1972 Volume 19 Issue 2 Pages 96-100
To elucidate the mechanism of the increase of reduced viscosity of soybean protein in alcohol solution, the behavior of the protein was studied using viscosity, ultracentrifugation, and turbidity. Reduced viscosity of soybean globulins was determined between 0.1 to 1.5% protein concentration in the presence of varying concentration of alcohols in 0.076 M tris-citrate buffer. Reduced viscosity as a function of alcohol concentration was found to be maximal at 30% propyl, 40% ethyl, and 50% methyl alcohol, and thus was a function of the size of the alkyl group. Ultracentrifugal analysis showed that the main component of soybean protein was polymerized in alcohol solution.
Therefore, the increase of viscosity of soybean protein in alcohol solution is a result of pylymerization of the protein molecule rather than unfolding.
The increase of viscosity of the protein in alcohol solution was accelerated by low concentration of 2-mercaptoethanol, a reducing agent of disulfide bonds. After 24 hours in the presence of 2-mercaptoethanol, viscosity and turbidity measurements showed similar increases. Therefore, it was clear that 2-mercaptoethanol accelerated the polymerization of protein in alcohol solution.
