Effect of α‐ and γ‐tocopherols on thermal polymerization of purified high‐oleic sunflower triacylglycerols

The antipolymerization effects of α‐ and γ‐tocopherols were compared in model systems composed of purified high‐oleic sunflower triacylglycerols at 180°C. γ‐Tocopherol was much more effective as an antipolymerization inhibitor than α‐tocopherol, partly due to lower oxidizability/disappearance. Purified triacylglycerols of sunflower, rapeseed, and high‐oleic sunflower oils were less stable than their nonpurified forms containing tocopherols. Results confirmed that tocopherols per se can act as antipolymerization agents in high‐oleic oils at frying temperatures. No synergism was observed when α‐ and γ‐tocopherols were present together although larger amounts of residuals were left for both tocols. Results suggested that high‐oleic/high‐γ‐tocopherol oils (such as high‐oleic canola and high‐oleic soybean oils) may provide better frying oils than high‐oleic/high‐α‐tocopherol oils (such as high‐oleic sunflower oil).