Supercritical fluid caffeine extraction with

Due to the relative success of the pure component solubility studies, the same series of experiments were carried out using the complex seed material. Three systems were investigated to evaluate the ability of supercritical fluids to extract monocrotaline from the seeds of Crotalaria spectabilis. Pure carbon dioxide was studied with the expectation that the oils would be preferentially extracted. Ethanol was added as a co-solvent to increase the solubility of monocrotaline. Also, due to its success in the extraction of caffeine and nicotine, water was used as a co-solvent. 

Literature citations of adsorption coupled with supercritical fluid extraction range from the "classical" caffeine extraction with CO2 (1) to recent attempts to separate cholesterol from butter using adsorbent beds of charcoal and silica gel (2). 

G. Extraktion F. extraction E. is the eluation of a (valuable) ingredient from a complex material by a suitable solvent. There are two types of e. liquid/solid and liquid/liquid. There are many different technologies and equipment applied (batch and continuous). A recent method is e. with supercritical fluids (mainly CO2) with already laige-scale uses, e. g., in the e. of hops and of caffeine from coffee. 

Adsorption and Desorption Adsorbents may be used to recover solutes from supercritical fluid extracts for example, activated carbon and polymeric sorbents may be used to recover caffeine from CO9. This approach may be used to improve the selectivity of a supercritical fluid extraction process. SCF extraction may be used to regenerate adsorbents such as activated carbon and to remove contaminants from soil. In many cases the chemisorption is sufficiently strong that regeneration with CO9 is limited, even if the pure solute is quite soluble in CO9. In some cases a cosolvent can be added to the SCF to displace the sorbate from the sorbent. Another approach is to use water at elevated or even supercritical temperatures to facilitate desorption. Many of the principles for desorption are also relevant to extraction of substances from other substrates such as natural products and polymers. 

The dense fluid that exists above the critical temperature and pressure of a substance is called a supercritical fluid. It may be so dense that, although it is formally a gas, it is as dense as a liquid phase and can act as a solvent for liquids and solids. Supercritical carbon dioxide, for instance, can dissolve organic compounds. It is used to remove caffeine from coffee beans, to separate drugs from biological fluids for later analysis, and to extract perfumes from flowers and phytochemicals from herbs. The use of supercritical carbon dioxide avoids contamination with potentially harmful solvents and allows rapid extraction on account of the high mobility of the molecules through the fluid. Supercritical hydrocarbons are used to dissolve coal and separate it from ash, and they have been proposed for extracting oil from oil-rich tar sands. 

In addition to common organic solvents, supercritical fluids (scf s) can be used for a great variety of extraction processes [158 165], Supercritical fluid extraction (SFE), mostly carried out with SC-CO2 as eluant, has many advantages compared to extractions with conventional solvents. The solvent strength of a supercritical fluid can easily be controlled by the pressure and temperature used for the extraction at a constant temperature, extraction at lower pressures will favour less polar analytes, while extraction at higher pressures will favour more polar and higher molar mass analytes. As supercritical fluids such as CO2 and N2O have low critical temperatures (tc = 31 °C and 36 °C, respectively), SFE can be performed at moderate temperatures to extract thermolabile compounds. Typical industrial applications using SC-CO2 include caffeine extraction from coffee beans [158] as well as fat and oil extraction from plant and animal tissues [165]. For some physical properties of supercritical solvents, see Section 3.2. 

The most common use of scC02 is in the extraction of caffeine from coffee or tea, nicotine from tobacco, and essential oils from plants. The isolation of products is simple, with the evaporation of the solvent with no residue. Another important application is in supercritical fluid chromatography (SFC). 

Hills et al. (1991) applied simultaneous supercritical fluid extraction to roasted coffee beans. This technique can be used with or without a derivatizing reagent In a dissociative mechanism, the adsorbed analyte must first desorb from a matrix active site and be dissolved in the supercritical fluid and then react to form the less polar derivative, which favors solvation in the supercritical carbon dioxide. In the associative mechanism, derivatization occurs while the analyte is adsorbed on the active site of the matrix. Reaction with the adsorbed analyte results in the desorption of the non-polar derivative into the supercritical fluid . Thus 2-hexenedioic acid (E.49) was identified for the first time as a native compound (without the use of a derivatizing agent). Benzenic and furanic compounds and caffeine were also identified. 

Supercritical extraction (SCE) is a modem separation technique that uses the dramatic increase in solubility of some solutes in supercritical fluids. Important applications have been found in food industry, as the extraction of caffeine from coffee, fats from butter, etc. Ethanol may be also recovered by extraction with COj. We should also mention the use of supercritical water to solve environmental problems, as the destmction of poly-chloro-benzenes (PCBs) by oxidation in supercritical water. 

There are many literature reports on industrial uses of supercritical fluids, and many patents have been issued for various uses of supercritical fluids as solvents in extraction processes. Randall (1) prepared an excellent review on the uses and patents issued up to 1982 in the area of supercritical fluid extraction and chromatography. Many of these applications deal with natural products such as flavors, fragrances, oils and fats, or the removal of unwanted components from natural materials such as caffeine from coffee or tea and nicotine from tobacco. 

For the design of extraction processes of mostly high boiling liquid or solid compounds with the help of supercritical fluids, for example, the extraction of caffeine from coffee beans using carbon dioxide the phase equilibrium behavior as a function, of the pressure without or in the presence of co-solvents is required. As in the case of all other phase equilibria, the isofugacity condition has to be fulfilled ... 

Snpercritical CO2 tluid extraction of caffeine from coffee beans is nsed by an Increasing nnmber of companies fo prodnce decaf coffee. After tbe coffee beans are soaked In water to bring tbe caffeine cioser to tbe snrface, they are placed nnder approximately 35 atm of CO2 at room temperatnre. This selectively extracts more than 98% of the caffeine from the beans with minimal effect on flavor and aroma. The caffeine Is soluble in the supercritical CO2, but precipitates when the pressnre Is lowered to convert the supercritical fluid to gaseous CO2. 

Process for the direct decaffeination of aqueous coffee extract solutions Process for extracting caffeine from solutions thereof in carbon dioxide under high pressure Process for the extraction of caffeine supercritical solutions Decaffeination process Method for decaffeinating coffee with a supercritical fluid Method for decaffeinating coffee with a supercritical fluid... 

Indeed, the most novel approach to decaffeinate green coffee beans, which has attained industrial application, is supercritical fluid extraction (SFE) using carbon dioxide CO Supercritical CO2 is selective for the extraction of caffeine, there is no associated waste treatment of a toxic solvent and extraction times are moderate. Moreover, supercritical CO2 coupled with ethanol or water was investigated to extract caffeine Ifom green tea leaves. 

Until recently, the principal method of decaffeinating coffee was to extract the caffeine with a solvent, such as methylene chloride (CH2CI2). This solvent is objectionable because it is hazardous in the workplace and difficult to completely remove from the coffee. Now, supercritical fluid CO2 is used. In one process, green coffee beans are brought into contact with CO2 at about 90 °C and 160 to 220 atm. The caffeine content of the coffee is reduced from its normal 1% to 3% to about 0.02%. When the temperature and pressure of the CO2 are reduced, the caffeine precipitates and the CO2 is recycled. 

In some cases, the solids themselves are subjected to extraction by a solvent. For example, in one process used to decaffeinate coffee, the coffee beans are mixed with activated charcoal and a high-pressure stream of supercritical carbon dioxide (carbon dioxide at high pressure and above its critical temperature) is passed over them at approximately 90°C. A supercritical solvent is a highly mobile fluid with a very low viscosity. The carbon dioxide removes the soluble caffeine preferentially without extracting the flavoring agents and evaporates without leaving a harmful residue. 

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