Drying of orange skin: drying kinetics modelling and functional properties

The effect of the drying air temperature on the drying kinetics and on the functional properties of dried orange skin has been studied. A mathematical model has been proposed to simulate these drying curves taking into account the sample shrinkage during drying and the influence of the local moisture content on the effective diffusion coefficient. The moving boundary problem has been solved by an explicit finite difference method and the parameters of the diffusional equation have been identified. A good agreement with experimental results was found (average percentage of explained variance and mean relative error were 99.5 ± 0.3% and 6.2 ± 2.2%, respectively). The water retention capacity and the fat adsorption capacity of the samples dried, milled and sifted through different mesh screens (0.355, 0.180 and 0.090 mm) were measured. A significant influence not only of the drying air temperature but also of the particle size on these functional properties was observed (p < 0.001).