18
Effect of intra-kernel moisture gradients on milling quality of rice. W. YANG (1), C.-C. Jia (1), T. J.
Siebenmorgen (1), and A. G. Cnossen (1). (1) Department of Food Science, University of Arkansas.
Moisture content gradient is a common phenomenon that refers to the
moisture difference between the surface and the center of a grain kernel during drying. It is usually obtained
by computer simulation of the moisture diffusion process inside a single grain kernel. In this study, the
effect of moisture content gradient, especially the maximum moisture content gradient (MMCG), on milling
quality of rice was examined. A diffusion equation describing the moisture movement inside a rice kernel
during drying was solved using the finite element method. Moisture distribution inside a rice kernel was
simulated and verified using the thin layer drying experiments. MMCG was then determined and compared
to the head rice yield trend obtained at various durations of drying. The results showed that MMCG existed
along the short axis of a rice kernel. High initial moisture, low equilibrium moisture content and high drying
air temperature produced high moisture content gradient during drying and finally resulted in a decrease in
HRY. It was found that HRY incurred a marked decrease after drying past the MMCG point. According to
the findings in this study, MMCG played an important role in regulating the milling quality of rice during
drying.
|
