2008 Annual Report
1a.Objectives (from AD-416)
To develop new knowledge about natural antioxidants that affect the quality and inherent stability of vegetable oils by investigating effects of tocopherols, tocopheron oxidation products and phytosterols and evaluating alternative technologies of oil processing.
1b.Approach (from AD-416)
We will conduct frying studies to evaluate the effects of various ratios of tocopherols for enhancing both the fry life of the oil and the shelf life of fried food. The effects of various phytosterols as antipolymerization agents will be investigated. Oxidation products from tocopherols such as quinones will be investigated as potential antioxidants. In addition, new cultivars of high gamma sunflower oil will be evaluated for frying stability in comparison with traditional low gamma/high alpha sunflower oil. We will use this information to recommend optimum levels and ratios of tocopherols in edible vegetable oils for both food manufacturers and plant geneticists. We will study alternative technologies such as pressing to retain better yields of natural antioxidants and produce oils with enhanced quality and oxidative stability. We will identify those inherent phytochemicals in pressed oils that positively affect oil quality and stability.
We developed new knowledge about the effect of tocopherols in inhibiting oxidation in stored fried food. Delta- and gamma-tocopherols were better at inhibiting oxidation of the aged fried food than alpha tocopherol. Although the tocopherols had a positive effect in the fried food, they did not have much of an effect in inhibiting deterioration of the frying oil. Since phytosterols help limit deterioration of frying oils, the combination of phytosterols to inhibit frying oil deterioration and tocopherols to inhibit oxidation in the fried food provides important information in the search for alternatives to hydrogenated oil for frying. 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. We obtained new knowledge about the effects of phytosterol structure on their activity as anti-polymerization agents. We found that the number of double bonds as well as their location in the phytosterol structure affected their antipolymerization activity. This knowledge is valuable in determining the best types of phytosterols for maximizing oil stability to high temperature applications such as frying. We developed a new method to remove free fatty acids and to concentrate valuable phytochemicals from oil extracted from corn dried distiller’s grains (DDG), the major co-product of ethanol production. Using short-path distillation and various temperatures we sequentially removed free fatty acids and then concentrated phytochemicals including Vitamin E and phytosterols from DDG oil. This technology results in several additional co-products including oil that would be suitable for biodiesel production along with the phytochemicals, which are valuable nutraceuticals. This technology may be useful to ethanol producers, who are currently highly interested in developing new markets for the DDG co-product. We also isolated ferulate phytosterol esters (FPE) from corn DDG. We found that these FPE had similar activity to FPE from rice bran oil in preventing oil polymerization. We also found that the FPE from corn DDG were slightly more stable to high temperatures. This knowledge may be important to the development of FPE as possible agents to improve oil stability to high temperature applications such as frying. This research progress addresses National Program 306, Component 1 of the Action Plan.
Concentrating phytochemicals from corn dried distiller’s grain extracts. Corn dried distillers grain (DDG) is a by-product of the growing ethanol industry, and there is great interest in developing new uses for this by-product. We previously found that the oil extracted from DDG is high in antioxidants and other desirable phytochemicals, however, it is important to develop relatively simple, cost-effective methods for isolating these compounds from the rest of the oil. A technique was developed to concentrate desirable phytochemicals, including tocopherols and tocotrienols (Vitamin E), phytosterols, and other antioxidants from oil extracted from DDG. These compounds are important as antioxidants and nutraceuticals in foods, therefore, this knowledge provides a possible new value-added market for the DDG by-product. This research accomplishment directly addresses NP306, Component 2, Problem Area 2a of the Action Plan.
Characterization and activity of ferulate phytosterol esters from corn dried distiller’s grains. Ferulate phytosterols esters (FPE) are a combination of an antioxidant, ferulic acid, with phytosterols, which can help lower blood cholesterol. FPE are found in many whole grains but are found to be in high concentrations in oil extracted from corn dried distiller’s grains. These FPE were isolated and found to contain a high concentration of saturated phytosterols, which is desirable for maintaining high stability to heat and oxygen. The isolated FPE were tested for their ability to prevent the thermal polymerization of heated soybean oil, and were found to have similar antipolymerization activity compared to FPE from rice bran oil. This research accomplishment directly addresses NP306, Component 1, Problem Areas 1a and 1b of the Action Plan.
Sunflower cultivars with high levels of gamma- and delta-tocopherols. Our studies on vegetable oils showed that gamma- and delta-tocopherols were much better antioxidants than alpha-tocopherol. Since sunflower oils contain mostly alpha-tocopherol, we recommended that Agricultural Research Service (ARS) plant geneticist develop sunflowers with high amounts of gamma- and delta-tocopherols to enhance the oxidative stability of sunflower oil. In March, 2008, a germplasm release of this modification was made through the ARS Germplasm Resources Information Network (GRIN). This new modified sunflower oil has the potential to help replace trans fat-containing hydrogenated oils for high stability uses such as frying and to produce good quality, healthful foods. This research accomplishment directly addresses NP306, Component 1, Problem Area 1a of the Action Plan.
5.Significant Activities that Support Special Target Populations
|Number of Non-Peer Reviewed Presentations and Proceedings||1|
Warner, K.A. 2007. Increasing gamma- and delta-tocopherols in oils improves oxidative stability. Lipid Technology. 19(10):229-231.
Winkler, J.K., Warner, K.A., Glynn, M.T. 2007. Effect of deep-fat frying on phytosterol content in oils with differing fatty acid composition. Journal of the American Oil Chemists' Society. 84:1023-1030.
Winkler, J.K., Warner, K.A. 2008. The effect of phytosterol concentration on oxidative stability and thermal polymerization of heated oils. European Journal of Lipid Science and Technology. 110:455-464.
Jham, G.N., Winkler, J.K., Berhow, M.A., Vaughn, S.F. 2007. Gamma-Tocopherol as a marker of Brazilian coffee (Coffea arabica L.) adulteration by corn. Journal of Agriculture and Food Chemistry. 55:5995-5999.
Warner, K.A., Fehr, W. 2008. Mid-Oleic/Ultra Low Linolenic Acid Soybean Oil: A Healthful New Alternative to Hydrogenated Oil for Frying. Journal of the American Oil Chemists' Society. 85:945-951.
Warner, K.A. 2008. Food uses for soybean oil and alternatives to trans fatty acids in foods. In: Johnson, L.A., White, P.J., Galloway, R., editors. Soybeans: Chemistry, Production Processing and Utilization. Chapter 15. Urbana, IL: AOCS Press. p. 483-498.
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.