Drying studies of patchouli spent charge – in special reference to its use in incense sticks production
The Patchouli (Pogostemon cablin Benth.) herbaceous medicinal plant is a member of the Lamiaceae family, and is grown for its essential oil extraction. Aromatic patchouli herbage after steam distillation of essential oil is currently a waste material that can be advantageously used in incense sticks production if dried and powdered to a suitable particle size. To use this waste spent charge (herbage after steam distillation) in the incense sticks production, drying study of this wet material was conducted. The drying characteristics of patchouli spent charge were studied under various methods, namely, tray, shade and sun drying. The initial drying bed thickness was uniformly maintained at 50 mm in all the methods and the spent charge was dried from 60%(wb) initial moisture to 8-9% final moisture. Under Bangalore climatic conditions (24.4-28°C; 25%-58% RH), patchouli spent charge required 46 h of drying time in shade while under sun, it took just 11 h of drying. In a convectional electrical tray dryer, the drying time at 50, 60 and 70°C was 10, 6 and 5 h, respectively.
Keywords: Patchouli, spent charge, drying, drying characteristics