C: Food Chemistry JFS C: Food Chemistry Comparison of Soybean Oils, Gum, and Defatted Soy Flour Extract in Stabilizing Menhaden Oil during Heating X. YUE, Z. XU, W. PRINYAWIWATKUL, J.N. LOSSO, J.M. KING, AND J.S. GODBER ABSTRACT: Capabilities of crude soy oil, degummed oil, gum, and defatted soy flour extract in preventing the oxi- dation of menhaden oil and its omega-3 fatty acids, DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid), during heating were evaluated. The menhaden oil mixed with defatted soy flour extract demonstrated the greatest stability by producing the lowest TBA reactive oxidation products and retaining the highest concentrations of DHA and EPA after heating at 150 ◦ C for 30 min. A range of 62.8% to 71.5% of DHA and 67.7% to 75.9% of EPA remained in the fish oil with defatted soy flour extract, while only 29.9% of DHA and 37.2% of EPA were retained in the fish oil with no addition. Stabilizing capability from highest to lowest was defatted flour extract > gum > degummed oil = crude oil. The defatted flour extract had the highest level of total phenolic content (11.3 μg catechin equivalent/g), while crude oil, degummed oil, and gum contained 7.1, 6.1, and 6.0 μg catechin equivalent/g, respectively. The level of isoflavones in the defatted soy flour extract was 55 mg/g, which was over 100 times higher than in the crude oil or gum. Although isoflavones were not detected in the degummed oil, it contained the highest level of tocopherols (414 μg/g), whereas the lowest level (215 μg/g) was found in the defatted flour extract. The order of free radical scav- enging capability measured from high to low was the defatted soy flour extract, crude oil, degummed oil, and gum. Keywords: antioxidant, fish oil, gum, isoflavone, phenolic, soy, tocopherol Introduction M any epidemiological and clinical studies confirmed that daily intake of omega-3 long chain polyunsaturated fatty acid (PUFA) from fish oil is beneficial for preventing various car- diovascular diseases (Dyerberg and others 1978; Crombie and oth- ers 1987; Wang and others 2006). Food products enriched with fish oil or omega-3 PUFA as a health promoting component offer po- tential in the burgeoning area of functional food product develop- ment. However, the omega-3 PUFAs in fish oil are readily oxidized to produce off- or rancid-flavor volatiles when exposed to light, oxy- gen, prooxidants, and high temperatures (McClements and Decker 2000). Thus, the quality of fish oil or foods fortified with fish oil usually deteriorates rapidly if not stabilized. While the instability of omega-3 PUFA has been solved for some food applications, there are serious hurdles for using fish oil in other foods, such as many functional foods, that still need to be overcome. Synthetic antiox- idants such as TBHQ (tertiary butyl hydroquinone), BHA (buty- lated hydroanisole), and BHT (butylated hydroxytoluene), alpha- tocopherol acetate, and EDTA (ethylenediaminetetraacetic acid) are used for retarding the fish oil oxidation. However, the addi- tion of those artificial chemicals is restricted by the FDA because of food safety concerns, not to mention emerging trends for con- sumer preferences toward more “green” food processing applica- tions. Kotsonis and others (2001) have suggested that even small amounts of artificial antioxidants could have potentially harmful health effects from long-term consumption. MS 20070580 Submitted 7/24/2007, Accepted 9/10/2007. Authors are with Dept. of Food Science, Louisiana State Univ. Agricultural Center, Baton Rouge, LA 70803, U.S.A. Direct inquiries to author Xu (E-mail: zxu@agctr.lsu.edu). Lately, the safety and health benefits of antioxidants from natu- ral sources, such as grains and cereals, have been reported in nu- merous studies and recognized by the FDA and many consumers (Truswell 2002; Martinez-Tome and others 2004; Nystrom and oth- ers 2005). The antioxidants from natural sources are generally con- sidered as safe food ingredients. However, information on using the natural antioxidants to replace synthetic antioxidants in pre- venting fish oil oxidation is limited. Several antioxidants, includ- ing isoflavones, have been identified in soybeans (Meng and others 1999). Soy isoflavones were well recognized to play an important role in reducing the formation and progression of certain types of cancers and some chronic diseases such as cardiovascular disease, Alzheimer’s disease, and osteoporosis (Messina 1999). They are ef- fective antioxidants because of their phenol structure and redox po- tential (Meng and others 1999). Thus, the antioxidants in soybean could be used as a natural “green” antioxidant ingredient to effec- tively stabilize fish oil and other food systems containing omega-3 PUFA. In this study, the capabilities of intermediate products and byproducts of soybean oil refining, including crude soy oil, degummed oil, gum, and defatted soy flour, for preventing long chain fatty acid (DHA and EPA) oxidation and stabilizing men- haden oil during heating were investigated. The DPPH (2,2’- diphenyl-1-picrylhydrazyl) free radical quenching activity and total phenolic, isoflavone, and tocopherol contents in the oils, gum, and defatted soy flour extract were determined. This information would be helpful in the development and utilization of soy products as a food antioxidant or an antioxidant nutritional supplement. Fur- thermore, this application will also increase the potential health benefits of fish oil with the additional health promoting functions of the soy antioxidants. C  2007 Institute of Food Technologists Vol. 73, Nr. 1, 2008—JOURNAL OF FOOD SCIENCE C19 doi: 10.1111/j.1750-3841.2008.00586.x Further reproduction without permission is prohibited