91C-41 |
A study of rice kernel fracture by three-point bending tests |
Q. Zhang, W. YANG, Z. Sun, and T. J. Siebenmorgen. Dept. of Food Science, Univ. of Arkansas, 2650 N. Young Ave., Fayetteville, AR 72704 Rice fissuring and subsequent breakage during milling has long been a major problem facing rice industry. An experimental study of the mechanical properties of rice kernels including fracture energy, fracture strength and elastic modulus would help understand the failure mechanism of rice kernels during processing. Thin-layer drying was performed for a long-grain rice variety (Cypress) with original moisture content of 21% wet basis at 60oC, 17% RH for preset durations to obtain samples with various moisture contents. Three-point bending tests were conducted in a Texture Analyzer (Texture Technologies, NY) with a loading speed of 0.5mm/s. Force-deformation curves were recorded during bending, through which the fracture energy, the fracture strength, and the elastic modulus were calculated. Results indicated that the fracture energy increased almost linearly with an increased drying duration (or decreased moisture contents). The fracture strength and elastic modulus also increased with reduced moisture contents. However, the deformation at breakage was not significantly influenced by moisture contents. These results could be interpreted by the hardening of materials due to higher glass transition temperatures induced by the loss of plasticizer (water) and the high crystallinity of starch in the rice kernels. The results from mechanical measurement by three-point bending provided basic experimental data for the study of rice breakage problem during processing.
Session 91C, Food Engineering: Food process engineering
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