ABSTRACT
Good-quality edible fats and oils are bland, odorless, and free of impurities and are oxidatively stable. However, fats and oils may become oxidized and develop objectionable tastes and odors during processing, storage, and culinary practices. Oil processing is designed partly to remove oxidized oils and free fatty acids, as well as contaminants that may initiate oxidative reactions. However, some processing steps such as bleaching and caustic re! ning, if not done properly, may promote oxidation. During storage and culinary practice, fatty acid oxidation may occur in the presence of a free radical initiator. Oxidized fatty acids formed may catalyze further oxidation and/or break down to form compounds that give the rancid odor and % avor that characterize oxidized fats and oils. Hydrolysis is another main degradation process for oils during culinary practice. In deep-frying, the fatty acids are hydrolyzed off the triglycerides at high temperatures in the presence of water, yielding free fatty acids, monoglycerides, diglycerides, and glycerol. These breakdown products may speed up oxidation and degradation of the remaining triglycerides as they enhance emulsi! cation of water from the food into the oil. In addition to polymerized fatty acids, prolonged oxidation may result in the formation of aldehydes, ketones, alcohols, short-chain fatty acids, and other compounds. Oxidized oils and their secondary products when consumed exert varying biological effects depending on the conditions of oxidation.
