Comparing hot air drying kinetics and color quality of organic and conventional sweet red peppers

Abstract

Aims: This study was conducted to compare the hot air drying kinetics and color quality of organically and conventionally produced sweet red peppers. Methods and Results: The pepper samples were dried at 60, 70 and 80°C using a hot air dryer. Drying kinetics, effective moisture diffusivity (Deff), activation energy (Ea) and color quality were studied. The drying process for both organic (OSRP) and conventional sweet red peppers (CSRP) occurred mainly in falling rate period. Increasing the drying temperature reduced the drying time considerably. Except 60°C, significant difference was found between the drying times of OSRP and CSRP samples. The Midilli model gave the best fit for all data points for pepper types. A positive relationship was found between the drying temperature and Deff values (OSRP: 39.6210-10 – 58.5810-10 m2s-1; CSRP: 38.9210-10 – 57.5910-10 m2s- 1). Differences between the Deff values of OSRP and CSRP samples were not significant. Conclusions: Characteristic drying curve profiles, Deff and Ea values followed the similar trajectory showing that the growing practice of the peppers did not significantly change the structural features related to heat transfer. The hot-air drying at 70°C and 80°C gave brighter and redder pepper powders; hence, these treatments are suggested as the suitable drying applications to produce high quality OSRP and CSRP powders in terms of color quality. By using 80°C instead of 60°C, about 25% and 32% savings in drying times could be obtainable for CSRP and OSRP samples, respectively. Significance and Impact of the Study: Organic production has an increasing trend in the world; however, research on the evaluation of drying kinetics and color quality of organic products is very limited. Thus, this study aimed at studying appraisal of the drying kinetics and related parameters of CSRP and OSRP samples.