Effect of moisture level on the crystallinity of wheat starch aged at different temperatures

Differential Scanning Calorimetry (DSC) was used to study retrogradation of wheat starch. For storage at 4 degrees C, enthalpy (Delta H) values of retrogradation endotherm (recrystallization) of wheat starch containing various moisture levels (25-80%) slowly continued to increase except in samples with moisture level of 50, 60 and 70%. For storage at 26 degrees C and 32 degrees C, most recrystallization of wheat starch occurred within one and two weeks of storage time, while recrystallization with a moisture level of 50% at 26 degrees C occured for 4 weeks. The peak temperatures of retrogradation endotherm at various moisture levels (25-80%) after 4 weeks of storage time increased largely as the storage temperatures increased from 4 to 32 degrees C. The enthalpy values of retrogradation endotherm after 4 weeks of storage occurred to a greater extent at a lower storage temperature. The glass transition temperature and starch recrystallization have a close relationship. In the recrystallization of wheat starch, the nucleation and propagation rate after 4 weeks of storage can be converted into enthalpy and peak temperature of retrogradation endotherm.