Changes in the physical properties of xanthan gum induced by a dynamic high-pressure treatment

Abstract

The effect of microfluidization, a dynamic high pressure treatment, on xanthan gum was investigated in views of enlarging its potential applications. Samples were characterized chemically and physically (molecular weight, intrinsic viscosity, flow behavior and flow induced birefringence). Particular interest was given to the correlation between the level of degradation and aggregate content to the flow behavior and flow-induced birefringence. A mechanism of degradation is proposed: initially, microfluidization reduces the aggregated state of xanthan and may even be able to dissociate the double helical structure into single chains; upon increasing treatment severity, a relatively mild degradation of the main chain can be achieved. Interestingly, samples treated at high ionic strengths were more sensitive to mechanical degradation, arguably since stiffer molecules in the ordered conformation presented a larger exposed surface and thus experienced stronger effective stresses when subjected to the high shear and cavitation forces present in the microfluidization chamber.