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Coffee break

Why did they decide to remove the caffeine from the coffee, and how do they do it? Or: Who took the caffeine out of my coffee?

Coffee Beans. Illustration: shutterstock
Coffee Beans. Illustration: shutterstock

Article: Naomi Ziv, young Galileo

The father of Ludwig Roselius, a German coffee merchant from the 19th century and founder of the Hague Coffee Company, loved coffee so much - that his son was convinced that he had died of caffeine poisoning. Therefore Roselius decided to find a way to remove the caffeine from the beloved drink. In 1905, he published with his colleague Karl Weimer the first method, out of three that are accepted today, for removing caffeine (decaffeination) from coffee beans.
In all methods, in the first step the green coffee beans are soaked in hot water or exposed to steam. When they absorb water, the pores on the surface of the pods open, and it is easier for the caffeine molecules to get out of them. At the end of the decaffeination process, when decaffeinated beans are obtained, they are roasted and ground.

1: The direct method
Wimer and Rosalius discovered that there are solvents that adsorb only the caffeine molecules in the beans, without harming the other components and without affecting the taste of the coffee. The use of a solvent is called the "direct method", and in it - after an initial soaking in water, the beans are soaked or washed in a solvent (this depletes the caffeine from them), steam them to remove the remaining solvent and dry them.

2: The Swiss water method
In the thirties of the last century, the "Swiss water process" was developed in Switzerland, which is used by most coffee companies today. In this process, the beans are soaked in hot water to extract the water-soluble molecules, and a liquid containing these molecules is obtained. The emptied beans are thrown away, and the extract is passed through activated charcoal filters to separate the caffeine from the other ingredients. So soak in the hot, caffeine-free liquid - new green beans. Since the composition of the soluble substances in the beans and in the liquid is the same, except for the caffeine that is in the beans and not in the liquid, a diffusion process will begin: caffeine will flow from the beans into the solution, until an equilibrium is reached in the concentration of caffeine in the beans and in the solution. The solution, which now also contains caffeine, is passed through charcoal filters to remove the caffeine from it. Repeat the process several times until there is almost no caffeine left in the beans. At the end of the process, the beans with the lowest caffeine content are dried and roasted. Filter the remaining caffeine from the liquid and soak new beans in it. The beans are placed in vertical containers, and the extract is poured from above and passes through a "tower" of beans, to reduce the contact time between the beans and the liquid, while the caffeine is still efficiently extracted.

3: supercritical carbon dioxide
In the XNUMXs, the German chemist Kurt Tzosel developed a method that uses supercritical carbon dioxide. At atmospheric pressure and room temperature, every substance is in its characteristic state of aggregation: solid, liquid or gas. It is possible to switch between the states of aggregation by changing the temperature or the pressure that the material is subjected to. We usually know carbon dioxide as a gas, and also as a solid known as "dry ice". But if you keep gaseous carbon dioxide under very high pressure, it goes into a special state of aggregation - supercritical carbon dioxide. If the coffee beans are soaked in supercritical carbon dioxide, the caffeine diffuses out of the beans and dissolves in the carbon dioxide. When the high pressure is released from the container, the carbon dioxide returns to a gaseous state and the beans evaporate, leaving them decaffeinated.

All three methods are successful, but each gives coffee with different flavors. However, removing the caffeine from the beans shortens their shelf life. Yes, it is difficult to remove only the caffeine from the beans, and other molecules will be absorbed with it, and therefore the taste and aroma of decaffeinated coffee is different from coffee containing caffeine.

Grows without caffeine
The two varieties of coffee used to produce the drink are Arabica and Robusta. In 2004, caffeine-free arabica plants were discovered in Brazil, and in 2008, a new variety of coffee that does not contain caffeine was discovered in Cameroon. Despite the intriguing discoveries, these discoveries did not lead to further developments. It is possible that the coffee produced by them is not of sufficient quality.

And why not develop coffee plants in the laboratory that do not contain caffeine? Such a plant was first developed by researcher John Stiles from the University of Hawaii in 1998. Stiles and his team identified the gene that codes for the creation of the enzyme that begins the stages of caffeine production in the plant, and succeeded in silencing it, and thus the plant produced only three percent of the normal amount of caffeine; In 2004, a Japanese team developed a coffee plant that contained seventy percent less caffeine. So far no follow-up data has been published for these projects. Although the solution of a caffeine-free plant sounds successful, it is possible that the public is afraid of genetically engineered plants, and it is also possible that the industry prefers to continue using up caffeine in the accepted ways. But who knows, maybe this vision will come true.

Did you know?
In order for coffee to be called "decaffeinated" it must meet strict standards: according to the European standard, 99.9 percent of the caffeine is eliminated, and according to the international standard (accepted in the countries of the Commonwealth), it is enough that 97 percent of it is eliminated.

> The writer is the owner of the blog Science on a plate

* The article was published in the December 2014 issue of Young Galileo

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