Effect of cooking and drying on the thermal conductivity of rice

The transient line source technique was used to determine the thermal conductivity of rice during cooking and drying of cooked rice. A temperature range of 50-70 degrees C, moisture content of 10-70% (wet basis), bulk (packing) density range of 500-850 kg/m(3) and porosity range of 0.265-0.7 were studied. Thermal conductivity increased with increasing temperature, moisture content and bulk density, and the values were in the range 0.082-0.543 W/m degrees C. This value is comparable with the literature values for granular and gelatinized starch. The data on the effect of phase change due to gelatinization have also been included. The experimental values were statistically analyzed and empirical polynomial equations were developed in terms of temperature, bulk density, porosity and moisture content of rice during cooking and drying the cooked material.