Methional as an antioxidant for vegetable oils

Abstract and summary Brief heating of safflower oil with 1% by weight of DL‐methionine at 200 C stabilized the oil to subse‐quent autoxidation. Since this treatment also caused development of a strong cabbage‐like aroma, it was difficult to follow the oxidation organoleptically. Measurements of oxygen absorption rate and per‐oxide development confirmed that the heated oil was quite stable. The major product of the reaction between methionine and safflower oil, N(3‐methyl‐thiopropyl) linoleic amide, was found to be a pro‐oxidant. There was evidence that methional (β‐methylmercaptopropionaldehyde), formed by de‐gradation of methionine, is the active antioxidant. Commercial methional contains significant quantities of a dimer and trimer, both of which were also found to have antioxidant activity. The dimer is a de‐hydrated aldol condensation product whereas the trimer is cyclic, a substituted trioxymethylene. Meth‐ional and its polymers have such strong objectionable odors, even at low concentrations in oil, that their usefulness as antioxidants may be very limited.