Autoxidation of Methyl Linoleate in Freeze‐Dried Model Systems. III. Effects of Added Amino Acids

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Abstract
SUMMARY: Oxidation of methyl linoleate in a model system based on microcrystalline cellulose was studied in the presence and absence of added amino acids in concentrations ranging from 10‐4 to 10‐2 moles‐ of additive per mole of linoleate. All experiments were conducted in freeze‐dried model systems, in absence of water; the oxidation was followed manometrically and by determination of diene conjugation. Parallel experiments were conducted on the same systems in the presence of conventional antioxidants including propyl gallate.Certain amino acids, including histidine, p‐amino‐butyric acid, lysine, and cysteine, had substantial antioxidant activity. The nature of this activity was found to be different from that observed with propyl gallate, since the main, if not sole, effect of the amino compounds was to prolong the induction period and to affect the initial rate of oxidation. No effect was present in the more rapid, bimolecular phase of oxidation; whereas propyl gallate had an inhibitory effect in this later stage also.Kinetic interpretation of the data and the significance of the findings to stability problems in dehydrated foods are discussed.