Net Isosteric Heats of Adsorption and Desorption for Different Forms of Hybrid Rice

Abstract

Hygroscopy of hybrid rice affects storage, handling, and processing. The thermodynamic relationship upon which the estimate of isosteric heat is based is the Clausius-Clayperon equation. The net isosteric heat of sorption was determined from the slope of the ln(rh) versus 1/T lines at a constant moisture content. Net isosteric heat of desorption was found higher than that for the adsorption within a moisture content range of 12-20% for all of the rice kernels. The net isosteric heats of desorption and adsorption were higher for hybrid rough rice kernels followed by brown rice and milled rice kernels, respectively. An empirical equation was fitted to describe the net isosteric heats of hybrid rice kernels as a function of moisture content and was found adequate to predict the net isosteric heats. The intercept K was also found to be a function of moisture content and the model predicted the K value well (r 2 = 0.85 for adsorption and r 2 = 0.92 for desorption). This set of two equations would be useful in the simulation of hybrid rice during storage.

Simulation of Storage Conditions of Mixed Biomass Pellets for Bioenergy Generation: Study of the Thermodynamic Properties

“…Using Equation 4, this means that the net isosteric heat of sorption is decreasing with the increase of the equilibrium moisture content. This observation is in agreement with the results obtained by Meze'e et al [25] and Ouertani et al [24], obtained for different kinds of wood, and Haque et al [22] for several sorts of rice. Indeed, the net isosteric heat of sorption varied from 13.26 kJ/mole for an EMC M = 4% to 0.29 kJ/mole at M = 12% for the spruce-switchgrass pellets.…”

“…As reported by Meze'e et al [25] and Ouertani et al [24], this decrease of the Q iso with the EMC increase is confirming the solid water-surface interactions. On the other side, as reported by Haque et al [22], no changes in the Q iso at high EMC is due to the existence of the free water.…”

“…As mentioned by Haque et al [22] and Seth et al [23], the net isosteric heat of sorption is representative of the difference between the total heat of sorption of water for the tested sample and the heat of vaporization of pure water. It is commonly well described mathematically using the Clausius-Clapeyron equation, written under the following form [22]:…”

Moisture sorption behavior and thermodynamic properties of dry‐crystallizedPalada payasam(rice flakes milk pudding) mix determined using the dynamic vapor sorption method

“…This phenomenon of a rapid initial decay with a near steady value has been classically attributed to the water adsorption with high binding energies at low moisture. The maximum isosteric heat of sorption for dry‐crystallized Palada payasam estimated in the present study (55.23 kJ mol −1 ) at mean temperature of 30 o C is comparable with the value obtained for rice (49.27 kJ mol −1 ) (Hque, Shimizu, Kimura, & Bala, 2007), gulabjamun mix powder (62.67 kJ mol −1 ) (Pushpadass et al, 2014), and orange juice powder (52.32 kJ mol −1 ) (Sormoli & Langrish, 2015). The value of differential entropy was also estimated and found to mirror the trend for isosteric heat with a decrease from 0.02545 kJ mol −1 K −1 at 1% moisture to 0.0074 kJ mol −1 K −1 at 40% moisture content, indicating that the disorder in the system was strongly moisture dependent.…”

Sorption isotherms and isosteric heats of sorption of Malaysian paddy

“…Haque et al (2007) and Iguaz and Vírseda (2007) reported that the isosteric heat of sorption of paddy was 9.980 kJ mol −1 and 9.230 kJ mol…”