Abstract :

Potatoes are important foodstuffs all over the world. The influence of slice thickness and varying temperatures on potatoes was studied during oven drying. This work on thin layer drying was carried out between 60oC and 80oC at different slice thicknesses of 0.4cm 0.6cm and 0.8cm. The sliced samples were pre-treated with 0.5% sodium meta bisulphite solution for five minutes and oven-dried at 60oC, 70oC, and 80oC. The results showed that pre-treated samples dried quicker than untreated samples. Experimental drying curves showed only a falling drying rate period. The Deff values of dried samples at a hot air-drying temperature of 60-80oC were varied in the range of 1.12x10-9 to 9.42x10-10m2/s for untreated samples and 1.4x10-9 to 7.09 x10-10m2/s for treated samples. Because of the increased mass transfer, the higher temperature increased effective moisture diffusivity. The activation energy was calculated from the graph of lnDeff (effective moisture diffusivity) versus 1/Tabs and thermodynamic properties of food sample drying were obtained using the method described by Jideani and Mpotokwana,2009. The values of activation energy were varied in the range of 25 to 36kJ/mol for untreated samples and 33 to 43kJ/mol for treated samples. The enthalpy, entropy, and Gibbs free energy values were -2733 to -2908J/mol, -298.85 to-345.58J/mol and 104238.6 to 115625.6J/mol respectively.