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

Impact of fatty acid, triacylglycerol fatty acid location and triacylg lycerol composition on canola oil oxidative stability was determined u sing oils from genetically modified (transgenic) canola varieties. Som e of the canola varieties had oils with a high content of saturated fa tty acids such as stearic and lauric. The purified oils were oxidized neat under static oxygen headspace under fluorescent light at 25 degre es C, and in the dark at 60 degrees C. These accelerated oxidative sta bility tests permitted investigation of canola oil deterioration at ox idation levels pertinent to oil storage conditions. Canola oil oxidati on was monitored by rate of peroxide value change, and formation of tr iacylglycerol hydroperoxides and triacylglycerol hydroperoxide volatil es. 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 accomplis hed by decrease of readily oxidizable fatty acids such as linolenic an d linoleic, and an increase of oxidation resistant fatty acids such as oleic plus an increase in saturated fatty acids such as stearic and l auric; (b) triacylglycerol structure modification accomplished by an i ncrease in oleic and decrease in linoleic at the glycerol moiety carbo n 2; and (c) compositional modification by a decrease in linolenic-and linoleic-containing triacylglycerols and an increase in triacylglycer ols with stearic and lauric acids in combination with oleic acid.