Extraction of Volatile oil

Content

Extraction of Volatile oil

Method of extraction

Advantages of extraction

Disadvantages of extraction

Objectives

At the end of this lecture, student will be able to

• Enumerate various extraction methods

• Explain method, advantages and disadvantages of extraction

• Identify suitable method of extraction based on nature of compound to be extracted

Isolation of volatile oil

Hydro distillation

Clevenger’s Apparatus

Mostly applicable to constituents are not degraded by boiling up to 100 0C

Method of Hydro distillation:

• Plant material is completely immersed in water

• Water is boiled by applying heat

• Plant material and boiling water is in direct contact

• Plant material must be kept in motion by charging loosely

Eg: Turpentine oil

Disadvantages of Hydro distillation:

• Complete isolation of oil is not possible

• Certain esters are partially hydrolyzed

• Aldehydes tend to polymerise

Water and steam distillation:

It is often suitable for,

• Plant material, whether fresh or dried

• Constituents of which undergo degradation by direct boiling

Method of Water and steam distillation:

• Plant material is lodged on a perforated grid

• Still is filled with water and heated

• Saturated low steam rises through the plant material

• Plant material comes in contact with steam only not with boiling water

Example: Clove oil, Cinnamon oil

Advantages of Water and steam distillation:

• Decomposition of volatile oil is less

• Requires less fuel, less time

• More yield

Disadvantages of Water and steam distillation:

In case of high boiling essential oils

• Large quantity of steam is required

• More time consuming

Direct steam distillation

Applicable to fresh drugs that is loaded with sufficient natural moisture and hence no maceration is required

Method of Direct steam distillation:

• Plant material is placed on a grid

• Steam is generated by means of open or perforated coils

• Saturated steam is passed through the charge

• Distillation is best started with steam of low pressure followed by high Pressure steam

Advantages of Direct steam distillation:

• Produces purest oil

• High yield without much human labour

• Economical

Disadvantages of Direct steam distillation:

• High temperature steam destroys unstable perfume components

• High pressure steam causes considerable decomposition

Enfleurage method

(Without the aid of heat)

Applicable for those flowers which continue to produce volatile oils even after they have been removed from the stem

Eg: Jasmine, Tuberose

Method of Enfleurage:

• Wooden frames (5 cm high & 50-80 cm square) with a glass plate in the centre known as chassis are used

• A glass plate is covered on either side with a thin coating (3 mm) of specially prepared odourless fat

• Freshly cut flowers are individually laid on to the fat

• Flowers enclosed in between 2 layers of fat release their aromatic components

• Length of exposure depends on flowers

• Flowers are removed by rap on the frame or using fingers (defleurer)

• Flowers are renewed with fresh material

• Process is repeated until the fat has absorbed sufficient amount oil

• Product obtained is known as pomade

• Pomade is extracted with alcohol to separate volatile oil

Expression (Eucelle method)

• Used for extraction of citrus oils

• Volatile oils found in rind of the fruit, such as orange, lemon are best obtained by expression, i.e by application of pressure

Method of Expression:

• Oil cells in rind are ruptured mechanically using pointed projections by twisting raw material over them in clockwise direction either mechanically or manually.

• In commercial scale, these oils are produced by expression so as to preserve the natural fragrance

Summary

• Distillation, extraction and expression

• Distillation – Hydro, water and steam and direct steam distillation

• Extraction – With volatile and nonvolatile solvents, expression and maceration

• Expression – Eucelle method

• Hydro distillation – In complete isolation, hydrolysis of esters

• Water and steam – Less decomposition, high yield and time consuming

• Steam distillation – Purest oil, high yield, decomposition