33A-8 |
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S. I. SHIN, H. Kim, and T. W. Moon. Center for Agricultural Bio-Materials, Seoul National Univ., National Research Laboratory for Functional Food Carbohydrate, San 56-1 Sillim Dong Kwan-ak Gu, Seoul, 151-742, South Korea Previous studies showed that hydrothermal treatment for starch granules induces changes in the physicochemical properties of starch without destroying the granule structure. Starches subjected to hydrothermal treatment showed resistance to enzyme digestion. The extent of enzyme digestion increased as the heating time increased at subgelatinization temperatures due to changes in the internal structure of the starch granule. The aim of this study was to investigate the effects of various hydrothermal treatments on formation and granular structure of slowly digestible sweet potato starch (SDS). Sweet potato starch was modified by various hydrothermal treatments. Moisture content of sweet potato starch was adjusted to 20, 50 and 90% with distilled water and heated at 40, 55 and 100oC for 12 h in a dry oven. Sweet potato starch with 50% moisture content and heated at 55oC showed the highest SDS content, increased by about 200% relative to raw starch. The swelling factor of the samples heated over 40oC decreased as heating temperature and moisture level increased. Microscopic observation of sweet potato starch with 50% moisture content and heated at 100oC showed cracks and damage on the granule surface. In addition, disruption of starch granules was observed in the sample with 90% moisture and heated at 100oC. In gelatinization parameters, peak temperature of the samples heated over 40oC increased with heating temperature and moisture levels, while enthalpies of the samples with 50% and 90% moisture content and heated over 100oC decreased greatly. Relative crystallinity of the samples with hydrothermal treatment decreased as heating temperature and moisture level increased. X-ray diffraction patterns of the samples changed depending on heating temperature and moisture level. These data suggest that increased SDS content by various hydrothermal treatments is caused by enhancement of the dense packing in amorphous region and decrease in the crystallinity of crystalline region.
Session 33A, Carbohydrate: General
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