Preparation and characterization of ovalbumin and carboxymethyl cellulose conjugates via glycosylation

Protein and polysaccharide complex has aroused increasing interest in food applications. In this study, ovalbumin (OVA) and carboxymethyl cellulose (CMC) conjugates were prepared by glycosylation reaction and characterized by SDS-PAGE, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and circular dichroism (CD) analysis. The degree of grafting (DG) and browning index (OD) increased with reaction time and 8 d was selected as the optimized reaction time to equilibrium the glycosylation and unfavorable browning effect. The weight ratio (OVA: CMC) was optimized at 4:1 and pH was 7 or 8. The glycosylation grafting was proven by SDS-PAGE and FTIR. DSC showed that the thermal stability of OVA was improved after glycosylation reaction, which was positively related with molecular weight and the degree of substitution DS of CMC. From CD spectra, the secondary structure of OVA was affected by the grafted CMC with increasing β-sheet and random coil and decreasing α-helix and β-turns. The information obtained from this study can enrich the theoretical frame of protein and polysaccharide interaction, broaden the possible applications of food ingredients from egg source and polysaccharide, and provide the theory evidence on developing tailored egg powder.