Studies on the Changes of the Properties of Soybean Protein by Freezing

Part V. Improved production of new textured protein by freezing

Abstract

With the purpose to increase the yield of the textured protein which was prepared by freezing soybean protein solution, effects of various conditions in the production were studied.
Addition of 2.0 to 2.5×10^-4mol CaCl₂ per g protein to protein solution caused 96% insolubilization of protein after freezing and thawing, resulting in the increase of the yield of the textured protein. Heatiug effects on the amount of SH contents of protein, and maximum amount of SH content was observed after 1min. of heating at 100°C, being its insolubilization by freezing increased compared with longer time heating. Addition of 5×10^-6mol Na₂SO₃ per g protein to protein solution, SH contents of which is less than ordinary one, accelerated insolubilization of protein by freezing. Quality of the textured protein was influenced by freezing rate. When protein solution was frozen very quickly at -70°C, the texture became too fine and weak. On the contrary protein solution which was frozen at -5°C had very coarse texture. To make good texture it is necessary to freeze at -20°C. From these results a standard process of the textured protein making is proposed.