2009 Annual Report
First, we found that the best profile of tocopherols in frying oils was a combination of three tocopherols--high gamma and delta tocopherols with low alpha tocopherol to keep frying oils and fried food from deteriorating. Adding the tocopherols individually was not as effective as all three tocopherols added together, indicating a possible synergistic effect. These results are of interest to oil processors and food manufacturers in determining the appropriate antioxidant composition of oils such as soybean, sunflower, cottonseed, canola, and corn oils to maximize their quality for the 8 billion pound/year frying oil industry so they can be used without hydrogenation.
Second, we found that phytochemicals extracted from distillers dried grain (DDG) oil significantly improved the oxidative stability of soybean, sunflower, and high-oleic sunflower triacylglycerols. Tocopherols, tocotrienols, and ferulate phytosterol esters in the oil all contributed to the antioxidant activity, though there may be other components in the DDG extract that also contribute to antioxidant activity. We have also isolated ferulate phytosterol esters from DDG oil that help to prevent polymerization in oils heated to frying temperatures. This is of interest to ethanol producers searching for additional markets for DDG, as well as to food processors seeking antioxidants and phytochemical compounds to enhance the nutritional properties of their food products. We are also investigating structure-function relationships of phytosterols by analyzing extracts from various plant sources such as soybean, sunflower, canola, Vernonia galamensis, and evening primrose oils which contain different profiles of some less common phytosterols. The phytosterols have been identified, and isolation is continuing. We are determining if there are differences in the antipolymerization activity of phytosterols from different plant sources and if there are any differences in activity of phytosterols with delta-5 double bonds versus delta-7 double bonds. This data will assist plant breeders in determining the best phytosterol profile to breed for better oil stability. Third, we determined that a new citric acid-based antioxidant that is heat stable to frying oil temperatures inhibits the deterioration of soy oil and food fried in it. This additive inhibited the formation of free fatty acids and total polar compounds in the frying oil and the development of off-flavor compounds in the fried food. This additive can be used as an alternative to hydrogenated oil to increase the stability of frying oil and fried food.
Lee, S., Inglett, G.E., Palmquist, D.E., Warner, K.A. 2008. Flavor and texture attributes of foods containing beta-glucan-rich hydrocolloids from oats. LWT - Food Science and Technology. 42(1):350-357.
Warner, K.A. 2009. Flavor Changes During Frying. In: Sahin, S., Sumnu, S.G., editors. Advances in Deep-Fat Frying of Foods. Boca Raton, FL: CRC Press. p. 201-213.
Warner, K.A. 2009. Oxidative and Flavor Stability of Tortilla Chips Fried in Expeller Pressed Low Linolenic Acid Soybean Oil. Journal of Food Lipids. 16:133-147.
Moser, J.K., Warner, K.A. 2008. Effect of Phytosterol Structure on Thermal Polymerization of Heated Soybean Oil. European Journal of Lipid Science and Technology. 110:1068-1077.
Warner, K.A. 2009. High-Temperature Natural Antioxidant Improves Soy Oil for Frying. Journal of Food Science. 74(6):500-505.
Moser, J.K., Vaughn, S.F. 2009. Antioxidant Activity of Phytochemicals from Dried Distillers Grain Oil. Journal of the American Oil Chemists' Society. 86:1026-1035.