temperature which can be done in the following ways:

i. When the fat starts giving a light smoke and becomes still it indicates that it has been heated to the right temperature.

ii. If a one-inch square piece of bread becomes golden brown and crisp in one minute, then the temperature of such fat is right for frying.

iii. Similarly, an easy way is to just try a little piece of the food first and if fries all right, then proceed with the rest.

Both sweets and savouries can be cooked by this method. Food cooked by deep fat frying has a much better appearance as compared to shallow fat frying as the food is evenly browned and is crisp. Though an initially large quantity of fat is required in deep fat frying the net absorption of fat by the food is less in deep-fried foods, as compared to shallow fried foods. Points to be considered for good results o Use fat with high smoking points as it can be heated to a higher temperature for

example oils have a higher smoking temperature as compared to pure ghee, and hence should be preferred for frying.

o See that the fat has been heated to the right temperature and maintain the temperature during frying so that the fat is not allowed to burn.

o Make the food into a suitable size and shape and see that there are no cracks on the surface.

o While deep frying products like cutlets, usually, a coating of breadcrumbs are used; make sure that there is an even and firm coating and all excess bread crumbs should be removed otherwise they come out in the frying fat.

o Do not put too many articles at one time as this lowers the temperature. o Turn the foodstuff frequently so that it is evenly browned on both sides. o Once the fat has been used for frying, strain it and store in closed containers in the

cool place. o Avoid using the same oil for frying repeatedly. Advantages 1. It is a quick method of cooking. 2. Fried food is very appetizing and tasty. 3. Fried foods have better-keeping quality e.g. poories can be kept for a longer time as

compared to chapattis, without spoiling their taste and flavour. 4. Frying introduces variety in the meals, as fried foods are crisp in texture. 5. Fried foods have a higher satiety value. 6. It increases the calorific value of food. 7. In shallow fat frying, the amount of oil consumption can be controlled.

109

Disadvantages 1. Fried foods are difficult to digest as the food gets covered with a layer of fat first. 2. Due to high temperature, the nutrient losses are higher, particularly of fat-soluble

nutrients. 3. As fats and oils are expensive, it is not an economical method of cooking. 4. Sometimes the food may become oily or soggy with too much absorption of oil. 5. More attention is required while cooking and care should be taken to avoid accidents. 6. Repeated use of heated oils may produce harmful substances and reduces the smoking

point.

COMBINATION METHOD

1) Braising It is a combination of two methods of cooking i.e. roasting and stewing. It is done in a suitable pan, which has a tight-fitting lid. It is usually used for meats, which is first roasted on all sides and then placed in the pan. Stock or gravy is then added which usually covers two-thirds of the meats. The lid is closed tightly, after adding flavouring and seasonings and then it is allowed to cook gently on fire as is done in stewing. It can also be done in an oven. When the meat is tender it is usually served with the little liquid, which is left in. Points to be considered for good results o Roasting should always be done uniformly so that even browning is achieved. o For stewing use a pan with a tight-fitting lid and right quantity of water. Advantages 1. The food is very tasty and full of flavour. Even most of the nutrients are retained. Disadvantages 1. It is a time-consuming method and requires constant attention. Many food preparations are made not by a single method but by a combination of cooking methods.

Vegetable Curry : Sautéing and simmering Upma : Roasting and boiling Meat cutlet : Boiling and deep-fat frying Matar Paneer : Frying and stewing

Thus, we can say that we cook our food by various methods to make it appetizing irrespective of the method used for cooking; the heat treatment definitely affects the colour, taste, flavour, and the nutritive value of the foodstuff. Similarly, other ingredients added during cooking i.e. fat, spices, vinegar, and soda etc. also have such effects.

110

SUM

MA

RY

OF

MET

HO

DS

OF

CO

OK

ING

Coo

king

met

hods

M

erits

D

emer

its

DR

Y H

EAT

MET

HO

DS

Roa

stin

g In

this

met

hod,

food

is c

ooke

d in

a h

eate

d m

etal

or

fryin

g pa

n w

ithou

t co

verin

g it.

e.

g. m

eats,

chi

cken

; pot

ato,

sw

eet p

otat

o,

and

brin

jal;

suji,

dal

iya,

ver

mic

elli.

A

qui

ck m

etho

d of

coo

king

.

It im

prov

es

the

appe

aran

ce,

Flav

our

and

text

ure

of th

e Fo

od.

Sp

ices

are

eas

ily p

owde

red

if th

ey a

re f

irst

roas

ted.

Fo

od c

an b

e sc

orch

ed d

ue to

car

eles

snes

s.

Roas

ting

dena

ture

s pr

otei

ns

redu

cing

th

eir

avai

labi

lity.

Baki

ng

Cook

ing

in h

ot a

ir in

a c

lose

d ov

en. e

.g. B

read

, cak

es, b

iscui

ts,

fish,

veg

etab

les l

ike

pota

to, s

tuffe

d to

mat

o, m

ushr

oom

s.

Ba

king

lend

s a u

niqu

e ba

ked

flavo

ur to

food

s

Food

s bec

ome

light

and

fluf

fy

U

nifo

rm a

nd b

ulk

cook

ing

can

be a

chie

ved.

Flav

our a

nd te

xtur

e ar

e im

prov

ed.

V

arie

ty o

f dish

es c

an b

e m

ade.

Sp

ecia

l equ

ipm

ent l

ike

oven

is re

quire

d

Baki

ng sk

ills a

re n

eces

sary

Care

ful

mon

itorin

g ne

eded

to

pr

even

t sc

orch

ing.

Gri

lling

/Bro

iling

G

rillin

g or

bro

iling

refe

rs to

the

cook

ing

of f

ood

by e

xpos

ing

it to

dire

ct h

eat.

In

this

met

hod,

foo

d is

plac

ed a

bove

or

in

betw

een

a re

d ho

t sur

face

. e.g

. Pap

ads,

corn

, phu

lkas

, chi

cken

En

hanc

es th

e fla

vour

, app

eara

nce

and

taste

of

the

prod

uct.

It

requ

ires l

ess t

ime

to c

ook.

Min

imum

fat i

s use

d.

Co

nsta

nt

atte

ntio

n is

requ

ired

to

prev

ent

char

ring.

FRY

ING

D

eep

fat F

ryin

g Co

okin

g fo

od in

hea

ted

oil o

r fa

t. Fr

ying

fo

od i

n a

larg

e am

ount

of

fat

in a

dee

p pa

n.e.

g.

Poor

ies,

kach

orie

s, ko

ftas,

cutle

ts, p

akor

as, s

amos

as, g

ujiy

a, m

athr

i, va

das,

chip

s, fis

h.

Q

uick

met

hod

of c

ooki

ng.

Ca

lorif

ic v

alue

of f

ood

is in

crea

sed

since

fat i

s us

ed a

s the

coo

king

med

ia

D

elic

ious

flav

our a

nd a

ttrac

tive

appe

aran

ce to

fo

ods

Ta

ste a

nd te

xtur

e ar

e im

prov

ed.

Ca

refu

l m

onito

ring

is re

quire

d as

foo

d ea

sily

gets

char

red

Food

may

bec

ome

sogg

y du

e to

too

muc

h oi

l ab

sorp

tion.

Frie

d fo

ods a

re n

ot e

asily

dig

este

d.

Re

peat

ed u

se o

f hea

ted

oils

will

hav

e ill

effe

cts

on h

ealth

. Sh

allo

w fa

t Fry

ing

It is

done

in

just

enou

gh f

at t

o pr

even

t sti

ckin

g. e

.g.

Eggs

, pa

rant

has,

dosa

s, pa

ncak

es, c

heel

as, t

ikki

s.

Saut

éing

Fr

ying

and

toss

ing

food

in a

sm

all a

mou

nt o

f ho

t fa

t in

a f

ryin

g pa

n w

ith r

ound

ed s

ides

. e.

g. V

eget

able

s lik

e ca

bbag

e, b

eans

, car

rots,

ca

psic

ums,

onio

ns, s

prou

ts.

Ta

kes l

ess t

ime

Si

mpl

e te

chni

que

M

inim

um o

il is

used

Co

nsta

nt a

ttent

ion

is ne

eded

as

ther

e is

a ch

ance

of s

corc

hing

or b

urni

ng.

111

Coo

king

met

hods

M

erits

D

emer

its

MO

IST

HEA

T M

ETH

OD

S D

irec

t ste

amin

g

Don

e in

an

ordi

nary

ste

amer

or

by p

uttin

g fo

od i

n a

met

al s

ieve

ove

r a

pan

of b

oilin

g w

ater

and

kee

ping

it

cove

red.

e.g

. Ca

bbag

e,

fish,

idli,

dho

kla,

pea

s, be

ans,

carro

ts.

Indi

rect

stea

min

g St

eam

ed b

y ha

ving

the

food

in a

cov

ered

dish

pla

ced

in s

team

or

ove

r boi

ling

wat

er. e

.g. S

team

ed p

uddi

ngs a

nd c

usta

rds.

Le

ss c

hanc

e of

bur

ning

The

text

ure

of f

ood

is be

tter

as i

t be

com

es

light

and

fluf

fy. E

g. Id

li.

Co

okin

g tim

e is

less

Fuel

was

tage

is le

ss.

St

eam

ed f

oods

con

tain

less

fat

and

are

eas

ily

dige

sted

Nut

rient

loss

is m

inim

ised.

St

eam

ing

equi

pmen

t is r

equi

red.

Lim

ited

to th

e pr

epar

atio

n of

sele

cted

food

s.

Pres

sure

Coo

king

To

coo

k fo

od u

sing

wat

er o

r oth

er li

quid

in a

se

aled

pot

, no

rmal

ly a

pre

ssur

e co

oker

e.g

. A

lmos

t all

type

s of f

oods

Co

okin

g tim

e is

less

co

mpa

red

to

othe

r m

etho

ds.

N

utrie

nt a

nd fl

avou

r los

s is m

inim

ised.

Cons

erve

s fu

el a

nd ti

me

as d

iffer

ent i

tem

s ca

n be

coo

ked

at th

e sa

me

time

Le

ss c

hanc

e fo

r bur

ning

and

scor

chin

g.

Co

nsta

nt a

ttent

ion

is no

t nec

essa

ry.

Th

e in

itial

inve

stmen

t may

not

be

affo

rdab

le to

ev

eryb

ody

K

now

ledg

e of

the

usag

e, c

are

and

mai

nten

ance

of

coo

ker i

s req

uire

d to

pre

vent

acc

iden

ts

Care

ful w

atch

on

the

cook

ing

time

is re

quire

d to

pre

vent

ove

rcoo

king

.

Stew

ing

Cook

ing

in a

cov

ered

pan

usin

g on

ly a

smal

l qu

antit

y of

liqu

id w

hich

is k

ept s

imm

erin

g.

e.g.

Che

ap c

uts

of m

eat,

toug

h or

und

er-ri

pe

mea

t, fru

its a

nd v

eget

able

s.

Lo

ss o

f nut

rient

s is

avoi

ded

as th

e w

ater

use

d fo

r coo

king

is n

ot d

iscar

ded

Fl

avou

r is r

etai

ned.

Ti

me-

cons

umin

g

W

asta

ge o

f fue

l.

Boili

ng

Boili

ng i

s a

met

hod

of c

ooki

ng f

oods

by

just

imm

ersin

g th

em in

the

wat

er a

t 100

0 C

and

mai

ntai

ning

th

e w

ater

at

th

at

tem

pera

ture

unt

il th

e fo

od i

s te

nder

. e.

g.

Rice

, egg

, dal

, mea

t, ro

ots

and

tube

rs a

re

cook

ed b

y bo

iling

.

Si

mpl

e m

etho

d

U

nifo

rm c

ooki

ng c

an b

e ac

hiev

ed.

Co

ntin

uous

exc

essiv

e bo

iling

lead

s to

dam

age

in th

e str

uctu

re a

nd te

xtur

e of

food

.

Loss

of h

eat-l

abile

nut

rient

s suc

h as

Vita

min

s B

and

C if

the

wat

er is

disc

arde

d.

Ti

me-

cons

umin

g

Lo

ss o

f col

our –

wat

er-s

olub

le p

igm

ents

may

be

lost.

C

OM

BIN

ATI

ON

MET

HO

D

Brai

sing

A

com

bine

d m

etho

d of

ro

astin

g an

d ste

win

g. e

.g. v

ario

us m

eats

and

vege

tabl

es.

Food

pr

epar

atio

ns

prep

ared

by

co

mbi

natio

n m

etho

ds a

re U

pma

-Roa

sting

and

boi

ling.

Cut

let -

Boili

ng a

nd d

eep-

fryin

g. V

erm

icel

li pa

yasa

m -

Roas

ting

and

simm

erin

g.

112


1. Enlist various purpose/objectives of cooking food? ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. What are the methods of cooking involved in the preparation of: a. Dosa --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- b. Cutlet --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- c. Brinjal bharta --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- d. Potato paratha ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3. Differentiate between: a. Direct and indirect steaming ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

b. Roasting and baking --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- c. Shallow frying and deep-frying ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

SUMMARY Cooking makes food tastier and more digestible. It improves the bioavailability of nutrients and makes the food safer for consumption. There are various methods of cooking food; some are moist methods while some used dry heat. Some of the moist heat methods are boiling, steaming, pressure-cooking, and stewing. Dry heat methods include baking, roasting and grilling/broiling. Methods in which oil is used as the medium of cooking are sautéing, shallow fat frying and deep-fat frying. However, a combination of methods may be used for cooking food.

113

KEYWORDS Broiling- it is same as grilling. Poaching- simmering food in some liquid (water, stock or milk) Searing- heating the surface of foods like meat to very high temperatures to prevent leakage of juices.

REFERENCES B. Srilakshmi. Nutrition Science. New Age International (P) Ltd Publishers 2016 (Fifth Edition)

114

LESSON 8

ROLE OF FOOD GROUPS IN COOKERY

Apart from having nutritional role/ function in the diet, the different food groups have their uses in cookery which are derived principally from their distinct physical properties.

Role of cereals in cookery

o Cereals form the staple diet as they are inexpensive and contribute to most of the calorie and protein in the diet.

o Cereals along with pulse improve the quality of protein by mutual supplementation.

o Also provide good amount of starch and B vitamins. o Cereals also contribute to satiety and are used to prepare the main dish. Meal is

incomplete without cereals. o As a thickening agent, e.g., corn flour in custards, rice flour in pulusu, vermicelli

in payasam, colour in white sauce, macaroni in soups. o As a coating agent, e.g. bread crumbs in cutlets or maida paste in cutlets o As a beverage, e.g. malted beverage. o As desserts, e.g., rice kheer, wheat halwa. o Used in making easy to cook products like macaroni, corn flakes and rice flakes o Cereals are used as covering for stuffing samosas, puran polis o Breakfast foods or snacks made for cereals from fermentation e.g., idli dhokla.

Role of pulses in cookery

o Rich source of protein and B vitamins. o Improve the quality of cereal protein by mutual supplementation. o Due to high proteins and fibre content pulses give satiety. o Improves consistency and flavour of dal, sambhar and rasam. o Used in fermentation preparation example idli and dosa. o Used in snacks like sundal, bajji, pani puri and bhel puri. o Used in salads, e.g. sprouted pulses o Used in desserts and sweets like paruppu payasam and besanladduorburfi. o Thickening agent and prevent curdling, e.g. bengal gram flour in kadhi. o Stuffing agent -poorna burelu, dal kachori. o Parched pulses are used in making chutneys and chutney powders. o As seasoning - in curries.

Role of nuts/oilseeds in cookery

Nuts and oilseeds are used in cookery as a whole, halved, flaked, ground or desiccated form.

a. As healthy snacks- fresh, raw, roasted or boiled or salted forms and also fried forms.

115

b. Thickening agents- Coconut, poppy seeds and cashewnuts in the preparation of gravy.

c. In making chutneys, e.g. groundnut and coconut. d. Sweets like chikki, burfi, kozhukattai, cashewnut cake are made from nuts. e. Oil is used as a cooking media for frying and seasoning. Oil is also used as

preservative in pickles. f. Nut powders like groundnut are used as chutneys and salad dressing. g. Used in desserts e.g. badam kheer, ice-creams, cakes, pastries, payasams and

chocolate. h. Peanut butter is used as a topping on the bread or as a side dish along with

chapatis. i. Oilseed cakes are used as weaning food or as thickening agents in vegetables like

capsicum. j. Nuts are used as garnishing material-raw, roasted, salted or boiled forms.

Role of milk in cookery a. Adds nutritive value (proteins and energy) of the diet, e.g. flavoured milk, plain

milk, milkshakes, cheese toast. b. Adds taste and flavour to the product, e.g. milk in tea, payasam, coffee. c. Thickening agent alongwith starch, e.g. cream soups or white sauce in pasta. d. Desserts, e.g. puddings, ice-cream. e. Leavening agent-to improve the texture, e.g. Curd or butter milk in bhatura,

dhokla. f. Marinating agent- Curdfo marinating chicken and meat. g. Souring agent- curd in rava dosa, dry curd chillies. h. Binding agent- Khoain carrot halwa. i. Milk and curd increase shelf-life of poories, preserve better when the dough is

mixed with milk/curd. j. To prevent browning in vegetables, e.g. buttermilk is used for preventing

browning when plantain stem is cut. k. Adds variety, e.g. buttermilk sambhar, avial and mutter paneer. l. Garnishing agent- Cheese m. Clarifying agent- in sugar syrup. n. Salted buttermilk is used for quenching thirst.

Role of egg in cookery a. Eggs are used as boiled, scrambled or poached for table use. b. Thickening agent-stirred custards and baked custards, soups, puddings. Help in gel

formation. c. Emulsifying agent-mayonnaise, ice-cream. d. Leavening agent – cakes, foamy omelette, soufflés, and meringue. Egg white foam

used in certain candies also improves the texture by controlling the crystallisation of sugar.

e. Binding and coating agent- cutlet, French toast or Bombay toast, banana fritters. f. Interfering substances – ice-creams. Beaten egg white act as the interfering

substance in frozen desserts. Tiny bubbles of air trapped in egg prevent ice crystals from coming together and creating large masses of icy material.

116

g. Clarifying agent- raw eggs can be added to hot broths and coffee. When protein in egg coagulates they trap the loose particles in liquid and clarify it.

h. Garnishing agent – hard-boiled eggs are often diced and used to garnish dishes. i. Flavouring agent-custards. j. Enriching agent- to enrich the nutritive value e.g. Bombay toast. k. Glazing agent – for pastries to give the surface a golden brown colour when

cooked. l. Improve colour – custards.

Role of Sugar in cookery Apart from making some foods more palatable and providing calories it also contributes to food’s appearance, texture and shelf-life. Some of the important roles sugar plays are:

a. Provides bulk, density, and viscosity– it contributes to the texture of food, example in meringue and biscuits. It provides viscosity in beverages and foods like syrups, chutneys and sweet sauces.

b. As a preservative- It reduces the water activity, and makes water inaccessible for use by microorganisms, which reduces microbiological activity in foods and beverages. Thus foods with high sugar concentration like jams, squashdo not need to be refrigerated. It also increases the shelf life of foods by acting as a humectant.

c. Enhancing flavour – Sugar makes food more appetising and also enhances fruit flavours in foods such as sour fruits (frozen berries), or porridge.

d. For colour– Sugar breaks down to produce the colour and caramel flavour on heating. This is caused by non enzymatic reaction between reducing sugars with amino acids (proteins), called as Maillard reaction. Sprinkling of powdered sugar on muffins gives a nice texture and appeal.

e. As an anticoagulant – Sugar delays the coagulation of proteins when heated, example baked custards and other desserts.

Role of fats/oils in cookery

a. As a medium of cooking Fat is used in deep or shallow frying. It is a good heat transfer medium than air and water as it heats up very quickly because of its greater specific heat, and its operating temperature of about 200◦ C is considerably higher than that of water. It provides the characteristic colour, flavour and texture of fried food. Pan-frying is used to cook dosas, chapatis, cutlets and tikkis. Deep fat frying is used in preparing pooris, vadas, cutlets and pakodas.

i. Fat improves the texture of foods It helps in the proper development of textures in cakes, cookies etc. Help in leavening/creaming

Leavening agent is substances used for the expansion the dough by the release of the gases (made from the main ingredients containing gluten). Fat, also build up a air

117

pockets to enclose air if beaten with a paddle,. This aeration, or creaming ability, is important for baking of a cake. Better the creaming ability, the lighter will be the cake. As a shortening agent / tenderizing agent

It helps to shorten the baked products which are merely solid masses firmly held together by gluten strands. For smoothness Fat has textual effects on ice creams and frozen desserts as they limit the

size of water crystal and maintains the smooth texture. It also prevents crystallisation of sugar example halwa. It prevents lump formation and brings smoothness example pulao or upma It also forms emulsions in mayonnaise and gives smooth texture.

ii. Improves palatability

It gives taste and flavour to the food. Fats like ghee also improve flavour and reduce pungency. Butter on bread also improves its palatability.


1 Define the following a. Leavening agent

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

b. Sugar in peventing cystallisation

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

c. Maillard reaction ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2 Explain how fat improves the texture of foods ? ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

SUMMARY Apart from having nutritional role/ function in the diet, the different food groups have their uses in cookery which are derived principally from their distinct physical properties.

REFERENCES B. Srilakshmi. Nutrition Science. New Age International (P) Ltd Publishers 2016 (Fifth Edition) https://www.srasanz.org/sras/basics-sugar/functionsuses-food/

118

LESSON 9

EFFECT OF COOKING ON FOOD COMPONENTS INTRODUCTION A number of changes occur in food during its preparation. To obtain acceptable food products, it is necessary to understand and manipulate these changes. Basically, the change is the net result of the changes of various components of food viz. its nutrients like carbohydrates, fats, proteins, their derivatives and water. In addition changes occur due to various inorganic, mineral components and a number of pigments, flavour components, vitamins, acids, enzymes etc. OBJECTIVES Identify various factors affecting the colour of plants pigments. Recognise the influence of cooking on texture, flavour and taste of food. Understand the effect of cooking on nutrients.

The changes which occur in food as a result of cooking are as follows: A. Colour Colour factors in food such as anthocyanins, carotenoids, chlorophyll etc, are affected by heat. In addition to heat, the acidity or alkalinity of the cooking medium, oxygen and presence or absence of metals, also contribute to colour changes when heated. In some cases, the colour changes that take place in food on cooking are desirable (as in baking) while in some other cases the changes may be undesirable (as in the prolonged cooking of cabbage). The cooking condition should be so organized as to obtain the desired colour qualities in the cooked food. Chlorophyll is the green pigment present in green plants, is not much affected by the heat. The colour of the green leafy vegetables is changed to olive green and then to the brown in the long run, especially when the medium of cooking is acidic i.e. in the presence of little vinegar or lemon juice. On the other hand cooking in the presence of baking soda i.e. in an alkaline medium, the colour intensifies or becomes bright green such bright colour look better in appearance, but cooking in an alkaline medium destroys vitamin C and the thiamine content of the food. To maintain the good colour of green leafy vegetables, it is advisable to cook them uncovered or leaving the pan uncovered for the first few minutes of cooking. Carotenoids- This is the yellow-orange colour pigment found in yellow, orange and red coloured vegetables and fruits, like papaya, carrot, tomato and green leafy vegetables etc. this pigment remains unaffected by heat or acidic medium but turns slightly blue in alkaline medium. Thus, the colour of the vegetables and fruits containing carotene remains unchanged on cooking.

119

Anthocyanins- This pigment is responsible for the red, magenta or purple colour of vegetables and fruits. It is found in black carrots, jamun, phalasas, beetroot, skin or brinjal etc. The heat has no marked effect on this pigment, and however, cooking in the acidic medium makes it lighter in colour, whereas in the presence of alkaline medium it turns to a bluish tinge. Flavones- This is the white pigment present in vegetables like potato, cauliflower, onion etc. This is also not much affected by heat or acidic medium, only alkaline medium makes it turn yellowish in colour. The effect of various factors (solubility in water, acid, alkali and prolonged heating) is summarized in Table 9.1

Table 9.1 Effect of various factors on the colour of plant pigments Name of the

pigment Colour Solubility

in water Effect of

Acid Effect of

alkali Effect of

prolonged heating

Chlorophyll Green Slightly Changes to olive green

Intensifies green colour

Olive green

Carotenoids Yellow and

Orange

Slightly Little effect

Little effect Little effect unless excessive which

may darken

Anthocyanins Red Slightly soluble

Stable (red)

Purple or blue

Little effect

Flavones White Very soluble

White Yellow Darken if excessive

Thus we see that usual cooking medium generally does not alter the natural colour of vegetables and fruits, but if cooked in acidic or alkaline medium, it can be adversely affected. Hence we should avoid the use of any acid or alkali during cooking. Apart from these characteristic changes in the colour of fruits and vegetables, there are also marked significant differences in the colour of other foodstuffs before and after cooking. For example, meat becomes brownish in colour from its original pinkish red, preparations from wheat flour attain a brownish colour on cooking, sugar syrup turns golden brown and finally dark brown in colour, as it is heated more and more. B. TEXTURE Cooking in general influences the texture of all foodstuffs. The cellulose present in them becomes softer and this makes the foodstuffs also softer, for example, cooked vegetables are much softer than raw. Cooking in an alkaline medium softens the cellulose much

120

faster and gives the foodstuffs a mushy appearance whereas cooking in an acidic medium makes the texture hard and such foodstuffs have to be cooked for a longer period. The starch granules present in the raw foodstuffs get gelatinised in the presence of moist heat i.e. when they are cooked in the presence of water, they absorb water and swell up, thus becoming softer and softer and finally, some granules even burst and release the starch into the medium. This makes the foodstuffs easily digestible. Such changes are seen in cooking of pulses, rice, potatoes etc., as they are rich in starches. On cooking, proteins get coagulated, for example egg white, but if overcooked they can become hard and over-cooking also renders the proteins indigestible. The texture of the food, after cooking, is also dependent on the method which is used for cooking. All the moist heat methods i.e. boiling, steaming, pressure cooking and stewing makes the foodstuffs soft and tender. For example, the texture of cooked rice and pulses is soft and tender, as compared to their raw state. Frying and roasting usually give a crisp texture to the foodstuffs. Similarly, baking and grilling also make the foodstuffs soft and give them some crispness. C. FLAVOUR AND TASTE The natural flavours and taste of the food are somewhat changed after cooking. However, the flavour and taste can be made to cater to one’s taste buds with the help of appropriate spices and condiments. The spices and other flavouring agents used while preparing food and combination of the natural flavours and taste of the foodstuffs imparts a characteristic flavour and taste to the cooked food. The use of fat brings tenderness in texture of cakes and biscuits and frying makes the food crisp. Flavour is sensed by taste and smell, the two sense organs of the body. Good flavoured food encourages the formation of saliva in mouth which is helpful in digesting food. D. NUTRIENTS Carbohydrates: Starch, sugar, gums, cellulose is important carbohydrate found in foods. On cooking the starch granules in foods swell as they absorb water. This process is called gelatinization and is, in fact, the reason for the thickening of soups, curries, stews to which cornflour paste is added. Gelatinization takes place in all starch-containing foods such as potatoes on heating in the presence of moisture. Dry heat causes the starch to break down into smaller molecules called dextrins. For example, in the toasting of bread and making of chapattis. Dextrin has a mildly sweet flavour. Sugar on heating forms syrup with water. On further cooking syrup thickens and changes colour. This is due to a process called caramelization. The brown, thick liquid formed is called caramel and is used in a number of preparations such as custard, cakes. Ordinary cooking causes little loss of carbohydrates. Cellulose is not digested by humans but becomes softer on cooking and is helpful in smooth movement of food through digestive tract.

121

Proteins- Proteins harden and solidify or coagulate on cooking. The liquid sets on heating and becomes solid. This is the process of coagulation. However, milk protein is an exception. Unlike other proteins, it does not coagulate. It is important to cook proteins to the right extent because proteins shrink and becomes harder on overcooking. This also renders them dry and rubbery which is indigestible. Excessive heating of foodstuffs also affects the nutritive value of proteins. Sugars like glucose and lactose form complexes with amino acids like lysine. These complexes cannot be broken down by the protein-digesting enzymes. The result, of course, is that these amino acids are no longer available to the body. Some pulses like soybean and Bengal gram contain certain substances which hinder the digestion of the proteins of these foods by the enzyme trypsin present in our intestines. During cooking these trypsin inhibitors are destroyed. This is why it becomes important not to consume these foods raw. In fact, the digestibility of protein in several foods improves as a result of moderate heating in day to day cooking. Fats & Oils- Ordinary cooking has no effect on fat, but prolonged heating, as in the case of frying for long periods thickens and darkens the fat. A part of essential fatty acids present in fat is destroyed and toxic polymerized products are formed. These changes are accompanied by changes in flavour also, which may not be acceptable. Fats and oils become rancid by action of air (oxidized), water (hydrolysis) and enzymes. These changes must be minimized so that the food in which fat is used remains acceptable. Minerals- There is no loss of minerals in normal cooking procedures. If cooking water is discarded water-soluble minerals may be lost. Vitamins- Thiamine and vitamin C are two vitamins, which are most affected by cooking. The losses may occur due to dissolved nutrients being discarded or destruction due to exposure of heat in cooking. The amount depends on the combination of these factors. Discarding the cooking water accounts for a loss of nearly 20-25 percent of thiamine, depending on the quantity of water used in cooking. If sodium bicarbonate is added to pulses during cooking, most of the thiamine is destroyed. Vitamin C is the most liable vitamin lost during washing vegetables after cutting, exposing cut vegetables to air for long periods before cooking and/or serving and leaching of vitamin C in the cooking water which is later discarded. There may be a loss of 10% to 60% depending on the vegetables cooked and the method of cooking used. Loss of riboflavin during cooking occurs in four ways

o Exposure of the food during cooking to strong light,

o Loss of riboflavin due to heat

o Loss of riboflavin due to leaching by discarding excess of the cooking water

122

o Loss of riboflavin due to addition of cooking soda during cooking of dal and

vegetables.

Bottled milk exposed to strong sunlight losses a part of riboflavin present. Loss of other water-soluble vitamins is mainly due to heat or loss in water.

Vitamin A and Carotene are insoluble in water, so no loss occurs by discarding cooking water. There is slight destruction of vitamin A and carotene during cooking in water due to oxidation by air. Frying, baking, roasting and toasting causes considerable losses of vitamin A and Carotene. LET’S CHECK THE PROGRESS

1. Differentiate between gelatinisation and dextrinization. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. What do you understand by the term caramelization? ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3. Name the colour pigment present and the effect of heat, acid and alkali in the following vegetables: a. Spinach ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ b. Carrot --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- c. Beetroot --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- d. Cauliflower ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

SUMMARY The food contains many nutrient and non-nutrient substances (e.g. colouring and flavouring substances). During food preparation a number of changes occur in food. Some of these changes are desirable whereas some are undesirable, making it essential to understand these changes in order to get the final anticipated product. The changes that

123

occur during the process of cooking involve changes in colour, flavour, texture, taste and nutrients. The critical aspects in cooking that have important bearing on these changes are the extent and duration of heat applied as well as medium of cooking (acidic/alkaline). All these can be manipulated to get the desired product.

KEYWORDS Cellulose- indigestible plant polysaccharide which is an important component of the plant cell wall. Dry heat- heating in the absence of water. Moist heat- heating in the presence of water. Caramelization- When sugar is heated it melts on further heating thick, brown liquid is formed called caramel and the process is known as caramelization.

REFERENCES B. Srilakshmi. Nutrition Science. New Age International (P) Ltd Publishers 2016 (Fifth Edition)

124

LESSON 10 WAYS OF CONSERVING AND ENHANCING NUTRIENTS

INTRODUCTION

Cooked food has its known characteristics—flavour, taste, texture and colour. Apart, from some beneficial effects on the food after cooking, significant amounts of some nutrients particularly vitamins and minerals are also lost during cooking. However, by judicious preparation of foods, these losses can be minimized to a large extent. Not only this, there are certain methods that can enhance the nutrient content of some foods. Food provides the ideal mix of vitamins, minerals, and other nutrients. But the nutrients in foods begin to decrease as soon as the fruit or vegetable is picked and continues to decline until the food is eaten. The sooner you eat the food, the less chance of nutrient loss.

OBJECTIVES

To identify ways of conserving nutrients before and during cooking. Importance of conserving nutrients while cooking Apply the methods of enhancing the nutritive value of foods in daily routine. To suggest measures to minimize nutrient losses during preparation and cooking

food

The cooking of food involves the pre-preparation of food i.e. before actually subjecting it to any heat treatment and the actual cooking of food. Many physical and chemical reactions occur during the processing or preparation of foods. Selection of the right cooking method to maximise the nutritional quality of your meal is the key to healthy eating. There is no perfect method of cooking that conserves all nutrients. Saving nutrients during the process of cooking is called conservation. The ways to conserve nutrients lost during cooking can hence be covered under two heads: 1. Conservation of nutrients lost before cooking 2. Conservation of nutrients lost during cooking

CONSERVATION OF NUTRIENTS LOST BEFORE COOKING

i. Wash the vegetables before peeling and cutting. Washing the vegetables after peeling and cutting results in loss of water-soluble vitamins and minerals, which also get drained out with dirt, dust and other micro-organisms.

ii. Peel vegetables thinly. Potatoes, sweet potatoes and beetroots can be peeled after boiling.

iii. Cut the vegetables only at the time of cooking and not long before cooking, as due to exposure to air, some vitamins are lost.

iv. Cut vegetables into moderate size pieces and not very small, because cutting into a small pieces increase the exposed surface area, thus increasing the losses.

v. Even dry foodstuffs like rice and pulses should not be washed excessively before cooking as the nutrients are leached in water.

vi. Similarly, meats and poultry should not be excessively washed before cooking. vii. Unsifted wheat flour should be used as the bran contains minerals and vitamins.

125

CONSERVATION OF NUTRIENTS LOST DURING COOKING

Cooking methods that minimize the time, temperature, and amount of water needed will help to preserve nutrients. The three R's for nutrient preservation is to reduce the amount of water used in cooking, reduce the cooking time and reduce the surface area of the food that is exposed. i. Always use pressure-cooker to cook food, as it conserves nutrients to the

maximum. ii. Do not cook food in excess water. If there is water left after cooking, then use the

water in some other preparations. For example, rice water can be added to pulses and water left after boiling the vegetables can be used to make soups and curries.

iii. Do not use cooking soda while cooking food, as its use results in loss of vitamins, especially thiamine and vitamin C.

iv. Cook vegetables for the least time. For this add the vegetables to boiling water and cook them covered.

v. Do not fry in overheated fat or oil. vi. Cook food according to the quantity needed, so that it does not get stale. If at any

time cooked food is left, store it at low temperature like in a refrigerator to minimize losses in nutritive value.

vii. Cook the food just before serving, so no reheating is required, as reheating further destroys the nutrients.

viii. Avoid exposure to direct sunlight. ix. Cooking in iron and copper pots can destroy some vitamin C, but it can also add

nutritious iron to the food, especially if the food is acidic. Unlined copper destroys vitamins C and E and folic acid. Cooking utensils made of glass, stainless steel, aluminium or enamel or lined with a non-stick coating have no effect on nutrient content.

x. Do not use baking soda to help keep the green colour of vegetables, as this increases the loss of vitamin C.

Thus adopting the above-mentioned ways in the preparation of food helps to conserve the nutrients which can otherwise be lost. Not only the nutritive value of our diets can be increased by conserving nutrients during preparation, but even the amount of nutrients present in foodstuffs and their availability can be increased by simple technologies. These methods are:

The first two that are – germination and fermentation can be carried out easily at home, but fortification and enrichment is essentially a technology adopted at the industrial level.

Germination Fermentation Fortification Enrichment

126

Germination- Germination is the process, whereby a new plant emerges from the seed, as marked by the presence of growing root and shoot, the nutrition for this new plant comes from the embryo of the seed. Germination can be done for whole cereals and pulses. The process consists of soaking, the pulse or cereals overnight, followed by wrapping them in a moist thin cloth preferably muslin cloth. The pulse/cereal must be kept in a dark and humid place. Water should be sprinkled on the cloth occasionally. It usually takes 12 to 48 hours depending upon the atmospheric conditions. The nutritive value of these germinated grains is increased much fold, as compared to the dried grains. Effect of Germination on nutritive value

1. During the germination process, vitamin C is synthesized in the growing shoot thus resulting in increase in the vitamin C content of germinated cereal or pulses, which otherwise have almost negligible content. For example, 100 grams of whole green gram (moong) has almost no vitamin C content, but after sprouting or germination of 1-2 days the vitamin C content is around 60-80 mg.

2. There is also an increase in the content of the B group of vitamins in these germinated pulses and cereals.

3. Dry pulses and cereals contain certain non-nutritional factors, such as tannins, phytates and trypsin inhibitors. Tannins and phytates hinder in the absorption of iron and calcium in the body, trypsin inhibitors prove to be an obstacle in the utilization of proteins. All these non-nutritional factors are destroyed to a large extent on germination, thus increasing the availability of the nutrients present in them. Destruction of phytates, tannins and increase in vitamin C content by germination, in turn, promotes absorption of iron in the body.

4. Germinated cereals and pulses are more easily digestible. Consumption of whole pulses results in flatulence in some individuals, which can thus be overcome by consuming germinated pulses.

5. Digestibility can be increased as complex substances are converted to simple substances e.g. starch to amylase.

6. Availability of proteins and amino acids is increased. 7. Germinated pulses can be easily incorporated in our daily diet in a number of

ways. They can be eaten raw, as chaat or in salads or can be used in different preparations, such as stuffed paranthas, tikkis, cutlets,pulao, raita etc.

Fermentation - Fermented food products are quite popular in all over the world. In India also preparations like idli, dosa, dhokla, uttapam, bread, naan, curd etc. are all examples of fermented food preparations. Fermentation is a process in which some micro-organisms are added to the food. They change nutrients already present in the foods into simpler and better forms and also make other new nutrients. For the fermentation process to initiate, some kind of microorganisms (like bacteria or yeast) are needed which are either present naturally in the foodstuffs or can be introduced artificially, like yeast.

127

These microorganisms then act on complex carbohydrate and cause their break down into simpler carbohydrates which are further broken down to ultimately release carbon-dioxide. The fermentation process is thus marked by the production of carbondioxide which helps to rise and increase the volume of food product, hence making it lighter. Fermented foods also have a typical sour taste.

Effect of fermentation on nutritive value

1. Fermentation results in an increase in the content of vitamin of B-group especially thiamine, riboflavin and niacin.

2. It also results in the destruction of phytates and trypsin inhibitor, thus increasing the availability of other nutrients like iron, calcium and proteins.

3. The resultant product is light and easily digestible as fermentation break down the indigestible protective coating and cell wall both physically and chemically, making the structure more permeable to the water of cooking as well as to man’s digestive juices.

4. Texture and taste are improved. 5. Quality of protein is improved as availability of some amino acids increases. 6. The shelf life of food product can be prolonged e.g. milk is converted to curd.

Fortification– Fortification signifies the addition of a specific nutrient to a food product which is lacking in the foodstuff or is present in limited amounts. For example, common salt is fortified with iodine, bread is fortified with lysine to enhance its protein utilization. Similarly, vanaspati is fortified with Vitamin A and Vitamin D.

As evident from the above examples fortification is usually done in such foodstuffs which are consumed commonly by people so as they can avail of its beneficial nutritional effects. Thus, fortification is a very important method to increase the nutritional value of foodstuffs. Enrichment - Another process, similar to fortification is enrichment. Enrichment means the addition of such nutrients to foodstuffs which were originally present, but they are lost in the processing. For example, certain nutrients which are present in whole wheat are lost in the processing of wheat into flour, particularly refined flour which is used for making bread. Thus, bread does not have these vitamins present in it, but it can be enriched with vitamins of B-group i.e. they can be added artificially during the process of bread making, thus making it more nutritious. Thus, both germination and fermentation process has beneficial effects on the nutritive value of food and can be easily carried out at the household level. Fortification and enrichment can only be carried out at industrial level.

LET’S CHECK THE PROGRESS 1. How is the germination of pulses beneficial?

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

128

2. Explain the advantage of fermenting food products. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3. Differentiate between fortification and enrichment. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

SUMMARY

By taking proper care during the preparation of foodstuffs the nutrients present in them can be conserved at a large extent. Use of simple household methods like germination and fermentation can further enhance their nutritive value and these can be easily carried out at household level without incurring any extra expenditure. The food thus prepared will not only be more nutritious, but also more interesting and tasty. Food fortification is being used as a cost-effective measure in overcoming micronutrient deficiencies. KEYWORDS Tannins- Polyphenolic biomolecule that binds to and precipitates proteins and various other organic compounds. Phytates- Compounds occurring in plants, especially cereal grains, capable of forming insoluble complexes with calcium, zinc, iron, and other nutrients and interfering with their absorption by the body. Trypsin inhibitors- Trypsin is an enzyme involved in the breakdown of proteins, thus important for digestion of proteins in humans and other animals. A trypsin inhibitor is a type of inhibitor that reduces the biological activity of trypsin.

REFERENCES B. Srilakshmi. Nutrition Science. New Age International (P) Ltd Publishers 2016 (Fifth Edition) http://www2.ca.uky.edu/HES/fcs/factshts/FN-SSB.006.PDF

discipline specific core course fundamentals of nutrition

Documents