Extraction Separation and Identification Methods

Extraction Methods

All these extraction methods have been reviewed by Van Beek (1991).

Besides the usual hydrodistillation, steam distillation, leaching, and pressing, extraction with supercritical carbon dioxide also has been widely used in the last 20 years for essential oils. For example, solvent extraction with acetone gives the ginger oleoresin, which contains the essential oils as well as the pungent principles and other nonvolatile compounds present in ginger. When compared with other methods, it gives the best results (Zhou et al., 1994; Roy et al., 1996; Yu et al., 1998; He et al., 1999; Zang et al., 2000).

Hydrodistillation and Steam Distillation

Hydrodistillation is principally used for laboratory purposes in a glass, copper, or steel reactor connected to a cooling and decanting flask. Krishnamurthy et al. (1970) studied the water-distilled oil from green and dry ginger. Green ginger oil has a more spicy odor and is considered superior to the oil from dry ginger. This is probably due to the greater amount of a-zingiberene in green oil. Since green ginger is perishable, the distillation must be done locally. More a-zingiberene and smaller amounts of other sesquiterpene alcohols are present in green oil than in the oils from Cochin and peeled ginger.

Steam distillation, an old and well-known method, is commonly used for commercial isolation of ginger oils. Yields ranged from 0.2% to 3% according to the origin and the state of the rhizome (fresh or dried) (Krishnamurthy et al., 1970; Connell, 1971; Anzaldo et al., 1986; Van Beek et al., 1987; Ekundayo et al., 1988). It leads to high levels of monoterpenes and low amounts of nonvolatile compounds, in part by thermal degradation of gingerols giving rise to straight-chain aldehydes and 2-alkanones (Badalyan et al., 1998).

Solvent Extraction

This method is used to obtain oleoresin extracts. Several solvents have been recommended. Oleoresin from Australian ginger rhizhome was prepared by acetone or ethanol extraction of dried ground ginger. Gingerols constituted about 33% of the freshly prepared oleoresin. It decomposes to afford shogaols and zingerone (see § 3.5). Ethyl ether, acetone, and hexane were used by Mathew et al. (1973), Jo (2000), and Nishimura (2001), respectively, as well as pentafluoropropane (Hill et al., 1999) and heptafluoro-propane (Dowdle et al., 2002). Antioxidant compounds in ginger rhizome from Korea were extracted using ethyl acetate from a crude methanol extract and separated by thin-layer chromatography (TLC). Ethyl acetate was also used by Harvey (1981). Dry root ginger from Jamaica (1.5 g) was crushed and left to stand with ethyl acetate for 30 min. The solution was filtered and evaporated to dryness to yield 200 mg of oil. This was dissolved in 20 mL of ethyl acetate to give the stock solution. A kinetic study of extraction of gingerols using acetone as solvent was carried out by Spiro and Kandiah (1989). The drawbacks and advantages of the method were reviewed by Koedam (1987) and Bicchi and Sandra (1987).

Solid-Phase Microextraction (SPME) Method

Solid-phase microextraction from the sampling in aromatic analysis was carried out by Faulhaber and Shirey (1998). They described an extraction and desorption process and method of solid-phase microextraction (SPME) for fruit, juice drinks, peppermint oil in chocolate, spearmint oil, gum ginger oil, and citrus oil. The latter method was presented as a quick and solvent-free alternative to conventional extraction methods.

Extraction by Supercritical Carbon Dioxide

For almost 20 years, supercritical carbon dioxide has been employed for extraction of natural products and particularly for ginger powder and other spices (Meyer-Warnod, 1984; Chen et al., 1986, 1987; Chen and Ho, 1988; Naik and Maheshwari, 1989). It is used mainly because supercritical carbon dioxide is safe, noncombustible, inexpensive, odorless, colorless, tasteless, nontoxic, and readily available solvent. Its low viscosity enables it to penetrate the matrix to reach the material extracted, and its low latent heat of vaporation and high volatility mean that it can be easily removed without leaving a solvent residue. Several reviews have been devoted to the CO2 extraction of essential oils

(Moyler et al., 1994; Meireles and Nikolov, 1994). According to Moyler et al. (1994), a distinction must be made between subcritical liquid CO2 (SLCO2) and supercritical fluid CO2 (SFCO2). In the first process, temperature and pressure ranged between 0 and 10° C and 50 to 80 bar, respectively. It is mainly used selectively to extract essential oils from ground plants. Supercritical CO2 is not currently used commercially to extract flavor oleoresins because of cost constraints. However, some supercritical CO2 is available commercially. Brogle (1982) showed that a fractionated extract can be obtained by reducing the pressure of a CO2 solution of a supercritical extract while still in the condenser. Insoluble components such as waxes, resins, and alcohols can be separated to give an essential oil similar to that of the subcritical CO2 extract. A third method consists of using CO2 with entraining solvents such as ethanol in order to obtain a specific flavor profile. The apparatus is generally used for 500 to 600 kg of powdered ginger under a blanket of CO2 gas to prevent surface oxidation. Liquid CO2 at low temperature is pumped around the circuit and the extract is collected in a condenser evaporator. The pressure is released, extract trapped, and the CO2 recycled. By varying the temperature and pressure during extraction, the flavor and odor components can be selectively extracted (Roy et al., 1996). Chen et al. (1986) extracted freeze-dried ginger powder with liquid CO2 (600 to 700 psi) for 48 hours. The oil was fractionated into a hydrocarbon fraction and oxygenated fractions by using silica gel column chromatography. Each fraction was then analyzed by gas chromatography (GC) on a Carbowax 20 M capillary column (60 m X 0.32 mm i.d.). Previously, Chen et al. (1986) also analyzed the oil by TLC on silica gel and high-performance liquid chromatography (HPLC) on a reverse phase column. The ginger oil had both the pungent and aromatic properties of ginger. Two cultivars of ginger from Korea were treated by simultaneous steam distillation and CO2 extraction (Kim et al., 1991). The oil from this latter process (6.96%) was fractionated into one hydrocarbon fraction and another oxygenated hydrocarbon fraction by using silica gel column chromatography. Each fraction was analyzed by GC and GC/mass spectrometry (MS).

Pellerin (1991) compared the extracts of Indian ginger root obtained by the conventional processes (steam distillation and hexane extraction) and that obtained by supercritical CO2 extraction (see Table 3.6).

Table 3.6 Gas chromatography (GC) comparison of some sesquiterpene hydrocarbons and zingerone obtained from Indian ginger extracts by three different extraction methods*

Percentages (%)

Table 3.6 Gas chromatography (GC) comparison of some sesquiterpene hydrocarbons and zingerone obtained from Indian ginger extracts by three different extraction methods*

Percentages (%)

Volatile Compound

Steam distillation

Supercritical C02

Hexane

ar-Curcumene

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You have probably heard the term Aromatherapy and wondered what exactly that funny word, „aromatherapy‟ actually means. It is the use of plant oils in there most essential form to promote both mental and physical well being. The use of the word aroma implies the process of inhaling the scents from these oils into your lungs for therapeutic benefit.

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Responses

  • Ayden
    What are the methods of extraction from ginger?
    3 years ago
  • Gloria Willis
    Which is the best solvent for ginger extract preparation?
    3 years ago
  • lassi wahlman
    What is the use of acetone in preparation of oleo resin from ginger?
    3 years ago
  • tommi
    How to do solvent extraction ginger oil?
    2 years ago
  • AMANDA
    What are the processes involved in extracting oil from ginger?
    2 years ago
  • arabella
    Why does ginger extract form ppt on seperating by distillation?
    2 years ago
  • valentin
    Which is the best method for ginger extraction?
    2 years ago
  • leona johnston
    What method is used to extract ginger liquid?
    2 years ago
  • Donald
    What method is used to extract the solution of a peeled ginger?
    2 years ago
  • Ishbel
    How to extract zingiberene?
    2 years ago
  • GILLY
    How to identify zingiber powder?
    2 years ago
  • jose
    Are acetone and ginger oil misible?
    2 years ago
  • isengrin
    How to make ginger extract in laboratory?
    1 year ago
  • jessica
    How to extract dry ginger plants?
    1 year ago
  • gorbaduc
    What the procedure for percolation method of oleoresin determination in ginger?
    1 year ago
  • quinzia trentini
    What % gingerols in supercritical extract?
    1 year ago
  • Nicole
    How to make ginger oleoresin locally?
    1 year ago
  • charlie ware
    How to extract zingerber from ginger?
    1 year ago
  • benjamin fink
    Where to buy ginger with supercritical extraction process?
    5 months ago
  • elisabeth
    Which parts of ginger are extarcts obtained from?
    5 months ago
  • Annika
    Why methanol used as solvent extraction of ginger?
    3 months ago

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