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Enthalpic Transitions in Native Starch Granules¹

¹Journal series no. 12537, Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln. ²Postdoctoral research associate and associate professor, respectively, Cereal/Oilseed Science and Technology Laboratory, Dept. Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE 68583-0919. ³Corresponding author. Phone: 402/472-2814. Fax: 402/472-1693.

Crystalline properties of native starch granule fractions that varied in apparent density and size were investigated using differential scanning calorimetry (DSC). Endotherms obtained at 80% hydration showed significant variations in enthalpy between the six fractions. Typical bi-phasic endotherms exhibiting significant variation in start temperature were obtained for the six fractions at 50% hydration. However, on annealing at 50°C/50% hydration for 48 hr, all fractions showed a single endotherm without any significant variability in endotherm characteristics. At 10% hydration, the six fractions exhibited single high-temperature endotherms with significant differences in their peak temperatures. It was observed that mechanically damaging starch, resulted in the disappearance of any enthalpic transition. These observations could not be satisfactorily explained on the basis of prevailing concepts about DSC enthalpic transitions.