Effects of Pretreatments on Drying Rate of Chili Pepper

Abstract The aim of this work was to investigate the influence of pretreatment on drying rates of chili pepper (Capsicum annum L.) at various air temperatures and pretreatment methods. Chilies were pretreated mechanically, chemically as well as by a combined form before drying. Moisture content changes were determined experimentally at temperatures of 35, 50, 60, 70, and 90o C for pretreated and untreated red chilies. The total drying time required for each case was evaluated based on the acceptable value of moisture content (dry basis) for safe storage of vegetables and fruits obtained from literature. In this work, a moisture content of 0.10 (kg of water /kg of dry chili) was taken as the final moisture content to determine the final drying time. The results of this experiment showed that much shorter drying times were achieved with application of pretreatments. Increasing of drying air temperature from 35o C to 50o C shortened the final drying time by 140 hours, which is 72% reduction of drying time. The shortest drying time at lower as well as higher temperatures were achieved by making a number of small holes on the skin of chilies (mechanical pretreatment method). In this case, at a temperature of 60o C the final drying time was shortened by 48% compared to untreated method at the same temperature and drying conditions Key Words: :Chili pepper, pretreatment method, moisture content, drying rate, temperature, Ethiopia