Caffeine removal processes in creating decaffeinated coffee
April 13, 2023
Caffeine is a naturally occurring compound found in coffee plants. It serves as a natural pesticide by releasing bitter odours that not only warn insects away, but also effectively paralyses and kills insects that feast on the plant.
While mostly beneficial to humans, it is unfortunately not the case for people who are allergic to caffeine, for whom the act of consuming caffeine may be a life-threatening endeavour.
Thankfully, for this group of people who love coffee and yet have somehow grown to become sensitive or allergic to caffeine, human ingenuity prevails once again – through certain processing methods, one is able to extract caffeine from coffee.
The process of decaffeination was commercialised by Ludwig Roselius along with his colleagues in the 1900s, who discovered his findings when a shipment of green coffee beans was inadvertently immersed in seawater during shipping, and was later found to have most of its caffeine content removed in the process.
While his initial method of steaming with various compounds before using benzene as the solvent to remove caffeine has now been rendered obsolete for health concerns, multiple variations of the method have come about to take its place today.
Types of Decaffeination
There are five methods of decaffeination in the market today, namely: the Direct Solvent method, Indirect Solvent method, Swiss Water method, Supercritical CO2 method, and Direct Contact method.
These methods aim to process a green coffee bean to remove 97% of the existing caffeine in the green coffee, or to be 99.9% caffeine-free by mass.
Direct Organic Solvent
Green coffee beans are steamed to open its pores before being rinsed with dichloromethane or ethyl acetate (derived from sugar canes), extracting the caffeine. This process repeats anywhere from 8-12 times until sufficient caffeine has been extracted.
Indirect Organic Solvent
This involves placing green coffee beans in hot water for several hours to extract the caffeine, before treating the hot water with the same organic solvents as in the previous method.
This hot water is then reused to process new batches of green coffee – in subsequent batches, the water begins to take on a similar composition to green coffee, sans caffeine. At this point, it would mainly be caffeine that will be removed from the green coffees during the process, and no longer any of the other compounds found in the green coffee bean.
A similar process with the exception of the usage of organic solvent, this method involves soaking green coffee in a Green Coffee Extract (GFE) that contains a chemical composition alike to green coffee beans without the caffeine, resulting in a chemical transfer of caffeine molecules from the green coffee beans to the GFE until equilibrium, before filtering the extract with a charcoal activated filter to remove the caffeine. This process repeats for 8-10 hours until the target caffeine level is achieved.
As its name suggests, after an initial preparation of soaking green coffee beans in a hot coffee solution, this method contacts the green coffee beans directly with coffee oils extracted from used coffee grounds.
Triglycerides in the coffee oils remove the caffeine from the surface of the green coffee beans. Subsequently, the coffee oils has its caffeine removed before being reused to once again extract caffeine from a new batch of green coffee beans.
An advanced technological process that involves carbon dioxide being used in its supercritical fluid form (with a combination of liquid and gas properties) at 65°C and 300 atmospheric pressure (atm), it is mixed with water passed through an extraction vessel containing green coffee beans. Caffeine dissolves into the CO2, but the other flavour compounds, which are insoluble in CO2, remains in the green coffee bean.
Like other processes, the resultant CO2 and water mixture will have its caffeine removed before being used to extract caffeine from the next batch of green coffees.
The process of decaffeination does not come without a cost. In many of the methods described above, the process of contact with various solutions and compounds usually comes with a non-perfect equilibrium between the solutions and the compounds found in green coffee, taking away some of the aroma and flavour compounds in the process.
As such, many perceive the Supercritical CO2 process to produce the best quality decaffeinated coffee, as it does not affect the flavour compounds in the green coffee bean. However, this process requires complicated equipment and extremely high quality carbon dioxide gas, often making it the most expensive process of the options available.
Unfortunately, Not Caffeine Free
Despite our best efforts to remove caffeine from a coffee bean, the truth is that decaffeinated coffee does not mean a caffeine-free coffee. Decaffeinated coffee usually contains less than 0.1% of caffeine by its mass, at levels where the effects of caffeine are minimal. For comparison, it might take anywhere between 14-20 cups of decaf coffee to provide the caffeine intake from a single cup of regular coffee!
As such, moderation is always key. However, for coffee drinkers who are unable to consume large amounts of caffeine, decaffeinated coffee allows for an equal playing field that is accessible to one and all to enjoy the wonders of the world of coffee.