Rancidity in fats

The oxidative degradation represented by the foregoing reactions is referred to as peroxidation. Peroxidation can lead to rapid development of rancidity in fats and oils. However, the presence of a small amount of tocopherol inhibits this decomposition, presumably by trapping the intermediate radicals in the form of the more stable tocopherol radicals (Eq. 15-54), which may dimerize or react with other radicals to terminate the chain. 

Shahidi, F. and Wanasundara, U. 1998. Methods of measuring oxidative rancidity in fats and oils. In Food Lipids. Chemistry, Nutrition, and Biotechnology (C.C. Akoh and D.B. Min, eds.) pp. 377-396. Marcel Dekker, New York. 

Shahidi, F., and Wanasundara, U. N. 1998. Methods of Measuring Oxidative Rancidity in Fats and Oils. In, Food Lipids Chemistry, Nutrition and Biotechnology Food Science and Technology Series (vol. 88, pp. 377-396). New York Marcel Dekker. 

The earlier literature on the effect of metals on rancidity in fats has been well covered by Lea (1939). The accelerating effect of copper and iron on oxidation of fats and fat-containing foods is well established by a wealth of experimental evidence. Other metals, particularly vanadium, cobalt, and manganese, may also be strong pro-oxidants but are less likely to contaminate foods. These metals can accelerate rancidity either in the form of the solid metal in contact with the fat or as water- or fat-soluble salts in heterogenous systems. Aluminum, tin, and zinc have little catalytic activity under most conditions, although tin can act as a surface catalyst for dry fats (Lea, 1946b). 

Chang, I., and Watts, B. M. 1960. Some effects of salt and moisture on rancidity in fats. Food Research 16, 1. 

Cook, W. H., and White, W. H. 1941. Effect of temperature and humidity on color of lean and development of rancidity in fat of pork during frozen storage. Can. J. Research 19D, 53. 

Lips, A., Chapman, R. A., and McFarlane, W. D. 1943. Application of the ferric thiocyanate method to the determination of incipient rancidity in fats and oils. OU ... 

Antioxidants are substances that prolong the shelf life of foods by protecting them against deterioration caused by oxidation, which is reflected in rancidity in fats and other easily oxidising food components. Lipid oxidation causes other chemical changes in foods that negatively affect their nutritional value (oxidation of vitamins), sensory value (oxidation of flavour-active components... 

The operation of refining is normally carried out to remove free fatty acids from the cmde oil. Free fatty acids are not harmfiil per se. However, they are precursors of peroxides and compounds that are responsible for unwanted odors and rancidity in fats, and their removal is usually the first step in the refining process. This removal is usually done by neutralizing the free fatty acids with a weak caustic solution (10-15%) and adding a slight excess to... 

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