- Preservatives are substances added to food to slow down or to prevent the growth of microorganisms so that food can be kept for longer period of time.
- Table below shows some examples of preservatives and how they work.
|PRESERVATIVES||EXAMPLES||HOW IT WORKS|
||Salt or sugar draws the water out of the cells of microorganisms and retards the growth of microorganism.|
|Vinegar||Pickled mango||Vinegar provides an acidic condotion that inhibits the growth of microorganism.|
||These preservatives slow down the growth of microorganism|
- Food containing fats and oils can turn rancid, taht is, the fats and oils are oxidised to become unpleansent-smelling acids, on exposure to the air.
- All foodstuff are vulnerable to oxidation. Examples are the browning of apples or potatoes exposed to the air.
- Antioxidants are added to food to prevent oxidation that causes rancid fats and brown fruits.
- Table below shows some examples of antioxidants.
|Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT)||Margarine||To retard rancidity in oils.|
|Ascorbic acid (vitamin C)||Fruit juice||To preserve the colour of fruit juices|
|Alpha tocopherol (vitamin E)||Vegetables oils||To retard rancidity in oils|
|Sodium citrate||Cooked cured meat||To stop fats from turning rancid|
- The use of BHA and BHT has been controversial as it has produced adverse reaction in dogs. Thus, there is a restriction on the amount of this antioxidants used.
- Vitamin C and E are among the safest antioxidants known.
- Vitamin C inhibits the formation of carcinogenic nitrosimines , stimulate the immune system and protect against chromosome breakage.
- Vitamin E neutralises free radical compounds before they can damage cell membranes and helps to reduce the risk of heart disease and cancer.
- Flavourings are used to improve the taste of food and restore taste loss due to processing.
- Examples of flavouring are sugar, salt, vinegar, monosodium glutamate (MSG), aspartame and synthetic essences such as pentyl ethanoate.
Monosodium glutamate (MSG)
|Frozen food,spice mixes, canned and dry soups, salad dressings and meat or fish based-product||To bring out the flavour in many types of food.|
|Diet drinks, low-calorie frozen desserts and some soft drinks.||To sweeten food|
|Pentyl ethanoate (banana flavour), ethyl butanoate (pineapple flavour), methyl butanoate (apple flavour) and octyl ethanoate (orange flavour)||To produce artificial flavours which resemble natural flavours.|
- Many food are actually emulsions. Emulsions are either oil droplets suspended in water or water droplets susupended in oil.
- Stabilisers are substances which help to prevent an emulsion from separating out.
- Stabilisers are used in food which contain oil and water. Examples of these foods are margarine,butter, ice cream and salad cream such as mayonnaise.
- Examples of stabilisers are lecithin, mono and di-glycerides of fatty acids.
- Thickeners are used to thicken food.
- Acacia gum can act as a thickener as well as a stabilisers.
- Table below shows some examples of thickeners.
|Modified starch||Instant soups and puddings.|
|Acacia gum||Chewing gum, jelly and wine|
|Xanthan gum||Sauce, salad dressing|
- Food colourings are dyes.
- Food processing often leads to a loss of colour.
- Food dyes are used to add or restore the colour in food in order to enhance its visual appeal and to maych consumers’s expectations.
- Food dyes can be classified into natural and artificial food dyes.
- Artificial food dyes are usually used because they are more uniform, less expensive and have brighter colour than natural food dyes.
- Many food dyes are azo compounds or triphenyl compounds.
- Azo dye have colours such as red, orange and yellow, whereas triphenyl dyes have colours such as blue and green.
- Tartrazine, a yellow azo dye, is used in orange drinks,custard powder,sweets and apricot jam. Tartrazine is believed to cause hyperactivity in children.
- Brilliant blue FCF, a blue triphenyl dye, is found in beverages, jellies, confections and syrups. It can be combined with tartrazine to produce various shades of green.