{"id":96,"date":"2018-07-08T23:59:35","date_gmt":"2018-07-08T23:59:35","guid":{"rendered":"http:\/\/www.essentialoilmach.com\/blog\/?p=96"},"modified":"2019-12-16T09:17:08","modified_gmt":"2019-12-16T09:17:08","slug":"extraction-methods-of-natural-essential-oils","status":"publish","type":"post","link":"https:\/\/www.essentialoilmach.com\/blog\/extraction-methods-of-natural-essential-oils\/","title":{"rendered":"EXTRACTION METHODS OF NATURAL ESSENTIAL OILS"},"content":{"rendered":"

Three Types of Hydrodistillation<\/strong>
\nThree are three types of hydrodistillation for isolating essential oils<\/a> from plant materials:
\n1. Water distillation
\n2. Water and steam distillation
\n3. Direct steam distillation<\/p>\n

1.Water Distillation<\/strong>
\nIn this method, the material is completely immersed in water, which is boiled by applying
\nheat by direct fire, steam jacket, closed steam jacket, closed steam coil or open steam coil. The
\nmain characteristic of this process is that there is direct contact between boiling water and plant
\nmaterial.
\nWhen the still is heated by direct fire, adequate precautions are necessary to prevent the
\ncharge from overheating. When a steam jacket or closed steam coil is used, there is less danger
\nof overheating; with open steam coils this danger is avoided. But with open steam, care must be
\ntaken to prevent accumulation of condensed water within the still. Therefore, the still should be
\nwell insulated. The plant material in the still must be agitated as the water boils, otherwise
\nagglomerations of dense material will settle on the bottom and become thermally degraded.
\nCertain plant materials like cinnamon bark, which are rich in mucilage, must be powdered so that
\nthe charge can readily disperse in the water; as the temperature of the water increases, the
\nmucilage will be leached from the ground cinnamon. This greatly increases the viscosity of the
\nwater-charge mixture, thereby allowing it to char. Consequently, before any field distillation is
\ndone, a small-scale water distillation in glassware should be performed to observe whether any
\nchanges take place during the distillation process. From this laboratory trial, the yield of oil from
\na known weight of the plant material can be determined. The laboratory apparatus recommended
\nfor trial distillations is the Clevenger system.<\/p>\n

During water distillation, all parts of the plant charge must be kept in motion by boiling
\nwater; this is possible when the distillation material is charged loosely and remains loose in the
\nboiling water. For this reason only, water distillation possesses one distinct advantage, i.e. that it
\npermits processing of finely powdered material or plant parts that, by contact with live steam,
\nwould otherwise form lumps through which the steam cannot penetrate. Other practical
\nadvantages of water distillation are that the stills are inexpensive, easy to construct and suitable
\nfor field operation. These are still widely used with portable equipment in many countries.
\nThe main disadvantage of water distillation is that complete extraction is not possible.
\nBesides, certain esters are partly hydrolyzed and sensitive substances like aldehydes tend to
\npolymerize. Water distillation requires a greater number of stills, more space and more fuel. It
\ndemands considerable experience and familiarity with the method. The high-boiling and
\nsomewhat water-soluble oil constituents cannot be completely vaporized or they require large
\nquantities of steam. Thus, the process becomes uneconomical. For these reasons, water
\ndistillation is used only in cases in which the plant material by its very nature cannot be
\nprocessed by water and steam distillation or by direct steam distillation.<\/p>\n

Traditional Method of Producing Attar Using Hydrodistillation<\/strong>
\nFloral attars are defined as the distillates obtained by hydrodistillation of flowers (such as
\nsaffron, marigold, rose, jasmine, pandanus) in sandal wood oil or other base materials like
\nparaffin. Attar manufacturing takes place in remote places because the flowers must be processed
\nquickly after collection. The apparatus and equipment used to manufacture attar are light,
\nflexible, easy to repair, and have a fair degree of efficiency. Keeping in view these facts, the
\ntraditional \u201cdeg and bhapka\u201d process has been used for centuries and is used even now with the
\nfollowing traditional equipment.
\n\u2022 Deg (still)
\n\u2022 Bhapka (receiver)
\n\u2022 Chonga (bamboo condenser)
\nTraditional bhatti (furnace)
\n\u2022 Gachchi (cooling water tank)
\n\u2022 Kuppi (leather bottle)<\/p>\n

Disadvantages of Water Distillation<\/strong>
\n\u2022 Oil components like esters are sensitive to hydrolysis while others like acyclic monoterpene
\nhydrocarbons and aldehydes are susceptible to polymerization (since the pH of water is often
\nreduced during distillation, hydrolytic reactions are facilitated).
\n\u2022 Oxygenated components such as phenols have a tendency to dissolve in the still water, so their
\ncomplete removal by distillation is not possible.
\n\u2022 As water distillation tends to be a small operation (operated by one or two persons), it takes a
\nlong time to accumulate much oil, so good quality oil is often mixed with bad quality oil.
\n\u2022 The distillation process is treated as an art by local distillers, who rarely try to optimize both oil
\nyield or quality.
\n\u2022 Water distillation is a slower process than either water and steam distillation or direct steam
\ndistillation.<\/p>\n

2.Water and Steam Distillation<\/strong>
\nIn water and steam distillation, the steam can be generated either in a satellite boiler or
\nwithin the still, although separated from the plant material. Like water distillation, water and
\nsteam distillation is widely used in rural areas. Moreover, it does not require a great deal more
\ncapital expenditure than water distillation. Also, the equipment used is generally similar to that
\nused in water distillation, but the plant material is supported above the boiling water on a
\nperforated grid. In fact, it is common that persons performing water distillation eventually
\nprogress to water and steam distillation.
\nIt follows that once rural distillers have produced a few batches of oil by water
\ndistillation, they realize that the quality of oil is not very good because of its still notes (subdued
\naroma). As a result, some modifications are made. Using the same still, a perforated grid or plate
\nis fashioned so that the plant material is raised above the water. This reduces the capacity of the
\nstill but affords a better quality of oil. If the amount of water is not sufficient to allow the
\ncompletion of distillation, a cohobation tube is attached and condensate water is added back to
\nthe still manually, thereby ensuring that the water, which is being used as the steam source, will
\nnever run out. It is also believed that this will, to some extent, control the loss of dissolved
\noxygenated constituents in the condensate water because the re-used condensate water will allow
\nit to become saturated with dissolved constituents, after which more oil will dissolve in it.<\/p>\n

Cohobation<\/strong><\/p>\n

Cohobation is a procedure that can only be used during water distillation or water and
\nsteam distillation. It uses the practice of returning the distillate water to the still after the oil has
\nbeen separated from it so that it can be re-boiled. The principal behind it is to minimize the
\nlosses of oxygenated components, particularly phenols which dissolve to some extent in the
\ndistillate water. For most oils, this level of oil loss through solution in water is less than 0.2%,
\nwhereas for phenol-rich oils the amount of oil dissolved in the distillate water is 0.2%-0.7%. As
\nthis material is being constantly re-vaporized, condensed and re-vaporized again, any dissolved
\noxygenated constituents will promote hydrolysis and degradation of themselves or other oil
\nconstituents. Similarly, if an oxygenated component is constantly brought in contact with a direct
\nheat source or side of a still, which is considerably hotter than 100\u00b0 C, then the chances of
\ndegradation are enhanced.
\nAs a result, the practice of cohobation is not recommended unless the temperature to
\nwhich oxygenated constituents in the distillate are exposed is no higher than 100\u00b0 C.
\nIn steam and water distillation, the plant material cannot be in direct contact with the fi re source
\nbeneath the still; however, the walls of the still are good conductors of heat so that still notes can
\nalso be obtained from the thermal degradation reactions of plant material that is touching the
\nsides of the still. As the steam in the steam and water distillation process is wet, a major
\ndrawback of this type of distillation is that it will make the plant material quite wet. This slows
\ndown distillation as the steam has to vaporize the water to allow it to condense further up the
\nstill. One way to prevent the lower plant material resting on the grid from becoming waterlogged
\nis to use a baffle to prevent the water from boiling too vigorously and coming in direct contact
\nwith the plant material.<\/p>\n

Advantages of Water and Steam Distillation over Water Distillation<\/strong><\/p>\n

\u2022 Higher oil yield.
\n\u2022 Components of the volatile oil are less susceptible to hydrolysis and polymerization (the
\ncontrol of wetness on the bottom of the still affects hydrolysis, whereas the thermal conductivity
\nof the still walls affects polymerization).
\n\u2022 If refluxing is controlled, then the loss of polar compounds is minimized.
\n\u2022 Oil quality produced by steam and water distillation is more reproducible.
\n\u2022 Steam and water distillation is faster than water distillation, so it is more energy efficient. Many
\noils are currently produced by steam and water distillation, for example lemongrass is produced
\nin Bhutan with a rural steam and water distillation system.<\/p>\n

Disadvantages of Water and Steam Distillation<\/strong>
\n\u2022 Due to the low pressure of rising steam, oils of high-boiling range require a greater quantity of
\nsteam for vaporization -hence longer hours of distillation.
\n\u2022 The plant material becomes wet, which slows down distillation as the steam has to vaporize the
\nwater to allow it to condense further up the still.
\n\u2022 To avoid that the lower plant material resting on the grid becomes waterlogged, a baffle is used
\nto prevent the water from boiling too vigorously and coming in direct contact with the plant
\nmaterial.<\/p>\n

3.Direct Steam Distillation<\/strong><\/p>\n

As the name suggests, direct steam distillation is the process of distilling plant material
\nwith steam generated outside the still in a satellite steam generator generally referred to as a
\nboiler. As in water and steam distillation, the plant material is supported on a perforated grid
\nabove the steam inlet. A real advantage of satellite steam generation is that the amount of steam
\ncan be readily controlled. Because steam is generated in a satellite boiler, the plant material is
\nheated no higher than 100\u00b0 C and, consequently, it should not undergo thermal degradation.
\nSteam distillation is the most widely accepted process for the production of essential oils on
\nlarge scale. Throughout the flavor and fragrance supply business, it is a standard practice.
\nAn obvious drawback to steam distillation is the much higher capital expenditure needed
\nto build such a facility. In some situations, such as the large-scale production of low-cost oils
\n(e.g. rosemary, Chinese cedarwood, lemongrass, litsea cubeba, spike lavender, eucalyptus,
\ncitronella, cornmint), the world market prices of the oils are barely high enough to justify their
\nproduction by steam distillation without amortizing the capital expenditure required to build the
\nfacility over a period of 10 years or more.<\/p>\n

Advantages of Direct Steam Distillation<\/a><\/strong>
\n\u2022 Amount of steam can be readily controlled.
\n\u2022 No thermal decomposition of oil constituents.
\n\u2022 Most widely accepted process for large-scale oil production, superior to the other two
\nprocesses.<\/p>\n

Disadvantage of Direct Steam Distillation<\/strong>
\n\u2022 Much higher capital expenditure needed to establish this activity than for the other two
\nprocesses.
\nEssential Oil Extraction by Hydrolytic Maceration Distillation
\nCertain plant materials require maceration in warm water before they release their
\nessential oils, as their volatile components are glycosidically bound. For example, leaves of
\nwintergreen (Gaultheria procumbens) contain the precursor gaultherin and the enzyme
\nprimeverosidase; when the leaves are macerated in warm water, the enzyme acts on the
\ngaultherin and liberates free methyl salicylate and primeverose. Other similar examples include
\nbrown mustard (sinigrin), bitter almonds (amygdalin) and garlic (alliin).<\/p>\n","protected":false},"excerpt":{"rendered":"

Three Types of Hydrodistillation Three are three types of hydrodistillation for isolating essential oils from plant materials: 1. Water distillation 2. Water and steam distillation 3. Direct steam distillation 1.Water Distillation In this method, the material is completely immersed in water, which…Read More »<\/a><\/span><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[41,40,43,42],"class_list":["post-96","post","type-post","status-publish","format-standard","hentry","category-essential-oil-distillation","tag-direct-steam-distillation","tag-essential-oil-extraction","tag-water-and-steam-distillation","tag-water-distillation"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\t