Water soluble fractions of rose-scented geranium (Pelargonium species) essential oil
Introduction
Rose-scented geranium (Pelargonium species, family: Geraniaceae) is a multi-harvest high value, aromatic plant cultivated for its essential oil which is widely used in the fragrance industry, in aromatherapy and for extraction of commercial rhodinol (mixture of linalool, citronellol, geraniol).
The essential oil is isolated from the shoot biomass either by steam distillation or by water plus steam distillation. This essential oil is referred to as `primary' or `decanted' oil. During distillation, a certain proportion of the essential oil becomes dissolved in distillation or condensate water (hydrosol). The hydrosol is discarded, leading to loss of dissolved essential oil. Losses upto 25% were reported in Israel (Fleisher and Fleisher, 1985). This phenomenon was observed in many other aromatic crops and attempts were made to recover the dissolved oil from hydrosol. The essential oils, thus recovered are often referred to as `secondary' or `recovered' oils. The methods tried to recover aromatic oils from hydrosol were: cohobation (Bohra et al., 1994; Gokhale, 1959), extraction with diethyl ether (Bouzid et al., 1997), adsorbing oil constituents on to an adsorbent followed by ethanol extraction (Bohra et al., 1994; Machale et al., 1997) and poroplast technique (Fleisher, 1991).
In the present investigation, a simple technique employing hexane as an extractant was used to recover essential oil of rose-scented geranium from hydrosol and the chemical composition of the recovered oil was compared with that of the primary oil.
Section snippets
Methods
Rose-scented geranium cv. Bourbon was grown in the Research Farm of Central Institute of Medicinal and Aromatic Plants Field Station, Hyderabad, following standard agricultural practices (Rajeswara Rao et al., 1989). Fully grown crop plants were harvested and steam distilled in a field distillation unit. The primary oil decanted from distillation water was filtered to remove extraneous particles, treated with anhydrous sodium sulphate to make it moisture-free, refiltered and measured. The
Essential oil yield
The results are summarized in Table 1. An average of 7.0% of the total oil yield could be recovered by hexane extraction from the hydrosol. The 7.0% loss of essential oil in rose-scented geranium hydrosol in this study is much less than 15–30% losses reported in the literature for this and other crops (Fleisher and Fleisher, 1985; Fleisher, 1991). The distillation water stripped of essential oil through hexane extraction can be recycled for the next batch of distillation.
Essential oil composition
Fifty-two compounds
Conclusions
In this investigation, a simple procedure using hexane as an extractant has been described to recover dissolved essential oil from distillation water (hydrosol) of rose-scented geranium. Employing this method, 7.0% of total oil yield was recovered from the hydrosol. The recovered oil was rich in organoleptically important oxygenated compounds. The distillation water stripped of essential oil can be recycled for the next batch of distillation.
Acknowledgements
The authors thank the Director, CIMAP, Lucknow and the Scientist-in-Charge, CIMAP Field Station, Hyderabad for facilities.
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