61A-30 |
Physicochemical properties of starch affected by water-steeping duration of waxy rice kernel |
H. S. CHUN1, S. B. Cho, and H. J. Kim. (1) Quality Assessment and Standard Division, Korea Food Research Institute, San 46-1, Baekhyun-dong, Bungdang-gu, Sung-nam, 463-746, South Korea Generally, steeping is considered as one of physical modification procedures for starch, which plays a very important role in controlling the texture and appearance of the rice snack. To produce waxy rice cracker with desired qualities in Asian countries such as South Korea and Japan, milled waxy rice is steeped in water for various time. However, little is known about the influence of this water-steeping on the physicochemical properties of waxy rice starch. The objective of this study is to estimate the influence of steeping period for waxy grain on the physicochemical properties of the starch. Milled waxy rice (Shinsunchalbyeo cultivar) was steeped in water at 25oC for 0, 1, 3, 6, 9, 12 and 15 days, prior to starch isolation. As the steeping period of milled waxy rice changed from 0 to 15 days, the contents of lipid and ash in waxy rice starch were decreased to 46% and 42% of initial contents, respectively. In particular, the contents of Mg and P were decreased by water-steeping treatment. Depending on the steeping duration of waxy rice kernel, starches showed differences in the surface appearance under SEM. As measured by Rapid Visco-Analyzer (RVA), the consistencies of waxy rice flours increased, while that of starch did not changed as the steeping duration increased. The water-steeping appeared to slightly reduce the crystallinity of the starch granules, as judged on X-ray diffraction. On the other hand, GPC analyses showed no differences in the molecular weight and typical two peaks among starches obtained from waxy rice with different water-steeping duration. These results indicate that water-steeping only affect the chemical composition, but do not or slightly affect the physical properties and molecular structure of waxy rice starch.
Session 61A, Carbohydrate
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