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Aroma expedition : Lecture note –4 저작권자 : 이동선 : 무단 전재 금지 / Copyright

Extraction methods of Aroma Sources / 2012 spring version

Extraction

Essential oils are extracted from plant material.  Each oil has many chemical compounds within it which vary according to climate, location, soil, methods of cultivating and harvesting. 

Essential oils are extracted from plant material by 4 main methods: Steam distillation Solvent extraction Expression Enfleurage

Aroma Expedition lecture notes / 2012-Spring version /CAT-Lab / SWU / Copyright © Dong-Sun Lee, Prof., Ph.D.

Extracting oil from the plants

The way in which oils are extracted from plants is important because some processes use solvents that can destroy the therapeutic properties.  The usual method of extraction is through steam distillation.  After extraction, the properties of a good quality essential oil should be as close as possible to the "essence" of the original plant.  The key to a 'good' essential oil is through low pressure and low temperature processing.  High temperatures, rapid processing and the use of solvents alter the molecular structure, will destroy the therapeutic value and alter the fragrance.

Early efforts at extraction used alcohol and a fermentation process.  Nowadays, a reputable distiller will try to preserve the original qualities of the plant, but the final therapeutic result is often not formed until after the extraction process.  During extraction, the qualities of the oil change to give it more value - for example, chamazulene (characteristic of the pure blue colour of German Chamomile) is formed during the steam distillation process.

Steam distillationA process where steam is passed over the plant material.  The steam is then condensed again, the liquid is collected, and the essential oil separated from the liquid.  The most pure essential oils are collected in this way.

Solvent extractionWhere solvents and alcohol are mixed with the plant material in order to produce an absolute, or very high quality flower water.  True essential oils are not produced in this way and there is some dispute as to their use in aromatherapy.

ExpressionUsed with citrus oils to make 'essences'.  The oils are extracted from the fruit by machinery which mechanically squeezes the oil from the peel, a process called scarification.

EnfleurageAn intensive and traditional way of extracting oil from flowers.  The process involves layering fat over the flower petals.  After the fat has absorbed the essential oils, alcohol is used to separate and extract the oils from the fat.  The alcohol is then evaporated and the essential oil collected.

Extraction methods used in the making of aromatic materials.

Aromatic Materials of Natural Origin

Steam Distillation

ExpressionMaceration Digestion

PercolationEnfleurage SFE

Distilled essential oils

Citrus oils

Concretes

Pomades

Absolutes

Fat or

Fixed oil

Alcohol tincture

Solvent Extraction

Petroleum benzin

Alcohol

SFE Absolute

Hydrosol

Chemical Analysis & Technology Lab / SWU

Distillation in the manufacture of essential oils.

We owe a great debt to the Arabian alchemist (and physician) Ibn Sina - also known as Avicenna, who lived 980 - 1037 AD, since he was the first one to perfect steam distillation - and his process was so good that it stayed unchanged for a couple of hundred years.

Distillation converts the volatile liquid (the essential oils) into a vapor and then condenses the vapor back into a liquid - it is the most popular, and cost effective method in use today in producing essential oils.

Saturated with the essence of the distilled raw material, the steam condenses in a serpentine before being recovered in an “essencier” (a decanting jar for essential oils). The water and esssence are separated automatically as a result of their differing densities.

The substance is removed from the “essencier” as distillation progresses, yielding in the following order “a head”, “a heart”, and “a tail”. Five to six tons of roses are needed to obtain one kilo of essential oil.

The downside of distillation is the fact that heat is used in this extraction method, which makes it totally unacceptable for use on very fragile material, or where the oils are extracted with great difficulty.

When this method of extraction is applied, great care has to be taken with the temperature and length of exposure of the heat to prevent damage to the oils.

This type of distillation can be divided into the following: 

Distillation per se

Water distillation  Steam distillation  Hydro diffusion  Water and steam distillation 

Other specialized distillations: 

Cohobation  Rectification Fractional distillation

Steam distillation apparatus.

Nyons_080404_DSC_0162

Water distillation in the extraction of essential oils.

In the manufacture of essential oils using the method of water distillation, the botanic material is completely immersed in water and the still is brought to the boil. This method protects the oils so extracted to a certain degree since the surrounding water acts as a barrier to prevent it from overheating.

When the condensed material cools down, the water and essential oil is separated and the oil decanted to be used as essential oil.

The water that is so separated in this process is also used and is marketed as "floral waters" (also called hydrosol or sweet water) - such as rosewater, lavender water and orange water. Water distillation can be done at reduced pressure (under vacuum) to reduce the temperature to less than 100 degrees, which is beneficial in protecting the botanical material, as well as the essential oils.

Neroli oil, which is sensitive to heat, can therefore be successfully extracted using this method.

If extended exposure to hot water is not indicated for a particular plant - such as lavender, it is best to find an extraction method better suited. Any botanical material that contains high amounts of esters do not take well to this extraction method, since the extended exposure to hot water will start to break down the esters to the resultant alcohols and carboxylic acids.

Steam distillation in essential oil manufacture.

When steam distillation is used in the manufacture and extraction of essential oils, the botanical material is placed in a still and steam is forced over the material.

The hot steam helps to release the aromatic molecules from the plant material since the steam forces open the pockets in which the oils are kept in the plant material. The molecules of these volatile oils then escape from the plant material and evaporate into the steam. The temperature of the steam needs to be carefully controlled - just enough to force the plant material to let go of the essential oil, yet not too hot as to burn the plant material or the essential oil.

The steam which then contains the essential oil, is passed through a cooling system to condense the steam, which forms a liquid from which the essential oil and water is then separated. The steam is produced at greater pressure than the atmosphere and therefore boils at above 100 degrees Celsius which facilitates the removal of the essential oil from the plant material at a faster rate and in so doing prevents damage to the oil.

Some oils, like Lavender is heat sensitive (thermolabile) and with this extraction method, the oil is not damaged and ingredients like linalyl acetate will not decompose to linalool and acetic acid.

Hydro diffusion in essential oil manufacture

When essential oils are extracted using hydro diffusion it is a type of steam distillation, and only varies in the actual way in which the steam is introduced into the still. With hydro diffusion the steam is fed in from the top onto the botanical material instead of from the bottom as in normal steam distillation.

The condensation of the oil containing steam mixture occurs below the area in which the botanical material is held in place by a grill. The main advantage of this method is that less steam is used, shorter processing time and a higher oil yield.

Combination water and steam distillation

This process is basically a marriage between normal water distillation and that of steam distillation. 

The botanical material is immersed in water in a still, which has a heat source, plus live steam is fed into the water and botanical material mixture.

Cohobation in essential oil extraction

When rose oil is extracted during water distillation, the one main constituent - phenyl ethyl alcohol - dissolves into the water of the distillation still and does not form part of the essential oil that is so extracted.

The oil so extracted is therefore not whole, and is deficient in this rose-smelling ingredient - and in order to produce a "complete" oil, the phenyl ethyl alcohol needs to be distilled from the water in which it dissolved and added back to the "incomplete oil".

When this phenyl ethyl alcohol is so distilled, it is added back to the original distillate, in the correct proportion, to form a complete and whole rose oil, and is then called Rose Otto.

Rectification in extraction of essential oils

When an essential oil contains any impurities, it can be purified by re-distillation - either in steam or in a vacuum, and this purification by re-distillation is referred to as rectification.

An example of this is eucalyptus oil that is marketed as "double-distilled". This is not the same as chemical or heat refining and is used to produce oil of standard quality.

Fractional distillation

When people talk about fractional distillation, it refers to a normal distillation process, but instead of the essential oil being collected continuously, it is collected in batches (the fractions that are referred to) and material normally so extracted is Ylang-Ylang.

Quality of lavender oil

For the genuine lavender, the essential oil obtained is of higher quality in altitude but the yields are not as good. Between 1000 and 1200 m high, and with an important sunlight, a very good quality of oil is obtained.

Here are a few figures which are only given as indicative average values according to the years, the areas as well as to the age of plants :

-130 kgs of fine lavender flowers have to be distilled to get 1 kg of essential oil.

-20 to 25 kgs of essential oil are obtained from 1 hectare of plants.

Distillation Process

Stills (often called steam generator) on open fire : 16~18 centuries

Stills for water bath

Steam stills

Stills for concretion

Stills for absolute

Steam distillation of lavender. King’s Lynn, Norfolk, UK

1 pint(=0.75 ml) essential oils are obtained from ¼ ton (=225 kg) of dried lavenders by steam distillation

Essential oils or otto are obtained by water or steam distillation from fresh petals.

DSC_0144_080504_Luberon_Les_Agnels_dist

Gulsen Rose Oil Factory, Senir Kasabasi,  Isparta, Turkey

This is steam distillation system of Gulsen Rose Oil Factory.

Pale yellow portion is rose essential oil obtained by steam distillation.

Solvent extraction and essential oil

When we talk about the broad term of solvent extraction, it does not only refer to chemical solvents like hexane, but also to other forms - such as solid oil and fat as well as carbon dioxide.

Solvent extraction is particularly suitable for botanical material that has a very low yield of essential oil, or where it is made up of mostly resinous components and as such delivers a far finer fragrance than that of distillation.

During this type of extraction, non-volatile components of the botanical material - such as waxes and pigments are also extracted and in some cases this is then removed during another process.

Under solvent extraction we can list the following methods:

Solvent Maceration Enfleurage Supercritical CO2 (carbon dioxide)

Solvent extraction in essential oil manufacture

Essential oils can be extracted by using solvents such as petroleum ether, methanol, ethanol or hexane and is often used on fragile material such as jasmine, hyacinth, narcissus and tuberose, which would not be able to handle the heat of steam distillation.

A solvent extracted essential oil is very concentrated and is very close to the natural fragrance of the material used.

Although solvent extraction is used extensively, some people do not believe that it should be used for aromatherapy oils since a residue of solvent could be present in the finished product.

Some reports site a solvent residue of 6 - 20% still present in the finished extraction, but this was normally the case when benzene was the standard solvent used. 

With hexane (a hydrocarbon) as the solvent material the solvent residue goes down to about 10 ppm (parts per million) and this is a extremely low concentration of solvent in the resultant product.

As mentioned, benzene is no longer used in the extraction method, since it is regarded as carcinogenic (cancer forming).

After the plant material has been treated with the solvent, it produces a waxy aromatic compound referred to as a "concrete".

Flowers or delicate smelling plant material are solvent extracted. Solvent Extraction is used for delicate flowers whose odors are damaged by the high heat needed to boil water. The oils are extracted using solvents which have lower boiling points than water. Various substances such as ether or high-grade petroleum, which evaporate rapidly, are used in modern perfumery to dissolve essential oils from fragrant plant and animal materials. This is an expensive and time consuming process, where solvents such as Benzene, Butane, Alcohol and waxes are used. Tonnes of flowers are macerated (infused) in the solvents till saturated with the fragrance (of the plant material). Then they are centrifuged to separate the oil and wax from the solvent. The product of this process is called a Concrete. This concrete is then mixed with alcohol to be distilled in vacuum with low temperature to obtain Absolute, and have the name mentioned E.g. Rose absolute, Jasmine absolute, etc.

The usual method involves placing the fragrant material on perforated metal plates in a container (the extractor); the solvent is passed over them and led into a still, where it evaporates, leaving a semi-solid mass known as concrete, which contains the essential oil together with stearoptene. The oil can then be separated from the stearoptene by extraction with alcohol in a 'batteuse', producing the substance called absolute, which is the purest and most concentrated form of essential oil known. Apart from these techniques there are various other operations such as rectification, fractional distillation, terpenes removal, decolourisation, etc., which improve and refine the numerous raw materials used for the blending and making of perfumes

Volatile solvent extraction

Extraction by volatile solvents consists in treating the raw material in an extractor with a volatile solvent such as hexane or ethanol. After repeated washes, the fragrance-laden solvent is transferred to a concentrator to undergo distillation.

A concrete is thus obtained that is then stirred into alcohol in a churn -called a batteuse then filtered and chilled so as to extract the unsoluble plant wax.

In this way, the pure essence or absolute is obtained after one last concentration. The yield is often superior to that of distillation and the process avoids the hydrolising action of steam.

“batteuse”

copper, iron, steel - former Roure factory - Grasse - first half of the 20th century

Absolutes are obtained by mixing a solid ( a concrete or resinoid) in a dissolving liquid (usually alcohol) in a vat equipped with rotating paddles accompanied by a vertical motion.

Loading of an extractor vat - Cal Pfizer factory - Grasse - 1995

Unloading of an extractor vat after straining the raw material Cal Pfizer factory - Grasse - 1995

Filtering the concrete - Cal Pfizer factory - Grasse - 1995

Pure essence or absolute - Cal Pfizer factory - Grasse - 1995

Maceration extraction method

With the maceration method, the flowers are soaked in hot oil to have their cell membranes ruptured when the hot oil then absorbs the essence. The oil is then cleared of the botanical material and decanted.

This is very much the same technique used in solvent extractions, where solvents are used instead of the hot oil as used in maceration.

Maceration is used to extract essential oils from animal ingredients, vanilla and iris. These materials are steeped into vats of oil until the scented parts dissolve. The oil may be heated to speed up the process. Maceration takes long periods of time (sometimes years).

Macerated or infused oils are also used in Aromatherapy, and are considered as Carrier or Base oils. This method of using essential oils is an ancient and a very fruitful way. A Vegetable Base oil has plant material added and heated or left in the Sun for a few days, till the plant material turns brown and there is no freshness left. Then it is redone with fresh plant material till the essential constituents are absorbed by the vegetable oil and smells strong enough. Ashwagandha, Lotus, Calendula, Hibiscus, Carrot, St. John’s Worth, Lime blossom, Melissa, Mullein flower are to name a few. When using them in a blend, we use 10% to 30% of infused oil with other carrier oil and are blended with essential oils or by themselves.

Vegetable oils, Base oils are also known as Carrier oils or Fixed oils and are used for dilution in Aromatherapy. Base oils are obtained as cold pressed, crushing to express the oil. These oils have a rich colour and a characteristic aroma with high contents of Vitamins and Minerals. Fixed oils is a compound of Glycerol and Fatty acids. Unlike Essential oils, Vegetable oils are greasy and do not evaporate leaving behind an oily stain on cloth or paper. Refined Vegetable oils have a complicated process of extraction, which involves heat. The colour is bleached; natural colour and odour are removed causing destruction to the Vitamin and Enzyme contents in the oil. The use of only cold pressed Carrier oils in Aromatherapy is therefore recommended. Base oils are of two types. Light oils which are easily absorbed by the skin and which contain a major proportion of a massage oil mix. Heavy oils which are difficult to be absorbed by the skin are blended with light Carrier oils to the tune of 10% to 30%, due to its thick texture or cost. Lastly, we also use Macerated or infused oils as Carrier oils as mentioned earlier. But the choice of the Base oil or blend of Base oils to be used is a matter of personal preference or therapeutical needs.

Tincture making

Certain substances which mature slowly, such as amber, musk, or vanilla were still steeped in vats of alcohol not so long ago.This extremely laborious process, requiring approximately six months of maceration to produce the slightest tincture is scarcely used nowadays.

Alternative motion mixer - wood, glass, metal, jute - Roure factory -Grasse - first half of the 20th century.

Heat maceration

Heat maceration or enfleurage à chaud was invented in Grasse. The flowers are steeped in a mixture of very pure fat at a temperature of around 60°C.

The flowers are stirred with a wood ladle for two hours and are replaced with fresh flowers every day until their smell is concentrated in the fat. This produces pomades, which are then processed to give absolutes.

This process is used at Grasse to extract the flowers of the orange, rose, and violet. The lard or oil is heated over a water bath, a charge of flowers added, and the mixture stirred continuously for some time. The exhausted flowers are removed, pressed, the expressed fluid returned to the hot fat, fresh flowers added, and the process continued until defined weights of flowers and solvent have been used. Again, a triple extract is prepared by extracting the perfumed lard or oil with alcohol.

Enfleurage à froid (cold maceration)

This method, no longer used today, served to extract the perfume from fragile flowers such as jasmine and tuberose.A layer of fat was spread on either side of a glass frame and covered with flowers. The flowers were replaced* every day until the fat was saturated with fragrance.

At the end of the season the perfumed fat was melted down and stocked in vats in cool cellars.It was then washed in alcohol, which absorbed the perfume. This perfumed alcohol was then evaporated in a vacuum leaving a residue of absolute.

It takes 40,000 tuberoses to produce one pound of tuberose enfleurage.

* the flowers were replaced between 30 and 40 times per frame.http://www.fragonard.com/@en-us/3/9/15/article.asp

This technique is very costly, and is rarely used today. It reached its peak in 1860 and made the reputation of Grasse. It is a labor-intensive process that yields the highest quality of absolutes because it does not involve heat. Heat always alters the fragrance. It is used on delicate flowers that can not stand up to the high heat, and that continue to release essential oils after they have been picked. Examples of these flowers are Jasmine, Violet, Tuberose and Rose

Enfleurage goes back thousands of years to the ancient Egyptians. It works on the principle that fats absorb smells. Petals or other fragrant parts of a plant are steeped in fat or non-evaporating oil which will absorb their fragrance. A mixture of pork, lard and beef suet are smeared on to a glass plate in a wooden frame called a chassis. The flowers are placed on the fat and left to release their oils for several days. This process was repeated several times with fresh flower heads until the fat was totally absorbed with essential oil, the resultant substance being known as “pomade”; the oil was then retrieved from the fat by dissolving in an alcoholic solvent. This is mechanically mixed with alcohol for up to one week, and is chilled to – 68 degrees F. The essential oils dissolve in the alcohol and the fat does not. The mixture is chilled and filtered several times to remove all the fat. The alcohol is then evaporated to leave the pure absolute. Sometimes enfleurage is now carried out with cloth soaked in olive oil or liquid paraffin, which is laid over the frames instead of fat, the resultant perfumed oil being then known as “huile antique”.

Enfleurage extraction

Enfleurage (en– + fleur : To put into flower) could be compared to certain aspects employed in maceration, but is done in a slightly different way. Glass plates in a frame (called a chassis) are covered with highly purified and odorless vegetable or animal fat and the petals of the botanical matter that are being extracted are spread across it and pressed in. The flowers are normally freshly picked before so encased in their fatty bed.

The petals remain in this greasy compound for a few days to allow the essence to disperse into the compound, where the then depleted petals are removed and replaced with a fresh harvest of petals.

This process is repeated until the greasy mix is saturated with the essence, and needs to be repeated a couple of times until saturation is achieved.

When the mix has reached saturation point the flowers are removed and the enfleurage pomade - the fat and fragrant oil - then washed with alcohol to separate the extract from the remaining fat, which is then used to make soap. As soon as the alcohol evaporates from the mixture you are left with the essential oil. This is a very labor-intensive way of extraction, and needless to say a very costly way to obtain essential oil and is nowadays only sometimes used to extract essential oil from tuberoses and jasmine.

Enfleurage

Since antiquity, man has known of the ability of fats and oils to absorb odors. But it isn't until the 19th century, with the help of ethyl alcohol, that the extraction of the odoriferous constituent of the raw materials isolated by fats becomes possible.

Cold enfleurage, used not long ago, consists in laying out fresh and fragile flowers (jasmine, tuberous, violets...) on a plate of glass set in a wooden frame and coated with fat ( a mixture of beef and pork). The flowers are changed every 3, 5 or 7 days over 60 days according to the species. These fragrant fats, once immersed in alcohol in churns or “batteuses”, allow the production of scented pommades used as such in cosmetics or the production of absolutes for use in perfumes, once the alcohol has been removed.

The less fragile flowers can stand high-temperature maceration, known as hot enfleurage. Plunged into fat melted down in a water-bath, they steep an average of 2 to 3 days. This fat is then filtered and the pomade obtained is used in the same manner as that obtained through low-temperature processes.

The extensive labor and extreme care that enfleurage requires combined with its feeble output explain why it is rarely used nowadays.http://www.museesdegrasse.com/MIP/fla_ang/techno_enfleurage.shtml

Enfleurage

Gravure (fin XIXéme). Les châssis préparés sont entassés derrière les ouvrières.http://www.ac-orleans-tours.fr/physique/docly/divers/parfum/enfleurage.html

L'enfleurage

Dès l'antiquité, l'homme avait remarqué le pouvoir des graisses et des huiles à absorber les odeurs.

Mais il a fallu attendre le XIXème siècle pour extraire, à l'aide de l'éthanol, le "principe odorant" des matières premières absorbées par les graisses.

Enfleurage manuel à froid (début du siècle)

Batteuses d'enfleurage à chaud. Atelier du début du siècle

Supercritical Carbon Dioxide gas (CO2) extraction of essential oils

The use of supercritical carbon dioxide extraction is a fairly new way to extract essential oils from botanical material and although a bit on the expensive side, does yield good quality oils.

Carbon dioxide gas isolated from the atmosphere becomes liquid when pressurized. Carbon dioxide becomes hypercritical at 33 degrees Celsius, which is a state in which it is not really gas or liquid, but has qualities of both, and is an excellent solvent to use in the extraction of essential oils since the low temperature required and the fact that the process is near to instantaneous. Submitted to a pressure of over 73.8 bars and a temperature of over 31° centigrade, it passes into a supercritical state where it possesses good solvent properties.Supercritical CO2 extraction allows the raw material to be treated at low temperatures and produces a clearer absolute more faithful to the original scent of the raw material. Furthermore, this process is non-polluting.

The carbon dioxide is furthermore inert and therefore does not chemically interact with the essence that is being extracted. To remove the carbon dioxide solvent, you simply need to remove the pressure under which it is kept.

This process has to take place in a closed chamber for the hypercritical pressure required for carbon dioxide is 200 atmospheres - that is 200 times the pressure of normal atmosphere. 

To achieve this type of pressure some heavy-duty stainless steel equipment is required, and this is where high capital investment is required for this extraction method.

Expression extraction in essential oil manufacture

When a “cold pressed” method is referred to in the manufacture of essential oils, it basically refers to the expression method, since no heat is involved in this method.

Most nut and seed oils are also extracted using a “cold pressed” method but here oil is forced from the material under high mechanical pressure and generally produces a good quality oil, but some manufacturers do impair this good quality by excessively refining the oil after extraction by means of chemicals or high heat.

But when we return to look at the expression method of extraction in the manufacture of essential oils, we find that most citrus essential oils are extracted this way and that three different ways are used to accomplish it:

Sponge  Ecuelle a piquer  Machine abrasion

Cold pressing

The extraction of essences by cold-pressing is used only in very specific cases, namely for citrus fruits : lemons, oranges, bergamots... In this process, the fruit rinds are squeezed to obtain the citrus essential oils they secrete.

Expression is a simple technique where the rinds of citrus fruits are cold pressed to extract their essential oils using rollers or sponges. There is no heat involved, leaving the oil to smell very close to the original plant. The ancient Egyptians gathered flowers in a cloth bag which was twisted until the oil dripped out. In Italy, lemon oil is also occasionally expressed by a process called ecuelle.

Very fragile, sensitive to temperature shifts, oxygen, chemical agents and particularly acids, these oils can tolerate only hand operated or hydraulic pressing.

The essence obtained is usually cloudy because of the water it contains in suspension. It must be purified either through distillation or filtering. In the latter case the essence is allowed to lie so as to facilitate the separation of the water, after which the essence is decanted under air-tight conditions.

Sponge extraction process

Most citrus essences are extracted by means of expression, and in the past were done by hand where the fruit pulp was removed, with the rind and pith then soaked in warm water to make the rind more pliable, since the pith of the fruit absorbed the water.

After the fruit has absorbed the water and become more elastic, it was inverted which helped to rupture the oil cells and a sponge placed next to the rind. It was then squeezed to release the volatile oil, which was then collected directly into the sponge.

As soon as the sponge became saturated with oil, it was squeezed and the essential oil collected in a vessel and then decanted.

Ecuelle a piquer extraction process

This form of expression extraction is used mainly to obtain citrus essential oils, and is a little less labor intensive than that of the sponge method.

This more modern way of essential oil extraction is referred to as the ecuelle a piquer process (direct translation = basin, to prick/stick/prod) where the fruit is placed in a device and rotated with spikes on the side puncturing the oil cells in the skin of the fruit.

This cause the oil cells to rupture and the essential oil, and other material such as pigment, to run down to the center of the device, which contains a collection area.

The liquid is thereafter separated and the oil is removed from the water-based parts of the mixture and decanted

Lemon oil, Oleum Limonis, is better and more valuable if obtained by expression instead of distillation. It is not very active, and so, is used chiefly for flavoring. The oil is usually prepared in Sicily and Calabria, and sometimes at Nice and Mentone, where the “Essence de Citron distillee” is prepared by rubbing fresh lemons on a coarse, tin grater, and distilling the grated peel with water. The better “Essence de Citron au zeste” is prepared with the aid of a saucer-shaped, pewter dish with a pouring lip at one side and a closed funnel sunk from the middle. In the bottom are sharp, strong brass pins on which the peel is rubbed. This vessel is called an ecuelle a piquer, but a machine called scorzetta is gradually coming into use. http://members.fortunecity.com/sawplants/library/lemon.htm

Machine abrasion

This method of expression extraction is very much like the ecuelle a piquer method, and is mostly used in the manufacture of citrus essential oils.

With machine abrasion a machine strips off the outer peel, which is then removed by running water and is then fed into a centrifugal separator.

The centrifugal separation is done extremely fast but it should be noted that due to the fact that the essential oil is combined with other cell content for some time, some alteration could occur due to enzymatic action.

Concentration

 

Concentration is applied mainly to fruit juices. Vacuum concentration and concentration by freezing (temperatures below 0°C) preserve the fruit juices' most subtle aromatic constituents.

Headspace

When flowers are treated using traditional isolation techniques such as steam distillation or extraction by organic solvents, the substances obtained are often distinctly different on the olfactory level from the orignal fragrance of the living flower. This discrepancy can be negative on the olfactory level, but it can also be positive.When headspace methods are used, the odoriferous molecules given off by the cut flower are transported by a current of conveyor gas, before being concentrated on a suitable absorber, such as active carbon or an organic polymer. They are then desorbed and analyzed through chromatography.The use of these methods does no damage to the plants, thus making it also possible to work in the field on rare or protected plant species.From freshly picked lilac flowers and using the headspace technique under vacuum, it is possible to isolate highly fragrant quality concentrates corresponding accurately to the fragrance of the living flower.

Capturing perfume with headspace - photo by R. Kaiser

http://www.museesdegrasse.com/MIP/fla_ang/techno_22.shtml