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I. B. SALA and S. Jung. Dept. of Food Science and Human Nutrition, Iowa State Univ., 2312 Food Sciences Bldg., Ames, IA 50011-1061 Soymilk consumption in Western countries is increasing due to the recognized nutritional value and beneficial health effects of soy foods. Thermal treatment, which is necessary to inactivate trypsin inhibitor, an anti-nutritional factor, and maintain soymilk sensory quality through the inactivation of lipoxygenase and b-glucosidase, may alter other soymilk constituents and properties. High Pressure Processing (HPP) can be used as an alternative to heat to inactivate undesirable components without affecting quality or nutritional value of soymilk. The objective of this work was to determine HPP parameters (pressure, holding time, temperature) that can inactivate trypsin inhibitor, lipoxygenase, and b-glucosidase and to investigate pressurized soymilk physicochemical and functional changes. The efficiency of HPP treatment was compared to thermal treatment. Raw soymilk and trypsin inhibitor were heated at 95° C, while lipoxygenase and b-glucosidase solutions were treated at 55° C. Pressures applied were between 100 and 800 MPa at 25° C. Inactivation rate constants after heat treatment were 3.31x10-2, 3.30x10-2, and 2.24x10-2 min-1 for trypsin inhibitor, lipoxygenase, and b-glucosidase, respectively. Treatment at 100 MPa for 30 min did not change the activity of any of these three enzymes. At 300 MPa, a 20% reduction of trypsin inhibitor activity was observed. Lipoxygenase activity was stable up to 400 MPa while b-glucosidase activity was lower than 10% above 400 MPa. Soymilk underwent an irreversible change to the progel state above 300 MPa that can be ascribed to protein structural changes. These changes were confirmed by differential scanning calorimetry and native PAGE. L* and b* values decreased gradually from 100 to 800 MPa. Apparent viscosity after treatment at 400, 500, and 600 MPa increased significantly compared to the control. These results contribute to the understanding of HPP and its effects on the quality and nutrition related constituents of soy foods.
Session 34, Nonthermal Processing: General I
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |