Factors affecting gel formation of inulin

Inulin gel can be made from shearing or heating¯cooling of inulin suspension. Heating of inulin suspension solubilized inulin, cooling caused precipitation of dissolved inulin, especially when a less hydrophilic solvent such as ethanol or glycerol is added. For gel made from heating¯¯cooling process, volumetric gel index (VGI), i.e. the ratio of gel to total volume, was a function of heating temperature, inulin concentration, pH, and solvent added. Minimal inulin concentration required for gel formation increased with increasing heating temperature. High heating temperature (>80°C) causes some degree of hydrolysis of dissolved inulin molecules leading to lower VGIʹs. A low degree of hydrolysis of inulin and a critical concentration of inulin are important for gel formation. The heating¯cooling process formed gels with stronger strength, smoother texture, more uniform and smaller particle size as compared to that obtained with a shearing process.