MODELING VARIETAL EFFECT ON THE WATER UPTAKE BEHAVIOR OF MILLED RICE (ORYZA SATIVA L.) DURING SOAKING

摘要

Milled rice is soaked until saturation before cooking and other processing. The soaking behavior of the milled rice is affected by varietal factor as well as initial moisture content (Mo) of the samples. In the present study, tests were performed for milled whole kernels of 10 rice varieties ranging from low to high amylose content (16-29% d.b.) with three initial moisture levels (approximately 8, 12 and 16% d.b.) for monitoring water uptake in rice kernels during soaking at room temperature (25 ± 1C), in relation to the varietal differences manifested by the physicochemical properties. The water uptake by milled rice kernels took place at a faster rate in the beginning and was followed by a diminishing rate finally leading to a saturated value during soaking. The water uptake of the kernels during soaking could be best expressed by a modified exponential relationship with R2 values ranging from 0.971 to 0.998 for all varieties. The slope of the fitted straight line between actual and estimated moisture contents of milled rice during soaking using a modified exponential relationship was about unity (0.998) with a high R2 value of 0.989 and a root mean square error of 1.2% d.b. The parameters of the fitted model were the function of the M_0 and the physicochemical properties of the milled rice. Using developed relationship, the water uptake of the milled rice during soaking could be estimated from its M_0 and the physicochemical properties within ± 10% of the actual values.