Infrared Drying Kinetics and Color Qualities of Organic and Conventional Sweet Red Peppers

Abstract

This study compares the infrared drying kinetics, effective moisture diffusivity, activation energy and color qualities of organically and conventionally produced sweet red peppers (Capsicum annum L.) dried at three different temperatures (60, 70 and 80°C). Results showed that the entire drying process for both organic and conventional sweet red peppers took place mainly in falling rate period. Increasing the drying temperature decreased the drying time considerably. No significant difference was found between the drying times of organic and conventional red peppers. The Midilli model yielded the best fit for all data points for organic and conventional peppers. The drying coefficient of the Midilli model increased with the increase in the drying temperature. The effective moisture diffusivity and activation energy values of organic pepper samples were found slightly higher than those of the conventional samples. This result was found to be compatible with the drying coefficient of Midilli model and characteristic drying rate curves. Higher drying temperatures resulted in brighter red pepper powder color which is more preferable by consumers. Infrared drying at 60°C for organic pepper samples produced the best pepper powders in terms of color quality. Moreover, infrared drying at 60°C and 70°C was also judged as the acceptable drying applications in terms of color quality since they gave the nearest redness to yellowness ratios and higher brightness values as compared to the color of fresh peppers. Overall, infrared drying at 70°C instead of 60°C resulted in about 22% savings in drying time and can be used to produce high quality organic or conventional sweet red pepper powder with better color quality.