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

Effect of maturity on the moisture sorption isotherm of chili pepper (Mareko Fana variety)

The moisture sorption isotherm at three maturity levels of the Mareko Fana chili pepper variety (red, brown and green) has been studied in this paper. The sorption isotherm was determined based on the standard static gravimetric method using a glycerol-water mixture in a relative humidity range of 10-92% at three temperature levels and nonlinear regression analysis was used to select suitable sorption models. The Clasius - Clapeyron equation was implemented to determine the isosteric heat of sorption of the chili pepper using the experimental equilibrium moisture content at different sorption temperature levels. The results showed that the GAB model was well fitted for green chili pepper, while the OSWIN model described well the brown and red chili variant. There was a difference in net isosteric heat between the adsorption and desorption isotherm of chili pepper maturity. For green chili, the maximum value of the net isosteric heat was 18 kJ mol-1 and 20 kJ mol-1 for adsorption and desorption isotherms, respectively and it decreased exponentially as moisture content increased. The desorption heat was higher than the adsorption heat for each maturity of chili pepper which indicated the existence of hysteresis in the sorption process. In comparison to literature data reported for different chili varieties, Mareko Fana has a lower heat of sorption and monolayer moisture content.status: publishe