FOOD TECHNOLOGYTechnology in Food Production

COLLOID STRUCTURES Colloid structures are formed when different ingredients are

mixed together. Colloid structures may be evenly mixed or dispersed into one

another in variety of ways.Name of structure

Example of Food Type

First part of structure

With Second part of Structure

Emulsion Mayonnaise Liquid (olive oil)

In Liquid (vinegar)

Foam Beaten egg white

Gas (air bubbles)

In Liquid (egg white)

Solid Foam Meringue Gas (air bubbles)

In Cooked egg white

Gel Jams and Jellies

Liquid (water, juice)

In Solid (fruit)

Suspension White sauce Solid (starch granules)

In Liquid (milk)

EMULSIONS Liquids such as oil and water do not mix, they are said to

be immiscible. When you put two substances together and shake, they

appear to mix but if you leave them to stand they will eventually separate, with the lighter liquid floating on top.

In the Food Industry an emulsifying agent (an additive) is added to thicken the product and stop this separation from happening.

This makes the product stable and fit to sell. Salad dressings are food products made from oil and

vinegar. A Vinaigrette or French dressing is an unstable emulsion

and mayonnaise is a stable emulsion.

FOAMS A foam is created when air is mixed into a liquid. A good example is whisking air into an egg white. The protein ‘albumen’ in the egg white stretches to hold the

air. The egg white has the ability to trap and retain a large

amount of air so the volume increases dramatically. The foam will remain stable providing:- There is no grease on the bowl or beaters of the whisk.- There is no egg yolk mixed in with the egg whites – egg yolk

contains fat. The presence of any kind of oil or fat will prevent the foam from being created.

- Fresh eggs are used and will hold more air at room temperature and not straight from the refrigerator.

- The foam is not over-beaten-over whisking will cause the foam to collapse.

FOAMS CONT.. Foams are used to add egg whites to mousses,

creams and cold desserts. The foam helps to aerate the product and make it

lighter. A solid foam is created when the mixture is cooked

to form a meringue such as a pavlova. This becomes a stable structure.

GELS A gel is formed when large amounts of liquid are set

by small amounts of solid. Fruit contains a substance called pectin which is the

setting agent for jams and marmalades. Different types of fruit contain different amounts of

pectin. Sometimes fruits are combined in the jam to ensure

sufficient pectin is present to create a good set. Gelatine is another solid used to set liquids. It’s

added to make jellies and can be added to cheesecake toppings and other desserts to make the mixture set.

SUSPENSIONS A suspension occurs when a solid is held

suspended in a liquid. The most frequently used is when flour or cornflour

mixtures are stirred into a liquid to make gravy or a sauce.

If the mixture is left to stand the solids sink to the bottom and if heat is applied at this stage a thick lumpy sauce would be made.

To prevent the sauce being lumpy the mixture needs to be well mixed before heating and stirred until it boils and the sauce thickens.

THE EFFECT OF FOOD PROCESSING ON THE NUTRITIVE VALUE OF FOOD

Water Soluble Vitamins:Oxidation Processed Food (cut/diced/chopped): Enzymes released

which catalyse the oxidation of ascorbic acid.Acid will retard the loss of oxidation.Present in small amounts of copper.

Heat When bicarbonate of soda is added during cooking, it prevents chlorophyll loss & keeping its bright colour in fresh vegetable. However will cause vitamin C loss.

Water Extraction Leaching – when vegetables are heated, water leaches the vitamins.

WATER SOLUBLE VITAMINS CONT..B Vitamin Complex This vitamin is mainly found in protein rich

foods such as liver, cheese and yeast.Thiamin B1 This vitamin is destroyed in heat, leaching in

cooking water, alkaline solutionRiboflavin B2 Not as soluble as thiamin and vitamin C but it

is lost by alkaline solutions. Best sources are liver and dairy products. Deficiency: Shown in skin problems such as

cracking skin and mouth.

WATER SOLUBLE VITAMINS CONT..

Pyridoxine B6 This vitamin can be lost via – Heat, light and the

milling process Dermatitis/ Nervous problems and some types of fits

may be caused by deficiency of the vitamin. 1-2mg per day is sufficient for most adults.Pantothenic Acid Vitamin loss can be caused by dry heat, acids and

alkalis.Folic Acid This vitamin can be destroyed by heat (especially in

the presence of oxygen)

FAT SOLUBLE VITAMINS

Vitamin A Prevents night blindness by making a substance

called visual purple. Too much however is poisonous. Vitamin A is stable in cooking and processing but

can be destroyed by oxidation in dried foods.Vitamin E A natural anti-oxidant and is found in lots of face

creams as it makes claims relating to youthful skin. It is lost during processing by oxidation.

LIPIDS, SUGARS AND SALT IN PROCESSED FOODS The methods used for processing foods include

canning, freezing, refrigeration, dehydration and aseptic processing.

While the perception is that processing is always bad, there are some foods that benefit from processing:

Milk – processed, pasteurised and homogenizeFrozen Vegetables – Freezing vegetables preserves

vitamins and minerals and makes them convenient to cook and eat all year round.

Fruit Juice – Some orange juice is fortified with calcium.

LIPIDS, SUGARS AND SALT IN PROCESSED FOODS CONT..Salt About 75% of the salt we eat is already in the foods we

buy, the majority is processed foods.Trans Fats

High dietary intakes of trans fatty acids can increase the risk of heart disease. Trans double bonds are found naturally in small amounts in foods produced from ruminant animals, e.g. Milk, beef and lamb.However, most of the trans fatty acids in the diet are produced during the process of partial hydrogenation (hardening) of vegetable oils into semi-solid fats. They are therefore found in hard margarines, partially hydrogenated oils, and in some bakery products, fried foods and other processed foods that are made using these fats. These can raise LDL cholesterol levels and high intakes can increase risk of heart disease.

LIPIDS, SUGARS AND SALT IN PROCESSED FOODS CONT..Sugar Added sugars include refined sugars such as table sugar

and other lesser known ones such as ‘corn syrup’, ‘maltose’ and ‘hydrolysed starch’.

Processed Meat Several studies have suggested that a high consumption of red and/or processed meat is linked with an increase in risk of colorectal cancer. Processed meat includes meats preserved by smoking, curing or salting, or buy adding chemical preservatives. There has been a lot in the media about processed meats, such as ham and bacon, and cancer risk. Overall studies suggest that eating 50g of processed meat a day (around 2 slices of ham or a slice of bacon) may increase colorectal cancer by around 20%.

FOOD ADDITIVES

1. What are additives?Are chemicals both synthetic and natural, that are

used to give various functional properties to foods. 2. What are the 4 main functions of additives within

foods?It’s physical characteristicsIt’s sensory characteristics, such as flavours/ texture/

coloursStorage lifeNutritional status

FOOD ADDITIVES CONT..

3. What is the significance of an E at the start of an additive’s number?

With an E, it signifies that it is controlled by the EU.4. Why are antioxidants used in foods?To reduce rancidity in fats by either absorbing oxygen/

preventing chemical changes involved in rancidity.5. Give 3 foods containing antioxidants Ascorbic Acid (E300) – fruit drinksPropyl Gallate (E310) – Vegetable oils & chewing gumButylated Hydroxyanisole (E320) – Cheese spreads,

stock cubes.

FOOD ADDITIVES CONT..

6. How are additives used in the production of cured meats?

Colour to produce pink/ potassium nitrate to cure meat (bacon).

7. Outline why colours are used in food production?Visual appearance is a vital selling feature.Colours are used to modify the appearance of a

product to make it more attractive to the consumer.Used to colour food deficient in colour due to certain

processing/ to ensure a consistent product colour.

FUNCTIONAL FOODS Where foods or their ingredients have a

physiologically beneficial action that goes beyond that of normal nutrition – e.g. ‘vitamin enriched’ foods with anti-oxidant carotenoid colouring agents.

It includes processed food or foods fortified with health-promoting additives.

Fermented foods with live cultures are considered as functional foods with probiotic benefits.

EXAMPLES OF FUNCTIONAL FOODS FishOmega 3 & Essential fatty acidsReduces CHD (coronary heart disease) YoghurtProbiotics – contains healthy bacteriaGastro-intestinal health Fruit & VegPhyto chemicalsReduces CHD and cancer Natural Colours (beetroot)Anti-oxidantsReduces risk of cancer Soy FoodsSoy proteinReduces Cholesterol

MANIPULATING AND COMBINING FOOD MATERIALS

Modified Starch A food additive which is prepared by treating starch

or starch granules, causing the starch to be partially degraded.

Used as a thickening agent, stabilizer, or an emulsifier.

Made by changing raw starch physically, chemically or treating it with enzymes.

MODIFIED STARCH CONT..Two examples:Acid Modified Starches Derivatized StarchStarch is treated with acid to reduce its viscosity (thickness/stickiness) and then is used in confectionary.Examples: Smartie coating, minstrels and jelly beans.

Starch is treated with alcohols (ethers and esters) to reduce the gelatinisation when hot water is added.Examples: Gravy granules and cuppa soups.

MODIFIED STARCH CONT.. Pre-gelatinized starch is used to thicken instant

desserts, allowing the food to thicken with the addition of cold water or milk.

Commercial pizza toppings containing modified starch will thicken when heated in the oven, keeping them on top of the pizza, and then become runny when cooled.

A suitably-modified starch is used as a fat substitute for low-fat versions of traditionally fatty foods e.g. reduced-fat salami.

It acts as an emulsifier for salad dressing by enveloping oil droplets and suspending them in water.

GELS Gels are formed when pectin (a complex

carbohydrate (CHO)) is put under the correct circumstances.

Factors affecting the consistency of gels: Ratio: If there is not enough sugar or pectin, a

suitable gel will not form. Acids: Certain level of acidity (below pH 3.5) must

be present for a jelly to form. If fruit is not sufficiently acidic, a gel won’t form. If too much acid the jelly will weep.

Sugar: Good gel is formed when there’s enough sugar (65-85%) because it acts as a dehydrator.

BREAD MAKING – HOW IS IT MADE?

Ingredients: Flour, Yeast, Water, Salt Ingredients are mixed with water at 27°C and the

dough is put in a warm place to rise. After 2 hours the dough is kneaded to even out the

temperature of the dough and to make sure that all gas is pushed out.

It is then divided into portions and left to rise for another hour.

The dough is then ‘knocked’ and left for a further 15 minutes and the final shape is made.

The dough is then rested for a further 45 minutes, then baked for 40-45 minutes at 230 – 260°C

BREAD MAKING – CHEMICAL AND PHYSICAL CHANGES When the ingredients are mixed they become hydrated. After mixing, fermentation takes place, releasing carbon dioxide

and the flour proteins produce gluten. The carbon dioxide causes the dough to rise and the gluten makes

the dough elasticated to allow expansion. Growth of lactic acid bacteria makes the bread more acidic. During the first stages of baking, the enzymes, yeast activity and

gas volume increase due to rise in temperature which causes the dough to rise.

At 65°C the physical changes increase rapidly. At 75°C starch begins to gelatinise and the proteins begin to

coagulate. The Maillard reaction causes the brown crust. The texture is changed due to the production of dextrines from the

starch.

CAKES, BISCUITS AND CEREALS

Why is a gluten network undesirable in these baked goods?

Gluten is needed, but without the elasticity, therefore flours produced from soft wheats (low in protein) yield better cakes than those from hard wheats.

High ratio flours are specially used in cake making as it contains more starch than protein due to milling and sieving production because the particles in the flour must be as small as possible.

CAKES CONT..

How is a satisfactory cake produced? Can be produced by a batter where there has been

adequate gas reduced and retained. Can be beaten into the mix and retained with help

of egg and cream fat. Using baking powder, it produces carbon dioxide in

moist batter and is formed by sodium carbonate. Starch also helps to keep the other 2 ingredients

dry and keep the mixture free flowing. A good cake needs lots of air to make it spongy.

CAKES CONT..

How does air contribute to the making process? Air whipped into the mix is important as it influences

the cake volume. The batter stretched around it retains the air as it

becomes mixed. Proteins from flour and egg do this, however, too

much protein forms a ‘rubbery’cake. Fat and sugar are needed to minimise the rubbery

texture.

CAKES CONT..

How are fats used when making cakes? Fats are used to interfere with the development of the

gluten network and allow protein particles to slide as it makes cakes more tender.

Emulsifying agents (e.g. Monoglycerides, diglycerides and lecithin) are added to fats to form ‘super-glycinerated’ fats.

By mixing more water in the batter more sugar is added, making the cake sweeter and moist.

How does sugar contribute to a satisfactory cake? It provides sweetness, tenderness and during mixing,

the water dissolves the sugar. Sugar is responsible for water retention and keeps the cake moist.

BISCUITS

Fat: A large amount of fat is used to ensure disruption of

gluten so that a crumbly texture is produced.Baking Powder: Only a small degree of gas production is usually

required.