I. Introduction

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Essential oils are generally high value, low volume commodities. This makes them attractive crops to grow and process for smallholder farmers and remote communities in the LDCs, where transport problems prevent them from marketing high volume cash crops.

Fourteen monographs on essential oil crops which are capable of yielding an income in a relatively short space of time have been prepared. The oils featured in the monographs have been selected for one of two reasons: i. there is an existing commercial market for the oil with room for new producers to enter, e.g. patchouli oil. ii. the oil contains a major ingredient for which shortages may occur in the future, e.g. safrole from sassafras oil.

The essential oil from a particular species of plant may vary depending on where it has been grown and how it has been processed. New producers should be prepared to meet with some resistance when attempting to market oils from new sources. They may be offered lower prices than expected and, initially, sales may be slow. In order to be successful a new supplier must satisfy buyers that his oil(s) will meet the following requirements. i. uniform good quality ii. stable price iii. continuity of supply

Building up buyer confidence will, of necessity, take some time and new producers of essential oils are encouraged to take this into account when beginning to distil commercially essential oils.


II. Distillation of essential oils

Essential oils are aromatic materials of vegetable origin, which are used in perfumery and flavourings. They represent the "essential aroma" of the plant from which they are obtained. The majority of essential oils are produced by the process of steam distillation.

2.1 Raw materials / processing

Essential oils occur in many different parts of plants, e.g. roots (vetiver), bark (cinnamon), heartwood (sandalwood), leaves (bay), herb (peppermint), seeds (nutmeg), flowers (cananga and jasmine).

The essential oil of a plant consists of many compounds which generally boil between 150 300 C. If attempts are made to remove these compounds by dry distillation many will decompose and the oil will be ruined. However, the compounds are steam volatile and can be distilled out of the vegetal materials at around 100 C.

When plant materials are steam distilled chemical changes inevitably occur and the oil obtained will not have an identical aroma to that of the original plant material.

Preparation of material for distillation varies with the material to be distilled. Some material must be distilled immediately after harvesting, whereas others can be (and are best) stored for a day or two before distilling and finally there are materials which can be stored indefinitely before distillation. In general, flowers should be distilled immediately, whereas herbaceous material often benefits from wilting for one or two days before distillation. Woody materials may need to be ground and/or soaked before distillation.

The preparation of the raw material, the packing of the still and the rate/type of distillation can be determined for a particular essential oil crop from the literature or from experimental trials.

2.2 Types of distillation

There are three basic types of essential oil distillation:

  1. water or "hydrodistillation"
  2. water and steam or "wet steam"
  3. steam or "dry steam"

i. "Hydrodistillation" - in this method the charge (which is usually comminuted) is immersed totally in water which is boiled. The stills are of the simplest type (see Figure 1: Simple still hydrpdistillation) and are used extensively by smallholder producers of essential oils. Often they are heated over an open fire. The disadvantages are that the heat is difficult to control and hence the rate of distillation is variable. Also the possibility exists for local overheating and "burning" of the charge which can lead to a poorer quality oil. Improved distillation control can be obtained by using steam from a separate boiler, which is passed into a jacket around the still or through a closed coil in the bottom of the still, to heat the contents of the still. A further disadvantage of this system is that it requires the heating of a large quantity of water adding to costs and time needed for each distillation. However, it is necessary for certain flower distillations e.g. rose and ylang. It is also necessary for the efficient distillation of certain woody materials e.g. sandalwood and cinnamon bark.

ii. Water/steam distillation this is an improved method, the still contains a grid which keeps the plant material above the water level (Fig. 2. Water/Steam still) The water is boiled below the charge and "wet" steam passes through the plant material. Consequently, if an open fire is used the plant material is protected from direct heat. In Fig. 2 the still is heated by a steam jacket. It is important in both water/steam and steam distillation that the still is packed evenly and not too tightly so that steam can extract from the complete charge efficiently. Over packing of the still can cause the steam to force "rat holes" through the charge and leave other parts of the charge unextracted.

iii. Steam Distillation - the most advanced type of distillation is by direct steam provided from a separate boiler. The still contains a grid plate under which an open steam pipe is fitted (see Fig. 3. Steam distillation unit).

The advantages of this type of "dry" steam distillation are that it is relatively rapid, therefore charging and emptying the still is much faster and energy consumption is lower. The rapid distillation is also less likely to damage those oils which contain reactive compounds, e.g. esters

As a general rule all stills should be insulated ("lagged") to reduce heat losses. Their design and losses . Their design and construction should also facilitate loading and unloading.

 

Condensers and Separators

The steam containing essential oil vapour leaves the still and passes into a condenser by way of a "gooseneck" (Fig. 4. Btillhead/Gooseneck). Some sort of gauze or screen is often fitted at the mouth of the gooseneck to prevent plant material being blown over into the condenser.

In the condenser the vapours are cooled and condense. The simple form of condenser is shown in Fig. 5. (see Fig. 5. Coil condenser). The vapours pass through a coiled tube contained in a water bath and condensate is obtained at the bottom of the condenser tube. It is important that condensation is complete or oil may be lost by evaporation.

A more efficient type of condenser is the multi-tubular type shown in Fig. 6 (see Fig. 6. Multi-tubular condenser) in which a series of parallel tubes are mounted inside a cylindrical jacket through which cooling water is passed. This design provides a large surface area for cooling in relation to its volume.

The mixture of water and essential oil leaves the condenser and flows into a separator, called a florentine flask, in which they separate into two layers.

The essential oil will generally be lighter than water, the oil floats to the surface and the distillate water drains away.

Fig. 7. Lighter-than-water separator

It is important that the oil separators should be large enough in volume to minimize turbulence because significant amounts of oil can be lost with the distillate water if the oil is not allowed to separate completely. In addition, the temperature of the distillate may have an important bearing on the efficiency of separation of essential oil and water. The optimum temperature for obtaining the best separation can be found by trial and error. Sometimes when separation of oil is difficult, the distillate water is run back into the still (cohobation) and redistilled.

Fig. 8. Heavier-than-water separator

Condensers and separators should be constructed of materials which do not react with essential oils or water. Mild steel rusts and is not suitable. However, copper has been used successfully for many years tend tinned copper were cooper reacts with the oil). The optimum material for stills, condensers and separators is stainless steel which is resistant and durable but is relatively expensive.

2.3 Storage and packaging

Most essential oils can be stored for long periods under suitable conditions: they should be dry, not in contact with the air or direct sunlight and kept cool.

It is important that essential oils do not come into contact with materials with which they might react, e.g. rubber or plastic bungs.

Glass containers are often used for smaller amounts of oil but larger quantities are invariably stored in metal drums. Mild steel drums lined with epoxy resin are very popular for essential oils. If secondhand drums are to be used, it is important that they are thoroughly cleaned and dried before being filled with essential oil. Plastic containers, e.g. polythene, should not be used because the oil may be absorbed by the plastic and contamination may occur. To ensure that the oil is not wet it should be left to stand for some time before being filtered into its container. Oils generally show no cloudiness when thoroughly dry.

Freshly distilled oils often possess some "still odours" which are unpleasant. These generally disappear after several weeks storage. Some oils gradually improve in storage and acquire a fuller more rounded aroma, e.g. vetiver and patchouli.


III. Individual monographs

Cajuput

I. GENERAL

COMMON NAME

Cajeput

BOTANICAL NAME

Melaleuca minor sm

FAMILY

Myrtacae

OTHER NAMES

Cajuput, Cajuputi, Kaju-Puti,Ti-Tree (not to be confused with Melalecua alternifolis or Melalecua viridiflora)

CULTIVATION CONDITIONS

Occurs in natural stands and with associated species in the Far East, principally Indonesia and the Philippines. The tree grows to a height of 10 - 12 metres, but only the shrub growth is used for the oil production. The oil is produced all year round from the young leaves and terminal branches (Guenther).

MAJOR PRODUCING COUNTRIES

Indonesia (Moluccas) (production fluctuates between 70 150 tonnes / pa) and Vietnam (2 tonnes).

YIELD AND DESCRIPTION

The young leaves yield approximately 1% pale green to yellow oil. The oil has a powerful fresh 'mildly medicated' odour. The taste is harsh and burning.

MAIN USES

For the inhabitants of South East Asia this oil which has several names (Cajuput oil, Cajuputi oil, Kaju-Puti oil, Ti-Tree oil, Cajaput oil), is a complete all-purpose home medicine. The

Vietnamese hail the oil for its antibacterial properties. Elsewhere it is widely used as an expectorant, for throat preparations, such as gargles and for stomach upsets. It is used in

Indonesia as an insecticide. Total production is estimated to be between 75 and 200 tons annually (Arctander).

It has not been fully considered outside S.E. Asia. The smoothness of this cajuputol containing oil, compared to the harshness of Eucalyptol oils for blending with other flavours, has yet to be exploited.

 

II. AGRICULTURAL ASPECTS

CULTIVATION

Natural cultivation and reforestation is sufficient for the present demand. It could be readily cultivated in a plantation provided the usual precautions are taken against tropical diseases and pests (Evans).

HARVESTING PERIOD

The leaves are collected all year round.

HARVESTING METHODS

By hand, however plantations could be harvested mechanically.

 

III. POST HARVEST TREATMENT, PRESERVATION, STORAGE

PRE-TREATMENT

There are no particular requirements

PRESERVATION AND STORAGE

There are no particular requirements

 

IV. PROCESSING

PROCESSING METHOD

By water/steam distillation in mobile field stills. The stills are carried by two men on bamboo poles. The spent leaf is used as the fuel. Modern equipment, in particular the collecting system, would improve the yield, as the oil does have some solubility in water.

COMPOSITION OF OIL

Terpenes

Cajeputol (Cineole) 50 - 60%

Terpineol

Linalol

EQUIPMENT

Simple distillation apparatus

 

BIBLIOGRAPHY

ARCTANDER, S "Perfume and Flavour Materials of Natural Origin" (Private Publication)

EVANS, J "Plantation Forestry in the Tropics" ISBN 0-19859464-X ISBN 0-19-8594895 Pbk

GUENTHER, E. "The Essential Oils". Vol lV p 542 ISBN 0-88275074-7

Clausena anisata

I. GENERAL

COMMON NAME

Clausena

BOTANICAL NAME

Clausena anisata, Hook

FAMILY

Rutaceae

OTHER NAMES

Various local native language names are used

CULTIVATION CONDITIONS

Clausena is a small tree that grows abundantly in tropical countries

MAJOR PRODUCING COUNTRIES

East Africa, Indonesia and the Philippines

No commercial production reported.

YIELD AND DESCRIPTION

Oil of Clausena anisata is a mobile yellow clear liquid with a strong anise odour. On a dry weight basis the yield is reported as 4.32% (Guenther).

MAIN USES

In Indonesia and the Philippines the oil is used as a medicinal flavour and in the Philippino local brandy "Anisdos". While the world interest in this oil was wiped out with the availability of synthetic anethole for aniseed, it has remained in use to save foreign currency. In East Africa the dried leaves are used as an insect repellent and the oil has been reported to be toxic to the grasshopper "Zonecerus variegate" (Okunade).

 

II. AGRICULTURAL ASPECTS

CULTIVATION

The shrub can be propagated from seed t Guenther) or more easily as grafts on Clausena excavate.

HARVESTING PERIOD

This has not been investigated but is considered to be "as required".

HARVESTING METHODS

By hand, no commercial mechanical harvesting is known.

 

III. POST HARVEST TREATMENT, PRESERVATION, STORAGE

PRE-TREATMENT

None specified

PRESERVATION AND STORAGE

The oil is susceptible to oxidation and, therefore, should be stored in full, airtight containers in a cool dark place.

 

IV. PROCESSING

PROCESSING METHOD

Water/steam or steam distillation is satisfactory

COMPOSITION OF OIL

Nineteen components have been identified in the leaves, with phenylpropanoids making up 96%, methyl havicol (estragole) being the most abundant at 92% (Ekundayo).

EQUIPMENT

Distillation retorts with heat exchangers made from stainless steel

There is no identifiable information for the following areas: PROCESSING oil extraction, and nomenclature of products

 

BIBLIOGRAPHY

EKUNDAYO, O; OGUNTIMEIN, B.O AND HAMMERSCHMIDT, F. J. "Constituents of the essential oil of Clausena anisata leaves". Planta Medica (1986) No 6 pp 505 - 506

GUENTHER, E. "The Essential Oils" (1950) Vol 3 "Oil of Clausena anisata" ISBN No 088275-163-8

OKUNADE, A; and OLAIFA, J "Estragole: an acute toxic principle from the volatile oil of the leaves of Clausena anisata" Journal of Natural Products (1987) 50: 5. pp 990 - 991

Davana

I. GENERAL

COMMON NAME

Davana or Davanum

BOTANICAL NAME

Artemisia pollens Wall

FAMILY

Compositae

OTHER NAMES

CULTIVATION CONDITIONS

Davana is an indigenous herb of Southern India but does not grow wild to any great extent and is cultivated mainly for the leaves and flowers used in Indian garlands (Arctander). It is an annual, grown from seed and it reaches maturity in four months.

MAJOR PRODUCING COUNTRIES

India (1 tonne)

YIELD AND DESCRIPTION

Yields have been reported ranging from 0.13 - 0.58% with an average value of 0.2%. The oil is brown in colour with a fine herbaceous sweet foliage odour which becomes balsamic on drying. Because of the price it has caused little interest outside the Indian sub continent.

The herb is susceptible to nematodes (Haseeb).

MAIN USES

As a perfumery material. Antifungal and antibacterial properties have been widely reported for the oil (Alankara Rao, Alankara Rao).

 

II. AGRICULTURAL ASPECTS

CULTIVATION

The plants are readily cultivated from seeds. These are planted in December and the seedlings are planted out after 4 - 6 weeks. Artificial irrigation is used. Davana farming has been very labour intensive, i.e. the propagation, planting out, weed control and harvesting (Kumar).

HARVESTING PERIOD

This is usually 4 months after planting and just prior to inflorescence. Artemisia pallens Wall.

HARVESTING METHODS

Reports indicate this has been by hand (Gowda). The herb is dried for a week in the shade.

 

III. POST HARVEST TREATMENT, PRESERVATION, STORAGE

PRE-TREATMENT

Nematodes have to be combatted (Arctander).

PRESERVATION

None required

STORAGE

In clean airtight drums

 

IV. PROCESSING

PROCESSING METHOD

Normal herbage distillation techniques are used (Denny). The herb is dried, as above. The spent herb can be used as fuel.

COMPOSITION OF OIL

The early reports were summarised by Lawrence (Lawrence). More recently the ketone and furan have been discussed with interest (Akhila). The main component is davanone and this, and related compounds, have been used to identify Davana Oil (Sandra).

EQUIPMENT

Usual primitive distillation apparatus suffices.

 

BIBLIOGRAPHY

AKHILA, A; TEWARI, R "Chemistry of Davana Oil; a Review" Current Research Medical Aromatic plants. Lucknow, India Central Institute of Medicinal and Aromatic Plants. July/Sept 1986 v 8 (3) pp 128 - 138

ALANKARA RAO, G.S.J.G; PRASAD, Y.R; "Investigations on the antibacterial activity of essential oils from Artemisia pollens Wall and Artemisia vulgaris Linn". Indian Perfumer. Nanpur Essential Oil Association of India January/March 1981 v 25 (1) p 110- 111

Artemisia pallens Wall

ALANKARA RAO, G.S.J.G; PRASAD, Y.R "Investigations on the antifungal activity of essential oils from Artemisia pallens Wall and Artemisia vulgaris Linn, Control of fungi, pathogens of plant diseases." As above pp 112 113.

ARCTANDER, S "Perfume and Flavour Materials of Natural Origin" (Private Publication)

DENNY, E.F.K. "Field Distillation for Herbaceous Oils" Lilydale, Tasmania, Australia (Private Publication)

GOWDA, D. R; RAMASWAMY, M. N; "Cultivation, harvesting and distillation of Davana pallens "Perfumery and Essential Oil Record 1965 56 (3) 152 - 158

HASEEB, A; PANDEY, R; "Root Knot nematodes, a constraint to cultivation of Davana, Artemisia pallens"

Trop Pest Manage. London : Taylor and Francis July/September 1990 v 36 (39) pp 317 319

KUMAR, Anup; GAUNIYAL, A. K; "Technology for growing Davana, an aromatic herb." Indian Farming 1988, 37 : 10 11 - 12

LAWRENCE, B.M. "Progress in Essential Oils". "Perfumer and Flavourist" April/May 1978 Vol 3 No 2 p 45

SANDRA, P; BICCHI, C "Capillary Gas Chromatography in Essential Oil Analysis Chromatographic methods". Huethig 1987 ISBN 3-7785-0860-1

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