Comparison of capillary column gas chromatographic and AOAC gravimetric procedures for total fat and distribution of fatty acids in foods

There is increasing interest in the fatty acid composition, including levels of trans fatty acids, of foods. The trans fatty acid content of American diets is increasingly studied because of reported adverse effects of trans fatty acids on risk of coronary heart disease. In this study, total fat content and fatty acid composition of 43 food products were determined after acid hydrolysis by gas chromatography using an SP-2560 flexible fused silica capillary column. Total fat content determined by the gas chromatographic method was compared with fat content determined by AOAC gravimetric method 922.06 for all food products. Total fat, saturated fat and unsaturated fat content of the foods determined by the gas chromatographic method ranged from 0.9 to 96.7, 0.2 to 16.8 and 0.5 to 89.3%, respectively. Trans fatty acids hexadecenoate (t-16:1), elaidic (t-18:1), and octa-decadienoate (t,t-18:2) were identified by comparison of their retention times with those of known standards and quantitated. These fatty acids were present in foods at levels of 0.25 to 1.50 (t-16:1), 0.87 to 268.32 (t-18:1), and 0.23 to 7.92 (t,t-18:2) mg/g.