Microbial transglutaminase-modified protein network and its importance in enhancing the quality of high-fiber tofu with okara.

Highlights • TGase enhanced the gel strength and water holding capacity of high-fiber tofu. • TGase alleviated the viscoelasticity loss of tofu gel induced by okara. • AB and A 1,2,4 subunits were more prone to aggregate during the heating of soymilk. • TGase-induced ε-(γ-glutamyl) lysine of strengthened the network of high-fiber tofu. • TGase promoted the ordered formation of protein aggregates and could wrap okara. Abstract Introducing okara to develop high-fiber tofu (HFT) can effectively increase the utilization of soy residues as well as enhance the nutrition of tofu. However, okara degrades the glucono-δ-lactone (GDL)-induced tofu quality. Current results showed that microbial transglutaminase (TGase) remarkably enhanced the gel strength, water holding capacity and viscoelasticity of HFT. During heating of soymilk, AB and A 1,2,4 subunits of 11S were more prone to aggregate via disulfide (SS) bonds to form larger soluble protein aggregates under neutral condition, while the SS-mediated insoluble aggregates were formed under acid condition by GDL and predominantly contributed to the structure of tofu without TGase. TGase-induced intermolecular ε-(γ-glutamyl) lysine strengthened protein network and contributed the most to HFT structure. TGase promoted formation of protein aggregates more orderly, and okara was well-wrapped by protein network. These results demonstrated that the macro-protein aggregates crosslinked by TGase conspicuously strengthened the gel network and significantly elevated the HFT quality. [ABSTRACT FROM AUTHOR]