Drying characteristics of ready-to-eat komal chawal rice: processing and modeling

A traditional ready-to-eat rice from Assam, India, known as komal chawal is produced by steaming of steeped chokuwa paddy, which is a low-amylose variety, and by drying the steamed paddy under shade as a measure of controlling the drying rate for sustenance of a quick rehydration quality. As an improvement over this traditional method in terms of production time, komal chawal is produced by parboiling the chokuwa brown rice with model predicted soaking and steaming conditions. Thin-layer drying behavior of the steamed brown rice was studied at drying temperatures of 40-60 °C, at an air velocity of 1 m/s. Among different thin-layer drying models, Page equation fitted best to the drying data, with the coefficient of determination (R²) and root mean square error as the measures for selection of the best fitted model. While the moisture diffusivity values were in the range of 2.08 × 10^-10-3.34 × 10^-10 m²/s, the effects of drying air temperature on the drying rate was modeled with an activation energy of 20.44 kJ/mol for an the Arrhenius kind of temperature dependence of diffusivity. Based on the effects of drying temperature on rehydration, textural, and pasting properties of the product a lower drying temperature is recommended.