Differential Thermal Analysis Applied to Examining Behavior of Starch in Foods (Thermal Behavior of High Molecular Substances in Foods Part II)

Abstract

It was indicated in previous paper that gelatinization of starch could be studied effectively by using differential thermal analysis (DTA). In the present experiments, authors applied DTA to study the thermal behavior of starch in food without isolating it from the other constituents.
The DTA curves of specimens from potato, indian lotus, taro and sweet potato indicated single endothermal peaks specific to species and agreed with those of starches isolated from the foods in shape and temperature region, except for slight shifts of 3_??_7 degrees to higher temperature region. In addition, these endothermal changes accompanied disappearance of polarization pattern of starch. Therefore it can be said that the DTA curves of specimens indicate the gelatinization of in situ starch in foods.
From the further examinations on potato specimen, the following findings were obtained. 1. Gelatinization temperature of the in situ starch in potato decreased from 61°C to 53°C in sodium chloride soln. at 20% conc. 2. In sucrose and ethyl alcohol soln. it increased to 80°C and 75°C at 50% conc. respectively. 3. Specimens from potato preserved for months at 30°C indicated some increase in gelatinization temperature of in situ starch and offered a suggestion that some change in heat slightly of starch in potato occured during its preservation.