The synergistic antioxidant effects of the fatty acid esters of polyglycerol, propylene glycol and sorbitan with tocopherol (Toc) on lard and palm oil were investigated by the oven and AOM tests. The same tests were also carried out on lecithin.
1) In the oven test, fatty acid esters of polyglycerol and sorbitan showed slight antioxidant effects on lard, but the fatty acid ester of propylene glycol had hardly any effect. All the esters slightly enhanced the antioxidant effects of Toc on lard. No effects were observed on palm oil.
2) In the AOM test, the esters had no antioxidant effects on lard, and did not influence those of Toc.
3) In the oven test, lecithin clearly had antioxidant effect on lard and palm oil, and synergistic cally enhanced the antioxidant effects of Toc on lard. The synergistic effects became more enhanced by the addition of L-ascorbic acid to lecithin, but not so by that of citric acid. No synergistic effects of lecithin with Toc could be observed on palm oil.
4) In the AOM test on lard in which the addition of lecithin was 0.05% or less, the antioxidant effect of lecithin was slight, but its synergistic effects on lard in the presence of Toc were clearly evident. Tests with lecithin levels exceeding 0.05% could not be carried out owing to bubbling of the sample by aeration.
5) In all tests on lecithin, carbonyl value of the samples increased with the amount of peroxide, whether lecithin was added or not.
