Coffee caffeine removal

To make an instant decaffeinated coffee product, the decaffeinated roast and ground coffee is extracted in a manner similar to nondecaffeinated coffee. Alternatively, the caffeine from the extract of untreated roasted coffee is removed by using the solvents described previously. 

Secondly, solid CO2 is relatively cheap. Finally, after caffeine removal, any occluded CO2 will vaporize from the coffee without the need to heat it or employ expensive vacuum technology. Again, we retain the volatile essential oils of the coffee. Even if some CO2 were to persist within the coffee granules, it is chemically inert, has no taste and would be released rapidly as soon as boiling water was added to the solid, decaffeinated coffee. 

The article Caffeine in coffee its removal why and how by K. Ramalakshmi and B. Raghavan in Critical Reviews in Food Science and Nutrition, 1999, 39, 441 provides an in-depth survey of the physicochemical factors underlying decaffeination of coffee with supercritical CO2. 

You won t find this happening in your fireplace, though. It doesn t have enough heat or high enough pressure. The cores of stars have supercritical fluids, and the planet Jupiter has some gaseous layers that are supercritical and denser than water. Most decaffeinated coffee has its caffeine removed using supercritical carbon dioxide. 

Decaffeinated coffee satisfies people who like the smell and taste of coffee but cannot tolerate the caffeine. How is caffeine removed from coffee ... 

Some people like the taste of coffee and the rituals associated with it (the customary cup of coffee after dinner) but do not like the effects of the caffeine. They may choose to drink decaffeinated coffee, which has 2-4 mg of caffeine per cup. A coffee must have at least 97% of its caffeine removed to be considered decaffeinated coffee. 

Tea yields better-quality caffeine than that obtained from coffee. Caffeine from tea is relatively colorless, whereas the caffeine extracted from coffee is highly colored. About 25 mg of caffeine is isolated in either case. Sublimation removes much of the color from the tea and coffee samples. 

Decaffeination Regulations. Eor decaffeinated roasted coffee, EEC standards indicate the maximum content of caffeine as 0.1% db for decaffeinated instant coffee it is 0.3% db. In the United States, decaffeination usually signifies that 97% of the caffeine has been removed. Permissible solvents for decaffeination processes are defined by national legislation, eg, EDA or EEC directive. The maximum residual solvent content after decaffeination, roasting, or instant coffee processing is to be kept within good manufacturing practice, ie, very low ppm levels or below at point of sale (46). 

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 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. 

The basic process outline is depicted in Figure 5.2 moist un-roasted coffee beans and CO2 are fed counter-currently into the extractor under supercritical conditions. Caffeine is selectively extracted into the CO2 and this stream is led to a water-wash column to remove caffeine at a reduced pressure, the CO2 being recycled back to the extraction column. Extraction of the caffeine into water is necessary to avoid dropping the CO2 pressure too low, since compression is energy-intensive. There is now the problem of separating the caffeine (which is used in soft drinks and pharmaceu-... 

A great deal of effort has been put into methods for removing only the caffeine from the extracting solvent, and somehow returning all of the other components to the coffee beans for reabsorption. The principle of the method most generally seen involves exposure of the extract-laden solvent to a caffeine-specific adsorbent. Once the solvent has been treated in this way, it is returned to remove more caffeine. Flowever, the solvent is already saturated with the other solvent-soluble components and does not extract them from the second and subsequent batches of steamed green coffee beans. Adsorbants used for this purpose include activated char-... 

Methods for the decaffeination of green coffee beans, mainly with solvents after a steaming, have already been described. Even with the selective adsorption techniques to remove only caffeine, it is unlikely that the full character of the starting beans can be realized in a final decaffeinated beverage the result is that Robusta coffees are generally used to prepare decaffeinated coffee. The cost is kept down and the treatment, anyway, reduces any harsh or bitter flavor that the Robusta coffee may have had. The resulting beverage will be relatively caffeine-free, but Robusta coffee will contribute more soluble carbohydrates, phenols, and volatile fatty acids, and much less of the diterpenes found in Arabica coffees. 

This state emphasises its capacity to dissolve chemicals and natural substances of similar way as do different organic solvents such as hexane, acetone or dichloromethane. Therefore, the first applications focused on the extraction of natural substances as an alternative to using organic solvents. Thus, removal of caffeine (coffee or tea) with supercritical C02 is the most mature application at industrial level and is also used in the extraction of hops or cocoa fat. 

Another challenge is to develop methods to replace the volatile organic solvents that are used in many industrial procedures. One choice is water as a solvent it is easily repurified, and has a harmless vapor. Another choice is supercritical carbon dioxide, a good solvent for many organic substances. It is not as innocuous as is water, but carbon dioxide can be easily recovered and reused. It is currently used to remove caffeine from coffee, and is being developed as a dry-cleaning solvent to replace organic solvents (Chapter 9). 

Figure 5.8 shows such a system we call it a Soxhlet apparatus. Solvent is passed continually through a porous cup holding the ground coffee. The solvent removes the caffeine and trickles through the holes at the bottom of the cup, i.e. as a solution of caffeine. The solvent is then recycled solvent at the bottom of the flask evaporates to form a gas, which condenses at the top of the column. This pure, clean solvent then irrigates the coffee a second time, and a third time, etc., until all the caffeine has been removed. 

Water is a good choice of solvent in a standard kitchen percolator because it removes all the water-soluble components from the coffee - hence the flavour. Clearly, however, a different solvent is required if only the caffeine is to be removed. Such a solvent must be cheap, have a low boiling point to prevent charring of the coffee and, most importantly, should leave no toxic residues. The presence of any residue would be unsatisfactory to a customer, since it would almost certainly leave a taste and there are also health and safety implications when residues persist. 

The preferred solvent is supercritical CO2. The reasons for this choice are many and various. Firstly, the CO2 is not hot (CO2 first becomes critical at 31 °C and 73 atm pressure see Figure 5.5), so no charring of the coffee occurs during decaffeination. Furthermore, at such a low temperature, all the components within the coffee that impart the flavour and aroma remain within the solid coffee - try soaking coffee beans in cold water and see how the water tastes afterwards Caffeine is removed while retaining a full flavour. 

Figure 5.8 Coffee is decaffeinated by constantly irrigating the ground beans with supercritical carbon dioxide schematic representation of a Soxhlet apparatus for removing caffeine from coffee...

Furthermore, supercritical CO2 does not behave as merely a mixture of liquid and gaseous CO2, but often exhibits an exceptional ability to solvate molecules in a specific way. The removal of caffeine from coffee relies on the chromatographic separation of caffeine and the other organic substances in a coffee bean supercritical fluid chromatography is a growing and exciting branch of chemistry. 

D. J. Adam, J. Mainwaring and Michael N. Quigley have described a simple experiment to remove caffeine from coffee with a Soxhlet apparatus see Journal of Chemical Education, 1996, 73, 1171. Their solvent was a chlorinated organic liquid rather than supercritical CO2. The abstract is available at http //jchemed.chem.wisc.edu/ journal/issues/1996/Dec/absll71.html. 

Caffeine can be extracted from coffee and tea using solvent extraction. A tea solution was mixed with the solvent ethyl ethanoate in a separating funnel and the funnel was shaken. The layers were left to settle and the lower aqueous layer was then removed and the ethyl ethanoate layer was drained and stored. 

In contrast to the decaffeination of coffee, which is primarily executed with green coffee, black tea has to be extracted from the fermented aromatic material. Vitzthum and Hubert have described a procedure for the production of caffeine-free tea in the German patent application, 2127642 [11]. The decaffeination runs in multi-stages. First, the tea will be clarified of aroma by dried supercritical carbon dioxide at 250 bar and 50°C. After decaffeination with wet CO2 the moist leaf-material will be dried in vacuum at 50°C and finally re-aromatized with the aroma extract, removed in the first step. Therefore, the aroma-loaded supercritical CO2 of 300 bar and 40°C will be expanded into the extractor filled with decaffeinated tea. The procedure also suits the production of caffeine-free instant tea, in which the freeze-dried watery extract of decaffeinated tea will be impregnated with the aromas extracted before. 

Folklore The French name for this herb is Pissenlit , which is self-explanatory. The herb is regarded as a good diuretic to help purify the system by removing toxins. For some time now the roots have been roasted and then extracted to make a caffeine-free dandelion coffee. Dandelion has also been used in root beers and soft drinks such as Dandelion and Burdock (Bown, 2003 British Herbal Medicine Association, 1983 Gruenwald et al, 2002 Hutchens, 1973 Shealy, 1998 Tierra, 1998). 

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