Investigation of optimal drying conditions of red chili peppers in a hot air cabinet dryer

Determining the optimal drying conditions in a controlled laboratory that preserves the quality of the chili peppers is crucial for designing an appropriate solar dryer. In this study, the drying behaviors of chili peppers at different stages of maturity and drying conditions were examined using a controlled hot air cabinet dryer. The aim was to investigate the optimal drying parameters for red chili peppers. The drying was performed at temperatures of 40°C, 50°C, and 60°C and relative humidity of 25%, 35%, and 45%. The central composite rotatable design (CCD) with a two-factor three-level was applied to evaluate the influences of drying parameters on drying time and quality attributes. The results of the study indicated that the color value of chili peppers deteriorated with an increase in temperature. The optimum drying conditions were found to be a relative humidity of 35% and a temperature of 50°C for all maturity stages. At these conditions, the drying times of red, brown, and green chili peppers were 80.41 hr, 75.64 hr, and 69.06 hr, respectively. In addition to drying time, quality attributes of the dried chili peppers were also evaluated. The optimal quality attributes of red chili peppers were found to be a lightness (L*) of 23.6, Redness/greenness (a*) of 2.4, Yellowness/blueness (b*) of 0.586, Chroma (c*) of 2.9, hue angle (ho) of 207.3 and total color difference (ΔE*) of 4.1. The study concluded that these optimal drying parameters are crucial for maintaining the quality attributes of dried food and are used as input parameters when designing suitable solar dryers for outdoor use.