The effects of procedures for preparation of fatty acid methyl esters for gas chromatography were investigated. A quantitative comparison of four procedures for the preparation of the fatty acid methyl esters from Korean sesame seed lipids which can be representative of fatty acid ranges of Korean vegetable oils has been made. The procedures employed were BF3-methanol, HCI-methanol, sodium methoxide-methanol, and tetramethylammonium hydroxide-methanol. Twelve fatty acids ranged from 14:0 to 24:0 were identified in the lipids from Korean white and black sesame seeds. All four procedures gave similar results for the fatty acids, 16:0, 18:0, 18:1, 18:2, and 18:3 present in the range of 1~44% but only in the HCI-methanol procedure, the fatty acids, 16:1, 20:0, 22:0, 24:0 present in the range of 0.02~1% showed the lowest values. When using tetramethylammonium hydroxide-methanol procedure for determination of total fatty acid composition from white and black sesame seed lipids, unsaponifiable matters including sesamol, sesamolin and sesamin present in the seed lipids are not removed from the resulting reaction mixture. Thus the transesterification mixture is used without further treatment for injection into the gas chromatography. However, the gas chromatographic analysis of the transesterification mixture showed that the unsaponifiable matters had no effect on the fatty acid composition of the seed lipids. From the results, it appears that the BF3-methanol, sodium methoxide-methanol and tetramethylammonium hydroxide-methanol procedures can be used to prepare fatty acid methyl esters from Korean vegetable oils. Among the methods, the tetramethylammonium hydroxide-methanol procedure, which give total fatty acid composition, glyceride fatty acid composition and composition of free fatty acids present, appears to be a simple, convenient and quantitative procedure and applicable to samples containing broad ranges of fatty acids.

• 윤태헌 | Yoon, Tai-Heon