Drying kinetics of tomato slices in vacuum assisted solar and open sun drying methods

A lab model vacuum-assisted solar dryer was developed to study the drying kinetics of tomato slices ( 4, 6, and 8mm thicknesses) compared with open sun drying under the weather conditions of Montreal, Canada. The drying study showed that the time taken for drying of tomato slices of 4, 6, and 8mm thicknesses from the initial moisture content of 94.0% to the final moisture content of around 11.5 +/- 0.5% (w.b.) was 360, 480, and 600 min in vacuum-assisted solar dryer and 450, 600, and 750 min in open sun drying, respectively. During drying, it was observed that the temperature inside the vacuum chamber was increased to 48 degrees C when the maximum ambient temperature was only 30 degrees C. The quality of tomato slices dried under vacuum-assisted solar dryer was of superior quality in terms of color retention and rehydration ratio. The drying kinetics using thin-layer drying models and the influence of weather parameters such as ambient air temperature, relative humidity, solar insolation, and wind velocity on drying of tomato slices were evaluated.