Changes in Microflora and Enzyme Activities of Cheonggukjang Prepared with Germinated Soybeans during Fermentation

Abstract

This study was carried out to investigate the changes in microflora, enzyme activity and sensory quality of four kinds of cheonggukjang during fermentation. Three different kinds of cheonggukjang were prepared with germinated soybeans using rice straw, Bacillus natto, B. natto plus Aspergillus oryzae, and the last one was prepared with non- germinated soybeans using rice straw. The pH values of cheonggukjang prepared with germinated or non-germinated soybeans increased up to 36 hr of fermentation and then decreased. The number of bacteria and molds increased significantly up to 24 hr of fermentation and then leveled off during fermentation. Acidic and neutral protease activities of all cheonggukjang continuously increased significantly during fermentation. α- and β-Amylase activities of cheonggukjang decreased slightly during fermentation except cheonggukjang prepared with germinated soybeans using the mixed culture. The number of microflora, protease and α-amylase activities were highest in cheonggukjang prepared with germinated soybeans using B. natto plus A. oryzae. The results of the sensory evaluation revealed that for overall acceptability, the cheonggukjang prepared with germinated soybeans using B. natto plus A. oryzae was similar to the cheonggukjang prepared with non-germinated soybeans using rice straw.