In vitro gelatinization of potato starch with excessive water content. 1. Kinetics of the process in isothermal conditions

The wide use of starches in the food industry determines their comprehensive study over many years. One of the key problems that need to be solved for the improvement of food technologies in which starch is used is the definition of the basic laws of the kinetics of the gelatinization process of starches. The purpose of this work was to determine the kinetic parameters of the gelatinization process of native potato starch with excessive water content in the reaction mixture (the modulus is 10 g/l) and to select the appropriate kinetic model. It was found that the kinetics of the gelatinization process of native potato starch is described by the Kruger-Ziegler equation. It is shown that the dependence of the rate constant of the gelatinization process on the temperature in Arrhenius coordinates has the shape of a convex curve. It can be assumed that at a temperature below 70 °С the process proceeds in the kinetic region with the limiting stage of the chemical reaction at the interface of the phases and when the temperature increases then transition to the diffusion region occurs. It is assumed that the essence of the specified chemical reaction means the formation or destruction of hydrogen bonds during the interaction between water molecules and amylose. The values of the imaginary activation energy of the gelatinization process calculated from experimental data are 191.3 kJ/mol in the temperature range of 60—70 °С and 22.2 kJ/mol in the temperature range of 80—90 °С. The high values of the activation energy at a temperature below 70 °С can be explained by the energy spent on breaking hydrogen bonds between the OH groups of amylose macromolecules. It is proposed to intensify the process of gelatinization of starch by increasing the temperature and using a catalyst at temperatures below 70 °С. If the process is carried out in the area of high temperatures, then its intensification can be achieved by grinding starch granules and increasing the mixing speed of the starch suspension.