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Characterization of broken rice kernels caused by moisture-adsorption fissuring – an extended study
S. MUKHOPADHYAY (1), T. Siebenmorgen (1) (1) University of Arkansas, Fayetteville, AR, U.S.A..

Fissuring caused by rapid moisture adsorption generates appreciable amounts of broken kernels upon milling, thereby reducing the economic value of rice. This study investigated the extent of kernel fissuring and resultant milling yield in rice lots that had incurred various levels of moisture adsorption-induced fissuring, as well as the physical and functional characteristics of broken kernels that resulted from milling such lots. Roy J, CL XL745 and Jupiter cultivar lots were conditioned to 9, 11, 13, 15, and 17% initial moisture content (IMC) levels, rewetted in water at 30°C for 2 h, gently re-conditioned to 12% moisture content (MC), and then milled. Results showed that as IMC prior to rewetting decreased, the extent of fissuring increased, and hence, milling yield decreased.  The mass-distribution of broken kernels was different between long-grain (LG) and medium-grain cultivar lots and also between the two LG cultivar lots. Peak and final viscosities were greatest for head rice, and decreased significantly with decreasing size of brokens. Although further investigation of the physical and functional characteristics of broken-kernel fractions is needed before conclusions on practical significance can be drawn, the paste viscosity-trends suggest that brokens of different sizes may have different functional properties and hence, may be best suited for different end-use applications.