Extraction by Steam Distillation

The simplest and most economical method of removing volatile oils from plant material is by distillation with a current of steam. This method cannot he used for flavors having oils that are unfavorably affected by the action of steam. Most volatile oils, however, can all be distilled by steam without serious decomposition. The chief advantages of the method are its simplicity, the comparatively brief time required for its operation, and the fact that large quantities of material can be handled at a small cost. It is the only method economically possible for the extraction of the great number of volatile oils of only nominal value, for which the more tedious processes would be impracticable. 

The steam distillation is based on the fact that volatile oils are vaporized when the material containing them is subjected to a current of steam and that, when the mixture of oil and water vapors is condensed, the oil separates as a liquid in a layer that may be readily removed from the water. To accomplish this result it is necessary to supply (1) a tub or retort in which the plant material may be subjected to the action of steam obtained from any conventional source, (2) a suitable condenser for condensing the mixture of vapors, and (3) a receiver in which the condensed water and oil may be collected. 

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Methyl salicylate is produced synthetically for commercial purposes by the esterification of salicylic acid with methanol or by extraction by steam distillation of wintergreen leaves or sweet birch bark. The source, natural or synthetic, is declared on the label. The methyl salicylate NF must assay not less than 98.0% and not more than 100.5% and be processed by Good Manufacturing Practice described in USP (20). 

The odour of pepper oil is described as fresh, dry-woody, warm-spicy and similar to that of the black peppercorn (Purseglove et al., 1981). The flavour is rather dry-wood and lacks the pungency of the spice since the alkaloids are not extracted by steam distillation. Very few studies are reported in the literature on correlation of oil composition to odour characteristics. Hasselstrom et al. (1957) attribute the characteristic odour of pepper oil to the small amounts of oxygenated constituents present. Lewis etal. (1969) consider that a number of monoterpenes present in the oil are necessary for strong... 

The essential oil from star anise fruits traditionally is extracted by steam distillation. This process is not expensive but can induce thermal degradation, hydrolysis and water solubilization of some fragrance constituents (Reverchon, 1997). 

Do not confuse sweet almond with bitter almond (Prunus amygdalus var umu. a). The essential oil is extracted by steam distillation after maceration of pressed nuts. A major component is benzaldehyde (95%), which is moderately toxic. Hydrocyanic acid is also formed, which is poisonous. It is not suitable for aromatherapy but is used in the food industry. 

PROP Extracted by steam distillation of leaves from Cinnamomum t lanicum Nees. Light to dark brown liquid spicy cinnamon, clove odor and taste. Sol in fixed oils, propylene glycol, mineral oil insol in glycerin. 

Water is seldom used alone to obtain a crude plant extract instead, an aque-ous-methanolic extract is generated as shown in Fig. 1 and partitioned between different solvents (29). Using this procedure, ethyl acetate and diethyl ether are prone to form emulsions with water, so the addition of sodium chloride to saturation may break the emulsion, although on certain occasions it is necessary to break the emulsion by centrifugation. Extraction by steam distillation is widely used to obtain volatile terpenes (30), although it has been observed that a fall of up to 2 pH units may occur because of the rupture of vacuoles, which may produce undesired reactions on sensitive compounds (31). 

Steam distillation In steam distillation, hot steam is forced through the matrix of raw material, opening the cavities in which the oil is held, and volatilizing the oils. This process is, in fact, pure steam distillation. The oil separates from the water in the distillate and is collected. As the steam is under pressure, the temperature can be carefully adjusted to provide the maximum rate of extraction with minimum thermal decomposition. Lavender oil, which is thermally, labile can be extracted by steam distillation without thermal damage. 

Melaleuca (Myrtaceae) is a native genus of Australia and has found widespread use in medicinal and cosmetic purposes. Essential oils extracted by steam distillation from Melaleuca species are mostly composed of 1,8-cineole, a-pinene, P pinene, and terpinen-4-ol, and they possess antimicrobial and antioxidant properties. Melaleuca oil is a commercial name for oil extracted from leaves of Melaleuca armillaris Sm. with 1,8-cineole (85.8%) as main compound, followed by camphene and a-pinene as constituents also in major concentrations, but to a lower extent. This oil showed a better effect on radical scavenging in the ABTS than in the DPPH assay. Vitamin C was a reference with a higher antioxidant activity for ABTS and DPPH assays (Chabir et al., 2011). 

Cassel, E. and Vargas, R. M. F., 2006. Experiments and modeling of the Cymbopogon winterianus essential oil extraction by steam distillation. Journal of Mexican Chemical Society 50(3) 126-129. 

In the laboratory, formic acid can be obtained by heating oxalic acid in anhydrous glycerol and extraction by steam distillation. Another preparation (which must be performed under a fume hood) is the acid hydrolysis of ethyl isonitrile (C2H5NC) using HCl solution. 

The SDK procedure was performed using a micro-version of a Likens-Nickerson apparatus [33] in the configuration for heavier-than-water solvents. The aroma components were extracted by steam distillation and the aqueous distillate was simultaneously extracted with dichloromethane. The organic extracts were analyzed by GC-FID and GC-MS. The DHS technique was carried out with adsorption on Tenax traps and thermal desorption with ctyofocusing of the volatile substances into the GC capillary column. 

Extraction of steam distillates by solvents. The apparatus, depicted in Fig. 11,58, 7, may be employed for the continuous extraction of substances which are volatile in steam from their aqueous solutions or suspensions. Solvents of the ether type (i.e., lighter than water) or of the carbon tetrachloride type (i.e., heavier than water) may be used. A reflux condenser is inserted in the Bl9 socket, whilst flasks of suitable capacity are fltted into the lower B24 cone and the upper. B19 cone respectively. For extraction with ether, the flask attached to the upper. B19 cone contains the ether whilst the aqueous solution is placed in the flask fltted to the lower B2i cone the positions of the flasks are reversed... 

If the presence of unreduced nitrobenzene is suspected (odour and/or high b.p. residue), treat all the product with excess of dilute hydrochloric acid and remove the nitrobenzene either by steam distillation or by ether extraction render the residue alkaline with sodium hydroxide solution and isolate the aniline os before. 

Aromatic alcohols are insoluble in water and usually burn with a smoky flame. Their boiling points are comparatively high some are solids at the ordinary temperature. Many may be oxidised by cautious addi-tion of dilute nitric acid to the corresponding aldehyde upon neutralis-tion of the excess of acid, the aldehyde may be isolated by ether extraction or steam distillation, and then identified as detailed under Aromatic Aldehydes, Section IV,135. 

The benzoic acid may be separated by steam distillation or by saturating the aqueous mixture of sodium salts with sulphur dioxide whilst maintaining the temperature below 40° the benzoic acid precipitates and can be separated by filtration or extraction with ether. Acidification of the filtrate with hydrochloric acid liberates the pyruvic acid. The pjTuvic acid may be oxidised < lth hydrogen peroxide to the arylacetic acid, for example ... 

Bisulphite compounds of aldehydes and ketones. These substances are decomposed by dilute acids into the corresponding aldehydes or ketones with the liberation of sulphur dioxide. The aldehyde or ketone may be isolated by steam distillation or by extraction with ether. Owing to the highly reactive character of aldehydes, the bisulphite addition compounds are best decomposed with saturated sodium bicarbonate solution so um carbonate solution is generally employed for the bisulphite compounds of ketones. 

The following are examples of the above procedure. A mixture of diethylamine and re-butyl alcohol may be separated by adding sufficient dilute sulphuric acid to neutralise the base steam distillation will remove the alcohol. The amine can be recovered by adding sodium hydroxide to the residue and repeating the distillation. A mixture of diethyl ketone and acetic acid may be treated with sufficient dilute sodium hydroxide solution to transform the acid into sodium acetate and distilling the aqueous mixture. The ketone will pass over in the steam and the non-volatile, stable salt will remain in the flask. Acidification with dilute sulphuric acid hberates acetic acid, which can be isolated by steam distillation or by extraction. 

Treatment of 3 5 dimethylphenol with dilute nitnc acid followed by steam distillation of the reaction mixture gave a compound A (CgH9N03 mp 66°C) in 36% yield The nonvolatile residue from the steam distillation gave a compound B (CsHpNOs mp 108°C) in 25% yield on extraction with chloroform Identify compounds A and B... 

The concern by consumers about cholesterol has stimulated the development of methods for its removal. Three principal approaches are in the pilot-plant stages use of enzymes, supercritical fluid extraction, and steam distillation. Using known techniques, it is not possible to remove all cholesterol from milk. Therefore, FDA guidelines identify cholesterol-free foods as containing less than 2 mg cholesterol per serving, and low cholesterol foods as containing from 2 to 20 mg (37). 

Aroma Distillate. Used by the flavor industry, aroma distillates are the product of continuous extraction of the plant material with alcohol at temperatures between ambient and 50°C followed by steam distillation, and, lastly, concentration of the combined hydro—alcohoHc mixture. On cooling, terpenes often separate from the aroma distillate and are removed. 

Pine Oil. This oil is obtained by extraction and fractionation or by steam distillation of the wood of Pinuspalustris Mill, and other species. Most of the oil is produced ia the southeastern United States. The composition of the oil depends on the fractions chosen, but the chief constituents are terpene alcohols, mainly terpiaeol. Piae oil finds use as a germicide ia disiafectants and soaps as an ingredient ia iasecticides, deodorants, poHshes, sweepiag compounds, and catde sprays and as raw material for the manufacture of perfumery-grade terpiaeol [8000-41 -7], anethole [104-46-1], fenchone (137), and camphor (35). 

Ced rwood. Many varieties of cedarwood oil are obtained from different parts of the world. They are produced mainly by steam distillation of chipped heartwood, but some are also produced by solvent extraction. The oils, which vary significantly ia chemical composition, are used ia perfumes as such, but the main uses are as distillation fractions and chemical derivatives. For the latter purposes the most used oils, which are similar ia composition, are from Texas ia the United States (Juniperus mexicand) and from China Cupressusfunebris). The principal constituents of these oils are cedrene [11028-42-5] (4), thujopsene [470-40-6] (5), and cedrol [77-53-2] (6). The first two of these are obtained together by distillation and used mostiy ia the form of acetylated derivatives. Cedrol is used as such and, to a greater extent, as its acetate ester. 

Analytical Techniques. Sorbic acid and potassium sorbate are assayed titrimetricaHy (51). The quantitative analysis of sorbic acid in food or beverages, which may require solvent extraction or steam distillation (52,53), employs various techniques. The two classical methods are both spectrophotometric (54—56). In the ultraviolet method, the prepared sample is acidified and the sorbic acid is measured at 250 260 nm. In the colorimetric method, the sorbic acid in the prepared sample is oxidized and then reacts with thiobarbituric acid the complex is measured at - 530 nm. Chromatographic techniques are also used for the analysis of sorbic acid. High pressure Hquid chromatography with ultraviolet detection is used to separate and quantify sorbic acid from other ultraviolet-absorbing species (57—59). Sorbic acid in food extracts is deterrnined by gas chromatography with flame ionization detection (60—62). 

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