Transglutaminase-mediated enhancement of co-protein effect improves okara noodle quality

Improving the quality of high-fibre staple foods is a research hotspot in the cereal food field. Herein, the effects of transglutaminase (TGase) on the quality and starch digestibility of okara noodles were investigated, and the mechanisms through which TGase-mediated co-protein effects on soy and gluten in okara noodles enhance heat-induced protein networks were elucidated. Assessments of appearance, cooking, texture and starch digestion showed that TGase improved okara noodle quality and reduced starch digestibility. Rheological analysis indicated that TGase enhanced the viscoelasticity of okara dough and enabled the formation of a tighter protein network structure. Analyses of the protein network structure, sodium dodecyl sulfate (SDS)-extractable proteins, protein subunits and free amino groups indicated the presence of soy-gluten co-protein effects in okara noodles. Furthermore, TGase enhanced these co-protein effects through disulfide and ε-(γ-glutamyl) lysine isopeptide bonds within the same heating time, thereby promoting the formation of a higher-polymerisation heat-induced protein network.