The effects of partial enzymatic hydrolysis of soymilk on the characteristics of transglutaminase (TG)crosslinked tofu gel were studied. SDS-PAGE showed that the molecular weight of the partially hydrolyzed soybean protein was reduced to that of a digested peptide (less than 43.0 kDa) when papain was added at more than 50 μL/100 mL soymilk. The content of free sulfhydryls, β-sheets, and random coils in papain-treated soymilk increased. When TG was added to soy milk after papain treatment and tofu gel was formed, its storage modulus increased from 957.44 to 1241.39 Pa. The gel strength, water-holding capacity, and nonfreezing water content of the tofu gel were greater than those without enzyme treatment. Scanning electron microscopy revealed that limited papain hydrolysis stimulated TG-catalyzed crosslinking of soymilk to form a dense gel network structure, whereas an extended enzymatic hydrolysis of soymilk did not promote crosslinking by TG.Practical Application: This work investigated the effect of partial hydrolysis on TG cross-linked tofu gel. Partial hydrolysis of soybean protein with papain can promote TG cross-linking reaction, thus form a dense network structure, increase gel strength, and water-holding capacity. Therefore, it can be used to produce a good gel product with higher gel strength, springiness, water-holding capacity, and a more dense microstructure.

Sufu is usually prepared by single-fungus fermentation with Mucor racemosus or Rhizopus oryzae. The quality of sufu fermented by different strains tends to differ. In this study, mixed fermentation (using M. racemosus and R. oryzae) and single-fungus fermentation (using only M. racemosus) were carried out, and the changes in physicochemical properties were assessed and compared. We found that the main enzyme activity of sufu in mixed fermentation was higher than that of M. racemosus fermentation, and the biochemical and texture properties of the sufu produced differed significantly between both fermentation processes. Thus, we demonstrated that mixed fermentation has several advantages over M. racemosus fermentation in terms of biochemical profile and texture of sufu. Our results provide insights for improving the efficiency of the industrial production of sufu, as well as sufu quality.