Physicochemical and rheological characterization of a novel hydrocolloid extracted from Althaea officinalis root

Althaea officinalis L. root polysaccharide (AOP) was extracted, and its physicochemical and rheological properties were investigated. Gel permeation chromatography results showed that the molecular weight was 1560 kDa. High-performance liquid chromatography indicated that it was an acidic heteropolysaccharide consisting of five types of monosaccharides including galacturonic acid (40.2%), rhamnose (31.7%), glucose (13.68%), galactose (9.07%), and arabinose (5.35%). The intrinsic viscosity value for AOP in deionized water was 9.4 dl g−1. The AOP solutions at different concentrations (0.5%, 1%, 2%, and 3% w/v), showed shear-thinning behavior, and the apparent viscosity decreased in the presence of different concentrations of NaCl and at different pHs. The frequency sweep test showed the AOP solutions at concentrations less than 0.5% and above 1% exhibited viscous and weak gel behavior, respectively. Since the hysteresis phenomenon was observed in the temperature sweep test of 2% AOP solution, it can be considered as a thermal irreversible gel during the heating and cooling process.