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

Abstract

Air-drying characteristics of fresh and osmotically pretreated (40°B, 50°B and 60°B sucrose solutions for 9h) four pepper cultivars namely, Rodo (Capsicum annuum), Shombo (Capsicum frutescens), Bawa (Capsicum frutenscens) and Tatashe (Capsicum annuum), and CIE L*a*b* parameters of air-dried (50, 60, 70 and 80°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 8.071 × 10(-10)-1.048 × 10(-8), 7.710 × 10(-11)-1.018 × 10(-9), 9.807 × 10(-9)-1.746 × 10(-8) and 8.748 × 10(-10)-1.464 × 10(-9)m(2)/s for Bawa, Rodo, Shombo, and Tatashe, respectively. Ea for moisture diffusion during drying of peppers varied from 53.86 to 84.86kJ/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.