Rose oil is a highly concentrated material often described as a ‘concrete‘ extracted from its petals and is valued for its aroma and therapeutic properties. It finds applications in perfumery, aromatherapy, skincare products, and more. Most rose oil is commercially obtained from Bulgaria with Turkey.
Historically, rose fragrance was produced in ancient times. There are references made in very old Chinese and Sanskrit texts. This was prepared by macerating fresh rose flowers in a liquid fixed oil. The process is still used in India to manufacture ‘Attar’. Hippocrates described “Rosaceum oleum”(Rose oil) being made in Anatolia, Turkey where fresh roses were crushed into olive oil (Baser, 1992).
Reference can be made to other rose oils rom Turkey (Daǧcioǧlu, 1971; Nicolov et al., 1976).
One of the most commercially important rose oils comes from the Middle Eastern rose, the Damascene Rose or Iranian Rose (Rosa x damascena Mill).
Distilling rose oil (Rosa damascena Mill.) on an industrial scale involves a process known as steam distillation, which is commonly used to extract essential oils from plant materials. Rose oil can also be fractionated using supercritical CO2 extraction or using ethanol solubilization.
Steam Distillation Process
The general overview of this distillation process for obtaining rose oil:
Harvesting
Roses are typically harvested early in the morning when the essential oil content is highest. The roses are carefully selected for their fragrance and quality.
Preparation
The harvested rose petals are carefully separated from the stems and leaves. Any damaged or discolored petals are removed to ensure a high-quality oil.
Distillation apparatus
A specialized distillation apparatus called a still is used for the extraction process. The still consists of a boiler (where water is heated), a condenser (which cools and condenses the vapor), and a collection vessel for the extracted oil and water.
Loading the still
The rose petals are placed in the still, and water is added to cover them. The ratio of water to rose petals can vary depending on the specific process and equipment used.
Heating
The still is heated, and the water begins to boil. As the water vaporizes, it passes through the rose petals, carrying the essential oil molecules with it.
Condensation
The vapor, carrying the rose oil and water vapor, travels from the still to the condenser. The condenser cools the vapor, causing it to condense back into a liquid state.
Separation
The condensed liquid is collected in a receiving vessel. Due to the difference in density, the rose oil separates from the water and floats on top.
Collection
The rose oil is carefully separated from the hydrosol (the aromatic water by-product of the distillation). The collected rose oil is typically further processed to remove any impurities and obtain a pure, concentrated oil.
It’s important to note that the specific details of the distillation process, such as temperature, time, and equipment, can vary depending on factors such as the type of roses used and the expertise of the distiller. Additionally, obtaining high-quality rose oil requires attention to detail, experience, and a deep understanding of the process.
Main Issues
Most producers of Rose Oil generate different fractions using steam distillation. Fresh rose petals are usually used but oils can also be generated by fermentation of the petals which are known as ‘paled’.
Analysis
Volatile oil fractions have been analysed by gas chromatography (Anac, 1984) and by gas chromatography-mass spectroscopy (GC-MS).
One analysis of volatile oils showed the presence of 68 compounds representing about 88 to 98% of all the oils. There were 27 hydrocarbons, 19 alcohols, eight aldehydes, six oxides and ethers, five esters, two ketones and one phenol. The main components were:-
Citronellol (24.47–42.97%), nonadecane (6.44–18.95%), geraniol (2.11–18.04%), ethanol (0.00–13.43%), heneicosane (2.28–8.90%), nerol (0.75–7.57%) and 1-nonadecene (1.80–5.40%) .
Rose oil contains at least 16 sulphur compounds which are probably responsible for its aroma. These are:-
n-butyl methyl disulphide, dimethyl trisulphide, n-hexyl methyl disulphide, 3-(4-methylpent-3-enyl)thiophene, 3-methyl-2-(3-methylbut-2-enyl)thiophene, 3-(4,8-dimethyl-nona-3,7-dienyl)thiophene, α-mintsulphide, 4-(4-methylpent-3-enyl)-1,2-dithiacyclohex-4-ene, 1,2-epithiohumulene, 4,5-epithiohumulene and 4,5-epithiocaryophyllene (Omata et al., 1994).
Chinese rose oil investigated by gas chromatographic–spectroscopy contains citronellol (30.71%), nonadecane (16.95%), geraniol (16.11%), nerol (7.57%), heneicosane (7.04%) and 9-eicosene (4.71%).
Use of Supercritical CO2 Extraction
Rose concentrate can be fractioned using supercritical CO2 extraction (SFE) at 80 bar pressure and 40°C using a two-stage separation process. The first and second separators contain paraffins and volatile oil respectively (Reverchon et al., 1997).
The volatile oils extracted by supercritical CO2 extraction were compared with the steam distillation product. The main difference is the 2-phenylethanol content which is 50% in the SFE product compared to 10.4% from the steam-distilled rose oil. The liquid product extracted by ethanol solubilization contains 28.3% 2-phenylethanol but more than 46% paraffins. The SFE volatile oil contains 15.1% of paraffins.
References
Anac, O. (1984). Gas chromatographic analysis on Turkish rose oil, absolute and concrete. Perfumer & Flavorist, 9(1), pp. 3-14.
Baser, K. H. C. (1992). Turkish rose oil. Perfumer and Flavorist, 17, pp. 45-45.
Bayrak, A., & Akgül, A. (1994). Volatile oil composition of Turkish rose (Rosa damascena). Journal of the Science of Food and Agriculture, 64(4), pp. 441-448 (Article).
Daǧcioǧlu, A. (1971). Studies on Turkish rose oils. Commun Fac Sci Univ Ankara Ser B Chim B, 18, pp. 32-40
Nicolov, N., Tsoutsoulova, A., & Nenov, N. (1976). Essence de Roses et autres huiles essentielles Bulgares. Rivista Ital, 58, pp. 349-365
, (1987) Importance of the odoriferous principle of Bulgarian rose oil in flavour and fragrance chemistry. J Chromatogr. 406 pp. 181–183 .
Omata, A., Yomogida, K., Nakamura, S., Ota, T., Toyoda, T., Amano, A., & Muraki, S. (1991). New sulphur components of rose oil. Flavour and Fragrance Journal, 6(2), pp. 149-152.
Reverchon, E., Della Porta, G., & Gorgoglione, D. (1997). Supercritical CO2 extraction of volatile oil from rose concrete. Flavour and Fragrance Journal, 12(1), pp. 37-41
(1981) History and utilization of Rosa damascena. Econ Botany 35 pp. 42–58
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