Drying Kinetics of Tomato Slices in Solar Cabinet Dryer Compared with Open Sun Drying

Abstract

Drying performance of a solar cabinet dryer newly developed to dry tomato slices was compared with open sun drying under the climatic conditions of Montreal, Canada. The tomato slices of 4, 6 and 8 mm thicknesses was dried from 94% to 11.5% wet basis moisture content, respectively in 300, 420 and 570 minutes in solar cabinet but it took 435, 615 and 735 minutes in open sun drying. Four thin layer drying models were used to optimize the ‘goodness of fit’. The models were compared using coefficient of determination, chi-square and root mean square error. The page model was found to fit the experimental data better as compared to other models. The moisture diffusivity of tomato slices ranged from 4.25 to 7.67 x 10 -7 m 2 /s in solar cabinet drying and from 3.09 to 9.28 x 10 -9 m 2 /s in open sun drying. Influence of air temperature, relative humidity, solar insolation and wind velocity on drying kinetics of tomato slices was discussed. Analyses on colour, water activity, rehydration ratio and ascorbic acid were also reported.