Oxidative Stability as Affected by Triacylglycerol Composition and Structure of Purified Canola Oil Triacylglycerols from Genetically Modified Normal and High Stearic and Lauric Acid Canola Varieties

Abstract

Impact of fatty acid, triacylglycerol fatty acid location and triacylglycerol composition on canola oil oxidative stability was determined using oils from genetically modified (transgenic) canola varieties. Some of the canola varieties had oils with a high content of saturated fatty acids such as stearic and lauric. The purified oils were oxidized neat under static oxygen headspace under fluorescent light at 25 °C, and in the dark at 60 °C. These accelerated oxidative stability tests permitted investigation of canola oil deterioration at oxidation levels pertinent to oil storage conditions. Canola oil oxidation was monitored by rate of peroxide value change, and formation of triacylglycerol hydroperoxides and triacylglycerol hydroperoxide volatiles. Oxidation results indicated that canola oils of improved oxidative stability compared to normal canola oil resulted from three types of oil modification: (a) modification of fatty acid composition accomplished by decrease of readily oxidizable fatty acids such as linolenic and linoleic, and an increase of oxidation resistant fatty acids such as oleic plus an increase in saturated fatty acids such as stearic and lauric; (b) triacylglycerol structure modification accomplished by an increase in oleic and decrease in linoleic at the glycerol moiety carbon 2; and (c) compositional modification by a decrease in linolenic- and linoleic-containing triacylglycerols and an increase in triacylglycerols with stearic and lauric acids in combination with oleic acid. © 1997 Academic Press Ltd.