Seedless grape (Sultana grape) is a very important commercial fruit grown in large quantities in Tunisia. This product is characterized by a high initial moisture content (the initial wet basis moisture content of the fruit is more than 80 %), and thus a high shrinkage during drying. The mature seedless grape is a spherically shaped fruit. Thermo-physical properties and drying kinetics of seedless grape is essential for the optimization of its drying processes. This paper is composed of two parts, the first one is reserved to the experimental study of seedless grapes, such as the establishment of the desorption isotherms which were determined at 40, 50, 60 and 70 °C by using static gravimetric method and these desorption data were fitted by GAB model. Then we were interested in measurement of the axial hydrous shrinkage of a grape berry and it was expressed as a function of moisture content. Indeed, the drying kinetics under different controlled conditions of air temperature and relative humidity were realized. In the second part, the moisture diffusivity of the seedless grape was determined by minimizing the sum of square of deviations between the predicted and experimental values of moisture content of convective drying kinetics. The adopted approach was based on a numerical solving of the conservation equation of the solid phase and the equation of diffusion/convection of liquid phase for spherical geometry, coupled by the solid phase velocity due to shrinkage. The moisture diffusivity of seedless grape increased with temperature and was correlated by an Arrhenius-type equation. Indeed, the effect of moisture diffusivity was expressed by an exponential function. The moisture diffusivity of seedless grape ranged between 3.5610−10 (m2/s) and 12.610−10 (m2/s). Activation energy was found equal to 57.76 kJ/mol.
The aim of this work was to determine sorption isotherms and thin layer convective drying behavior of apple slices and to compare the experimental and calculated results by using models available in the literature. The sorption isotherm was determined at four temperature levels 40, 50, 60 and 70 °C and at water activity ranging from 0.058 to 0.89, using the static gravimetric method. A non-linear regression procedure was used to fit experimental sorption isotherms and drying curves with most used empirical mathematical models available in literature. It was found that the Peleg model suitably represent the sorption experimental data in the mentioned investigated ranges of temperature and water activities. The Midilli et al. model satisfactorily described the thin layer drying behavior of apple slices. The drying characteristic curve and the thin layer drying rate expression of apple slices have been established from experimental convective drying kinetics. The values of the diffusivity coefficients at each condition were obtained using Fick's second law of diffusion. They varied from 8.51 × 10 -8 to 3.28 × 10 -7 m 2 /s in the temperature range of 40-70 °C and in the relative humidity range of 20%-40%. The activation energies for moisture diffusion were calculated to vary from 26.72 to 35.83 kJ/mol.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.