Comparison of various analytical techniques for the determination of essential fatty acids in hardened fats

Abstract

AbstractIn partially hydrogenated fats containing residual linoleic acid, linoleic acid isomers are found which have no essential fatty acid activity but contribute to the C‐18 diene acid values; i.e., to the so‐called linoleic acid values obtained by the usual physicochemical methods. Such hydrogenated fats and oil blends, particularly margarine oils, have now been analyzed by a biochemical procedure in the attempt to measure specifically the essential fatty acid content by a direct method. The latter procedure makes use of a lipoxidase enzyme specific for thecis, cis, methylene interrupted diene structure in polyunsaturated fatty acids having two or more double bonds. It is concluded that the biochemical method is equally as reliable as the combined use of the spectrophotometric and thiocyanometric procedures for estimating with precision the essential fatty acid content of hydrogenated fats containing residual dienes; the simplicity and speed of the biochemical method make it the procedure of choice.