Flavor differences of soybean and defatted soybean fermented soy sauce and its correlation with the enzyme profiles of the kojis

Abstract

BACKGROUND Soybeans and defatted soybeans, commonly used as protein ingredients, have different flavors of their fermented soy sauce. Clarifying the differences between the two soy sauces, as well as the formation mechanism, is an important prerequisite for improving the flavor of defatted soybean soy sauce. To this goal, the aroma characteristics of two soy sauces and their volatile profiles were compared by sensory evaluation and gas chromatography‐mass spectrometry, and eight enzyme activities and volatile profiles of matured koji were determined. RESULTS Sensory results showed that the acids, fruity and cooked potato‐like attributes were higher in whole soybean fermented soy sauce, whereas defatted soybean soy sauce exhibited higher smoky and malty attributes, closely related to the contents of aroma‐active compounds in soy sauce, such as isobutyl acetate, 2/3‐methylbutanal, acetic acid and 2/3‐methylbutanoic acid. The content of most volatiles in the matured kojis showed a consistent trend with that of soy sauce: alcohols, acids, furan(one)s and ketones. Interestingly, acid protease and cellulase activities were 3.3 and 1.6 times higher in the whole soybean koji than in defatted soybean koji, respectively, whereas neutral protease, aminopeptidase, glucoamylase and β‐glucosidase were approximately 2.0 times higher in defatted soybean koji. CONCLUSION In summary, the flavor differences between soybean and defatted soybean fermented soy sauce were not only caused by the differences in the content of flavor precursors in the materials, but also closely related to the differences in the enzymatic profiles accumulated during the koji‐making process. © 2022 Society of Chemical Industry.

Proteomics analysis of enzyme systems and pathway changes during the moromi fermentation of soy sauce mash

“…and various acid‐producing microorganisms increased, 18 ultimately causing the pH value of the soy sauce mash to decrease to 4.0 and 5.0. A low‐pH environment was more favorable for the effect of acid protease 19 . Bacillus sp.…”

“…In general, the cell wall of plants was mainly composed of cellulose, hemicellulose and pectin 6 . Cellulase, xylanase, β ‐glucosidase and pectinase could degrade the cell wall of raw materials during fermentation and release intracellular nutrients into the fermentation system for microbial growth and multistage transformation of substances 4,6,19 . During the first 30 days of fermentation, the activity of cellulase was more stable than that of xylanase, β ‐glucosidase and pectinase, probably due to the excellent salt and acid resistance of cellulase and the proliferation of microorganisms capable of producing highly active cellulase, such as Bacillus sp 20,22,23 .…”

“…A low-pH environment was more favorable for the effect of acid protease. 19 Bacillus sp. could produce neutral protease with higher activity, 20 which may explained the slower decrease in the activity of neutral protease in soy sauce mash at the beginning of fermentation.…”

“…6 Cellulase, xylanase, ⊎-glucosidase and pectinase could degrade the cell wall of raw materials during fermentation and release intracellular nutrients into the fermentation system for microbial growth and multistage transformation of substances. 4,6,19 During the first 30 days of fermentation, the activity of cellulase was more stable than that of xylanase, ⊎-glucosidase and pectinase, probably due to the excellent salt and acid resistance of cellulase and the proliferation of microorganisms capable of producing highly active cellulase, such as Bacillus sp. 20,22,23 Xylanase and ⊎-glucosidase showed similar trends in activity from day 0 to day 75 in the fermentation, which indicated that both enzymes were similar in properties and probably originated from the same type of microorganism.…”

Effect of Sequential Inoculation of Tetragenococcus halophilus and Wickerhamomyces anomalus on the Flavour Formation of Early-Stage Moromi Fermented at a Lower Temperature

“…In addition, the highest acetic acid content was found in sample T0, accounting for 19.3 g/100 mL at day 30, followed by T0W5, accounting for 19.1 g/100 mL. Previous studies showed that the production of lactic acid could improve the taste of fermented soy sauce by neutralising the saltiness of soy sauce, making the flavour more refreshing, whereas the formation of acetic acid, as a volatile fatty acid, contributes to the sour smell of soy sauce [ 5 , 39 , 40 , 41 ]. The inoculation of W. anomalus accelerated the production of lactic acid, which could be beneficial to flavour formation in moromi fermentation.…”