Rheological and microstructural properties of gelatin B/tara gum hydrogels: Effect of protein/polysaccharide ratio, pH and salt addition

The roles of protein gelatin B (GB) and nonionic polysaccharide tara gum (TG) in gel formation induced by polymers incompatibility were evaluated. GB (1 g/dL) were mixed with TG (from 0.05 g/dL to 0.5 g/dL) to prepare GB/TG mixed gels. The influences of pH (3.5-11.0) and NaCl (0-300 mmol/L) on the gel properties were studied. Self-supporting hydrogels were successfully formed under different GB/TG ratios when pH ranged from 5.5 to 10.0 and synergistic effect occurred during the formation of hydrogels. Under no NaCl addition, pH 5.5 was appropriate for gel formation near the IEP of GB. NaCl addition might result in screening effect, inhibition of the energy for promoting complex coacervation and salting-in effect which could influence the microstructure and rheological property of mixed gels. GB/TG hydrogels exhibited thixotropic behaviors affected by GB/TG ratios. The microstructure of hydrogels, observed by confocal scanning microscopy varied from homogenous to protein continuous or bicontinuous in various gel-forming environments during the present research.