  2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center  |
|
221
Molecular mobility of waxy rice starch paste at low temperature studied by using MDSC and NMR. H. M. LAI and Y. L. Chung. Dept. of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan.
The thermal properties of the waxy rice starch-disaccharide-water system were studied by using a Modulated Differential Scanning Calorimetry (MDSC) to investigate the properties of gelatinization and ice melting during frozen. The self-diffusion coefficient (D) was determined by using a NMR spectroscopy to study the effect of three disaccharides (sucrose, trehalose and maltose) on the microstructure of starch gel under various cycles of freeze/thaw treatment. The addition of disaccharide would delay the starch gelatinization with the order of sucrose>trehalose>maltose, and the retardation increased with the increase of sugar concentration. The amount of ice formation and melting temperature of ice of starch gel significantly decreased and lowered with the increase of sugar concentration, respectively. Sucrose had the most significant influence on them among three sugars. The NMR results showed that the additions of sugar on waxy rice starch paste would decrease its D value and it was dependent on sugar concentration. The type of sugar and cycle of freeze/thaw treatment would not affect its D value. Sugars would prevent starch gel from microstructural destruction under freeze/thaw treatment because water mobility was lower and less water was available for the ice formation when sugar was added.
Copyright 2001
The American Association of Cereal Chemists