Studying the drying characteristics and quality attributes of chili pepper at different maturity stages: Experimental and mechanistic model

The drying characteristics of chili pepper at three maturity stages under different drying conditions were studied under a hot air drying cabinet. The drying was performed at a relative humidity of 25%, 35%, and 45% and temperatures of 40 °C, 50 °C, and 60 °C. The response surface methodology was performed to find the optimal drying conditions. A mass transfer model was developed based on mechanistic Biot (Bi)- Dincer (Di) number correlations using those optimal drying conditions. The study showed that the color value of chili pepper was deteriorated with an increase in temperature. The suitable drying condition that produced the highest quality within the shortest drying time was a RH of 35% and a temperature of 50 °C for all maturity stages. The values of Bi numbers were affected by the maturity stage of the chili. Effective diffusivity and mass transfer coefficient of moisture increased with an increase in drying air temperature but decreased with an increase in drying air RH. The average value of moisture diffusivity and mass transfer coefficient decreased with chili maturity. The results indicate the capability of the mechanistic mass transfer model in predicting the drying characteristics, moisture diffusivity and mass transfer coefficient during the drying of chili pepper at different maturity stages.