Abstract
A non-isothermal moving-boundary model for food dehydration, accounting for shrinkage and thermal effects, is proposed and applied to the analysis of intermittent dehydration in which air temperature, relative humidity, and velocity vary cyclically in time. The convection-diffusion heat transport equation, accounting for heat transfer, water evaporation, and shrinkage at the sample surface, is coupled to the convection-diffusion water transport equation. Volume shrinkage is not superimposed but predicted by the model through the introduction of a point-wise shrinkage velocity. Experimental dehydration curves, in continuous and intermittent conditions, are accurately predicted by the model with an effective water diffusivity that depends exclusively on the local temperature. The non-isothermal model is successfully applied to the large set of experimental data of continuous and intermittent drying of Rocha pears.
Highlights
Food process engineering represents one of the research fields that could benefit most from theoretical/computational support, that is the accurate modeling of all the complex heat and mass transport phenomena involved in many processes of interest to the food industry.Natural and convective drying, for food production and preservation, is undoubtedly one of the most investigated processes [1]
This article stems from the idea of verifying the predictive capabilities of the moving-boundary dehydration model, recently proposed by Adrover et al [13,14], by analyzing the large set of experimental data of intermittent drying of Rocha pears reported by Silva et al [11]
Like in the isothermal moving-boundary model, volume shrinkage is not superimposed but predicted by the model via the introduction of the pointwise shrinkage velocity that depends on the local volumetric water flux
Summary
Food process engineering represents one of the research fields that could benefit most from theoretical/computational support, that is the accurate modeling of all the complex heat and mass transport phenomena involved in many processes of interest to the food industry. This article stems from the idea of verifying the predictive capabilities of the moving-boundary dehydration model, recently proposed by Adrover et al [13,14], by analyzing the large set of experimental data of intermittent drying of Rocha pears reported by Silva et al [11] This isothermal moving-boundary model has been already successfully applied to describe the continuous dehydration kinetics and shrinkage of different food materials and sample shapes, e.g., eggplant cylindrical [13] and discoidal samples [15], chayote slices [16], potatoes sticks [14] and square slices [13], ellipsoidal cocoa beans [17].
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