PHYSICAL MODIFICATION OF XANTHAN GUM

Because of its high chain stiffness xanthan will form an anisotropic liquid crystalline phase at lower concentrations than other food hydrocolloids. The appearance of this phase can result in a decrease in viscosity with increasing concentration. A consequence of this is that on concentration of xanthan through phase separation or exclusion, viscosity decreases can be observed. Examples of this unusual behaviour are shown for blends of xanthan with polyelectrolytes and with cold swelling starches. The recovery of viscosity on subsequent dilution has potential in a number of applications including a liquid product for thickening foods for consumers with swallowing difficulties. A new form of xanthan can be prepared by extrusion. A limited amount of water is injected into the extruder barrel and the product is dried and ground. This form behaves like a polyelectrolyte particle showing excellent dispersibility and a strong salt dependence on the degree of swelling. Under appropriate conditions the viscosity development of dispersions on heating is similar to starch thus xanthan can be produced which combines the desirable dispersibility and heat transfer properties of starch, with the end use advantages of xanthan.