Caffeine is an exciting substance contained in coffee and for many, the reason why they drink this beverage. But precisely because it is exciting, some choose to drink coffee without caffeine, at least after a certain time to avoid affecting sleep. Today we want to tell you how to remove the caffeine from coffee to make it decaffeinated.
Whether it is for medical reasons, because you drink many cups of coffee or simply because you like it better, if you drink decaffeinated coffee you will be interested in knowing how the caffeine is removed from the coffee beans to facilitate its consumption for those who do not want to give up coffee but are affected if they drink this beverage with their usual caffeine.
In the XIX century, the process of discovering how to remove the caffeine from coffee without damaging the bean began to continue making quality coffees free of the exciting substance. The cup quality of decaffeinated coffee is completely on par with that of non-decaffeinated coffee. All the many different varieties and origins of coffee conserve their specific flavor properties.
Friedlieb Ferdinand Runge was a 19th-century German chemist who caught the attention of Goethe, the German poet who was also a science enthusiast. Goethe had heard of Runge's pioneering research on belladonna, a poisonous plant. Runge had succeeded in isolating from the plant a compound that caused the eye muscles to dilate if ingested. Goethe had recently received a box of coffee beans and asked Runge to analyze them.
Surprisingly, the German scientist isolated the active ingredient that we now know as caffeine, and thanks to him, we know that this is what gives a special touch to this beverage that is indispensable for keeping up with the pace of today's world. Runge invented the first coal tar dye, was the first to isolate quinine, create an early technique for separating chemicals - paper chromatography - and discovered purine, the blue dye aniline, pyrrole, quinoline, phenol, thymol, atropine, and caffeine, of which scientists are still trying to determine its evolutionary origin and why plants produce it.
One of the latest discoveries in this field is the study conducted by the University of Buffalo (USA) and published in the journal Science in 2014. According to their research, the production of caffeine has its origin in a precursor compound called xanthosine, which in coffee plants changes due to the effects of enzymes present in these plants (N-methyltransferase) that add or remove atoms from xanthosine. The result is caffeine.
This transforming capacity, according to scientists, is the effect of millions of years of evolution, which has allowed plants such as coffee plants to control their environment. Cocoa trees and tea plants have also done so, although in their case, the enzymes that modify xanthosine are different from those of coffee. Still, the result is the same. According to the scientists, this is a double evolution of caffeine or a convergent evolution that they are still investigating.
In turn, to make decaffeinated coffee, we start with the varieties of arabica coffee that usually have lower caffeine content. Within these, coffee cultivated at high altitudes is preferred. Although research continues in the laboratory when strains or varieties of coffee with lower caffeine content appear, as a consequence of genetic crosses and mutations, since the objective would be to obtain a coffee plant that produces coffee with a lot of flavor and body with little caffeine.
Until research allows reaching this variety of caffeine-free coffee, what is done is to remove the caffeine contained in the bean, using humid or chemical methods or through the application of pressure. The decaffeination process is carried out on green coffee beans in industrial facilities.
There are four methods of decaffeination, depending on the substance used to extract the caffeine: water, ethyl acetate, supercritical or liquid CO2, and methylene chloride.
These four methods of processing have the same basic stages:
Swelling the green coffee bean with water or steam so that the caffeine can be extracted.
Extracting the caffeine from the bean
Steaming off all solvent residues (when applicable) or regenerating the adsorbents (when applicable)
Dry the decaffeinated coffee bean until it recovers its normal moisture content.
Under carefully controlled process conditions of temperature, pressure, and time, the caffeine extraction step is based on a physical phase of transport mechanisms. Due to the difference in concentration, the caffeine spreads out of the cell structure and enters the solvent surrounding the bean until the caffeine concentration is the same inside and outside the bean.
What differentiates the four methods is the choice of the substance used for extraction:
This method consists of wetting the coffee beans which are then mixed with water and coffee extract without caffeine, allowing a process of osmosis to transfer the caffeine from the beans to the liquid in which it is dissolved. The beans are then dried in an air current and are ready to be packaged or roasted. This water method is carried out with green coffee, which is immersed in water and the caffeine content is dissolved and removed, but along with this much of the aromatic character of the coffee can be lost. To overcome this drawback, the liquid is saturated with the water-soluble components of the coffee; the caffeine is then removed from the solution using activated carbon or other caffeine-preserving adsorbents, and the caffeine-depleted extract can then be recycled.
The green coffee beans are moistened and soaked in a chemical solvent whose active ingredient is methylene chloride, a substance that dissolves the caffeine. Once dissolved, the chloride is evaporated using heat and the beans are washed with water to eliminate any residue. The coffee is then dried with hot air.
This is the most common method since it is the cheapest method for the coffee industry, although the most demanding consumers prefer decaffeinated coffee obtained by the other methods.
In the case of this method methylene chloride (i.e., methylene dichloride-DCM) selectively extracts the caffeine and has a low boiling point. To extract the caffeine, methylene dichloride is circulated in the water-soaked beans in the extraction vessel. The mixture of methylene chloride and caffeine is then emptied from the extraction vessel. This is repeated several times until the residual caffeine content is at the maximum regulatory level of 0.1% or less. This process ensures that possible solvent residues are kept below the limits set by European legislation.
Physical pressure method
By this method, the caffeine is removed by a system combining pressure with CO2 intervention. To eliminate the caffeine, the coffee is subjected to a pressure of 275 atmospheres, causing the CO2 to circulate between the beans, penetrating them as a consequence of the pressure and contributing to dissolving the caffeine.
When the beans are washed and dried, the caffeine is no longer present and no chemical products have been used on the beans, which is why this method is very good for obtaining quality decaffeinated coffee. The problem is the cost of this method, which makes the industry reserve it for the most expensive or highest quality coffees.
This method of supercritical carbon dioxide and liquid carbon dioxide makes CO2 a substance of great natural purity that is found in the air we breathe and in the bubbling water we drink. Under certain conditions a selective extraction of caffeine can be made with this substance, leaving most of the other constituents of the coffee bean unaltered.
To use carbon dioxide in its supercritical state (between its liquid and gaseous state), very high pressure of up to 250 atmospheres is required. This method requires large-scale production to be economically viable. Liquid CO2 can also be used for caffeine extraction at lower pressure and temperatures, requiring more time to achieve extraction.
Ethyl acetate occurs in several natural products and contributes to the characteristic aroma of many fruits. Ethyl acetate is also found, in different concentrations, in food products including green and roasted coffee. In the decaffeination process, a combination of water and ethyl acetate is used. To extract the caffeine, the ethyl acetate is circulated in the extraction container around the beans soaked in water; afterward, the mixture of ethyl acetate and caffeine is emptied from the extraction container. The extraction step is repeated several times until the residual caffeine content is at the maximum regulatory level of 0.1% or less.
What is done with the caffeine withdrawn by the coffee industry? Every year, such caffeine is purified and recovered and is destined for the pharmaceutical and food industries to produce additives, medicines, sports supplements, beverages, and other products such as those of the cosmetics industry.
Thus, if you like to drink caffeine-free coffee the next time you prepare one, you should raise your cup and toast to the memory of Friedlieb Ferdinand Runge.