Thin layer modelling of hybrid, solar and open sun drying of tomato slices

Abstract

The thin layer drying behaviour of tomato slices dried using hybrid drying method as well as solar and open sun drying was investigated. Six thin layer drying models (Page, Logarithmic, Henderson and Pabis, Newton (Lewis), Wang and Singh and Parabolic) were used to optimize the goodness of fit to the experimental data. The models were compared using coefficient of determination (R2), chi-square (c2) and root mean square error (RMSE). The tomato slice dried faster when subjected to hybrid drying method compared to other methods. Tomato slices of 4, 6 and 8 mm thicknesses were dried from 94.22 to 10% (wet basis), for 300, 360, 420 minutes respectively in hybrid drying method. However, it took 420, 510, 600 and 510, 630, 840 min in solar and open sun drying respectively. The drying took place only in a falling rate drying period. The Page model was found to fit the experimental data better as compared to other models. The effective moisture diffusivity values were found to be between 2.00 x 10-10 and 5.84 x 10-10 m2/s in hybrid dried slices, 1.37 x 10-10 and 4.40 x 10-10 m2/s in solar dried slices and 1.33 x 10-10 and 4.01 x 10-10 m2/s in open sun dried tomato slices of 4 to 8 mm thicknesses. The results of these measures have confirmed the consistency of the developed model to describe satisfactorily the thin-layer hybrid, solar and open sun drying characteristics of tomato slices.