This study investigated the effect of drying methods and pepper varieties on the quality characteristics of red pepper powder, which were dried by using three different methods: hot-air drying, far-infrared drying and sun drying. Hot-air drying was conducted at air temperature of 60°C, and far-infrared drying was carried out at air velocity of 0.8 m/s and drying temperature at 60°C. Sun drying was performed the mean temperature at 18°C and average humidity at 60%.
Drying rate of far-infrared drying was faster than other drying methods. According to the drying methods, there were little difference between the number of air cells, and sun drying sample was observed thick and hard structure. Particle size distribution exhibited normal distribution all drying methods and the sun dried samples were consisted of bigger particle size than other dried samples. As the results, sun drying method needs greater grinding power comparing with the other drying methods. Loose bulk density range between 0.4197-0.4274 g/cm3 and hot air drying was showed highest value with Cheonyang. Tapped bulk density range between 0.523-0.586. The highest value was measured infra-infrared radiation drying with Hanbando and the lowest value was 0.523 g/cm3 for Hanbando cultivar by sun drying. Hausner ratio was the highest value of 1.370 for Hanbando cultivar by far-infrared drying. Compressibility ranged between 0.0016 for Cheongyang cultivar by sun drying and 0.0023 for Hanbando cultivar by far-infrared drying. Compression ratio was the highest value of 1.032 for Hanbando cultivar by hot-air drying. Dynamic angle of repose ranged between 37.47 and 42.97°. In the case of irrecoverable work, range of 76 to 81.7 percent was observed. Sun drying method shows relatively low value, which gives prediction that sun dried samples are more flowability than other samples. Relaxation was higher value of 24.31% for Cheongyang cultivar by far-infrared drying.
Key words : red pepper powder, physical properties, drying methods, sun drying, far-infrared drying