APPARENT VISCOSITY OF COEXTRUDED STARCH AND XANTHAN GUM

Xanthan gum is a polysaccharide which forms viscous, pseudoplastic aqu eous solutions useful in numerous food and industrial applications. Th e viscous properties of starch and xanthan gum co-extruded with inject ion of adipoyl chloride were determined. Viscosities of aqueous soluti ons of ground extruded and nonextruded samples were compared at differ ent temperatures, NaCl concentrations, and pH's. The effect of alpha-a mylase at 50 degrees C also was studied. Extruded samples had higher v iscosities in distilled water solutions than the nonextruded materials . The apparent viscosity decreased at pH's higher and lower than neutr al, at temperatures higher than 60 degrees C (in water) and with the a ddition of NaCl. Solutions of extrudates were less pseudoplastic than solutions of nonextruded samples in all solution conditions. The addit ion of alpha-amylase had little effect in any of the solutions.