Thermostability of genetically modified sunflower oils differing in fatty acid and tocopherol compositions

Abstract

The objective of the study was to investigate the performance at frying temperature of a new sunflower oil with high content of oleic and palmitic acid (HOHPSO) and containing γ-tocopherol as the most abundant natural antioxidant. HOHPSO either containing α- or γ-tocopherol (HOHPSO-α and HOHPSO-γ, respectively) were obtained from genetically modified sunflower seeds and refined under identical conditions. The oil stability against oxidation, as measured by Rancimat at 120 °C, was much higher for the oil containing γ-tocopherol, suggesting the higher effectiveness of γ-tocopherol as compared to α-tocopherol to delay oxidation. Experiments at high temperature (180 °C) simulating the conditions applied in the frying process clearly demonstrated that, for the same periods of heating, the oil degradation and the loss of natural tocopherol were significantly lower for the oil containing γ-tocopherol. Comparison of different genetically modified sunflower oils with different fatty acid compositions confirmed that oil degradation depended on the fatty acid composition, being higher at a higher degree of unsaturation. However, the loss of tocopherol for a similar level of oil degradation was higher as the degree of unsaturation decreased. Overall, the results showed that HOHPSO-γ had a very high stability at frying temperatures and that mixtures of HOHPSO-α and HOHPSO-γ would be an excellent alternative to fulfill the frying performance required by the processors and the vitamin E content claimed by the consumers.