Effect of drying temperature and drying method on drying rate and bioactive compounds in cassumunar ginger (Zingiber montanum)

Abstract

In this study, influences of drying of cassumunar ginger (Zingiber montanum) slices using a hot air dryer at 40, 50, 60, 70, and 80 °C, a large-scale greenhouse solar dryer, and sun drying on drying kinetics, color, bioactive compounds, and antioxidant capacities were investigated. The Page model was adequate for describing the drying kinetics and increasing of the temperature accelerated the drying rate, therefore the drying time at 80 °C was shortest (1.5 h). The hot air drying effectively preserved curcumin content and color of the dried products. Drying at higher temperatures, however, resulted in losses of essential oil yield. In contrast, solar and sun drying significantly degraded curcumin and therefore adversely affected the color of dried products. Although, all conditions of drying resulted in volatile oil losses of 18–36 %, different drying conditions did not affect the obtained oil compositions. In addition, it was found that the dried sample from the hot air dryer and the greenhouse solar dryer exhibited slightly higher antioxidant capacities than those from sun drying.