Comparative analysis of the kinetics of dehydration and dextrinization of potato and corn starch

Abstract

In order to compare the kinetic characteristics of the heat treatment of starches and solve the question of what has a greater influence on the processes of their dextrinization, the chemical composition or their botanical origin, we carried out research by using methods of thermogravimetry and differential scanning calorimetry. It was shown for the first time that there is a process with heat absorption at 1300C in the temperature range of 25–2000C, in addition to the stages of dehydration of starches, which is not accompanied by a decrease in weight. This endoeffect is well explained by the melting process of the low-molecular amylose fraction of starches. In contrast to literature data, it was also established that the stage of starch decomposition in the temperature range of 200–3500C should be considered as a set of three consecutive processes. It was established that the activation energies of dehydration processes of pre-dehydrated starches are equal to 60 kJ mol–1. The average activation energy аor the stages of destruction of starches is 400–500 kJ mol–1. Such values of the activation energy of starch destruction processes are explained by the presence in their composition of a number of semi-crystalline subcomponents characterized by different thermal stability. When comparing the values of the activation energies of the dehydration and dextrinization processes of the investigated starches, a linear correlation was established for the first time, which testifies to the uniformity of such processes and their independence from the botanical origin of the starches.