33A-17 |
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M. -I. KUO1, Y. -J. Wang, and H. He. (1) Dept. of Food Science, Univ. of Arkansas, 2650 N. Young Ave., N-214 Food Science Bldg., Fayetteville, AR 72704 Rice is preferred by some brewers because of its low protein and lipids contents as compared with other cereals. The physicochemical properties and particle size of rice grits are important factors to evaluate concerning the quality of rice for brewing. The objectives of this study were to investigate the influence of particle size on physicochemical properties of rice grits and to compare the differences between two U.S. long-grain rice cultivars. Two long-grain cultivars, Cocodrie and Wells of the 2002 crop, were separated into fractions of different particle sizes, including >1.4 mm, 1.0-1.4 mm, 0.6-1.0 mm, 0.25-0.60 mm, and <0.25 mm. Each fraction of rice samples was analyzed and compared for chemical composition and physicochemical properties, including water sorption profile, water holding capacity, swelling power, water solubility index, and thermal and pasting properties. As particle size decreased, starch and amylose contents of rice grits decreased, while protein, lipid, and damaged starch increased. Rice grits with larger particle sizes exhibited polymodal endotherms and greater gelatinization enthalpies but no peak viscosity was observed as measured by Micro Viscoamylograph. The water holding capacity, swelling power, and water solubility index of rice grits increased as particle size decreased. During 2 wk of storage, moisture contents of rice grits with different particle sizes decreased when the relative humidity was below 31% and increased when the relative humidity was equal to or higher than 56%. Composition results of rice grits with different particle sizes suggested that rice grits with a particle size <0.25 mm might be from the surface layer of rice endosperm and rice grits with larger particle sizes might be from the inner endosperm. Some differences in physicochemical properties between Cocodrie and Wells rice grits with different particle sizes could be attributed to their differences in their chemical compositions.
Session 33A, Carbohydrate: General
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