Abstract
Studies on autoxidation of polyunsaturated fatty acids in the presence of antioxidants have shown that there can be significant differences in the proportions and types of products produced in ‘inhibited’ autoxidations, as compared with control autoxidations, in the absence of an antioxidant. The autoxidation of methyl linolenate has been used as a model system with which to study the effects of different concentrations of both natural and synthetic antioxidants on the proportions of the various types of oxidation product formed. The antioxidants studied included α‐, γ‐, and δ‐tocopherol, α‐tocotrienol, 2,2,5,7,8‐pentamethylhydroxychroman (PMHC), 2,6‐di‐tert‐butyl‐4‐methylphenol (BHT), 3‐tert‐butyl‐4‐hydroxyanisole (BHA), and mono‐tert‐butylhydroquinone (TBHQ). In order to investigate the effect of the antioxidants, the oxidation products were analysed for the proportions of diperoxides and monohy‐droperoxides present, and the monohydroperoxide class was further analysed for the proportions of cis, trans and trans, trans dienes and ‘inner’ and ‘outer’ hydroperoxides. In all cases where any significant oxidation occurred the extent of the change in product distribution caused by the antioxidant increased as the antioxidant concentration increased. In many cases the extent of methyl linolenate oxidation occurring under standard conditions (after 100 h at 40°C) also increased as the antioxidant concentration increased, but this was not so for δ‐tocopherol, BHT and TBHQ. The importance of these findings in relation to food systems and to the understanding of antioxidant behaviour is discussed.