Linolenic Acid as the Main Source of Acrolein Formed During Heating of Vegetable Oils

Acrolein, which is an irritating and off-flavor compound formed during heating of vegetable oils, was estimated by the gas–liquid chromatography (GLC). Several vegetable oils such as high-oleic sunflower, perilla, rapeseed, rice bran, and soybean oils were heated at 180 °C for 480 min and then the concentration of acrolein in the head space gas was determined by GLC. The formation of acrolein was greatest in perilla oil among the tested oils, while it was much lower in rice bran oil and high-oleic sunflower oil. There was a good correlation between the level of acrolein and linolenate (18:3n-3) in the vegetable oils. To investigate the formation of acrolein from linolenate, methyl oleate, methyl linoleate, and methyl linolenate were also heated at 180 °C, and the amounts of acrolein formed from them were determined by GLC. The level of acrolein was the greatest in methyl linolenate. Acrolein was also formed from methyl linoleate, but not from methyl oleate. Acrolein in vegetable oils may be formed from polyunsaturated fatty acids, especially linolenic acid but not from glycerol backbone in triacylglycerols.