Detection of amount of Hydrogenated and trans fatty acids on fast and fried food surface

Abstract

Background: Trans-Fatty acids are formed during the process of partial hydrogenation in which liquid vegetable oils are converted to margarine and vegetable shortening. In the 20th century, fast food was spread all over the world and the consumption is increased among all age. According to statistical analysis in Egypt, in the last 10 years the fast food consumption is increased annually 46.5%. Fast food is rich in trans-fatty acids which provided increase plasma concentrations of low-density lipoprotein cholesterol and reduce concentrations of high-density lipoprotein (HDL) cholesterol relative to the natural fat, increase in glucose concentrations and high pressure. Aim: This study is purposes to detect the hydrogenated and trans-fatty acids on the surface of various fast food by using HPLC and Gas Chromatography Assay. Methods: HPLC method was used for the determination of total trans-unsaturated fatty acid (trans) content and gas-liquid chromatographic method was used for determination of fatty acid composition of partially hydrogenated vegetable oils (PHVO) were studied collaboratively in various fast food samples. The test samples were methylated and analyzed for total trans-content by HPLC and for fatty acid composition by GC using a capillary column coated with SP-2560. Results: Our investigation observed that trans-octadecenoate (18:1t) content was calculated with the formula: 18:1t = HPLC trans-0.84 x (18:2t + 18:3t) - 1.74 x 18:2tt. The cis-octadecenoate (18:1c) content was obtained as the difference between total octadecenoates (18:1) and 18:1t. Reproducibility relative standard deviations (RSDR) for 15 to 35% trans-content determined by HPLC were in the range of 8.8-11.7%, whereas RSDR for the test sample with 5% trans-content was 34.6%. RSDR values for 18:1t by the GC/HPLC followed the same pattern as that of HPLC trans- values: 36.4% for the test sample with 4.9% 18:1t versus 7.8-12.5% for test samples with 14.9 to 32.6% 18:1t. The content of 18:1c in the test samples varied from 24.7 to 34.5% and their RSDR values ranged from 3.8 to 10.5%. The mean values for 18:1t and 18:1c compared favorably with the absolute levels determined by a silver nitrate-thin layer chromatography/GC procedure. Conclusions: HPLC and GC methods are recommended for determination of trans content and fatty acid composition, respectively, of partially hydrogenated fats derived from vegetable oils, terrestrial animal fats or such oils and fats isolated from food products containing > 5% trans fatty acids.