Studies of the Improvement of Antioxidant Effect of Tocopherols. XII

Abstract

The synergistic antioxidant effects of tocopherol (Toc) and 20 kinds of methyl esters of amino acids on lard and palm oil were investigated by the oven and AOM tests. The amino acid derivatives were used in consideration of the insolubility of their free forms in fats. They were homogeniously dissolved using monoglyceride as the medium, as previously described. The antioxidant effects of them were also studied in the same manner.1) The solubility of the amino acid derivatives was found in most cases to be less than 40ppm.2) On lard, 14 amino acid derivatives had rather antioxidant effects according to the oven test, particularly so in the case of methyl L-tryptophan (L-Trp) and methyl lysine (Lys), but dimethyl L-glutamate (Glu-2) tended to accelate oxidation. However, such effects were not observed by the AOM test. All the derivatives except Glu-2 enhanced the antioxidant effect of Toc according to the oven and AOM tests, and the addition of L-Trp, Lys, methyl proline (Pro) or methyl tyrosine (Tyr) along with the mixture of d-Toc (m-Toc) was particularly effective for this.3) On palm oil, 9 of the amino acid derivatives had rather antioxidant effects by the oven test. Pro and L-Trp did so markedly, but Glu-2 and methyl serine tended to accelate oxidation. With Toc, 12 derivatives showed synergistic effects and the addition of Pro, L-Trp, Try or dimethyl cystine along with m-Toc was particularly effective. Similar effects were observed by the AOM test.