Changes in enzymatic activities during “koji” incubation and natural fermentation of soybean paste

Abstract

Soybean paste production requires two steps “koji” incubation and natural fermentation. During the incubation of the koji, the protease activity was gradually increased and the highest activity was obtained on 30th day. Neutral protease was the predominant protease and it was significantly increased during the incubation of the koji. The nitrogen solubility index, nonprotein nitrogen (NPN), aminophenol nitrogen, and peptides concentration were gradually increased and they were 69.07%, 42.07%, 3.73%, and 38.34%, respectively, at the end of the fermentation process. The activities of α‐amylase, glucoamylase, and cellulase have different changing periods. All enzymes showed a significant increase followed by a gradual decrease to reach a linear shape at later koji incubation times. During the moromi fermentation, all enzymes showed a gradual decrease. This result is of immense importance for understanding the enzymatic mechanism involved and improving the final product by acting at different stages along the fermentation process. Practical applications Soybean paste production requires two steps “koji” incubation and natural fermentation. This study aims to understand changes in enzymatic activities during soybean paste production. This result is of immense importance for understanding the enzymatic mechanism involved in the fermentation process and supposed to improve the quality of final products. It may help to improve the final product by acting at different stages along the fermentation process.

Jujube (Zizyphus lotus L.): Benefits and its effects on functional and sensory properties of sponge cake

“…The soluble dietary fibers (SDF) and insoluble dietary fibers (IDF) contents were determined according to the gravimetric enzymatic method as previously described by Prosky et al [7]. Protein content (N×6.25) was estimated by the Kjeldahl digestion method followed by spectrophotometric determination of the resulting ammonia according to the method reported by Elfalleh et al [8]. Total carbohydrates were evaluated by the phenol sulphuric acid method [9], after hot digestion with 1.5 M sulphuric acid.…”

Changes in lipids distribution and fatty acid composition during soy sauce production

“…Meanwhile, Azad Shah, Tokunaga, Kurihara, and Takahashi () reported that lipolysis and lipid oxidation are responsible for the thickness, mouthfulness, and continuity taste in migaki‐nishin, a dried fish product. To date, published studies have focused on proteins (Chou & Ling, ; Kaewkrod, Niamsiri, Likitwattanasade, & Lertsiri, ; Yong & Wood, ) and starch (Elfalleh, Sun, He, Kong, & Ma, ; Liu, Chen, Fan, Huang, & Han, ) degradation and umami peptides (Kim et al., ; Zhuang et al., ) of soy sauce. And the changes of lipid and its relationship with volatile compounds have been investigated during the koji fermentation of soy sauce (Feng et al., , ; Gao et al., ).…”

Development and physicochemical characterization of a new grass pea (Lathyrus sativus L.) miso

“…The fact that grass pea misos have a higher starch content than soybean misos may lead to a greater impact of degradation over time. The proteolytic enzymatic action of koji 43 may have contributed to the availability of non‐digestible starch for degradation, promoting a faster kinetic of maturation. However, soybean misos G ' 1 Hz values were the first to stabilize (after 90 and 60 days for salty and sweet miso, respectively), indicating an earlier matured state as was observed by the apparent colour evolution of misos (Fig.…”