Enthalpic transitions in native starch granules

Crystalline properties of native starch granule fractions that varied in ap parent density and size were investigated using differential scanning calor imetry (DSC). Endotherms obtained at 80% hydration showed significant varia tions in enthalpy between the six fractions. Typical bi-phasic endotherms e xhibiting significant variation in start temperature were obtained for the six fractions at 50% hydration. However, on annealing at 500 degrees C/50% hydration for 48 hr, an fractions showed a single endotherm without any sig nificant variability in endotherm characteristics. At 10% hydration, the si x fractions exhibited single high-temperature endotherms with significant d ifferences in their peak temperatures. It was observed that mechanically da maging starch, resulted in the disappearance of any enthalpic transition. T hese observations could not be satisfactorily explained on the basis of pre vailing concepts about DSC enthalpic transitions.