DRYING CHARACTERISTICS AND QUALITY OF RED PEPPER SLICES UNDER HOT AIR FOLLOWED BY MICROWAVE FINISH DRYING

Abstract

Red pepper slices were subjected to hot air, microwave and hot air followed by microwave finish drying. Hot air followed by microwave finish drying decreased the drying time required when compared to drying with hot air drying. Among the five thin layer drying models that were used to fit the experimental data, Page and Modified Page models gave the highest correlation coefficient, lowest root mean square error, and reduced chi-square, thus indicating that Page and Modified Page models best described the hot air drying of red pepper slices. In this study, ascorbic acid degradation and color changes during drying were also investigated. In the drying process at 65ºC for 9 hours, ascorbic acid content decreased to 330.94±1.45 mg/100g dry matter after 8 hours. After 8 hours, no ascorbic acid was found. Moreover, the kinetics of ascorbic acid and color changes of red pepper slices, due to drying by hot air drying were studied. It was confirmed that ascorbic acid degradation followed first order kinetics.  The results indicate that hot air followed by microwave finish drying may be an alternative method for the drying of red pepper slices since it provides good quality product in shorter time.