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Preservatives:
These include chemical preservatives against bacteria, yeasts, and molds such as sodium benzoate used in soft drinks and acidic foods, the sodium and calcium propionates used in breads and cakes as mold inhibitor, sorbic acid used on cheese and canned foods to control mold, and compound of chlorine used as a germicidal wash for fruits and vegetables. These preservatives also include fumigants such as ethylene oxide and ethyl formate used to control microorganisms on. spices, nuts and dried fruits. Preservatives which control browning of fruits and vegetables caused by enzymes, such as suiphurdioxide, also are included.
Colouring agents:
These include colour stabilizers, colour fixatives, colour retention agents, etc. They consist of synthetic colours. Colours natural or synthetic are used to improve the asthetic appeals of food. Colours naturally present in foods may be classified as water-soluble and water-insoluble, and may be of plant or animal origin. The choice of natural colours for use in food is limited as their stability during processing and storage is influenced by pH, heat, light, oxidation etc. Even though synthetic colours add nothing to the nutritive value of foods. But they are frequently added to restore the natural ones lost in food processing or to give the preparation the natural colour we expect. Colours of synthetic origin, such as the certified coal tar dyes, extend the range of colouring applications that can be satisfied with the natural colouring agents of which extract of annatto, caramel, carotene, and saffron are examples. Further, in many cases natural colouring materials do not exist for a desired hue. Carbonated beverages, candies, gelatin desserts, and bakery goods are among items coloured with certified coal tar dyes. In addition to the organic coal tar dyes and the natural organic colouring agents, food colours also include such materials as iron oxide to give redness and titanium dioxide to intensify whiteness. Organic colouring materials also can be combined with metallic salts and the coloured products are known as lakes.
A number of natural food colours extracted from seeds, flowers, insects and foods are also used as food additives. One of the best known and most widespread red pigments is bixin, derived from the seed coat of Bixa orellana, the lipstick pod plantof South American origin. Another natural red coloured colour, cochineal is obtained by extraction from the female insect cocens cniti, grape skin extract and caramel, the brown colour obtained from burnt sugar.
Antioxidants:
These include the compounds used to prevent oxidation of fats. Without them potato chips, breakfast cereals, salted nuts, fat-containing dehydrated foods, crackers and many fatty foods could not be stored for any length of time without developing rancidity. Principal among those antioxidants are butylated hydroxy anisole (BHA), butylated hydroxy toluene (BHT), and propyl gallate. Nordihydroguaiaretic acid (NDGA), previously used as an antioxidant, was removed from food use. Antioxidants include such diverse materials as ascorbic acid, stannous chloride, and tocopherols (Vitamin E). Sulphur dioxide tested as preservative is further listed as an antioxidant. Many other food chemicals also exhibit dual roles
Emulsifiers:
They are group of substances used to-obtain a stable mixture of liquids that otherwise would not mix or would separate quickly. They also stabilize gas-in-liquid and gas-in-solid mixtures. They are widely used in dairy and confectionery products to disperse tiny globules of an oil or fatty liquid in water. Emulsifying agents are also added to margarine, salad dressings and shortenings. It addition to emulsifers of natural origin such as lecithin, which is found in milk, egg, and soybean, emulsifiers can be prepared synthetically such as mono and diglycerides and their derivatives and bile acid as such are important in digestion, e.g. propylene glycol monostearate, sorbitan monostearate and polysorbates
Stabilizers and Thickeners:
These compounds function to improve and stabilize the texture of foods, tnhibit crystallization (sugar, ice), stabilize emulsion and foams, reduce the thickness of icings on baked products and encapsulate flavours. Substances used as stabilizers and thickners are polysaccharides, such as gum arabic, guar gum, carrageenan, agar-agar, starch and its derivatives, carboxymethyl celluloses (CMC),pectin, amylose, hydrolyzed vegetable proteins and others. Stabilizers and thickeners are hydrophilic and are dispersed in solution as colloids. These swell in hot or even cold water and help thicken food. Gravies, pie fillings, cake toppings, chocolate milk drinks, jellies, puddings and salad dressing are some among the many foods that contain stabilizers and thickeners.
Bleaching and Maturing Agents:
Freshly milled flour has yellowish tint and suboptimum functional baking qualities. Both the colour and baking properties improve slowly in normal storage. These improvements can be obtained more rapidly and with better control through the use of certain oxidizing agents. Benzoyl peroxide is an oxidizing agent which bleaches the yellow colour. Oxides of nitrogen, chlorine dioxide, and other chorine compounds both bleach colour and mature the flour
Oxidizing agents such as hydrogen peroxide also are used to whiten the colour of milk for certain kinds of cheese manufacture and to bleach tripe. Bromate and iodate oxidizing agents are also used to condition bread doughs for optimum baking performance. Starch modifiers include compounds such as sodium hypochlorite which oxidize starches to a higher degree of water solubility
Sequestrants:
These are the chelating agents or sequestering compounds. They are also referred to as metals such as iron and copper and remove them from solution. The trace metals are active catalysts of oxidation and also enter into many off-colour reactions in foods. Their removal by chelating additives such as ethylene-diamine-tetra-acetic-acid (EDTA), poly-phosphates, and citric acid prevents these defects.
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