2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Since few studies have completely evaluated the properties of sweet potato starch, beside the structure of this starch has not been studied in detail, it will be important to know both the structure and swelling properties of sweet potato starch. These properties determine how they function during food processing. The objective of this study is to determine the effect of the cooking temperature on microstructure of the sweet potato starch granules. The effect of heating the starch pastes on granule morphology of the starch was evaluated using scanning electron microscopy (SEM). Samples of the starch slurries were taken from the amylograph bowl at specific temperatures ( 30, 50, 60, 70, 80 y 90°C) during gelatinisation. Samples were cooled and dried. The dry samples were prepared for examination by SEM. The raw sweet potato starch granules (30°C) showed mainly intact granules with egg- truncated shapes, it was also observed both spherical and polygonal shapes. When increasing the temperature at 50°C swollen and intact starch granules forming aggregate structure were observed. It can be due to bounding forces among the granules. Reaching 60°C the aggregated structure disappears, start material leached out from some granules and then some starch granules are interconnected Starting the 70°C, increased the interconnection among granules by amylose release, but the majority of the granules keep yet on swollen. After the 80°C sweet potato starch lose their granular structure and many ghosts remain embedded in the amylose network structure. The structural differences showed were dependent on the temperature gradient that occurred during cooking.