Cereal Chem 64:121-124 | VIEW
The Glass Transition in Starch.
K. J. Zeleznak and R. C. Hoseney. Copyright 1987 by the American Association of Cereal Chemists, Inc.
An investigation of the glass transition temperature (Tg) of wheat starch revealed that Tg was extremely sensitive to the percentage of moisture present. It was possible to detect the Tg by differential scanning calorimetry only within a narrow moisture range (13-22%). The glass transition occurred below room temperature at moisture contents greater than 22%, and the transition was broad and ill-defined below 13% moisture. This may indicate that inter- and intrachain hydrogen-bonding is facilitated as water is lost from amorphous regions of starch. A comparison of granular and pregelatinized starches showed that a higher degree of crystallinity elevated Tg and enhanced the system's sensitivity to moisture. These findings are consistent with reports for snythetic semicrystalline polymers and contradict the suggestion that Tg immediately precedes melting in starch.