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Title: A High-Protein Soybean Cultivar Contains Lower Isoflavones and Saponins but Higher Minerals and Bioactive Peptides than a Low-Protein Cultivar

item Berhow, Mark

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2009
Publication Date: 1/10/2010
Citation: Paucar-Menacho, L.M., Berhow, M.A., Mandarino, J., Gonzalez-De Mejia, E., Chang, Y. 2010. A High-Protein Soybean Cultivar Contains Lower Isoflavones and Saponins but Higher Minerals and Bioactive Peptides than a Low-Protein Cultivar. Food Chemistry. 120:15-21.

Interpretive Summary: This research has shown that the use of soy-seed germination in food preperation enhances several key nutritional factors in soy. These factors can be used to develop new and improved soy foods and ingredients with altered levels of health enhancing components. A number of compounds found in soy have been shown to have important health benefits. Most soy products are prepared from the dry mature soybean. When the soybean is allowed to germinate before it is processed into flour and other products, however, the levels of a number of beneficial compounds can be increased. Using a new mathematical model, the effects of germination on a number of phytochemicals in soybeans from the cultivar BRS 133 were examined. An optimal germination time and temperature of 42 hours at 25 degrees C enhanced the levels of soy isoflavones, saponins and the protein lunasin, while decreasing the levels of the antinutritive proteins BBI, lectin and lipoxygenase. This could result in new foods and formulations for soy ingredients in foods.

Technical Abstract: Consumption of soybean products has increased considerably in the last few years, possibly due to the functional properties and the presence of bioactive compounds which bring health benefits to consumers. The process of germination has been shown to increase the concentration of a number of these bioactive compounds. The objective of this study was to optimize the effect of germination time and temperature on the concentration of soluble protein, lunasin, BBI, lectin, saponins, and isoflavones in soybean seeds from cultivar BRS 133. Isoflavone and saponin concentrations were analyzed by HPLC. Lunasin, Bowman-Birk Inhibitor (BBI) and lectin were analyzed by ELISA and western blot. The effects of the variations in germination time and temperature on bioactive compounds were analyzed using the Response Surface Methodology (RSM), with a 22 central composite rotational design. Germination of soybean cultivar BRS 133 for 42 h at 25°C resulted in an increase of 61.7% of lunasin, a decrease of 58.7% in lectin and a decrease of 70.0% in lipoxygenase activity. Optimal increases in the concentrations of isoflavone aglycones were observed in combination of 63 h of germination and 30°C. A significant increase in the concentration of soyasaponins was observed in combination of 42 h of germination and 25°C.