Effect of Partial Hydrolysis with Papain on the Characteristics of Transglutaminase‐Crosslinked Tofu Gel

Abstract

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.

Properties of transglutaminase‐induced myofibrillar/wheat gluten gels

“…Sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE) used 15% acrylamide separating gel and 5% acrylamide stacking gel, according to the method described by Li et al. (2018). The gel samples prepared with different concentrations of enzyme preparations were vacuum freeze‐dried.…”

Tofu products: A review of their raw materials, processing conditions, and packaging

“…This is a new type of tofu with high gel strength that could be produced using the enzymatic cross-linking of MTGase and an appropriate thermal treatment. However, each type of coagulants used in the traditional tofu production process has its own inherent disadvantages, which are summarized as follows: tofu was typi-cally made using GDL as an acid coagulant, although it is easy to control because it acidifies slowly; the resulting tofu is slightly sour and not suitable for frying due to its soft texture (Li, Wu, et al, 2018). Residual undissolved CS or rapid release of MC in tofu products typically results in poor quality (a coarse texture) (Cao et al, 2017;.…”

“…They showed that tofu coagulated using papain resulted in higher protein content (9.3%) compared with that of tofu coagulated using CS (6.5%). Independently, Li, Wu, et al (2018) studied the effect of papain-pretreated soymilk on Transglutaminase (TG)-cross-linked tofu products. The quality of tofu products (in terms of strength, WHC, and nonfreezing water content) was better than tofu products without enzyme treatment.…”

“…Residual undissolved CS or rapid release of MC in tofu products typically results in poor quality (a coarse texture) (Cao et al., 2017; Li et al., 2015). In addition, the residual salt coagulants (after addition into soymilk) usually produce tofu with bitter taste, and produce a large amount of yellow slurry, which can cause environmental pollution problems during the extrusion process (Li, Wu, et al., 2018). Tofu made using the MTG enzyme usually has low gel hardness, and the process is often time‐consuming (Cao et al., 2017).…”

“…Independently, Li, Wu, et al. (2018) studied the effect of papain‐pretreated soymilk on Transglutaminase (TG)‐cross‐linked tofu products. The quality of tofu products (in terms of strength, WHC, and nonfreezing water content) was better than tofu products without enzyme treatment.…”