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 VGI's. 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.