Thermoxidative stability of triacylglycerols from mutant sunflower seeds

Thermoxidative stability was evaluated in triacyl-glycerols (TAG) from the oils of the mutant sunflower lines CAS-3, CAS-4, and CAS-8 (with a high per centage of stearic acid), CAS-5 (with a high percentage of palmitic acid), all from standard high-linoleic genetic backgrounds, and the mutant sunflow er line CAS-12 (with a high percentage of palmitic acid), from a high-oleic genetic background. These oils contained unusually high contents of TAC mo lecular species with one or two saturated fatty acids at the sn-1,3 positio ns. Purified total TAC devoid of tocopherols were subjected to controlled t hermoxidative treatment at 180 degrees C. Polymerized TAG were determined a t 2-h intervals for 10 h. After this time, total polar compounds, oxidized TAC monomers, TAC dimers, and TAC oligomers were determined. TAG from highl y saturated sunflower oils with levels of linoleic acid similar to those fo und in conventional sunflower oils (40-50%) showed enhanced thermal stabili ty. In these TAG, the amount of polar compounds formed during the thermoxid ative treatment was similar to that formed in the high oleic acid line. Exc ellent results were obtained for the TAG of the CAS-12 oil, which had the h ighest thermal stability, producing half the amount of polar compounds as t he conventional line and less than two-thirds that of the high-oleic line.