STUDY BY X-RAY MICROTOMOGRAPHY OF THE TOMATO SLICES SHRINKAGE DURING THE CONVECTIVE DRYING

In this study, the shrinkage phenomenon taking place during the convective drying
of tomato slices is investigated with 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/V0) v.s. the water content ratio (X/X0) are determined by
X-ray microtomography.
The results show that the tomato presents an anisotropic and independent of temperature
shrinkage and then a single shrinkage curve is proposed. On average, the volume decreases of
70 % of its initial value.The height and the diameter shrinkages have a linear dependence with
the water content until X/X0 = 0.2, but for X/X0 < 0.2, the diameter and especially the
thickness decrease rapidly, following a polynomial and a logarithmic trend, respectively.