Effect of osmotic pretreatment on air drying characteristics and colour of pepper (Capsicum spp) cultivars

Air-drying characteristics of fresh and osmotically pretreated (40 degrees B, 50 degrees B and 60 degrees B sucrose solutions for 9 h) four pepper cultivars namely, Rodo (Capsicum annuum), Shombo (Capsicum frutescens), Bawa (Capsicum fruten-scens) and Tatashe (Capsicum annuum), and CIE L*a*b* parameters of air-dried (50, 60, 70 and 80 degrees C) peppers were investigated. Moisture diffusivity and activation energy (Ea) were calculated from Fick's law and analogous Arrhenius equation, respectively. Colour difference, chroma and hue angle of fresh-and osmo-oven dried peppers were evaluated. Drying rates occurred predominantly in the falling rate. Moisture diffusivity varied from 8.071x10(-10)-1.048x10(-8), 7.710x10(-11)-1.018x10(-9), 9.807x10(-9)-1.746x10(-8) and 8.748x10(-10)-1.464x10(-9) m(2)/s for Bawa, Rodo, Shombo, and Tatashe, respectively. E a for moisture diffusion during drying of peppers varied from 53.86 to 84.86 kJ/mol and was affected by cultivars and osmotic pretreatment concentration. Osmotic pretreatment and drying temperature had significant effect (p<0.05) on a*, b*, chroma and hue angle values of dried peppers.