Optimization of convective drying process for Persian shallot using response surface method (RSM)

Abstract

Abstract: Optimization of convective drying process of Persian shallot was investigated using dependent variables of effective moisture diffusivity (D_eff), specific energy consumption (SEC), shrinkage and color changes.  The central composite design (CCD) was selected for design and optimization of the process.  The second-order polynomial models with transformed responses were developed from experimental data to generate three dimensional response surfaces and contour plots.  Experiments were performed at air temperatures of 40°C, 55°C and 70°C, air velocities of 0.5, 1.5 and 2.5 m/s and slice thicknesses of 2, 4, and 6 mm in triplicate.  Based on response surface and desirability functions, the optimum conditions for Persian shallot drying were: air temperature 70°C, air velocity 2.5 m/s and slice thickness 4.58 mm.  At this point, D_eff, SEC, shrinkage and color changes were obtained as 1.18675×10^-9 m²/s, 13.83 MJ/kg, 35.04% and 42.27%, respectively.

Keywords: color, diffusivity, energy, central composite design, shrinkage