ON THE SWEETNESS O F FAT THERE is today a gradual trend toward industrial control over rancidity. Rancidity is the generic term for any developed unpleasantness from a fat or oil. In foods such as lard rancidity may pertain either to odor or taste. In fatty non-foods rancidity usually refers to odor alone. Oxidation is the common source of odor deterioration, but some paint oils oxidize readily, and in doing so improve in odor, for oxidation does not necessarily produce bad odors. Whiie strong light may speed up oxidation and produce rancidity in such substances as soybean oil, other causes of rancidity include enzyme action such as that producing strong butter by the release of amines giving a fishy flavor, low bacterial count, metallic contamination in butter, and the enzyme action causing wheat germ to turn bitter. Any rancidity due to oxidation by the air takes place sooner and faster as the storage temperature increases. It may be initiated by exposure to light. The presence of even minute traces of copper, iron, or a few other metals, greatly accelerates the onset and speed of oxidative rancidity. Moisture generally speeds the rate of oxidation, but in the special case of cornflakes may retard it. In general, any rancidity is latent as long as some protective factor is active, and then develops at a relatively rapid rate. The useful life of a fat ends with the termination of the "induction period," after which deterioration may develop with runaway speed. Control over fat quality consists preferably in conserving any naturally occurring rancidity-retarding influences, and in protecting the fat from outside unfavorable con-
ditions. Sometimes it is permissible to add an antioxidant. Spoilage of fats, in the final analysis, has to be determined organoleptically, i. e., by taste and by smell. Since this personal testing varies with the skill and experience of the operator and is limited by many factors, effort has been made to find impersonal chemical and physical aids or partial substitutes. Several chemical tests, such as the accelerated peroxide technic, are of value in detecting types of rancidity, and numerous machines have been devised in which oils are measured for their rate of oxygen absorption against time and temperature. In comparing samples of the same oil, the oxygen-absorption rate is usually found to bear some relationship to the tendency to rancidity. Most oils, especially vegetable oils, are associated with natural antioxidants. The oils are protected so long as the antioxidant is being produced, or commercially, until it is all used up. These "inhibitors" probably vary greatly in different plants. A sizable business has grown up around the extraction of "inhibitors" from plants particularly rich in them and around their concentration for use in fatty c mpositions. For non-food uses, fats may be preserve with commercial antioxidants of a considerable v4ety. By keeping fats away from the known unfbvorable influences other than the oxygen as metallic contamination and heat, they can usually be -From the
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