Water Uptake and Solid Loss During Soaking of Milled Rice Grains

摘要

Water uptake and solid loss of milled rice grains from three Thai rice varieties, most commercially available—waxy, jasmine, and Sao Hai rice, with varied amylose con-tents of 7.17%, 16.63%, and 29.06%, respectively—were analyzed in the temperature range of 35°-85°C. An increasing rate of water uptake was observed at the beginning of the soaking process, and a reducing rate was detected thereafter, in particular at temperatures above 60°C for waxy and jasmine rice and above 75°C for Sao Hai rice. The parameters of the kinetics involving the simultaneous unsteady-state water diffu-sion and first-order irreversible water-starch interaction were evaluated by using five empirical models and the Fickian diffusion model. The Page model was found to suitably describe the water-absorption characteristics of milled rice grains. Water absorption rate, as well as solid loss, expressed as a power function of soaking dura-tion were found to decrease with increasing amylose content of rice grains.