Subject: Leaving Certificate Home Economics Teacher: Ms Tracy McDonagh Week: Week 4 Lesson: Lipids & Fats and Oils

Carbohydrates & Cereals Homework Questions Corrections

2016 Q1. Section B. b) Suggest three strategies to increase the intake of dietary fibre in order to meet the European Food Safety Authority (EFSA) recommendation. (12)

(c) Evaluate the benefits of a diet rich in fibre. (15)

(d) Name and give an account of one bowel disease. Refer to symptoms / effects. (9)

b) 12 marks = 3 points @ 4marks each

1. When preparing breakfast choose wholegrain options such as wholewheat toast with scrambled eggs or include kiwis and apples with their skins on in smoothies. It is important to check on packaging of breads if it has a minimum of 3g of fibre per 100g to be a source of fibre or 6g per 100g to be in high in fibre. 2. Another strategy to increase fibre intake would be to include seeds such as sunflower seeds, sesame seeds, pumpkin seeds and linseeds. They can be eaten whole or milled and you should aim to get 2 tablespoons of seeds each day. They could be added into breakfast cereals e.g. porridge, sprinkled yoghurt, used in homemade bread or sprinkle then over lunch salads. 3. Switching from white pasta and rice to brown rice or pasta will also help to boost fibre intake daily for example with spaghetti bolognese or in pasta salads.

c) 15m = 3 points @ 5marks each

1. A diet rich in fibre is important as it absorbs water as it passes through the intestinal tract helping peristalsis. This is beneficial to the body as it speeds up the passage of food and waste, preventing bowel disorders like constipation.

2. Fibre is also important for giving a feeling of fullness which helps to prevent snacking and maintaining a healthy weight, for example porridge for breakfast will keep you fuller for longer than white toast or no breakfast where you might end up snacking on high sugar foods.

3. Fibre is also important as it helps waste passes through the digestive system more quickly which allows less time for the development of toxins in the body and bowel which can lead to the development of certain cancers .

Name Account Symptoms

Diverticular Disease

Small pouches develop in the walls of the intestine. They

fill with food waste, bacteria and gases that inflame

diverticula.

Pain & discomfort. Bloating

Some blood loss in stools. If severe it may lead to

anaemia.

d) 9m = name = 1m account =4m symptoms = 2 points @ 2m each

2013 Q4. Name three types of flour and suggest a different culinary use for each. (6m) 2% of the paper

Type of Flour Culinary use

Wholemeal flour Brown bread

Gluten free flour e.g. rice flour

coeliac products e.g. gluten free banana bread

Strong flour Pizza dough / bread

2008

Q5. Name three cereals grown for food production and give one example of a different product manufactured from each cereal. 6m (2% of the paper)

Cereals Products

Wheat Flour, pasta, bread

Maize Cornflakes

Rice Rice cakes

• Elemental composition and chemical structure of lipids • Classification of fatty acids • Distribution of saturated, monounsaturated and polyunsaturated fatty acids in

food. • Essential fatty acids (EFA’s), omega 3 fatty acids and CIS and TRANS fatty

acids. • Classification of lipids by source • Properties, biological functions, RI and energy value of lipids • Digestion of lipids • Classification, average nutritional composition of fats & oils • Manufacture of vegetable oils & margarine • Types of margarine & culinary uses of fats & oils.

Learning Intentions

Lipids Lipids are one of the MACRONUTRIENTS. They provide a concentrated source of energy.

The term ‘lipid’ refers to both

• fats (solids at room temp) and • oils (liquid at room temp).

Lipids last appeared on the 2013 paper on Q1. *Short questions are very popular with lipids. Due an appearance soon as Q1. Section B. Parts of Lipids that have not be examined recently include: >Properties >Biological functions >Essential fatty acids >Cis and Trans fatty acids (polyunsaturated fatty acids)

Exam paper Appearance

*Lipids contain the elements Carbon, Hydrogen and Oxygen.

*They are composed of TRIglycerides. A Triglyceride contains: One glycerol molecule and 3 fatty acids.

Lipids are classified into 3 main groups: 1. Saturated fatty acids

2. MonoUNsaturated fatty acids

3. PolyUNsaturated fatty acids

Classification of Lipids

Saturation refers to the

amount of hydrogen

1. Saturated Fatty Acid NO DOUBLE BONDS = Each carbon has its full quota

of hydrogen atoms

Methyl group (CH3)

Carboxyl group

• Solid @ room temperature • High melting point • Generally found in animal sources • E.g. Stearic acid in meat & Butyric acid in butter • Increases cholesterol levels

2. Monounsaturated fatty Acid

Carboxyl group

Methyl group (CH3)

• Each structure is not fully saturated with a full quota of hydrogen atoms. • There is ONE double bond = between the carbon atoms. • Soft or liquid at room temp (18ºC ) • Low melting point • Generally found in plant and marine sources • E.g. Oleic acid in olive oil

ONE DOUBLE BOND =

3. Polyunsaturated Fatty acids More than one DOUBLE BOND =

Carboxyl group

Methyl group (CH3)

• Each carbon atom is not fully saturated with a full quota of hydrogen atoms. • There is more than one double bond between the carbon atoms. • Soft / liquid at room temperature (18ºC) • Lowest melting point of all the fatty acids. • Generally found in plant & marine sources. • E.g. Linoleic acid in nuts + linolenic acid in seeds

Cis & Trans Fatty AcidsIn Polyunsaturated fatty acids, the hydrogen atoms in the chemical structure can be arranged in TWO ways.

*Have Two hydrogen atoms on the same side of the double bond (either above or below)

*Most naturally occurring unsaturated fatty acids are CIS FATTY ACIDS.

*Found in all foods containing fat or oil.

*Generally good for health as they increase HDL while lowering LDL decreasing the risk of CHD.

Have Two hydrogen atoms on the opposite sides of the double bond

Formed from CIS fatty acids during the heating or frying of oils at high temperatures and during processing e.g. the addition of hydrogen atoms to oil to produce hard margarine

Also found in foods that contain hydrogenated fats e.g. pastries & crisps *Lower HDL levels while increasing LDL therefore increasing chance of CHD.

ESSENTIAL FATTY ACIDS

*Essential fatty acids (EFA’s) must be obtained from food as our bodies

cannot manufacture them.

*Linoleic acid (omega 6) and alpha-linolenic (omega 3)

are both EFA’s as they cannot be made by the body.

SOURCES of EFA’s: Nuts, seeds, olive oil, oily fish

FUNCTIONS of EFA’s: *Aid cell formation essential for growth

*Reduce the risk of CHD by raising HDL which helps remove cholesterol from the blood, and lowering LDL which deposits cholesterol in the blood.

Omega 3 fatty acids Have a double bond between the 3rd and 4th carbon atoms along their

hydrocarbon chain.

Functions of Omega 3 fatty acids: *reduces the risk of CHD, heart attacks and strokes by raising HDL and lowering LDL. *Increases the viscosity of blood, preventing clots or blockages in the coronary arteries. *Aids foetal brain development during pregnancy as well as helping improve memory and cognitive functioning throughout life.

Classification of Lipids by source:

ANIMAL Mainly saturated

Meat, meat fats, butter, cream, cheese, egg yolks

& milk

PLANT: Mainly unsaturated Vegetable oils, nuts

and nut oils, avocados, olives, soya beans

MARINE:Oily fish and fish liver oils

~Biological functions of Lipids~ >Lipids provide the body with heat and energy.

>Excess lipids are stored as adipose tissue and provide the body with

insulation.

>Lipids provide the body with fat soluble vitamins A,D,E,K.

>Lipids provide essential fatty acids e.g. omega 3 fatty acids.

Properties of Lipids 1. Lipids are insoluble in water. 2. Lipids absorb flavours quickly e.g. butter left unwrapped in the fridge will absorb

flavours from other foods 3. Effect of heat on lipids:

Melting point Smoke point Flash point

Solid fats melt when heated to

30-40ºC.

If lipids are heated to 200ºC (fats) or 250ºC (oils) they begin to

decompose, causing the glycerol to separate from the fatty acids.

Glycerol is then broken down into acrolein and produces a blue smoke

and an acrid smell.

Extreme overheating of lipids to 310ºC (fats) and 325ºC (oils) causes a vapour to be

emitted that can spontaneously ignite.

4. Rancidity - refers to the spoilage of lipids and can happen in 2 ways: 1. Oxidative rancidity: occurs when oxygen in the air reacts with the carbon atoms of a double bond in an unsaturated carbon chain. Antioxidants such as Vitamin C and Vitamin E prevent rancidity by reacting with oxygen in the air and thus making it unavailable.

2. Hydrolytic rancidity - caused by reaction of enzymes or micro-organisms with the lipid. The enzyme lipase hydrolyses the lipid, breaking it down into its component parts glycerol and fatty acids.

5. Hydrogenation: Used in the manufacture of margarine and cooking fats. -Using nickel as a catalyst, hydrogen (H2) is added to the unsaturated fatty acid. -This converts the unsaturated fat into a solid saturated fat. -The double bond is broken and the hydrogen attaches itself to the carbon atoms.

6. Emulsions: Oil and water will not dissolve into one another. An emulsion is where you force them to stick together without separating. >Two types of emulsions: Temporary and Permanent 1. Temporary emulsion - if oil and water are vigorously shaken together the oil will disperse into the water for a short period of time before separating again due to its instability.

2. Permanent emulsion - a third substance is required known as an emulsifier. An emulsifier lowers surface tension between the oil and water. It contain two parts: hydrophilic (water loving) and hydrophobic (water hating) tail. The hydrophilic part attaches itself to the water and the hydrophobic attaches itself to the oil. This stabilises the mixture and prevents it from separating. Lecithin is a natural emulsifier found in egg yolks and is used in the manufacture of mayonnaise.

Digestion of Lipids

- Hydrolysis breaks down the triglyceride into its basic parts - glycerol and three fatty acids

- The liver produces bile salts which emulsify (break down) the lipids.

- The enzyme lipase which is produced in the pancreas aids hydrolysis

- Intestinal lipase continues the breakdown of lipids into fatty acids & glycerol.

Hydrolysis is the opposite to condensation

Organ Secretion Enzymes Substrate Product

Liver Bile Large fat molecules

Emulsified fat (small molecules)

Pancreas Pancreatic juice Lipase Lipids Fatty acids and glycerol

Small intestine

Intestinal juice Lipase Lipids Fatty acids and glycerol

Exam Paper Questions Lipids

2016 Section A. Q2. State one function of omega 3 fatty acids in the diet.

Name two different food sources of omega 3 fatty acids. i) ii)

2015 Section A. Q4. In relation to lipids explain each of the following: (6)

i) Smoke point

ii) Flash point

2014 Section A. Q2. Complete the following table in relation to the digestion of lipids. (6)

2013 Section A. Q2. In relation to lipids, explain each of the following terms: (6)

i) Oxidative rancidity

ii) Hydrolytic rancidity

2013 Section B. Q1. (b) Identify and give an account of the main factors that are contributing to the prevalence of obesity in Ireland. (16)

(c) Outline the significance of fatty acids in the diet. (8)

(d) Describe the structure of each of the following: -cis fatty acids

-trans fatty acids

-omega 3 fatty acids. (12)

2008 Section B. Q1. (b) Describe the structure and give one example of each of the following:

•saturated fatty acids •monounsaturated fatty acids •polyunsaturated fatty acids. (24)

(c) Write an explanatory note on each of the following properties of lipids:

• rancidity • emulsification. (12)

Fats & Oils

Animal Fats (saturated)

Cream, suet (fat surrounding organs of animals), lard, butter, dripping (fat from roasted meat).

Plant Oils (polyunsaturated) Vegetable oils e.g. olive and corn oil, nut oils e.g. coconut and peanut, seed oils e.g. rapeseed and sunflower seed, margarine (80% vegetable fat and water)

Marine Oils (polyunsaturated)

Cod liver oil and herring oil

Classification of Fats & Oils

• Proteins: Contain trace amounts of HBV protein. • Fat: Fat content varies depending on the type of oil, e.g.

vegetable oil contains 99% unsaturated fat, butter contains 82% saturated fat and dairy spreads contain approx 40% saturated and unsaturated fat.

• Carbohydrates: lack carbohydrates, for this reason fats and oils are usually served with carbohydrate rich foods e.g. bread.

• Vitamins: Butter and dairy spreads contain trace amounts of Vitamin A and D. Margarine is fortified with A and D.

• Minerals: Butter and margarine contain trace amounts of calcium.

• Water: Content varies depending on fat content. Higher the water content the less fat present.

Nutritional value of Fats & Oils

Manufacture of Vegetable Oil

1. Seed Preparation: seeds e.g. rapeseed are prepared by being cleaned,

grinned and crushed through break rollers and heated.

2. Oil extraction: oil is removed from seeds by pressing or by the addition of

a solvent.

3. Refined: oil undergoes a refining process to remove impurities.

4. Bleached: oil is bleached with Fuller’s earth which removes the deep

colour of oil.

5. Filtered: oil is filtered to produce a clear liquid.

6. Deodorisers are added to remove putrid odours.

7. Packaged and labelled in varying sizes.

Manufacture of Margarine1. Oil extraction: oils from various sources e.g. olives and rapeseed are extracted

and refined to remove impurities.

2. Hydrogenated: Oil is hydrogenated by forcing hydrogen gas through the

double bond of an unsaturated oil in the presence of a nickel catalyst. This

converts it into a saturated semi solid fat. This creates the consistency of

margarine.

3. Other ingredients added: skimmed milk or water is added along with salt,

colourings and flavourings. Fortified with vitamin A and D.

4. Emulsification: Lecithin is added to prevent the fat and liquid in the margarine

from separating.

5. Churned: A machine churns the oil and water based ingredients together to

form an emulsion.

6. Weighed: margarine is weighed into retail size portions.

7. Packaged and labelled: packaged into varying materials e.g. plastic or foil.

Types of Margarine

Block Margarine Soft Margarine Made from mainly vegetable oil but can include marine and animal oils.

Made mainly from vegetable oil and is designed to spread straight from the fridge

Wrapped in waxed paper or foil Sold in plastic tubs

Generally high saturated fat content High saturated fat content

Used in baking and frying Used for baking and frying

Culinary Uses of Fats & Oils

Flavour: add flavour to foods e.g. potatoes and

salads

• Frying: Oils are suitable for shallow and deep frying due

to their high burning point e.g.

rapeseed oil

Emulsions: Fats and oils create emulsions when mixed with water and vinegar e.g. mayonnaise.

Aeration: Fats assist the aeration of cakes, as they

entrap air producing a well risen product.

shortening: fat gives a crumbly texture to pastry, cakes and biscuits.