Caffeine is found naturally in coffee and is one of more than 400 chemical substances that make it up. Known for its stimulating effect, the number of people eager to enjoy the aroma and taste of a good coffee without undergoing this effect on their bodies increases every day.

The methods for obtaining decaffeinated coffee have evolved over the years. Since its discovery by the chemist Runge in 1820, different systems have been developed to extract the caffeine from the coffee beans in order to keep the rest of the beverage's properties as intact as possible.

The first batch of decaffeinated coffee was marketed by the German company Kaffe HAG, founded by Ludwing Roselius. His decaffeination technique consisted of moistening the green coffee beans, so that they increased their porosity, and then applying a solvent that extracted the caffeine.

From the 19th century to the present day, different decaffeination methods have been developed, the main objective being not only to eliminate the caffeine, but also to obtain decaffeinated coffees with the same sensory characteristics as the coffee before decaffeination.

1. DECAFFEINATION PROCESS BY CHEMICAL SOLVENTS

Following Roselius´ initial technique, this process uses methylene chloride or ethyl acetate as solvents to eliminate this compound from coffee, and they can be applied directly or indirectly.

Direct decaffeination process

The coffee is moistened with water or steam, so that its volume increases and it becomes more porous. After this step, the solvent is applied directly in the extraction vessel at high temperatures between 70 and 100ºC. Subsequently, the solvent together with the caffeine is transferred to another vessel where it is distilled and returned, clean of caffeine, to the extraction vessel to start a new cycle.

Any remaining solvent in the coffee beans is removed by vaporisation and the coffee is ready for drying.

Indirect decaffeination process

In this process, the coffee beans do not come into direct contact with the solvent, but the solvent is applied to an aqueous extract of the green beans containing all the soluble elements of coffee, including caffeine.

The extraction of the caffeine is carried out in a separate container by applying the solvent to the extract.

Once the caffeine has been dissolved, the extract is returned to the green beans which, after cleaning of any remaining solvent by steam, are ready for drying.

2. DECAFFEINATION PROCESS BY CARBON DIOXIDE

In this process, the previously hydrated coffee is subjected to streams of carbon dioxide which, in a physico-chemical state known as supercritical (applying a certain pressure and temperature) presents properties of both liquid and gas, exerting a selective extraction of the caffeine.

The caffeine is then extracted from the carbon dioxide by an effective adsorbent and returned to the initial extraction vessel to begin a new cycle.

Carbon dioxide has a lower extraction capacity than methylene chloride or ethyl acetate, so in order to extract the caffeine down to the 0.1% allowed by the EU, the coffee must undergo a greater number of extraction cycles, making it a more costly process.

3. DECAFFEINATION PROCESS BY WATER

In water extraction of caffeine, the green beans are immersed in a water solution together with a coffee extract supersaturated with the water-soluble components of coffee except caffeine.

Through a process of osmosis, the caffeine passes from the bean to the extract, which in turn passes through carbon filters that remove the caffeine before returning to the extraction vessel, repeating the process until 99% of the caffeine is removed.

In this way, and by controlling the time and temperature, the caffeine is extracted from the bean while preserving the rest of its properties practically intact.

This decaffeination system is the most widely used in the speciality coffee market.

In addition to those mentioned above, other methods have been developed to decaffeinate coffee, although with less impact and which have not achieved the same market presence. Since their discovery and up to the present day, these processes have undergone constant evolution and it is expected that they will continue to do so.

It will be interesting to see where research and the decaffeinated coffee market will take us in the coming years.