An improved and simple method for determining diene conjugation in autoxidized polyunsaturated fatty acids.

The autoxidation of linolenic acid was produced at room temperature in a rotating apparatus by passing a stream of dry air over a thin layer of polyunsaturated fatty acid (PUFA). During these experiments, volatile thiobarbituric acid positive product(s), were recovered. The extent of fatty acid autoxidation was measured either (a) by the production of malonaldehyde (MDA) or (b) by the height of the peak at 233 nm of the second derivative spectrum, corresponding to the hidden maximum at 235 nm in the normal absorbance spectra of autoxidized PUFA. The identification of the conjugated double bond structure, arising from the autoxidation of linolenic acid was further confirmed by 1H-NMR spectrometric determinations.