Preparation of Fermented Soymilk Curd withCommercial Proteinases

Abstract

Soymilk curd was prepared by using three kinds of proteinases having soymilk-clotting activity (subtilisin, thermolysin and bromelain) as a coagulant followed by lactic acid fermentation. Among these fermented soymilk curds, the curd made with thermolysin showed a little higher moisture content than the others. On the other hand, the curd made with bromelain had a little higher protein recovery and yield than the others. In order to estimate the extent of proteolysis in fermented soymilk curd, analyses were made on electrophoretic patterns, the ratio of water soluble nitrogen to total nitrogen, and free amino acid content. The results of these experiments showed that thermolysin and subtilisin hydolyzed the protein in fermented soymilk curd more than bromelain did. None of the soymilk curd which was fermented for 2 weeks developed bitterness or rancidity. The fermented soymilk curd made with thermolysin was slightly superior in texture (smoothness) to that made with the others. The results of this study suggest that thermolysin, as compared with subtilisin and bromelain, is more suitable for making fermented soymilk curd with respect to proteolysis and texture (smoothness).