Acid resistance of different polysaccharide hydrocolloids: pH effects

Abstract

The acid resistance of polysaccharide hydrocolloids is very important for its application in food industry. In this study, the acid resistance of tamarind seed polysaccharide (TSP), xanthan gum (XG), and locust bean gum (LBG) at different pH was investigated. Results showed that the shear viscosity of TSP and LBG was significantly decreased at pH 1. Structural analyses showed that molecular degradation on the side chain of TSP and LBG occurred at pH 1, whereas the composition of the monosaccharides of XG showed no significant difference. Molecular degradation led to a decrease in the molecular weight of TSP and LBG with the gradual decrease of pH, accompanied by a shift in solution conformation, i.e., from semi-flexible chain to rigid rod for TSP and LBG, whereas XG did not undergo significant structural changes with the gradual decrease of pH. In addition, the SEM results showed that with the gradual decrease of molecular weight, the structures of TSP and LBG were gradually broken and showed fragmentation, while XG only showed slight cracks. These results show that the structure of the polysaccharides changes with the gradual decrease of pH, resulting in a change in the solution conformation and a decrease in viscosity. This study provides a new theoretical basis for the application of these polysaccharide hydrocolloids in food processing.