Influence of microwave roasting on positional distribution of fatty acids of triacylglycerols and phospholipids in sunflower seeds (Helianthus annuusL.)

Whole sunflower seeds were exposed to microwave roasting for 6, 12, 20 or 3 0 min at a frequency of 2450 MHz. The kernels were then separated from the sunflower seeds, and the lipid components and the positional distribution o f fatty acids in triacylglycerols (TAGs) and phospholipids (PLs) were inves tigated. Major lipid components were TAGs and PLs, while steryl esters, fre e fatty acids and diacylglycerols were also present in minor proportions. T he greatest PL losses (p <0.05) were observed in phosphatidyl ethanolamine, followed by phosphatidyl choline or phosphatidyl inositol. Significant dif ferences (p <0.05) in fatty acid distributions occurred (with few exception s) when sunflower seeds were microwaved for 20 min or more. Nevertheless, t he principal characteristics for the positional distribution of fatty acids still remained after 20 min of microwave roasting; unsaturated fatty acids , especially linoleic, were predominantly concentrated in the sn-2-position and saturated fatty acids, especially stearic and palmitic acids, primaril y occupied the sn-1- or sn-3-position. These results indicate that no signi ficant changes in fatty acid distribution of TAGs and PLs would occur withi n 12 min of microwave roasting, ensuring that a good-quality product would be attained.