Sorption isotherms and isosteric heats of sorption of Malaysian paddy

Abstract

Understanding the water sorption characteristics of cereal is extremely essential for optimizing the drying process and ensuring storage stability. Water relation of rough rice was studied at 20, 30, 40 and 50°C over relative humidity (RH.) between 0.113 and 0.976 using the gravimetric technique. The isotherms displayed the general sigmoid, Type II pattern and exhibited the phenomenon of hysteresis where it was more pronounced at lower temperatures. The sorption characteristics were temperature dependence where the sorption capacity of the paddy increased as the temperature was decreased at fixed (RH). Among the models assessed for their ability to fit the sorption data, Oswin equation was the best followed by the third order polynomial, GAB, Smith, Chung-Pfost, and Henderson models. The monolayer moisture content was higher for desorption than adsorption and tend to decrease with the increase in temperature. Given the temperature dependence of the sorption isotherms the isosteric heats of sorption were calculated using Claussius-Clapeyron equation. The net isosteric heats decreased as the moisture content was increased and heats of desorption were greater than that of adsorption.

Thermodynamic properties of Buriti (Mauritia flexuosa) tree gum

“…Ot can also be seen that this loop decreases as temperature increases, virtually disappearing at 55 °C. A similar behavior was observed by Mousa et al (2014) for the sorption isotherms of Malaysian paddy (20-50 °C). Countless qualitative propositions involving factors such as the presence of local metastable domains, fixation of molecules by chemisorption, phase transition, and capillarity phenomena can be used to explain the appearance of the hysteresis loop in sorption processes (Oglesias & Chirife, 1982).…”

Sorption behavior and isosteric heat of maize-millet based protein enriched extruded product

“…Similar trends of behavior had also been demonstrated of other dried food materials by earlier researchers (Iglesias and Chirife, 1976;Ayranci and Duman, 2005). This might be due to reduced accessibility of hydrophilic site and less capacity of polymers to make hydrogen bonding (Quirijns et al, 2005;Mousa et al, 2014). The connection between monolayer moisture content (M o ) and absolute temperature has also been developed through regression equation.…”

“…The value of percentage RMSE below 10% is considered to be adequate for acceptability of the isotherm model (Koc, Yilmazer, Balkir and Ertekin, 2010). A model is also measured to be appropriate if the value of P is less than 10% (Jena and Das, 2012;Mousa et al, 2014).…”

MODELING DYNAMIC ADSORPTION ISOTHERMS AND THERMODYNAMIC PROPERTIES OF SPECIALTY GROUND ROASTED-COFFEE (Coffee Arabica L.)

“…For the proper handling of ground roasted-coffee it is necessary to know, among other properties, the water sorption isotherms, which describe the relationship between the equilibrium moisture content and the water activity at constant temperature and pressure (BASTIOĞLU et al, 2017). There is a large numbers of sorption equations for the characterization of the water sorption behavior of foods (MOUSA et al, 2012), such models can be theoretical, empirical or semi-empirical equations. Because of the complex nature of food matrices, there is not a unique model to entirely describe agri-food products (BON et al, 2012); therefore, is necessary to validate the best model for both the material and the environment conditions using experiment data.…”