Starch gelatinization is associated with granular structure disruption that can cause starch molecules to disperse in water. The effect of increasing water temperature on starch granular structure, and eventual starch polymer dispersion is poorly understood. It is important to understand starch structure transformations during heating to fully explain the gelatinization process. The objective of this study was to investigate starch granular and polymorphic changes at different temperatures during gelatinization in water. Starch (6% w/v) was heated to specific temperatures (35-85 at 5 increments) for 30 min in excess (6% w/v) water. Freeze dried samples were observed by scanning electron microscopy for morphological changes. Changes in molecular structures were evaluated by high performance size exclusion chromatography (HPSEC). Differential scanning calorimetry (DSC) was used to characterize the changes in intermolecular interactions. HPSEC data showed that the relative proportions of amylose and amylopectin dispersed in water varied depending on the temperature treatment. The extent of amylopectin dispersion increased with increasing temperatures for all starches. Samples exposed to increasing heat treatments initially exhibited increasing DSC endotherm values up to a specific temperature characteristic to each starch, and then those values decreased rapidly with increased heat treatment temperatures. Heat energy absorbed by granules facilitates "rearrangement" or formation of new bonds among molecules prior to gelatinization.
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