WATER desorption isotherms of pork liver and thermodynamic properties

ABSTRACT Thermodynamic properties provide information on energy demand and kinetic parameters in water sorption processes in agricultural products. Such information is essential to analyze and scale drying and storage equipment. The objective of this study was to determine the thermodynamic properties involved in the water desorption process in Buchenavia capitata (Vahl) Eichler seeds with moisture contents ranging from 13.31 to 7.21% dry basis (d.b.), obtained by the indirect static method, at temperatures of 10, 20, 30 and 40 °C. The latent heat of vaporization, differential entropy and Gibbs free energy increase with the reduction of the moisture content of the seeds. The enthalpy-entropy compensation theory is valid for the desorption process, which is controlled by the enthalpy. The desorption of water in the seeds is not a spontaneous process.

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Moisture desorption isotherms of cucumber seeds: modeling and thermodynamic properties

Journal of Seed Science ◽

10.1590/2317-1545v37n3149549 ◽

2015 ◽

Vol 37 (3) ◽

pp. 218-225 ◽

Cited By ~ 8

Author(s):

Paulo Cesar Corrêa ◽

Maycon Fagundes Teixeira Reis ◽

Gabriel Henrique Horta de Oliveira ◽

Ana Paula Lelis Rodrigues de Oliveira ◽

Fernando Mendes Botelho

Keyword(s):

Free Energy ◽

Relative Humidity ◽

Thermodynamic Properties ◽

Moisture Content ◽

Gibbs Free Energy ◽

Content Increase ◽

Statistical Parameters ◽

Thermodynamic Relation ◽

Differential Enthalpy ◽

Desorption Isotherms

Hygroscopic equilibrium curves or sorption isotherms are important in order to define dehydration limits of the product, estimate moisture content alterations under environment conditions and to acquire moisture content values for safe storage. This work aimed to determine desorption isotherms of cucumber seeds stored at different temperature (10, 20, 30, 40 and 50 ºC) and relative humidity (0.11 to 0.96) and the thermodynamic properties of this process. Mathematical models were fitted to experimental data in order to represent the agricultural products hygroscopicity. Net isosteric heat of desorption was performed based on the Clausius-Clapeyron thermodynamic relation and Gibbs free energy through the Van't Hoff equation. Based on statistical parameters, Modified Henderson model was the one that best represented hygroscopicity of cucumber seeds. Equilibrium moisture content of cucumber seeds decreased with temperature increment at a constant value of relative humidity. Differential enthalpy values, representing the energy required to remove moisture from the cucumber seeds, ranged from 2923 to 2469 kJ. kg-1. Values of differential entropy and Gibbs free energy decreased with moisture content increase. Enthalpy-entropy compensation theory is valid for the sorption of cucumber seeds, in which the water sorption mechanism in cucumber seeds can be considered to be enthalpy controlled.

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