Studying the convective-dried tomato shrinkage by X-ray micro-CT imaging

The use of X-ray micro-CT imaging (X-ray microtomography), which is an effective imaging technique that provides multiple advantages across different fields (non-destructive, high resolution, density contrast, versatility, in-situ analysis, and 3D modeling), for experimentally determining shrinkage during fruit drying has not been extensively researched. Therefore, the main goal of this paper is to examine the shrinkage phenomenon during convective drying of tomato slices, using three different temperatures (40, 50, and 60°C) at constant air velocity of 1 m.s-1 and very low humidity. Indeed, the shrinkage curves showing the evolution of the volume ratio (V*) versus the water content ratio (X*) are determined by X-ray microtomography. According to the findings, the tomato exhibits anisotropic shrinkage that is not affected by temperature, and a single shrinkage curve is proposed. On average, the volume decreases of 70% of its initial value. The water content affects both thickness and diameter shrinkage in a linear manner until X* is 0.2. However, when the values are below 0.2, the diameter and especially thickness decrease quickly, with a polynomial and logarithmic trend, respectively.