In order to study an the preparation of improved soysauce, Koji(soybean and wheat mash fermented by the strain Aspergillus sojae), Koji-Natto(mixed with the various proportion of Koji to Natto; 8:2, 6:4, 4:6, 2:8) and Natto (prepared using the strain: Bacillus subtilis) were prepared as soysauce materials. Sensory evaluation for the soysauces made from above-mentioned soysauce materials and the contents of total nitrogen, amino nitrogen, ammonia nitrogen, reducing sugar, total acid and enzyme activity mere determined. The results were summarized as follows:
1. Protease activity of Natto was over twice higher than that of Koji and amylase activity of Koji was three tines higher than that of Natto. Koji-Natto slowed successive increase of amylase activity and successive increase of protease activity as Koji proportion was increased to Natto.
2. The contents of total nitrogen and amino nitrogen in all the soysauce mashes displayed linear increases or no changes of these contents as aging. The contents of total and amino nitrogen in the mahes were higher as Natto proportion increase to Koji during the aging period.
3. In Natto soysauce mash and Koji-Natto soysauca mashes the contents of ammonia nitrogen were gradually increased until 1∼2 months and rapidly reduced after that period, while Koji soysauce mashes were continuatively increased.
4. In all the soysauce mash the reducing sugar increased preeminently until the two months and after then there was a rapid decrease as aging the content, of reducing sugar in the mash were higher as Natto proportion increased to Koji during aging period.
5. The total acid of Koji and Koji-Natto (8 : 2) soysauce mash showed gradual increase as aging, while contents of total acid in Natto and other Koji-Natto soysauce mashes increased preeminently until 50∼70 days aging, after then decreased.
6. The results of sensory evaluation for three-month-fermented soysauces showed the most excellent in Koji-Natto (6 : 4) and successive order in the soysauces consisting of Koji and Natto proportion: 8 : 2, 30 : 0, 4 : 6, 2 : 8, 0 : 10.
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