Effects of Enzyme Profiles of Two Different Aspergillus oryzae Strains on Physicochemical Indexes and Quality of Soy Sauce

In this paper, two strains of Aspergillus oryzae (A. oryzae) with different enzyme profiles were selected for soy sauce fermentation. This study aimed to preliminarily explored the relationship between the enzyme profiles and the quality of soy sauce by morphological analysis, physicochemical indexes analysis and sensory evaluation. SWJS-AO-K had higher enzyme activities of protein degradation, i.e. the activities of neutral protease, acidic protease and aminopeptidase in SWJS-AO-K koji were 2.2, 2.6 and 4.4 times of those in SWJS-AO-D koji. SWJS-AO-D had the higher activities of carbohydrate hydrolysis, i.e. the activities of saccharification and cellulase was 1.8 and 1.3 times of them in other strain. The enzyme profiles were closely related to the physicochemical indexes and sensory characteristics of soy sauce. Higher contents of total nitrogen, Maillard reaction, and total bitter amino acid were detected in soy sauce fermented by SWJS-AO-K, the strain with higher enzyme activities of protein degradation. While higher contents of reducing sugar, total umami amino acids and total sweet amino acids were observed in soy sauce fermented by SWJS-AO-D, which had higher enzyme activities of carbohydrates hydrolysis. Compared with those contents in SWJS-AO-K soy sauce, the contents increased 80.80%, 5.14% and 4.10%, respectively. The results agreed with the sensory evaluation, i.e. SWJS-AO-D soy sauce has higher intensities of umami and sweet than those of SWJS-AO-K soy sauce. The results showed that the enzyme of carbohydrate hydrolysis had positive effects on the production of umami and sweet compounds in fermented soy sauce. This study will provide important theoretical guidance for the screening and breeding of Aspergillus oryzae. © 2021, Editorial Office of Journal of CIFST. All right reserved.