Optimization of convective drying process for Persian shallot using response surface method (RSM)
Keywords:color, diffusivity, energy, central composite design, shrinkage
Abstract: Optimization of convective drying process of Persian shallot was investigated using dependent variables of effective moisture diffusivity (Deff), 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, Deff, 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