| Abstract: | Morphological changes that occur in starch granules of sweet potato, tania and yam tubers from native to cooked states, were studied both by electron microscopy and differential scanning calorimetry. In the first stages of heating, the same event was observed in all samples: a central cavity appeared at hilum level of the starch granules just before granule expansion started. Differences in gelatinization behaviour between these three starches were enhanced by mechanism by which amylose leached out. In the sweet potato starch granules, amylose was released through micropores formed in the starch granules during the phase of expansion whereas in tania starch granules, both micropores and pin-holes were observed. In yam starch granules, amylose escaped only by pin-holes formed across the starch granules. When cooking was achieved, spongy-like structures were observed in cooked sweet potato parenchyma cells while folded gelatinized granules remained in yam. In cooked tania tuber, both types of cell contents were observed. Sweet potato, tania and yam starches presented DSC endotherms at 72.7, 69.9 and 74.4°C with enthalpy change of 13.6, 12.9 and 20.9J/g, respectively. |
