Water uptake and solid loss during cooking of milled rice (Oryza sativa L.) in relation to its physicochemical properties

Tests were performed for milled rice of 10 Thai varieties ranging from low to high amylose content (16–29%) with three initial moisture levels (approximately, 8%, 12% and 16% d.b.) for monitoring water uptake in rice kernels and solid loss during cooking in relation to the varietal differences manifested by their physicochemical properties. Water uptake of milled rice increased with an increasing rate in the beginning followed by a diminishing rate during cooking in excess water while the solid loss was a power function of cooking duration. The moisture content during cooking could be best expressed by a modified exponential relationship with R2 values ranging from 0.995 to 0.999 for all varieties. The regression coefficients of the fitted relationship for describing moisture adsorption by cooked rice were found to be the function of physicochemical properties, namely, the AC and AS of milled rice. It was concluded that the water uptake during cooking of milled rice could be estimated by the physicochemical properties of the milled rice within ±10%.