Rheological properties of a β-1,3-polyglucuronic acid derivative from 4-acetamido-TEMPO-mediated oxidation of curdlan

Abstract

The rheological properties of a carboxylic curdlan bearing a β-1,3-polyglucuronic acid structure were investigated as a function of concentration and temperature. Carboxylic curdlan solutions exhibited shear thinning behavior that became more evident with increasing concentration. This behavior was further described by a consistent index (k) and a flow behavior index (n) based on the power law model. Activation energy (E_a) decreased with increasing concentration, as calculated by the Arrhenius rule. The mechanical spectra of carboxylic curdlan were classified as dilute solution (<1.0%, w/v), entanglement network (2.0%, w/v), and weak gel (4.0%, w/v or above) according to frequency sweep, complex viscosity η*, and tan δ results. Moreover, changes in the storage modulus (G′) and the loss modulus (G′′) were found to be dependent on frequency and concentration. This finding suggested that carboxylic curdlan could be explored as a potential thickener or stabilizer for various applications in the food industry.