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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCING FLAVOR QUALITY AND OXIDATIVE STABILITY OF EDIBLE VEGETABLE OILS WITH PHYTOCHEMICAL ANTIOXIDANTS
2005 Annual Report


1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter?
Edible vegetable oils account for 75% of the U.S. production of vegetable oils or approximately 16 billion pounds each year. Vegetable oils intended for high stability uses such as frying currently need additional processing such as hydrogenation and chemical additives to be suitable for the 8 billion pounds/per year frying oil industry. Food manufacturers are currently looking for alternatives to hydrogenated oils because of trans fatty acids; however, oils that are processed without hydrogenation are not stable enough for frying oils. Most oils with fatty acid compositions modified to increase oleic and/or to decrease linoleic or linolenic acids are still not as stable for frying as hydrogenated oils. Naturally occurring minor oil constituents such as tocopherols and phytosterols could further enhance the stability of modified oils to have equal or better stability than hydrogenated oils. However, not enough information is available on how these phytochemicals affect product quality, stability, and end use performance. Basic research is needed to determine the relationship between product composition and desired flavor quality and stability attributes in soybean, sunflower, corn and other oils. Technologies are also needed to process oils to have better yields of naturally occurring antioxidants. If not enough appropriate edible oils for high stability applications can be produced in the U.S., food manufacturers may look to imported tropical fats such as palm or coconut as alternatives. We are developing new knowledge about naturally occurring phytochemical antioxidants in vegetable oils that affect the quality and inherent stability of edible oils. We are using various approaches to enhancing the flavor quality and oxidative stabilities of vegetable oils such as characterizing pressed oils to understand the sources of their enhanced stability. In other efforts to improve frying oil and fried food stability, we will add natural antioxidants to oils that lack the stability needed for high stability uses such as frying. We will make recommendations to food manufacturers, oil processors and plant geneticists to develop oils with enhanced stability using phytochemicals.

This project contributes to National Program 306 under Component I for "Quality Characterization, Preservation and Enhancement." This research contributes new knowledge to understand the roles of product composition for optimum end-use performance and quality of edible vegetable oils (problem area 1a on factors and processes that affect quality and problem area 1c on definition and basis of quality). This research also contributes to meeting the ARS goal for genetic improvement of oilseeds for improved attributes for good quality products in which plant breeders target particular quality attributes in the germplasm (problem area 1d on preservation and/or enhancement of quality).


2.List the milestones (indicators of progress) from your Project Plan.
Year 1: Evaluate high gamma tocopherol sunflower oils; determine levels of oxidation products in frying oils; and evaluate pressed oils for frying stability.

Year 2: Optimize tocopherol ratios in vegetable oils; continue studies to determine levels of oxidation products in frying oils; continue to evaluate high gamma tocopherol sunflower oils; and continue studies to evaluate pressed oils for frying stability.

Year 3: Conduct studies with phytosterols; continue to optimize tocopherol ratios in vegetable oils; continue to evaluate high gamma tocopherol sunflower oils; and continue studies to evaluate pressed oils for frying stability.

Year 4: Continue to optimize tocopherol ratios in vegetable oils; continue to evaluate high gamma tocopherol sunflower oils; continue studies to evaluate pressed oils for frying stability; and continue to conduct studies with phytosterols.

Year 5: Continue to optimize tocopherol ratios in vegetable oils; continue to evaluate high gamma tocopherol sunflower oils; continue studies to evaluate pressed oils for frying stability; and continue to conduct studies with phytosterols.


4a.What was the single most significant accomplishment this past year?
Based on our initial studies of the antioxidant effects of gamma tocopherol in oils, we recommended to sunflower plant geneticists that they breed sunflowers with high levels of gamma tocopherol as an alternative to the current sunflower seed with low gamma tocopherol with the intent of producing more oxidatively stable sunflower oil. Jerry Miller, an ARS plant geneticist, developed several cultivars of sunflower seeds with high levels of gamma tocopherol and grew these sunflowers for us. We extracted the oil from the seeds and conducted oxidative stability tests on the oils. Results indicated that the sunflower seed oils with high amounts of gamma tocopherol were more oxidatively stable than traditional sunflower oil with low levels of gamma tocopherol.

In addition, frying studies with soybean oils that had been commercially processed using expelling and physical refining were conducted to determine existence of any differences between soybean oils processed using traditional solvent extraction and chemical refining. The frying stability of expeller pressed soybean oil was significantly better than soybean oil with no additives, but similar to the stability of soybean oil with Tertiary Butyl Hydroquinone (TBHQ) or hydrogenated soybean oil. We found that the Maillard reaction products from expeller pressing were a possible source of the enhanced oil stability. Food manufacturers may want to consider using expeller pressed oil as an alternative to hydrogenation or added antioxidants in edible oils.


4b.List other significant accomplishments, if any.
None.


4c.List any significant activities that support special target populations.
None.


4d.Progress report.
We evaluated oil extracted from the high gamma sunflower seeds and found that the oil was significantly more oxidatively stable than sunflower oil with the typical low gamma tocopherol content. We also determined that quinones were formed from the breakdown of tocopherols during frying. Because quinones are known to have antioxidant activity, this helps explain at least in part why oils that lose all of their tocopherol content still have some inhibition to oxidation. We found that pressed soybean oil had enhanced frying stability compared to traditional solvent extracted soybean oil. Compositional analyses of the oils indicated few differences to explain the enhanced stability. However, additional tests showed that the pressed oils contained Maillard reaction products that are known to act as antioxidants. The conditions that are used to process pressed soybean oil produce these Maillard reaction products.


5.Describe the major accomplishments over the life of the project, including their predicted or actual impact.
We determined the effects of gamma tocopherol, ferulic acid and oryzanol in frying oils and found that they each inhibited deterioration of both the frying oil and the fried food during storage. Even when the gamma tocopherol was at very low levels or not detectable, we still saw a positive effect of the addition of gamma tocopherol, presumably because of the tocopherol oxidation products such as tocopherol quinones that have antioxidant activity. Based on this knowledge, we asked plant geneticists to develop sunflowers with high levels of gamma tocopherol as an alternative to traditional sunflower, which has low levels of gamma tocopherol. Analyses of the resulting oil showed that sunflower oil bred to have high levels of gamma tocopherol were more oxidatively stable than regular sunflower oil with low amounts of gamma tocopherol. 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.


6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
We recommended that ARS plant geneticists develop sunflower seeds with high levels of gamma tocopherol. Our results of the high gamma sunflower oil showed significant improvement of the oxidative stability of the oil. The high-gamma cultivars will be grown in large amounts in 2005. These sunflower seeds have the potential to be a value-added product within the next several years. In addition, new knowledge about the role of antioxidants during frying and during storage has been developed and transferred to oil processors and food manufacturers through presentations, publications and visits with company representatives. They can use this information to develop new oils that will provide healthful, better tasting foods. In addition, plant breeders can use this information to develop new cultivars of oilseeds with enhanced profiles of tocopherols.


7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).
Warner, K. 2005. Assessing the effects of antioxidants in frying oils and fried foods. American Chemical Society, Second International Congress on Antioxidants, Orlando, FL.

Warner, K. 2005. Quality of fried food. 5th International Symposium on Deep-Fat Frying. Euro-Fed Lipid, San Francisco, CA.

Warner, K. 2005. Frying oils and fried foods. Lipid Oxidation Short Course, American Oil Chemists' Society meeting, Salt Lake City, UT.


Review Publications
Rennick, K.A., Abidi, S., Warner, K.A. 2005. Effect of elevated temperatures on development of tocopherolquinones in oils. Annual Meeting and Expo of the American Oil Chemists' Society. p. 46.

Decker, E.A., Warner, K.A., Richards, M. 2005. Measuring antioxidant effectiveness in foods. Journal of Agricultural and Food Chemistry. 53:4303-4310.

Warner, K.A., Laszlo, J.A. 2005. Addition of ferulic acid, ethyl ferulate, and feruloylated monoacyl- and diacylglycerols to salad oils and frying oils. Journal of the American Oil Chemists' Society. 82(9):647-652.

Warner, K.A., Gupta, M. 2005. Potato chip quality and frying oil stability of high oleic acid soybean oil. Journal of Food Science. 70(6):395-400.

Pintauro, P.N., Gil, M., Warner, K.A., List, G.R., Neff, W. 2005. Electrochemical hydrogenation of soybean oil with hydrogen gas. Industrial and Engineering Chemistry Research. 44:6284-6292.

Warner, K.A. 2004. Effects of tocopherol ratios on oxidative stability of soybean oil triacylglycerols. American Chemical Society Abstracts. p. 251.

Last Modified: 4/19/2014
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