ARS | Publication request: Oxidative stability of crude mid-oleic sunflower oils from seeds with high gamma and delta tocopherol levels

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 25, 2008
Publication Date: June 16, 2008
Citation: Warner, K.A., Miller, J.F. 2008. Oxidative Stability of Crude Mid-Oleic Sunflower Oils from Seeds with High Gamma- and Delta-Tocopherol Levels. Journal of the American Oil Chemists' Society. 85:529-533.

Interpretive Summary: Currently the oil and food industries are formulating oils that can be alternatives to hydrogenated oils for frying. Hydrogenated oils contain trans fatty acids that some consumers try to avoid. In an effort to make sunflower oils more suitable for frying without hydrogenation, we evaluated sunflower oils that had the levels of natural antioxidants increased to improve the oil quality. We found that when two types of antioxidants, gamma and delta, were increased in the sunflower oils, the oils did not become rancid as fast as when the levels of these two antioxidants were low. We also found that the levels of another important antioxidant, alpha, could be in the oils at a high enough level to be a good source of vitamin E.

Technical Abstract: Sunflower oil typically has a tocopherol profile that consists primarily of alpha-tocopherol - usually 95% of the total tocopherol content. Gamma-, delta-tocopherols are better antioxidants in vitro than alpha-tocopherol. Therefore, the oxidative stability of sunflower oil could possibly be enhanced if it contained a different tocopherol profile with higher proportions of gamma-, delta-tocopherols. In this study, mid-oleic and high oleic sunflower seeds were developed with high levels of gamma-, delta-tocopherols. Sunflower seeds containing various profiles of tocopherols ranging from traditional high alpha, low gamma, low delta to those with high gamma, high delta and low alpha were extracted and the crude oil evaluated for oxidative stability. After aging at 60 deg C, oils were measured for peroxide value and hexanal as indicators of oxidation. We found that when the gamma-tocopherol content of mid-oleic sunflower oil was increased from its regular level of 20 ppm to 300-700 ppm, the oxidation of the oil was decreased significantly compared to mid-oleic sunflower oil with its regular low gamma-tocopherol level. The modified oils had alpha-tocopherol contents of up to 300 ppm without negatively affecting the stability of the oil. An oil with one of the best oxidative stabilities had a tocopherol profile of 470 ppm gamma, 100 ppm delta and 300 ppm alpha indicating that mid-oleic sunflower oil could be more oxidatively stability and be a good source of Vitamin E from alpha-tocopherol.