Drying characteristics and sorption isotherm of tomato slices

The drying behaviour of tomato slices was investigated at 45, 60 and 75 °C. Three falling rate periods were observed with diffusion coefficients in the range 3.72–12.27 × 10−9 m2 s−1. The water vapour sorption isotherm of dehydrated tomato slices in the water activity (aw) range of 0.08–0.85 was also determined at three temperature levels, i.e., 25, 30 and 40 °C. Five sorption models were fitted with the adsorption data generated from the gravimetric method. GAB and Oswin models describe the adsorption characteristics of dehydrated tomato at 25 °C better than other models with GAB model being the best applicable model. The isosteric heat of adsorption decreases with increasing moisture.