Plasticizing Effect of Methyl Glucoside on Starch at Limited Moisture Contents

Abstract Thermal transitions of starch are important phenomena occurring during processing or storage of starch‐based materials. Glass transition and melting of starch are highly dependent on the type and content of plasticizer. Water is the most prevalent plasticizer in starch‐containing foods, but it readily vaporized prior to the thermal transition of starch at low moisture contents. Ingredients such as sugars in many intermediate or low moisture foods behave as non‐volatile plasticizers or diluents. In this study, methyl glucoside (methyl α‐D‐glucopyranoside) was examined as a plasticizer of starch in a low moisture range (6‐11%) by using a differential scanning calorimetry. Methyl glucoside addition (5‐10%) to corn starch depressed the onset temperature (5‐10°C) and enthalpy (1‐2J/g) for starch melting and glass transition temperature (5‐10°C). The increased level of addition did not significantly affect the degree of depression of transition temperatures. The endothermic peak for starch melting, however, was changed biphasic by the methyl glucoside addition. New melting peak at high temperature range (200‐210°C) which was not found on the thermogram of corn starch with moisture alone was found on the thermogram of the sample containing methyl glucoside. Although methyl glucoside functioned as a plasticizer, it caused non‐uniform melting and new crystal structure formation at low moisture contents.