Microwave heating influences on fatty acid distributions of triacylglycerols and phospholipids in hypocotyl of soybeans(glycine max L.)

Soybeans were exposed to microwave heating for 6, 12 or 20 min at a frequency of 2450 MHz. The hypocotyls were then separated from the other tissues, and the lipid components and the positional distribution of fatty acids in triacylglycerols (TAG) and phospholipids (PL) were investigated. Major lipid components were TAG and PL, while steryl esters (SE), free fatty acids (FFA), and 1,3- and 1,2-diacylglycerols (DAG) were minor ones. Following microwave heating, a significant increase (p<0.05) was observed in FFA and in both forms of DAG (primarily 1,3-DAG). The greatest rate of PL losses (p<0.05) was observed in phosphatidylethanolamine (PE), followed by phosphatidylcholine (PC) and phosphatidylinositol (PI). Significant differences (p<0.05) in fatty acid distributions occurred (with few exceptions) when soybeans were microwaved for 12 min or more. Nevertheless, the principal characteristics for the positional distribution of fatty acids still remained after 20 min of microwave heating.