49B-10 |
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N. D'SOUZA1, D. I. Skonberg1, M. E. Camire1, and J. A. Malison2. (1) Dept. of Food Science & Human Nutrition, Univ. of Maine, 5735 Hitchner Hall, Orono, ME 04469-5735, (2) Dept. of Animal Sciences, Univ. of Wisconsin, Madison, 1675 Observatory Dr., 658 Animal Science Bldg., Madison, WI 53706-1284 The growth of aquaculture with a corresponding decrease in fish meal has spurred research on alternate plant protein sources to be used in fish feeds. Soybean is a logical solution since it is a readily available source of high-quality protein. Genistein is a naturally occurring isoflavone present in soybean. Isoflavones may impart off-flavors and mimic estrogenic activity, thus affecting the full utilization of soy in fish feeds. The objective of the present study was to evaluate the quality of rainbow trout reared on diets in which genistein was added as a component. Quality evaluation included instrumental and sensory analyses of the fish fillets. Genistein was isolated and then quantified by high performance liquid chromatography. Three methods, using 80% aqueous methanol, citrate buffer (0.025M, pH 5.0) and Tris buffer (0.1M, pH 7.4) were used in the estimation of genistein in trout fillets. Fillets from trout fed the 0 and 3,000 ppm genistein concentrations were analyzed. A triangle test (n=24) on the fillets from the 0 and 3,000 ppm treatments was also performed to determine if there were any detectable flavor differences. Color measurements of the fillets were taken on a Hunter Colorimeter. The methanol and citrate buffer methods failed to detect genistein in all samples. No genistein was detected in fillets from the 0 ppm feed level while the fillets from the 3,000 ppm were found (Tris buffer method) to contain 4.66 pmol genistein/mg of fish tissue. Triangle test panelists were unable to detect any differences between the fillets fed the 0 and 3,000 ppm genistein concentrations. There were also no differences in color between the fillets from the two treatments. These results indicate that genistein at a level of 4.66 pmol/mg tissue did not result in any sensory changes in the fish. These findings are indicative only of genistein and cannot be generalized to the application of soybean meal as a whole in fish diets. Sensory descriptive and affective studies of trout fed soybean meal based diets are scheduled for 2004.
Session 49B, Aquatic Food Products: General
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