Chemistry In The Kitchen: Food Additives

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In our daily diets, carbohydrates, fats, proteins and water are the main components in our food. However, if the food is left untreated, oxidative deterioration of the flavor and odor of fats and fatty constituents in it will be resulted. Hence, antioxidant are used widely in the production of food which fats and oils are used as raw materials and in the marketing of foods containing fats under modern conditions.

The major factor in quality degradation of fats and fatty portions of foods is oxidation. In the oxidative deterioration of fats and fat-like substances, off-flavors and off-odors are usually reported. Rather than the breakdown of the unsaturated fat molecules, there are four types of fat deterioration. Hydrolysis is the formation of free fatty acids and glycerol, which will give ¡§soapy¡¨ flavor. Nevertheless, triglycerides with fatty acids having shorter chain lengths normally produce off-flavors upon hydrolysis. The autoxidation of unsaturated fatty acids resulting in a mixture of volatile components leading to off-flavors is rancidity.

By the oxidation of linolenic-type acids, reversion causes flavor and odor degradation associated with vegetable, fish and other unsaturated oils. Oxidation of fats also results in polymerization that occurs between two fatty acid chains. Oxygen bonding then can be found at the unsaturated site. Although antioxidants are effective in reducing rancidity and polymerization, they do not affect hydrolysis and reversion.

Unsaturated and saturated fatty acids can be oxidized by the usual chemical oxidizing agents, for instance nitric acid, ozone and potassium permanganate. However, these are not the concern for the food technologist. Autoxidation (atmospheric oxidation) under the mild processing and storage conditions of the food industry is of utmost importance due to the resultant malodor- and malflavor-producing aldehydes and ketones. The oxidation of the highly unsaturated fats resulting in polymeric end products and the oxidation...