Rheological, gelling and emulsifying properties of a glycosylated and cross-linked caseinate generated by transglutaminase

The impacts of oligochitosan glycosylation and cross-linking on some properties of a commercial caseinate were investigated in this study. The glycosylated and cross-linked caseinate with glucosamine content of 4.74gkg(-1) protein was generated by transglutaminase (TGase) and oligochitosan at pH 7.5 and 37 degrees C, with fixed substrate molar ratio of 1:3 (acyl donor to glucosamine acceptor), caseinate content of 50gL(-1), TGase of 10kUkg(-1) protein and reaction time of 3h, respectively. In comparison with the caseinate, the glycosylated and cross-linked caseinate had decreased reactable amino groups (0.58 vs. 0.51molkg(-1) protein), higher apparent viscosity, decreased emulsifying activity index (about 14.5%) and statistically unchanged emulsion stability index (92.6 vs. 90.5%). Based on the mechanical spectra of the acid-induced gels, the glycosylated and cross-linked caseinate showed shorter gelation time (95 vs. 200 or 220min) than the caseinate or cross-linked caseinate. The gels prepared from the glycosylated and cross-linked caseinate also had enhanced hardness, springiness and cohesiveness. The results indicated that TGase-mediated oligochitosan glycosylation and cross-linking has the potential to obtain new protein ingredients.