ANTIOXIDANTS IN LIPID FOODS AND THEIR IMPACT ON FOOD QUALITY

This paper reviews the antioxidant properties of tocopherols and ascor bic acid in edible oils, and the impact of interfacial phenomena on th eir activities in emulsions and the effects of edible oil processing. Tocopherols are the most important natural antioxidants found in veget able oil-derived foods, These antioxidants can interrupt lipid autoxid ation by interfering with either the chain propagation or the decompos ition processes. alpha-Tocopherol at high concentrations inhibits hydr operoxide decomposition but promotes hydroperoxide formation. The effe ct of antioxidants in inhibiting hydroperoxide decomposition may thus be critical in preserving food quality by reducing rancidity due to al dehyde formation. Ascorbic acid can regenerate alpha-tocopherol, inact ivate metal initiators and reduce hydroperoxides. The activity of natu ral antioxidants is greatly affected by complex interfacial phenomena in emulsions and multicomponent foods. In an oil-in-water emulsion sys tem, the lipophilic antioxidants alpha-tocopherol and ascorbyl palmita te are more effective than in bulk oil, while the opposite trend is fo und for the hydrophilic antioxidants Trolox and ascorbic acid. The met hodology to evaluate natural antioxidants must be carefully interprete d depending on whether oxidation is carried out in bulk oils or in emu lsions, and what method is used to measure lipid oxidation. Copyright (C) 1996 Elsevier Science Ltd