Oxidation-Induced Changes in Foods

Abstract

A frequent cause of poor shelf life and off-flavors in processed foods is oxidation of lipids, primarily the unsaturated fatty acids of storage oil and membrane lipids in plant foods, and the saturated fats in animal products and cooking fats used for cooking/processing both plant and animal foods. Even during storage, fats can undergo oxidative changes that give rise to objectionable flavors and odors. In general, the higher the unsaturation of the fat, the greater the susceptibility to oxidation. Oxidation of fats proceeds via a free radical mechanism in three basic steps: initiation (addition of oxygen to the fat), propagation (generation of hydroperoxides and free radicals), and termination (combination of free radicals with each other or with other compounds, the formation of further peroxides and the release of oxygen back to the system). Hydroperoxides are the major products of lipid oxidation. They can break down to secondary products (aldehydes, alcohols, ketones, acids), or they can react with proteins and enzymes in the food products. Oxidized lipid free radicals, which were studied for scientific interest only a few years ago, have stimulated considerable interest by food scientists and clinicians because of increasing evidence for their association with toxic or carcinogenic agents.