Roasting influences on molecular species of triacylglycerols in sesame seeds (Sesamum indicum)

Sesame seeds were roasted at different temperatures (180-220 degrees C) using a domestic electric oven. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from total lipids in the sesame seeds were analysed by a combination of argentation thin-layer chromatography (TLC) and gas-liquid chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester analysis was performed to determine the composition of each zone. Eleven molecular species of TAGs were still detected in the sesame seeds following roasting treatment. Dilinoleolein (33.7-35.8%), palmitoleolinolein (20.3-22.80/s), dioleolinolein (15.0-15.4%) and trilinolein (8.8-10.7%) were the main components during roasting. However, roasting for 10 min at 220 degrees C caused a significant decrease (P < 0.05) not only in molecular species containing more than four double bonds, but also in the amount of diene and triene species present in TAGs (with a few exceptions). These results suggest that no significant changes in molecular species or fatty acid distribution of TAGs would occur within 25 min of roasting at 180 degrees C, ensuring that a good-quality product would be attained. (C) 2000 Society of Chemical Industry.