Growth Characteristics of Genus Rhizopus Incubated on Steamed Soybeans

Studies on Fermented Soybean Food Manufacture Using Various Mold (part 3)

Abstract

Growth characteristics of genus Phizopus, including 6 strains employed for making tempeh and sake were examined. Pile culture was carried out employing these molds on steamed soybean comparing with Aspergillus oryzae. Following results were obtained:
1. Growth temperature of these Rhizopus was 25-40°C, and optimum temperature was 30-35°C 2. They grew at pH 3.5-8.0 and optimum pH was 5.0-6.0.
3. Addition of 2-4% level lactic acid to soaking water reduced pH value below 5.0 and resulted in the reduction of bacterial count of fermented soybeans, whereas the effect of addition of acetic acid was less than that of lactic acid.
4. Culturing on mashed soybeans increased the activity of neutral and acidic protease and NSI compared with that on whole soybeans.
5. Amounts of glucosamine in fermented soybeans were same in both mashed and whole soybean. Rhizopus produced glucosamine about 60% of the amount produced by Aspergillus.
6. Fermented soybeans by Rhizopus had the tendency of solubilizing protein more rapidly than that by Aspergillus.
7. Rhizopus produced mainly neutral and acidic protease differing from Aspergillus, the protease of which was affected by ratio of C/N in substrat
8. Culturing mold on cooked soybeans, the product showed a tendency to increase the emulsifying property and water holding capacity.