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This work aimed to evaluate alterations on the water sorption of coffee due to roast, grind, and storage. Crude grain coffee ( Coffea arabica) was roasted at two levels: medium light and moderately dark. Grain was grinded in fine (0.59 mm), medium (0.84 mm), and coarse (1.19 mm) particle sizes, besides the whole coffee lot. Samples were then stored at polypropylene bags and kept at biochemical oxygen demand type chambers in two storage temperatures (10 and 30C). These were analyzed at 0, 30, 60, 120, and 180 days, regarding water content and water activity. Mathematical modeling and thermodynamic properties of coffee moisture adsorption process were accomplished. It was concluded that particle size did not significantly affect water content of coffee, independently of roast degree. Sigma-Copace model best represented hygroscopic equilibrium of roasted coffee. Water content reduction increases the differential enthalpy and entropy of sorption and Gibbs free energy. Practical Applications Commercialization of crude grain coffee, soluble coffee, roasted, and grinded coffee, among others (extract, essences, and concentrated) represents 9.2% of Brazilian exportation. Higher distances lead to physical, chemical, and microbiological changes in agricultural products. This trend could cause the deterioration of food products. Information on the sorption characteristics of roasted and grinded coffee could not be found in the literature, regardless of this culture importance. Sorption isotherms data are key information to predict optimum storage and trading conditions to ensure quality. Finally, the lack of quality may affect employees, entrepreneurs, and other professionals that works with coffee. This article presents the adsorption isotherms and thermodynamic properties of roasted and grinded coffee ( Coffea arabica L.). [ABSTRACT FROM AUTHOR]

The desorption isotherms and thermodynamic properties of sugar beet seeds of cv. ' Chata do Egito' variety was determined at 10, 20, 30, 40 and 50C over a range of water activities ( Aw) from 0.11 to 0.96. Equilibrium moisture content data were correlated by the Guggenheim-Anderson-de Boer model, which presented good fit to the data, according to statistical procedures. Equilibrium moisture content ranged from 1.50 to 20.0% d.b. (dry basis). Desorption isotherms of sugar beet seeds exhibited type II sigmoid shape. Thermodynamic properties were determined related to desorption process. Differential enthalpy values varied between 3,614.51 and 4,093.90 kJ/kg. Differential entropy and Gibbs free energy presented values between 3.67-4.08 kJ/kg.K and 0.75-508.11 kJ/kg, respectively. The enthalpy-entropy compensation theory is valid for the moisture desorption phenomena of sugar beet seeds, being enthalpy controlled. Practical Applications Almost 100% of the Brazilian sugar beet seeds are imported throughout the world and its commerce between different countries. Higher distances lead to physical, chemical and microbiological changes in sugar beet seeds. This trend could cause the deterioration of food products. Information on the sorption characteristics of sugar beet seeds could not be found in the literature, regardless of this culture importance. Sorption isotherms data are key information to predict optimum storage and trading conditions to ensure quality of sugar beet seeds for crop production. Finally, the lack of quality may affect employees, entrepreneurs and other professionals who work with sugar beet. This paper presents the desorption isotherms and thermodynamic properties of ' Chata do Egito' sugar beet seed variety. [ABSTRACT FROM AUTHOR]

The objective of this work was to study and model the drying process of corn ears at different air temperatures. Thermodynamic properties associated with the drying process of this product were also determined. Corn ears with initial moisture content of 0.45 dry basis (kgwkgdm-1) were dried until they reached a final moisture content of 0.12 (kgwkgdm-1) at temperatures of 45, 55 and 65°C. Traditional models used to describe the drying process of several agricultural products were employed to fit the observed data of the drying process of corn ears. The effective diffusion coefficient (Def) was determined by means of an analytical solution of Fick's second law. It was concluded that the Logarithmic model was the one that best fit the observed data representing the drying process. Def values increased with temperature increases, ranging from 5.490 x 10-10 to 1.163 x 10-9 m² s-1. Based on the dependence of the drying constant of the Logarithmic model with temperature, thermodynamic properties were determined, concluding that the drying kinetics variation is dependent on the energy contributions of the surrounding environment. [ABSTRACT FROM AUTHOR]

The water sorption isotherms of pearl millet grain and the thermodynamic properties obtaining during the process of drying pearl millet were examined. Equilibrium moisture content ( Xeq) was determined under several temperature ( T) and relative humidity (RH) conditions. The Xeq data were correlated by six mathematical models. The modified Henderson was the model that best fitted the experimental data. The Xeq decreased with an increase in T at constant RH. Hysteresis was also studied; increasing T led to a decrease in this phenomenon. Integral isosteric heat of sorption ( Qst), differential entropy (Δ S) and the enthalpy–entropy compensation theory were studied. Qst values decreased when Xeq increased because the Qst values of adsorption were lower than Qst desorption values. The values of Δ S decreased with increases in Xeq, because Δ S values were higher for desorption than for adsorption. The enthalpy–entropy compensation theory is valid for describing the water sorption processes of pearl millet grain. [ABSTRACT FROM AUTHOR]