GAB model and the thermodynamic properties of moisture sorption in soursop fruit powder

Fernanda Machado Baptestini,Iasmine Ramos Zaidan,Mateus Da Silva Junqueira,Afonso Mota Ramos,Paulo Cesar Corrêa

doi:10.5935/1806-6690.20200006

Abstract

The aim of this study was to model and determine the thermodynamic properties of moisture sorption in soursop fruit powder. The isotherms were determined by the static method at temperatures of 10, 20, 30, 40 and 50 °C, and a water activity of between 0.113 and 0.868 (decimal). The GAB model effectively described the moisture sorption phenomenon of soursop powder. The monolayer moisture content ranged from 12.589 to 9.109% db. The enthalpy values related to the GAB model were negative, with -2581.035 kJ kg-1 for C0 and -107,758 kJ kg-1 for K0. The isosteric heat of sorption, entropy and Gibbs free energy had a high correlation with the equilibrium moisture content, and the correlation between enthalpy and entropy was confirmed for moisture sorption in soursop powder.

Highlights

Dehydrated foods tend to gain water from the storage environment, thereby altering their water activity until equilibrium is again restored
According to Damodaran, Parkin and Fennema (2010), information derived from these curves is useful for studying and controlling the processes of preservation and dehydration, for formulating food mixtures to prevent water transfer between the ingredients, for determining the necessary water-barrier properties of the packaging material, for ascertaining the water content that will reduce the growth of microorganisms of interest in a system, and for predicting the physical and chemical stability of foods as a result of changes in their water content
The monolayer moisture content decreased with the increase in temperature of the sorption process, ranging from 12.589 to 9.109% db; 3

Summary

Introduction

Dehydrated foods tend to gain water from the storage environment, thereby altering their water activity until equilibrium is again restored. Alterations in powdered foods include agglomeration, changes in texture, a change in colour and even microbial growth, with such changes tending to lead to rejection of the product (MEDEIROS; LANNES, 2010). According to Damodaran, Parkin and Fennema (2010), information derived from these curves is useful for studying and controlling the processes of preservation and dehydration, for formulating food mixtures to prevent water transfer between the ingredients, for determining the necessary water-barrier properties of the packaging material, for ascertaining the water content that will reduce the growth of microorganisms of interest in a system, and for predicting the physical and chemical stability of foods as a result of changes in their water content.

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Conclusion