Influence of Different Methods and Time of Post Harvest Drying on The Essential Oil Content and Composition in Palmarosa (Cymbopogon Martinii (Roxb.) Wats. Var. Motia Burk.)

Palmarosa (Cymbopogon martinii (Roxb.) Wats. var. motia Burk.) herb harvested at optimum time was dried both under shade and sunlight for a period of 23 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 and 23 days after harvesting. The essential oil was obtained by hydro-distillation of the leaves dried under both methods and 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 7 to 9 days after harvest. Sun drying resulted in significantly more geraniol content (77.02%) compared to shade drying (76.26%). The differences observed in the geraniol content in the essential oil for first five days of drying were not significant.The content of the geranyl acetate was more in shade dried herb (14.60%) and increasing post harvest drying period significantly increased geranyl acetate content of essential oil. Day temperature exhibited a significant negative influence on oil yield, geranyl acetate and linalool contents and a significant positive influence on geraniol content. NTRODUCTION The leaves of palmarosa ( Cymbopogon martinii (Roxb.) Wats. var. motia Burk. Family Poaceae) on steam distillation yield a pale yellow volatile oil possessing a pleasant odour with high content of compounds called Geraniol (75%) and Geraniol acetate (20%). Concentrations of linalool (2%), alpha-terpineol, geranyl isobutyrate and geraniol were relatively higher in the essential oils of mature to older leaves (Rao et al.,2005). Essential oil recovery and percentages of myrcene, beta-caryophyllene, geranyl acetate, (E.Z) farnesol and geranyl hexanoate were higher in the essential oils of young expanding leaves. Oil obtained from the palmarosa grass is widely used in many industrial applications like perfumes, cosmetics and bath products. Palmarosa oil is valued highly in the perfumery industry as a source of high-grade geraniol (Mallavarapu et al.,1998) and it also is commercially important because of its antifungal action attributed to the presence of high concentration of geraniol (Bard et al.,1988). It is fungistatic against the filamentous fungi Aspergillus niger, Chaetomium globosum and Penicillium funiculosum (Delespaul et al.,2000) and is considered to provide protection against mosquitoes (Anopheles culcifacies) (Ansari and Razdan,1995). Essential oil also showed the highest activity against both gram positive and gram negative bacteria among the other tested essential oils (Lodhia et al.,2009). Palmarosa oil has been shown to be an effective insect repellent when applied to stored grain and beans, an antihelmintic against nematodes, and an antifungal and mosquito repellent. It helps in clearing up minor infections and prevents ugly scarring in healing wounds. The leaves of aromatic plants are often dried before extraction to reduce moisture content. During this process, many compounds which permeate to the leaf surface by the evaporating water are lost (Moyler,1994). The method of drying usually has a significant effect on the quality and quantity of the essential oils from such plants. A literature search revealed that drying method had a significant effect on oil content and composition of aromatic plants (Basver, 1993, Deans and Svoboda,1992, Karawya et al.,1980, Raghavan Rao et al.,1997). For example, the oil content of shade-dried Roman chamomil flowers was found to be higher (1.9% w/w) than that of sun-dried (0.4%) and oven-dried at 400C (0.9%) flowers. This type of information is not available for the aromatic grass palmarosa, hence this experiment is taken up to study the effect of different drying methods and post harvest storage on the quantity and chemical composition of the essential oil of palmarosa variety Trishna during February to April,2013. 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. Experimental details One experiment was conducted during the period February 2013 to April, 2013. Mature palmarosa herb ready for harvest was collected from 75 days old plants. The herb was made in to bundles of 250 g. In total 120 bundles were made. Sixty bundles were kept for shade drying and sixty bundles were kept in sun light for drying. The bundle were loosely tied and care taken to see that excess heat does not develop inside. The bundles were made in to lots of four each and each lot consisting of the four bundles were spread on papers. In total