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Meeting Abstract

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Functional properties of soy protein modified by an endoprotease at low degrees of hydrolysis. S. JUNG, P.A. Murphy, and L.A. Johnson. Department of Food Science and Human Nutrition, Iowa State University, 2312 Food Science Bldg., and Center for Crops Utilization and Research, 1567 Food Science Bldg., Ames, IA 50011.

Soy protein products often present less than ideal functional properties because the steps necessary to their preparation denature the protein altering the excellent native functionality of soy protein. This study was undertaken to characterize four soy protein products (hexane-extracted soy flour, extruded-expelled partially defatted soy flour (EE), ethanol-washed soy concentrate and soy protein isolate) modified by an endoproteinase at low degrees of hydrolysis (DHs 2 and 4%). Functional properties including solubility profile; emulsification capacity (EC), activity and stability; foaming capacity and stability; and viscosity were determined. Hydrophobicities and electrophoretic profiles were also determined. The time necessary to reach different DHs was substrate-dependant. The EC values of the modified hexane-extracted soy flour and EE flour decreased after hydrolysis but the EC values for the soy concentrate and soy isolate increased. Hydrolysis improved the foaming properties and decreased viscosity. These functional modifications were related to hydrophobicity and SDS profiles. Some of the modified functional properties observed would be useful when incorporating soy proteins in food products.