Thin layer modeling for drying of black pepper in an agricultural waste fired dryer

Abstract

Black pepper (Piper nigrum) of Sreekara variety was dried in an agricultural waste fired reverse flow dryer and thin layer drying characteristics of blanched and unblanched pepper was studied. Blanching was done by dipping in boiling water for 1 min. The experimental data for moisture loss was converted to moisture ratios and fitted to nine thin layer drying models to describe the drying process mathematically. The results were compared for their goodness of fit in terms of coefficient of determination (R2), root mean square error (RMSE), mean bias error (MBE) and mean square of deviation (c2). Diffusion approximation model was found most suitable to describe the drying process of black pepper. The unblanched pepper took 30 h and blanched pepper took 28 h to dry from moisture content of 178.55% to 9.56% and 9.29% d. b, respectively. The effective moisture diffusivity varied from 4.67 x 10-07 to 5.20 x 10-07 m2s-1 for unblanched and blanched pepper.