Influence of Different Methods and Time of Post Harvest Drying on the Essential Oil Content and Composition In Eucalyptus Citriodora

Eucalyptus citriodora herb harvested at optimum time was dried both under shade and sunlight for a period of 29 days after harvest. Observations on the loss of weight , essential oil content and composition were observed at 0,1,3,5,7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27 and 29 days after harvesting. The essential oil was obtained by hydro-distillation of the leaves dried under both methods (sun and shade) and the oil samples were analyzed by GC. A significant decrease in the weight of herb was noticed due to drying. Significant differences were also noticed in the essential oil content and composition. Drying methods resulted in significant improvement in the oil content, which exhibited an increase up to 5 days after harvest. Sun drying resulted in significantly lesser citronellal (60.91%) and higher isopulegol content (10.73%) compared to shade drying (72.01% and 7.95%,respectively). Citronellol content of the essential oil increased up to five days after harvesting in case of shade drying. Isopulegol increased significantly with increase in time after harvest in both methods of drying. INTRODUCTION Essential oils obtained by distillation of the leaves of Eucalyptus have essential oils characteristic of the particular species used. The oils may be roughly divided into three important classes viz., (1) the medicinal oils, which contain substantial amounts of cineole); (2) the industrial oils, containing terpenes, which are used for flotation purposes in mining operations; (3) the aromatic oils, such as Eucalyptus citriodora (E.citriodora), which are characterized by their aroma. Some of the species commonly grown in India are red gum (E. camaldulensis), lemon-scented gum (E. citriodora), Tasmanian blue gum (E. globulus) and Cider gum (E. tereticornis). Among these, E. citriodora is a large, quick-growing tree with smooth and white bark and lemon-scented leaves. It is extensively planted and coppiced for the extraction of essential oil that is rich in citronellal and used in perfumery and as flavouring agent. The oil is known to possess a wide spectrum of biological activities including fungicidal (Ramezani et al., 2002), insecticidal (Isman, 2000), nematicidal (Pandey et al., 2000) and allelopathic properties (Kohli, 1990). It was shown that the oil of Eucalyptus citriodora exerted it’s antimicrobial activity through the synergistic action of citronellal and citronellol (Ramezani et al., 2002). The information available about post harvest drying of herb on the quality and content of essential oil in E. citriodora is meagre, hence this study was taken up to study the influence of two methods of drying over a period of one month on the essential oil content and composition. MATERIAL AND METHODS Experimental site The experimental site is located at the altitude of 542 m above mean sea level with a geographical bearing of 78.38 longitudes and 17.32 latitude. Weather condition Semi-arid tropical climate zone of Hyderabad has the average rainfall of 800 mm per year. The average monthly weather conditions of the experimental site during the experimental period are presented in Table-1. Table 1. Daily weather data at the experimental site during the period April to May, 2013 Days after harvest Date Max (°C) Min (°C) RH % Sunshine (hrs) 0 10-Apr-13 32.00 16.60 56.50 7.70 1 12-Apr-13 29.40 19.40 82.50 9.80 3 14-Apr-13 29.40 13.00 64.50 10.20 5 16-Apr-13 32.50 17.70 82.00 7.90 7 18-Apr-13 31.00 17.20 68.50 8.50 9 20-Apr-13 32.60 15.50 59.50 9.70 11 22-Apr-13 33.00 16.40 58.00 9.50 13 24-Apr-13 33.20 16.50 56.00 9.80 15 26-Apr-13 32.80 14.50 52.00 9.90 17 28-Apr-13 33.00 14.60 70.50 8.20 19 30-Apr-13 33.00 17.00 75.00 9.50 21 02-May-13 34.00 18.00 71.00 9.30 23 04-May-13 35.60 21.00 62.00 4.40 25 06-May-13 39.40 23.90 83.00 38.00 27 08-May-13 38.80 27.00 69.00 33.00 29 10-May-13 41.00 29.30 54.00 23.00 Experimental details An experiment was conducted during the period April 2013