Analysis of trans-18:1 isomer content and profile in edible refined beef tallow

The trans 18:1 acid content and profile for several samples of edible refined beef tallow were determined monthly over a period of one year. For this purpose, gas-liquid chromatography was combined with silver-ion thin-layer chromatography. The mean content of trans-18:1 isomers was 4.9 +/- 0.9% (n = 10) of total fatty acids with a minimum of 3.4% and a maximum of 6.2%. The distribution profile of individual isomers was also established. As in other ruminant fats (milk fat, meat fat), the main isomer is vaccenic (trans-11 18:1) acid. Other isomers, with their ethylenic bonds between positions 6 and 16, were found in lesser amounts. However, some slight but definite differences exist between beef tallow and cow milk fat. The relative proportion of vaccenic acid is higher in the former than in the latter. However, the distribution pattern of trans-18:1 isomers in beef tallow closely resembles that in beef meat fat (lean part).