Effect of sorbitol addition on the physicochemical characteristics of starch–fatty acid systems

Aqueous maize starch dispersions (20%) were heated at 100 °C, in the presence of myristic, palmitic or stearic acid potassium salts as well as of sorbitol added at concentrations up to 60% (dry starch). Flow behaviour measurements at 100 °C indicated that interactions took place between the starch–fatty acid systems and sorbitol resulting in viscosity increase which was more pronounced as the sorbitol content increased. Water solubility measurements showed that a major part of sorbitol was easily extracted by excess water whereas sorption experiments revealed that the moisture uptake rate was proportional to sorbitol content of the starch systems examined. Thermomechanical studies indicated that the starch–fatty acid samples containing sorbitol up to 40% exhibited antiplasticizing behaviour. Scanning electron microscopy studies revealed that at sorbitol concentrations over 30%, free sorbitol crystals were formed on the surface of starch–fatty acid samples, whereas the percentage crystallinity as well as the crystallite size of samples were proportional to sorbitol content.