Studies on the Improvement of Antioxidant Effect of Tocopherols. II

Abstract

The synergistic antioxidant effect of tocopherol (Toc) and citric, malic or succinic acid in lard and palm oil was investigated. The acids were dissolved homogeneously in a commercial distilled monoglyceride and then added to the fats.1) The monoglyceride manufactured from cotton seed oil was selected as the medium because of lower melting point and higher dissolubility for citric acid than that manufactured from beef tallow.2) The monoglyceride showed a little antioxidant effect in the lard.3) The antioxidant effect of Toc in the lard was little affected by the addition of citric acid. It seemed that few pro-oxidant metals such as iron, copper, etc, were contained in the fat. Also no synergistic effect of the acid was observed in the palm oil. These results suggested that current oils and fats with the progress of oil-refining technique contained a smaller amounts of metal compounds than previous oils and fats.4) Malic and succinic acids in the lard did not show the synergistic effect with Toc and neither did citric acid.5) In the case of lard containing 4.4 ppm of iron, the addition of citric acid to the substrate remarkably improved the antioxidant effect of Toc. The results lead to the conclusion that the effect is indicated on the basis of the function of citric acid as metal deactivator.