Determination of the temperature of gelatinization and energy of transformation of starch by dielectric dissipation induced changes

In this work we present a new method which allows to determine the structural changes of starches subjected to a thermal process. Using that method, the initial and final gelatinization temperatures and the amount of energy required to induce the thermal changes can be deduced. The method takes the advantage of the dielectric dissipation of electrical energy in the system consisting of a mixture of starch grains and water enclosed in a specially designed sealed cell. AC electrical power at a fixed voltage and frequency is applied to the material to be studied. The magnitude of the electric current is then monitored as the temperature is raised (by Joule effect) up to temperatures of 120°C. The plots of the electric current Vs temperature in all the samples studied yield two distinct extreme values: the onset and the ending temperatures of the gelatinization of the processed samples. Analyzing the current Vs time plots during the gelatinization of starch, we are able to determine the energy required for the transformation process. The method as such, demonstrates to be a useful technique to determine the basic parameters during starch gelatinization and it is much simpler then those known in the field.