Experimental study of the kinetics and shrinkage of tomato slices in convective drying

This work focuses on the convective drying of tomato slices with hot air at temperatures of 50 and 60°C and at velocities of 0.1, 0.25 and 0.5 m.s-1. The kinetics and drying rates are determined according to the temperature and velocity of the drying air. The equation of “Gaussian”, used for the first time and in this work, is more adaptable to the drying curves. Two methods have been used to determine the coefficient of effective diffusion (with and without the effect of shrinkage). The energy of activation is evaluated with the Arrhenius relationship. In this study, we are interested in the phenomenon of shrinkage, in particular, and the evolution of the relative thickness of the slice of tomato according to drying duration and moisture content. The study shows that on hot air drying, the influence of velocity is dominant as compared to temperature. We observed that for the same final moisture content, the final relative thickness of the product is not constant. It varies depending on the operating conditions.    Key words: Tomato drying, drying kinetics, drying speed, coefficient of effective diffusion, activation energy, shrinkage.

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