Canola oil triacylglycerols from genetically modified canola lines {InterMountain Canola Co., Cinnamlnson, NJ) have been evaluated for their photooxidative and autoxidative stabilities, as influenced by their fatty acid compositions and their triaeylglycerol compositions and structures. Purified canola oil triacylglycerols were oxidized in duplicate in fluorescent light at 25~ and in the dark at 60~ under oxygen, and their oxidative deterioration with time was monitored by determining eolorimetric peroxide values. Also monitored with time, oxidation products were determined by reversed-phase high-performance liquid chromatography with ultraviolet absorbance detection. Total volatiles, generated by thermal decomposition of the oxidized triacylglycerols, were quantitated by static-headspace gas chromatography. These experimental parameters were statistically correlated with predicted oxidizability, fatty acid composition, position of fatty acids on glycerol carbons and triaeylglyeerol composition. Oxidative de terioration of canola triacylglycerols correlated negative ly with oleic acid composition, with oleie add content at carbon 2 and with trioleoylglycerol content of the oil. Deterioration was positively correlated with the amount of linolenic acid on nonspecific locations on glycerol cap bons 1,2 and 3, the amount of linoleic acid on glycerol cap bon 2 and with sn~)leoyllinoleoyllinolenoyl glycerol content. Differences in character or quantity of volatile product and triacylglycerol hydroperoxides were low, whether generated during autoxidation or photooxidation of the canola triacylglycerols.

Improvement of oxidative stability of soybean oil by blending with a more stable oil was investigated. Autoxidation of blends and interesterified blends (9:1, 8:2, 7:3 and 1:1, w/w) of soybean oil and palm olein was studied with respect to fatty acid composition, fatty acid location and triacylglycerol composition. Rates of formation of triacylglycerol hydroperoxides, peroxide value and volatiles were evaluated. The fatty acid composition of soybean oil was changed by blending. Linolenic and linoleic acids decreased and oleic acid increased. The triacylglycerol composition of blends and interesterified blends was different from that of soybean oil. Relative to soybean oil, LnLL, LLL, LLO, LLP, LOO and LLS triacylglycerols were lowered and POO, POP and PLP were higher in blends and interesterifled blends (where Ln, L, O, P and S represent linolenic, linoleic, oleic, palmitic and stearic acids, respectively}. Interesterification of the blends leads to a decrease in POO and POP and an increase in LOP. Linoleic acid concentration at triacylglycerol carbon-2 was decreased by blending and interesterification~ Rates of change for peroxide value and oxidation product formation confirmed the improvement of soybean oil stability by blending and interesterification. But, blends were more stable than interesterified blends. Also, the formation of hexanal, the major volatile of linoleate hydroperoxides of soybean oil, was decreased by blending and interesterification.

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