Studies on the coagulation of soymilk-protein by commercial proteinases.

Abstract

A coagulation test of soymilk-protein was carried out with various commercial proteinases originating from microorganisms, plants and animals. The soymilk-protein was coagulated by the following proteinases: Bacillus amyloliquefaciens, Bacillus subtilis, Bacillus polymyxa, Streptomyces griseus, Streptomyces caespitosus, Aspergillus oryzae, Aspergillus sojae, Endothia parasitica, Rhizopus sp., Mucor miehei, bromelain, papain and trypsin. However, such proteinases as Aspergillus saitoi, rennin and pepsin did not coagulate the protein. The coagulability of enzymes decreased as the pH of the soymilk was increased from 5.9 to 6.7. The optimum temperature for soymilk-clotting activity varied widely with the enzyme origin; for example, 55°C in the case of proteinases of Bacillus polymyxa and Rhizopus sp., 65°C in that of Aspergillus oryzae, Aspergillus sojae and trypsin, 75°C in that of Bacillus amyloliquefaciens, Streptomyces griseus, Streptomyces caespitosus and Endothia paracitica, and 85°C in that of Bacillus subtilis and Bacillus thermoproteolyticus. The coagulum made with the enzyme was separated into soymilk-curd and whey in a volume ratio of 1 to 1 by centrifugation at about 1600 × g. The moisture content of the curd was about 87%.