45C-7 |
Comparison of off flavor volatiles generated from whole and defatted soy flour during heating |
Q. WU, Z. DAI, Z. XU, and J. S. GODBER. Dept. of Food Science, Louisiana State Univ. Agricultural Center, 111 Food Science Bldg., Baton Rouge, LA 70803-4200 Soy foods have been reported to have benefits due to soy proteins and isoflavones, which have been found to lower serum cholesterol and the formation of certain types of cancer. However, objectionable flavors associated with soybean are not acceptable to most people. The beany off-flavors of soybean may be produced, in part, by the oxidation of lipids. Alcohols and carbonyl compounds have been found to be major contributors. Defatted soy flour is a by-product of oil extraction that retains most of the beneficial proteins and isoflavones. Its reduced lipid content may not be as susceptible to the formation of the beany off-flavors, which could improve the utilization of the by-product and benefit to the soy industry. To investigate differences in off-flavor production from whole and defatted soy flour during heating. Defatted soy flour was prepared by using hexane to remove fat. The flask containing whole soy or defatted soy flour was mixed with distilled water and an internal standard and incubated at 80oC for 45 min. The headspace volatile compounds were extracted using a PDMS SPME fiber method. GC-olfactory and GC-MS were used to describe the odor characteristics and chemical structures of extracted and separated volatiles. The four major peaks in the chromatography that described strong grassy, sting, beany, and rancid oil flavors in the olfactory examination were tentatively identified as hexanal, hexanol, hexyl ester, and pyran-contained chemicals, repesctively. The levels of hexanal, hexanol, hexyl ester, and pyran-contained chemicals in defatted soy flour were lowered to 49.3%, 77.7%, 49.6%, and 19.2% compared with whole soy flour, respectively. Soy off-flavors generated during heating were significantly lower in defatted soybean flour. The finding that less off-flavor was generated in defatted soy flour may provide insight in the manufacture of soy or soy supplemented foods with acceptable flavors while retaining the most important health promoting compounds. It also provides potential value-added utilization for the soybean oil processing industry.
Session 45C, Food Chemistry: Flavor and aroma chemistry
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