Rheological characterization and microstructural depiction of xanthan gum and its hydrolysates

In this work, xanthan gum was hydrolyzed through three different methods using acid (HCl), base (NaOH) and enzyme (cellulase) to improve its rheological properties and various other characteristics. Hydrolysis resulted decrease in moisture content, increase in protein and fiber content in case of enzyme hydrolyzed xanthan gum, ash content of acid and base hydrolyzed xanthan gum. Rheological measurements showed shear-thinning non-Newtonian behavior in all the gums with the reduction in viscosity after hydrolysis as 2.08, 1.16, and 1.90 Pa.s in acid base and enzyme hydrolyzed xanthan gum respectively as compare to native xanthan gum (2.5 Pa.s). Oscillatory properties revealed rectangular characteristic type of polymer solution curves for all the gum types. Fourier transform infrared (FTIR) spectrums depicted no major transformation in functional groups for hydrolyzed forms of xanthan gum exhibiting non-momentous change in xanthan gum basic structure due to hydrolysis. Scanning electron microscope (SEM) characterization revealed fibrous and amorphous morphology for native and enzyme hydrolyzed gum whereas, acid and base hydrolyzed gums exhibited crystalline structure. X-ray diffraction (XRD) results indicated an increase in crystallinity as a result of acid and base hydrolysis whereas enzyme hydrolysis did not alter the amorphousness as presented by native gum. Hence, xanthan gum could be modified to increase its applications without altering it integrity and basic structure. (author)