Calcium-induced disaggregation of wheat germ globulin under acid and heat conditions

This work evaluated the potential of wheat germ globulin (WGG) disaggregation to improve acid and thermal stability in the presence of salts and determine the mechanism of improved solubility. Effects of CaCl2 on disaggregation of wheat germ globulin solution (0.5%, w/w) heat-treated ranging from 55 °C to 95 °C at pH 2.0 were investigated by turbidity, solubility, H0 (surface hydrophobicity), ζ-potential and microstructure. Maximum turbidity and minimum solubility occurred at the isoelectric point (pI 5.0) and 95 °C. The addition of Ca2 + resulted in a steady decrease of the turbidity and increase of the solubility. Both H0 and ζ-potential of soluble aggregates increased during disaggregation process. The results suggest that the electrostatic repulsion between the particles is sufficiently strong to overcome the attractive forces (hydrophobic interaction), leading to a degradation of large lumps and a homogeneous distribution of WGG particles. Microstructure analysis revealed that the WGG heat-treated contained rough and irregular aggregates at pH 2.0, while the CaCl2-induced disaggregates showed a smooth and loose dispersion, suggesting a dispersive distribution of WGG and a degradation of large lumps. Separating the formation of aggregates may provide a means to manipulate the protein solution properties.