Rheological and kinetic study of the ultrasonic degradation of xanthan gum in aqueous solution: Effects of pyruvate group

•Ultrasonication can manipulate the molecular weight of xanthan in aqueous solution.•The pyruvate content of the xanthan affects ultrasonication efficiency.•The sensitivity of the ultrasonication to salt content depends on pyruvate content. The influence of the pyruvate group on the efficiency of ultrasonic degradation of xanthan gum in aqueous solution has been studied. Blends of natural and pyruvate-free xanthan gums were ultrasonicated at 20°C for up to 30min and evaluated for molecular-weight degradation by viscometry. Solutions of pure pyruvate-free xanthan exhibited the highest stability to degradation among all blend ratios studied. Removing the pyruvate group is believed to enable the molecular chains to adopt a more compact conformation, which renders the polymer less susceptible to ultrasonication. In addition, the effects of salt on ultrasonic degradation efficiency were studied by using 0.1, 10−2, or 10−4M of NaCl or Na2SO4 in solution prior to ultrasonication. A degradation kinetics model was developed to quantify the degradation behavior. The absence of pyruvate groups renders the xanthan gum less sensitive to the influence of salt, and hence decreases the ultrasonic degradation efficiency.