Physicochemical Properties and Adhesion Performance of Canola Protein Modified with Sodium Bisulfite

The objective of this research was to study the adhesion properties of sodium bisulfite (NaHSO3)-modified canola protein. Protein was extracted from canola meal through alkali solubilization and acid precipitation methods, then modified with different concentrations of NaHSO3 (0-15 g/L) during the isolation process. As NaHSO3 concentration increased, canola protein purities decreased. Amino acid profiles showed that the hydrophobic amino acids in canola protein constituted only 27% of total protein, indicating that canola protein is mostly hydrophilic. The reducing effects of NaHSO3 were exerted on canola protein through the breaking of disulfide bonds in both its cruciferin and napin components, as reflected by the protein electrophoresis profile, DSC data, and morphological images. The wet protein isolates were used as adhesives. The greatest wet shear strength of canola protein adhesive without modification was 3.97 MPa with 100% wood cohesive failure (WCF), observed at a curing temperature of 190 degrees C. NaHSO3 had slight weakening effects on the adhesion performance of canola protein. Canola protein modified with 3 g/L NaHSO3 exhibited wet shear strength similar to the control at 190 degrees C and higher strength at 150 and 170 degrees C. The NaHSO3 modification significantly improved handling and flowability of canola protein adhesives.