Changes in the Chemical and Physical Properties of Starch During Dextrinization

Abstract

Corn starch was roasted at 150°C and 180°C for various periods of time to determine the changes in the chemical and physical properties during the heat treatment. The samples prepared by the above mentioned process were characterized by the determination of amylography, photopastegraphy, cold water solubility, iodine absorption, β-amylolysis and reducing value. The rheological properties which were determined by amylography were drastically changed even at the initial stage of the treatment both at 150°C and 180°C. On the other hand, the structural changes of the starch molecule, such as rebranching occured by heat, were easily estimated by the determination of the limit of β-amylase degradation, cold water solubility and the spectra of iodine absorption. We could observe slight depolymerization of starch molecule by the 150°C roasting, but almost no sign of rebranching or repolymerization of the liberated short chain was observed at this temperature. Evidences of the both reaction were observed in the sample roated at 180°C. It was considered that there was a critical temperature between 150°C and 180°C where rebranching and repolymerization reaction began to occur.