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Rose oil

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Rose oil, meaning either rose otto (attar of rose, attar of roses) or rose absolute, is the essential oil
Essential oil
An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile oils, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove...

 extracted from the petal
Petal
Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...

s of various types of rose
Rose
A rose is a woody perennial of the genus Rosa, within the family Rosaceae. There are over 100 species. They form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Flowers are large and showy, in colours ranging from white through yellows...

. Rose ottos are extracted through steam distillation
Steam distillation
Steam distillation is a special type of distillation for temperature sensitive materials like natural aromatic compounds....

, while rose absolutes are obtained through solvent extraction or supercritical carbon dioxide extraction
Supercritical carbon dioxide
Supercritical carbon dioxide is a fluid state of carbon dioxide where it is held at or above its critical temperature and critical pressure.Carbon dioxide usually behaves as a gas in air at STP or as a solid called dry ice when frozen...

, with the absolute being used more commonly in perfumery. Even with their high price and the advent of organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

, rose oils are still perhaps the most widely used essential oil in perfumery.

Components



Two major species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of rose are cultivated for the production of rose oil:
  • Rosa damascena
    Rosa damascena
    Rosa × damascena, more commonly known as the Damask rose , the Damascus rose, or sometimes as the Rose of Castile, is a rose hybrid, derived from Rosa gallica and Rosa moschata...

    , the damask rose, which is widely grown in Bulgaria
    Bulgaria
    Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

    , Turkey
    Turkey
    Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

    , Russia
    Russia
    Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

    , Pakistan
    Pakistan
    Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

    , India
    India
    India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

    , Uzbekistan
    Uzbekistan
    Uzbekistan , officially the Republic of Uzbekistan is a doubly landlocked country in Central Asia and one of the six independent Turkic states. It shares borders with Kazakhstan to the west and to the north, Kyrgyzstan and Tajikistan to the east, and Afghanistan and Turkmenistan to the south....

    , Iran
    Iran
    Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

     and China
    China
    Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

  • Rosa centifolia
    Rosa centifolia
    Rosa × centifolia , the provence rose or cabbage rose or Rose de Mai is a hybrid rose developed by Dutch rose breeders in the period between the 17th century and the 19th century, possibly earlier...

    , the cabbage rose, which is more commonly grown in Morocco
    Morocco
    Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...

    , France
    France
    The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

     and Egypt
    Egypt
    Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...


Bulgaria produces about 70% of all rose oil in the world. Other significant producers are Morocco, Iran and Turkey. Recently, China has begun producing rose oil as well.

The most common chemical compounds present in rose oil are:
citronellol
Citronellol
Citronellol, or dihydrogeraniol, is a natural acyclic monoterpenoid. Both enantiomers occur in nature. -Citronellol, which is found in citronella oils, including Cymbopogon nardus , is the more common isomer. -Citronellol is found in the oils of rose and Pelargonium geraniums.Citronellol is...

, geraniol
Geraniol
Geraniol is a monoterpenoid and an alcohol. It is the primary part of rose oil, palmarosa oil, and citronella oil . It also occurs in small quantities in geranium, lemon, and many other essential oils. It appears as a clear to pale-yellow oil that is insoluble in water, but soluble in most common...

, nerol
Nerol
Nerol is a monoterpene found in many essential oils such as lemongrass and hops. It was originally isolated from neroli oil, hence its name. This colourless liquid is used in perfumery. Like geraniol, nerol has a sweet rose odor but it is considered to be fresher.Isomeric with nerol is geraniol,...

, linalool, phenyl ethyl alcohol, farnesol
Farnesol
Farnesol is a natural organic compound which is an acyclic sesquiterpene alcohol found as a colorless liquid. It is insoluble in water, but miscible with oils...

, stearoptene, α-pinene, β-pinene, α-terpinene, limonene
Limonene
Limonene is a colourless liquid hydrocarbon classified as a cyclic terpene. The more common D isomer possesses a strong smell of oranges. It is used in chemical synthesis as a precursor to carvone and as a renewably-based solvent in cleaning products....

, p-cymene, camphene
Camphene
Camphene is bicyclic monoterpene. It is nearly insoluble in water, but very soluble in common organic solvents. It volatilizes readily at room temperature and has a pungent smell. It is a minor constituent of many essential oils such as turpentine, cypress oil, camphor oil, citronella oil,...

, β-caryophyllene, neral
Citral
Citral, or 3,7-dimethyl-2,6-octadienal or lemonal, is either of, or a mixture of, a pair of terpenoids with the molecular formula C10H16O. The two compounds are double bond isomers. The E-isomer is known as geranial or citral A...

, citronellyl acetate, geranyl acetate, neryl acetate, eugenol
Eugenol
Eugenol is a phenylpropene, an allyl chain-substituted guaiacol. Eugenol is a member of the phenylpropanoids class of chemical compounds. It is a clear to pale yellow oily liquid extracted from certain essential oils especially from clove oil, nutmeg, cinnamon, basil and bay leaf. It is slightly...

, methyl eugenol
Methyl eugenol
Methyl eugenol is a phenylpropene, a type of phenylpropanoid compound, the methyl ether of eugenol. It is found in various essential oils....

, rose oxide
Rose oxide
Rose oxide is an organic compound of the pyran class and the monoterpene class and a fragrance found in roses and rose oil. The compound has both a cis- and a trans-isomer, each with a - and -stereoisomer, but only the -cis isomer is responsible for the typical rose fragrance...

, α-damascenone, β-damascenone, benzaldehyde
Benzaldehyde
Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. This colorless liquid has a characteristic pleasant almond-like odor...

, benzyl alcohol
Benzyl alcohol
Benzyl alcohol is an organic compound with the formula C6H5CH2OH. The benzyl group is often abbreviated "Bn", thus benzyl alcohol is denoted as BnOH. Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor. It is a useful solvent due to its polarity, low toxicity, and low vapor...

, rhodinyl acetate, phenyl ethyl formate


The key flavor
Flavor
Flavor or flavour is the sensory impression of a food or other substance, and is determined mainly by the chemical senses of taste and smell. The "trigeminal senses", which detect chemical irritants in the mouth and throat as well as temperature and texture, are also very important to the overall...

 compounds that contribute to the distinctive scent of rose oil, however, are beta-damascenone, beta-damascone, beta-ionone, and rose oxide
Rose oxide
Rose oxide is an organic compound of the pyran class and the monoterpene class and a fragrance found in roses and rose oil. The compound has both a cis- and a trans-isomer, each with a - and -stereoisomer, but only the -cis isomer is responsible for the typical rose fragrance...

. Beta-damascenone presence and quantity is considered as the marker for the quality of rose oil.
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 threshold
Odor detection threshold
The odor detection threshold is the lowest concentration of a certain odor compound that is perceivable by the human sense of smell. The thresholds of a chemical compound is determined in part by its shape, polarity, partial charges and molecular mass...

s.

Production


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
Sunrise
Sunrise is the instant at which the upper edge of the Sun appears above the horizon in the east. Sunrise should not be confused with dawn, which is the point at which the sky begins to lighten, some time before the sun itself appears, ending twilight...

 and material is distilled the same day.

There are three main methods of extracting the oil from the plant material:
  • Steam distillation
    Steam distillation
    Steam distillation is a special type of distillation for temperature sensitive materials like natural aromatic compounds....

    , 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
    Supercritical carbon dioxide
    Supercritical carbon dioxide is a fluid state of carbon dioxide where it is held at or above its critical temperature and critical pressure.Carbon dioxide usually behaves as a gas in air at STP or as a solid called dry ice when frozen...

    , yielding an essential oil that may be marketed as either an absolute or as a CO2
    Carbon dioxide
    Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

     extract.

Distillation


In the process of distillation, large still
Still
A still is a permanent apparatus used to distill miscible or immiscible liquid mixtures by heating to selectively boil and then cooling to condense the vapor...

s, traditionally of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

, are filled with roses and water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

. The still is fired for 60–105 minutes. The vaporized water and rose oil exit the still and enter a condensing apparatus and are then collected in a flask. This distillation yields a very concentrated oil, direct oil, which makes up about 20% of the final product. The water which condenses along with the oil is drained off and redistilled, cohobation
Cohobation
In pre-modern chemistry and alchemy, cohobation was the process of repeated distillation of the same matter, with the liquid drawn from it; that liquid being poured again and again upon the matter left at the bottom of the vessel....

, in order to obtain the water-soluble fractions of the rose oil such as phenyl ethyl alcohol which are a vital component of the aroma and which make up the large bulk, 80%, of the oil.
The two oils are combined and make the final rose otto.

Rose otto is usually dark olive-green in color and will form white crystals at normal room temperature
Room temperature
-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...

 which disappear when the oil is gently warmed. It will tend to become more viscous at lower temperatures due to this crystallization
Crystallization
Crystallization is the process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas. Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid...

 of some of its components.

The essence has a very strong odor
Odor
An odor or odour is caused by one or more volatilized chemical compounds, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction. Odors are also commonly called scents, which can refer to both pleasant and unpleasant odors...

, but is pleasant when diluted and used for perfume
Perfume
Perfume is a mixture of fragrant essential oils and/or aroma compounds, fixatives, and solvents used to give the human body, animals, objects, and living spaces "a pleasant scent"...

. Attar of roses was once made in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, Persia, Syria
Syria
Syria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....

, and the Ottoman Empire
Ottoman Empire
The Ottoman EmpireIt was usually referred to as the "Ottoman Empire", the "Turkish Empire", the "Ottoman Caliphate" or more commonly "Turkey" by its contemporaries...

. The Rose Valley
Rose Valley, Bulgaria
The Rose Valley is a region in Bulgaria located just south of the Balkan Mountains and the eastern part of the lower Sredna Gora chain to the south...

 in Bulgaria
Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

, near the town of Kazanlak
Kazanlak
Kazanlak, formerly Kazanlık is a Bulgarian town in Stara Zagora Province, located in the middle of the plain of the same name, at the foot of the Balkan mountain range, at the eastern end of the Rose Valley...

, is among the major producers of attar of roses in the world.

Due to the heat required for distillation, some of the compounds extracted from the rose undergo denaturing
Denaturation (biochemistry)
Denaturation is a process in which proteins or nucleic acids lose their tertiary structure and secondary structure by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent , or heat...

 or chemical breakdown. As such, rose otto does not smell very similar to "fresh" roses.

The hydrosol portion of the distillate is known as rosewater
Rosewater
Rose water or rose syrup is the hydrosol portion of the distillate of rose petals. Rose water, itself a by-product of the production of rose oil for use in perfume, is used to flavour food, as a component in some cosmetic and medical preparations, and for religious purposes throughout Europe and...

. This inexpensive by-product is used widely as a food flavoring as well as in skin care.

Solvent extraction


In the solvent extraction method, the flowers are agitated in a vat with a solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

 such as hexane
Hexane
Hexane is a hydrocarbon with the chemical formula C6H14; that is, an alkane with six carbon atoms.The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC nomenclature, however, hexane is the unbranched isomer ; the other four structures...

, which draws out the aromatic compounds as well as other soluble substances such as wax
Wax
thumb|right|[[Cetyl palmitate]], a typical wax ester.Wax refers to a class of chemical compounds that are plastic near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents...

 and pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

s. The extract is subjected to vacuum processing which removes the solvent for re-use. The remaining waxy mass is known as a concrete. The concrete is then mixed with alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 which dissolves the aromatic constituents, leaving behind the wax and other substances. The alcohol is low-pressure evaporated, leaving behind the finished absolute. The absolute may be further processed to remove any impurities that are still present from the solvent extraction.

Rose absolute is a deep reddish brown with no crystals. Due to the low temperatures in this process, the absolute may be more faithful to the scent of the fresh rose than the otto.

Carbon dioxide extraction


A third process, supercritical
Supercritical
Supercritical may refer to:* Critical mass, the smallest amount of fissile material needed for a sustained nuclear chain reaction* Critical temperature, Tc, the temperature above which distinct liquid and gas phases do not exist...

 carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 extraction, combines the best aspects of the other two methods. When carbon dioxide is put under at least 72.9 atm of pressure and at a temperature of at least 31.1°C (the critical point
Critical point (thermodynamics)
In physical chemistry, thermodynamics, chemistry and condensed matter physics, a critical point, also called a critical state, specifies the conditions at which a phase boundary ceases to exist...

), it becomes a supercritical fluid with the permeation properties of a gas and the solvation properties of a liquid. (Under normal pressure CO2 changes directly from a solid to a gas in a process known as sublimation.) The supercritical fluid CO2 extracts the aromatics from the plant material.

Like solvent extraction, the CO2 extraction takes place at a low temperature, extracts a wide range of compounds rendering an essence more faithful to the original, and leaves the aromatics unaltered by heat. Because CO2 is gas at normal atmospheric pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...

, it leaves no trace of itself in the final product. The equipment for CO2 extraction is expensive, which is reflected in the price of the essential oils obtained from the process.

Adulteration


It takes many pounds
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...

 of rose petal
Petal
Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...

s to distill one ounce of essential oil. Depending on extraction method and plant species, the average yield can range from 1:1500 to 1:10000. To mitigate the cost, some dishonest dealers will dilute
Dilution
Dilution may refer to:* Reducing the concentration of a chemical* Serial dilution, a common way of going about this reduction of concentration* Homeopathic dilution* Dilution , an equation to calculate the rate a gas dilutes...

 rose oil with geranium
Pelargonium
Pelargonium is a genus of flowering plants which includes about 200 species of perennials, succulents, and shrubs, commonly known as scented geraniums or storksbills. Confusingly, Geranium is the correct botanical name of a separate genus of related plants often called Cranesbills. Both Geranium...

 (Pelargonium graveolens) or Palmarosa (Cymbopogon martinii
Cymbopogon martinii
Cymbopogon martinii is a species of grass in the lemon grass genus best known by the common name palmarosa. Other common names include Indian geranium and rosha or rosha grass. This perennial grass is native to southeast Asia, especially India , and it is cultivated for its oil...

) EO's, both of which are rich in geraniol
Geraniol
Geraniol is a monoterpenoid and an alcohol. It is the primary part of rose oil, palmarosa oil, and citronella oil . It also occurs in small quantities in geranium, lemon, and many other essential oils. It appears as a clear to pale-yellow oil that is insoluble in water, but soluble in most common...

, the main constituent of rose oil. Some of these 'rose oils' are up to 90% geranium or palmarosa to 10% rose. This is referred to as extending the Rose fragrance. This may be done to compensate for chemotype, e.g. Bulgarian distilled Rose oil is naturally low in phenylethanol, and Ukrainian or Russian rose oil is naturally high in phenylethanol.