Effect of temperature on enzymatic stability in shio-koji during the maturation process
2015
Maehashi, K. ((Tokyo University of Agriculture, Setagaya-ku, Tokyo (Japan). Department of Fermentation Science), (Graduate School of Tokyo University of Agriculture, Setagaya-ku, Tokyo (Japan). Department of Fermentation Science and Technology)) | Ohto, A. | Yamamoto, T. | Asari, M. | Kashiwagi, Y.
Shio-koji is a gruel-like fermented rice seasoning that is obtained from the digestion of rice under high-salt conditions. The average chemical composition of 14 commercially available shio-koji products was analyzed and determined as : 11.0% NaCl, 21.9% reducing sugar, 0.07% formal nitrogen, and 50.2% water. Amylolytic and proteolytic enzyme activities were detected in the majority of the shio-koji products, although they were not detected in others. It is currently accepted that maturation at 60degC for more than 6 hours is required for sufficient digestion of starch and proteins. However, maturation at either 50degC or 60degC for 6 hours resulted in increased formal nitrogen levels without loss of enzyme activity. Upon comparison of shio-koji and amazake, in a solution of 10% NaCl-containing koji extract, here we report that a 10% NaCl solution led to the decreased thermal stability of alpha-amylase while that of proteases was augmented.
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