Rose oil, meaning either rose otto or rose absolute, is the essential oil extracted from the petals of various types of rose. Rose ottos are extracted through steam distillation, while rose absolutes are obtained through solvent extraction or supercritical carbon dioxide extraction, with the absolute being used more commonly in perfumery. Even with their prohibitive price and the advent of organic synthesis, rose oils are still perhaps the most widely used essential oil in perfumery.
Two major species of rose are cultivated for the production of rose oil:
Rosa damascena, the damask rose, which is widely grown in Bulgaria, Turkey, Russia, India, Iran and China
Rosa centifolia, the cabbage rose, which is more commonly grown in Morocco, France and Egypt
Most rose oil is produced in Bulgaria, Morocco, Iran and Turkey. Recently, China has begun producing Rose oil as well.
More than 300 compounds have been identified in rose oil. The most common are:citronellol, geraniol, nerol, linalool, phenyl ethyl alcohol, farnesol, stearoptene, α-pinene, ß-pinene, α-terpinene, limonene, p-cymene, camphene, ß-caryophyllene, neral, citronellyl acetate, geranyl acetate, neryl acetate, eugenol, methyl eugenol, rose oxide, α-damascenone, ß-damascenone, benzaldehyde, benzyl alcohol, rhodinyl acetate, phenyl ethyl formate
The key compounds that contribute to the distinctive scent of rose oil, however, are beta-damascenone, beta-damascone, beta-ionone, and rose oxide. Even though these compounds exist in less than 1% quantity of rose oil, they make up for slightly more than 90% of the odor content due to their low odor detection thresholds.
Due to the labor-intensive production process and the low content of oil in the rose blooms, rose oil commands a very high price. Harvesting of flowers is done by hand in the morning before sunrise and material is distilled the same day. Harvesting of roses starts in the second year after planting, reaching its maximum yield in year five.
After twelve years the productivity of a planting declines rapidly. On average, in France, a single rose bush produces 250 g of flowers per season. A yield of 3,000 kg of roses per hectare is considered very satisfactory. Yields of flowers and oil are very variable, depending on variety, region and weather conditions, and time of picking. Kitchounow (1937) reported that flowers picked after 10 am yielded 59% less oil than those picked during early morning hours. According to experience in Bulgaria, around 400 to 450 kg of Rosa damascena Mill are required to yield 1 kg of rose concentrate which in turn produces about 520 g of alcohol-soluble absolute.
There are three main methods of extracting the oil from the plant material:
Steam distillation, which produces an oil called rose otto or attar of roses.
Solvent extraction, which results in an oil called rose absolute.
Supercritical carbon dioxide extraction, yielding an essential oil that may be marketed as either an absolute or as a CO2 extract.