Cis-Methylene-Interrupted Polyunsaturated Fatty Acids in Edible Oils and the Effect of Hydrogenation upon these Acids

Abstract

Many different natural fats and oils were analyzed for cis-methylene-interrupted polyunsaturated fatty acids by the enzymatic method of MacGee (1959). The method was found to be fairly reproducible and in most cases gave standard deviations of less than 1%.The effect of hydrogenation on the level of cis-methylene-interrupted polyunsaturated fatty acids in sunflowerseed, soybean and rapeseed oils was investigated and it was found that the major portion of these acids was lost before a solid fat index of about 4 was reached, this loss being most marked for the rapeseed oil. The use of non-selective (low temperature, high pressure) hydrogenation conditions rather than selective (high temperature, low pressure) conditions resulted in more of the cis-methylene-interrupted polyunsaturated fatty acids being retained for a given total unsaturation.The analyses on finished products showed that the soft margarine, liquid shortening and salad oils (sunflowerseed, corn) tested meet the Food and Drug Directorate requirements (1968) to make specific label claims for polyunsaturated and saturated fatty acids, whereas the normal margarines, shortenings and hydrogenated soybean salad oil tested did not meet these requirements. No specific label claims for polyunsaturated and saturated fatty acids were made for these latter products.