Physico-chemical properties of camelina protein altered by sodium bisulfite and guanidine-HCl

•We unfolded camelina protein isolate by two reagents: NaHSO3 (cleave SS) and guanidine–HCl (destroy hydrogen bond).•Both treatment decreased camelina protein isolate dispersion's viscosity and protein-protein interaction.•NaHSO3 modified camelina protein isolate was more hydrophobic than guanidine–HCl modified camelina protein.•NaHSO3 was more efficient in destroying the structure of camelina protein isolate, while Gdm-HCl treatment reduced more viscosity and water resistant.

The objective of this research was to investigate the unfolding behaviors of camelina protein isolate (CPI) induced by sodium bisulfite (NaHSO3) and guanidine–HCl (Gdm.Cl). Protein was extracted from defatted camelina meal through alkali solubilization and acid precipitation and modified with varying amount of NaHSO3 (0–12% of the protein dry basis) and Gdm.Cl (0–250% of the protein, dry basis). NaHSO3 treatment broke the disulfide bonds of the CPI and increased free sulfhydryl content and surface hydrophobicity. As NaHSO3 concentration increased, the viscosity, elastic modulus (G’) and water resistant of NaHSO3-modified camelina protein (SMCP) dispersion decreased, and the protein became aggregated due to high surface hydrophobicity. Gdm.Cl treatment broke the CPI's hydrogen bonds but decreased their surface hydrophobicity. Similarly, viscosity, G’, and water resistant of Gdm.Cl-modified camelina protein (GMCP) dispersions decreased as Gdm.Cl increased and protein aggregation formed. The reducing effect of NaHSO3 was greater than Gdm.Cl for CPI’s protein–protein interaction and less obvious for the viscosity and water resistant. Gdm.Cl reduced CPI's decomposing temperature at high concentration, but no remarkable effect was observed for NaHSO3 treatment. These findings on physicochemical changes of SMCPs and GMCPs may contribute to the application of camelina proteins in the biodegradable materials products.