Convective drying of fruit: Role and impact of moisture transport properties in modelling

Abstract

Continuum modelling of fruit dehydration relies on accurate predictions of moisture permeability or diffusivity. These properties are often taken from literature instead of being explicitly determined for the species, cultivar or drying application of interest. As a large variability on these moisture transport properties is reported, this study targets their role and impact on simulations of the fruit drying process. Using a validated hygrothermal model, significant differences in drying rate and internal moisture content distribution are quantified for a realistic range of tissue permeabilities. Particular differences in drying kinetics are identified between constant permeability and diffusivity formulations, but in general both exhibited roughly similar drying behavior. Previous contradictory findings on the impact of the air speed, thus convective transfer coefficients (CTCs), on the drying process are shown to be most likely related to the magnitude of the tissue permeability. A lower sensitivity of the drying process to the CTCs is found for low permeabilities. A new parameter is introduced to facilitate quantitative comparison of multiple drying processes, namely by characterizing each drying curve with a single characteristic value. This modelling study provides a better quantitative insight in the fruit drying behavior and its link to the moisture transport properties of the tissue.