Effects of transglutaminase-induced modification in the presence of oligochitosan of 1 kDa on the structure and gelling properties of caseinat

Caseinate, transglutaminase (TGase), and an oligochitosan of 1 kDa were used to prepare a glycated and cross-linked caseinate (GC-caseinate), aiming to assess potential changes in both the structure and gelling properties of such caseinate. The results of Fourier transform infrared analysis revealed that only GC-caseinate contained saccharide portions in its molecules, evidencing TGase-induced caseinate glycation. Circular dichroism results showed that GC-caseinate possessed a more ordered secondary structure than caseinate. Other results also demonstrated that TGase-induced modification resulted in a lower gelation temperature of GC-caseinate (59°C vs. 68°C) and increased the final tan δ value (0.30 vs. 0.15) compared to caseinate during the development of acidified gels. In addition, the acidified gels from GC-caseinate were detected to have lower water holding capacity (0.720 vs. 0.781 g/g gels), expanded gel network, and larger pore sizes than those from caseinate. It is thus evidenced that the used TGase-induced modification could confer caseinate with ordered secondary structure, expanded gel network but lower water holding capacity.