Starch Gelatinization at Different Temperatures as Measured by Enzymic Digestion Method

The gelatinization process of potato starch was isothermally investigated at 52.5∽65.3°C. The degree of gelatinization was measured by an enzymic digestion method using glucoamylase. When the starch–water suspension was incubated at a definite temperature the gelatinization reached a limit at each temperature after 30∽60 min incubation. So, it can be supposed that starch gelatinization reached an equilibrium state. It was found that gelatinization of potato starch occurred even at 52.5°C, a temperature which is lower than the so-called gelatinization temperature generally reported. Starch gelatinization was found to follow first order kinetics, and from the temperature dependence of the rate constants obtained, the activation energy was calculated to be 22±5 kcal/mol. The relationship between the degree of gelatinization of the starch whose gelatinization reached an equilibrium state at a definite temperature and the incubation temperature gave a transition curve expressed, by the fraction of gelatinized potato starch granules as a function of temperature, and the half-transition temperature was found to be 59.1°C. From the transition curve.the van’t Hoff enthalpy for gelatinization was determined to be +130±3 kcal/mol.