Abstract:In order to investigate the role of transglutaminase (TG) on the modification of vegetable proteins using Maillard reaction, rice dreg protein (RDP) was used in the present study for glycosylation reactions in a dry state with glucose, ribose, and maltodextrin separately in a mass ratio of 1:1, and the effect of adding TG (10 u/g RDP) on the structure and rheological properties of RDP-sugar conjugates was studied. The results showed that the Maillard reaction products (MRPs) of RDP with ribose exhibited the highest degree of substitution (DS) and TG could enhance the DS. The λmax of the intrinsic fluorescence was redshifted and their intensity decreased. Additionally, FTIR spectra showed significant changes in the structure of different products, while TG had little effect on the structure of the products. Glycosylation reaction could reduce the surface hydrophobicity, while TG could increase it. During the Maillard reaction, lysine (Lys) and arginine (Arg) contents were reduced and the histidine (His) content was increased. Additionally, ribose was conducive for the reaction with free amino groups, while TG had no impact on the amino acid composition. Rheology measurement indicated that all MRP solutions were pseudoplastic fluid. The maximum apparent viscosity was detected in ribose-grafted products and TG promoted the increase in apparent viscosity. Mechanical spectra showed that the dynamic shear moduli of the three kinds of MRPs displayed significant changes with increasing frequency. The MRPs of RDP-ribose exhibited gel-like characteristics with G' > G" and both values were higher than that of RDP. TG increased G' and G" values of MRPs from ribose or glucose glycosylated and cross-linked RDP.
