1.Preservatives are chemicals that are added to food to retard or to prevent thegrowth of microorganism such as bacteria, mould or fungus, so that the food canbe stored for a long time.
2.In ancient times, food additives from natural sources such as salt, sugar andvinegar were used to preserve food and to make the food taste better.
3.Nowadays, synthetic preservatives are used, table below shows the types of preservatives commonly used. Many of the preservatives are organic acids and salts of organic acids.
preservatives: Sodium nitrite, Sodium nitrate
uses:1)To preserve meat, cheese and dried fish.
2) To prevent food poisoning in cannedfoods.
3) To maintain the natural colour of meatand to make them look fresh.
preservatives: Benzoic acid, sodium benzoate
use: To preserve sauce (olyster, tomato or chilli), fruit juice, jam and margarine.
preservatives : sulphur dioxide, sodium sulphite.
uses: 1) Used as bleaches and antioxidants to prevent browning in fruit juices.
2) Maintain the colour and freshness of vegetables.
3) To prevents the growth of yeast.
Antioxidants
1. Antioxidants are chemicals that are added to foods to prevent the oxidation of fatsand oils by oxygen in the air.
uses: 1) Used as bleaches and antioxidants to prevent browning in fruit juices.
2) Maintain the colour and freshness of vegetables.
3) To prevents the growth of yeast.
Antioxidants
1. Antioxidants are chemicals that are added to foods to prevent the oxidation of fatsand oils by oxygen in the air.
2. Foods containing fats or oils are oxidized and become rancid when exposed to air.
3.When the fats and oils are oxidized, rancid product are formed. This makes thefood unpalatable. The rancid product are volatile organic compound with foulodours.
4. Antioxidants are added to fats, oils, cakes, sausages, biscuits and fried foods toslow down the oxidation process so that these foods do not become rancid.
Flavouring agents
1. There are two types of flavouring agents : artificial flavours and flavour enhancer.They are added to foods to make them taste better.
1. There are two types of flavouring agents : artificial flavours and flavour enhancer.They are added to foods to make them taste better.
2. Flavour enhancer have little or no taste of their own. They are chemicals that areadded to food to bring out the flavours or to enhance the taste of food.
3. An example of a flavour enhancer is monosodium glutamate (MSG). MSG is used toenhance the flavours of other foods.
4. Artificial flavour includes sweeteners and other flavours such as peppermint or vanilla. Aspartame and saccharin are examples of artificial sweeteners.
5. Both aspartame and saccharin can be used as a substitute for sugar to enhance thesweetness in food and drink. However, the used of saccharin is banned in manycountries because it is carcinogenic. Aspartame has largely replaced saccharin asthe artificial sweetener or choice.
abilizers and thickening agents
1. Stabilizers and thickening agents improve the texture and the blending of foods.
abilizers and thickening agents
1. Stabilizers and thickening agents improve the texture and the blending of foods.
2. Stabilizers are chemicals that are used to enable oil and water in the food to mixtogether properly in order to form an emulsion of oil and water. Examples of stabilizers are gelatin and acacia gum.
3. Stabilizers are adde
Std to improve the texture of foods. For examples, stabilisers areadded to ice-cream and peanut butter to keep them smooth and creamy.
Std to improve the texture of foods. For examples, stabilisers areadded to ice-cream and peanut butter to keep them smooth and creamy.
4. In the presences of stabilizers, the emulsions of oil does not separated from water. this mean that the stabilizers improves the stability of food such as ice cream and salad dressing (mayonnaise).
5. Without stabilisers, ice crystals would form in ice-cream, particles of chocolatewould settle out of chocolate milk, oil and vinegar in salad dressing will separateas soon as mixing is stopped.
6. Thickening agents are chemicals that are added to foods to thicken the liquid andto prevent the foods from becoming liquid. Thickening agents (also calledthickeners) absorb water and thicken the liquid in foods to produce a jelly-like structure.
7. Most thickening agents are natural carbohydrates. Gelatin and pectin are added tohelp jams and jellies to set.
Dyes
Dyes
1. Dyes (colouring agents) are chemicals that are added to foods to give them colour so as to improve their appearance.
2. Some foods are naturally coloured, but the colour is lost during food processing.The foods industry uses synthetic food colours to :a)Restore the colour of food lost during food processing.b)Enhance natural colours, so as to increase the attractiveness of foods.c)Give colour to foods that do not have colour.
3. Some dyes are naturally plant pigments while others are synthetically prepared.The synthetic colours used in foods are azo and triphenyl compounds. Both thesecompounds are organic compounds.
4. The synthetic dyes , brilliant blue, is an example of triphenyl compound. Thesynthetic dye, tartrazine and sunset yellow are examples of azo compounds.
5. Azo compounds are organic compounds containing the diazo group, - N = N -, andare usually yellow , red, brown, black in colour. Triphenyl compounds are organiccompounds containing three phenyl groups, and are usually green. Blue or purple in colour.
