Effect of Electrolytic Reduction on Viscosity and Gel Formation of Soybean Protein Solution

Food Technological Studies on Gelation of Soybean Protein Part IV

Abstract

The effect of electrolytic reduction on viscosity and gel formation of an acid precipitated soybean protein solution was investigated. The electrolytic reduction current was set at 10mA (current density, 2.5mA/cmcm²). Acid precipitated protein was prepared from U.S. soybeans (1979 crops, Ohio) stored under the conditions of 40°C and R.H. 75% for 30 days. The amount of sulfhydryl group and pH value of the soybean protein solution increased with the application time of electrolytic reduction. The relative viscosity of the solution researched to a maximum value after 120 min-electrolytic reduction. On further application, the viscosity decreased gradually. The increase of viscosity of the solution by heating was remarkable in the absence of electrolytic reduction treatment. GDL (glucono-delta-lactone)-gel prepared from the acid precipitated protein solution treated with the electrolytic reduction was harder than that obtained from the solution without the application of the treatment. The hardness of GDL-gel as well as the viscosity of the solution showed a maximum at 120 minutes after the start of electrolytic reduction. It was suggested that the decrease of hardness of GDL-gel prepared from the protein solution heated excessively was farily restrained by applying the electrolytic reduction to the solution.