Drying Kinetics and Retention of 6-Gingerol in Ginger Slices During Vacuum Tray Drying

The demand on traditional herb medicine shows a tremendous increase. Anti-carcinogenic, antibacterial, antifungal, hypoglycaemic, anti-atherosclerotic activity of medicinal ginger rhizome (Zingiber officionale R.) can be traced back thousands of years. It is needed to improve the traditional methods of drying for better quality of the dried ginger. Drying kinetics of ginger rhizomes was assessed by drying 5 mm thick slices in vacuum tray dryer. Ginger slices were dried at various drying conditions to study the quality degradation of the ginger during drying. Vacuum drying was carried out at four different temperature levels 400, 500, 600, & 65 0C at pressure of 8 kPa. Auto vacuum controller (Danfoss-Genuine) was installed on dryer to maintain the set value of vacuum level inside the drying chamber by control loop feedback mechanism. The drying temperature was maintained by a PID temperature controller. Vacuum drying of ginger slices was investigated for effects on the 6-gingerol yield of dried ginger. Highest retention of 6-gingerol was found in ginger dried at temperature 50 0C with pressure of 8 kPa. Since the effect of different drying conditions on total 6-gingerol retention was found significant, vacuum drying at temperature 50 0C and pressure of 8 kPa was proposed as the most favourable condition for drying of ginger.