Determination of Fatty Acid Composition at sn-2 Acyl Position in Triacylglycerol by Capillary Gas Chromatography with Lipase from Rhizopus delemar^*1

Abstract

Determination of fatty acid composition at sn-2 acyl position in triacylglycerol was carried out by capillary gas chromatography,with a microbial lipase from Rhizopus delemar. Triacylglycerol was partially hydrolyzed at 40°C, pH 7 for 3 minutes with the lipase. The sn-2 monoacylglycerol fraction of the lipase product was separated by thin-layer chromatography with a developing solvent which was composed of petroleum ether, diethyl ether and acetic acid (50: 50 : 1v /v /v). The sn-2 monoacylglycerol fraction was methylated with sodium methoxide and analyzed by capillary gas chromatography. Three collaborative studies with 7 laboratories on capillary gas chromatography with a reference standard, beef tallow fatty acid analysis by means of methyl esterification with sodium methoxide, and the determination of fatty acid composition at the sn-2 acyl position in beef tallow were carried out. The reproducibility coefficients of variation of major fatty acids in the samples in the above collaborative studies were less than 1.60%, 3.28% and 5.05%, respectively.