INTERFACIAL PHENOMENA IN THE EVALUATION OF ANTIOXIDANTS - BULK OILS VS EMULSIONS

Antioxidants have been difficult to evaluate in oils and food emulsion s due in part to the complex interfacial phenomena involved. Lipophili c and hydrophilic antioxidants were evaluated with corn oil stripped o f natural tocopherols in bulk and in emulsion systems. Oxidation was f ollowed by determining formation of hydroperoxides and hexanal. The li pophilic antioxidants alpha-tocopherol and ascorbyl palmitate were mor e effective in an oil-in-water emulsion system than in bulk oil, white the opposite trend was found for the hydrophilic antioxidants Trolox and ascorbic acid. The oil-insoluble ascorbic acid was a particularly efficient antioxidant in suspension in the bulk oil system. Mixtures o f alpha-tocopherol and ascorbic acid were more active in bulk oil, whi le mixtures of alpha-tocopherol and ascorbyl palmitate were more effic ient in emulsion systems. Differences observed in the efficiency of an tioxidants may be explained by their affinities toward the air-oil int erfaces in bulk oil and the oil-water interfaces in emulsions.