Estimating the theoretical energy required to dry rice

The total heat of desorption of rice (Qt) was determined for several rice types as a function of moisture content (MC), and kernel temperature, using a semi-theoretical approach in which desorption isotherms were used in conjunction with the Clausius–Clapeyron equation. Qt decreased exponentially as MC increased, decreasing sharply for MCs above 15% and approaching the latent heat of vaporization of free water at MCs around 20%. Qt of parboiled rice at 12.5% MC was significantly less than that of non-parboiled lots. Qt of medium-grain “Jupiter” was significantly greater than that of long-grains at 12.5% MC. Equations that predict the energy required to dry a unit mass of rice from an initial MC to a final MC were derived.

► Equations that predict the energy required to dry a unit mass of rice were developed. ► Parboiled rice generally required less energy than the non-parboiled rice lots. ► Medium-grain rice generally required more energy to dry than long-grain rice. ► The energy required to dry rice decreased as temperature increased.