Drying kinetics of chilli under sun and microwave drying

Abstract

Chilli (Capsicum annuum L.) is a popular spice used in Asia as a food flavour enhancer. Fresh chilli can not be stored for a long time because the water content reaches 70–80%. Drying can overcome the problem of storage and price fluctuations. The quality of dried chilli is determined by the water content, colour and content of active substances. A proper drying process is needed because an improper drying process can result in brown due to enzymatic or non-enzymatic reactions and loss of flavour. Prolonged drying using sun and hot air drying conduce brown colour, so a fast drying method is needed. This study aims to determine the drying kinetics of chilli dried by sun-drying and microwave drying. The experimental data were compared with several thin-layer models, while the diffusivity of the experimental results was compared with calculations based on the Ficks diffusion model. For sun drying, the best fitted model is Logarithmic with R2 = 0,8267, RMSE = 0.1669, and SSE = 0,0592. While for microwave drying, the best-fitted model is Verma with R2 = 0.9881, RMSE = 0.0473, and SSE = 0.0114. By using the mass transfer model it is known that the value for the evaporation constant is equal to 2,4531 × 10−12 (sun drying); 5,24 × 10−11 (microwave) and for the diffusivity value are 9.0695 × 10−8 m2/s for sun drying while microwave drying is 6.1177 × 10−7 m2/s.