If you say the words “Decaffeinated Coffee” to many coffee lovers, you are often met with some antagonism or even flat-out disgust. Some coffee connoisseurs even consider that decaffeinated coffee goes against the natural order of things, as caffeine occurs naturally in coffee, writes Coffee Confidential, one of our favourite publications about coffee. There are, however, a lot of people who love to enjoy coffee, but prefer not to have the stimulating effect of caffeine.
For those people (estimated to about 10% of coffee drinkers), there is decaffeinated coffee. Decaffeinated coffee is not necessarily 100% caffeine free, but the USDA requires coffee to be only 97% free of caffeine to be classified as caffeine free. This means that you would still get about 3% of the caffeine that you are trying to avoid in your favourite serving of decaffeinated coffee.
What all decaffeination processes have in common
There are four main ways to decaffeinate coffee, and they vary greatly in the way the process is done, but all decaffeination processes have some things in common:
- Water is used in all decaffeination processes.
- Coffee is always decaffeinated in its green (or unroasted) state.
- All decaffeination processes use a decaffeining agent.
Four main methods to produce decaffeinated coffee
The first commercially successful process, called the Roselius process, was invented by a German coffee merchant. Ludwig Roselius developed the process in 1903. He was motivated that his father died of caffeine poisoning by drinking excessive amounts of coffee. This process is no longer used today, due to the fact that benzene is now known to be a human carcinogen. Benzene was used to extract caffeine in this process.
- Indirect-Solvent Process
- Direct-Solvent Process
- Swiss Water Process
- Carbon Dioxide Process
In solvent-based methods, a solvent such as methylene chloride is used. The solvent can be used directly (the beans are soaked in the solvent) or indirectly (the caffeine-laden water is transferred to a separate tank and then treated).
The two main solvents used to decaffeinate coffee are methylene chloride and ethyl acetate. There are other solvents, but they are not approved any more due to health risks associated with them. Coffee Confidential has a very complete explanation of these solvents, and various other aspects we will only touch upon.
The Indirect-Solvent Based Process
This process is very popular in Europe, and uses methylene chloride. It is also sometimes known as “The European Method”, “Euro Prep” or “Methylene Chloride Method”, among others.
- The beans are soaked in near boiling water for several hours, which extracts the caffeine as well as other flavour elements and oils from the beans.
- The water is transferred to a separate tank where the beans are washed with the solvent, which selectively bonds with the caffeine.
- The mixture is then heated to evaporate the solvent and caffeine.
- The beans are added to the liquid again to reabsorb most of the flavour elements and coffee oils.
The Direct-Solvent Process
This process is also known as “The Natural Decaffeination Method” or “Ethyl Acetate method”.
- The beans are steamed for about 30 minutes to open their pores.
- They are then repeatedly rinsed with the solvent.
- After about 10 hours, the caffeine-laden solvent is then drained away.
- Once drained, the beans are steamed again to remove any residual solvent.
The Swiss Water Process
This method is also referred to as the SWP Method, Activated Charcoal Decaffeination or Dihydro-oxide Process, among others. it is a chemical free process pioneered in 1933 in Switzerland and became commercially viable in 1980. It is almost exclusively used to decaffeinate organic coffee.
- It relies on solubility and osmosis to decaffeinate the beans.
- The beans are soaked in very hot water to dissolve the caffeine.
- Next, the water is then drawn off and passed through an activated charcoal filter.
- This filter captures the larger caffeine molecules, while allowing the smaller oil and flavour molecules to pass through.
- This results in the beans being totally flavourless and caffeine free
- These beans are then discarded, but the water is reused to remove the caffeine from a fresh batch of beans.
- The water is saturated with flavourants, so the flavours in the fresh batch cannot dissolve. This means that the caffeine is removed without a massive flavour loss.
The CO2 Process
The CO2 Process is the most modern method. A scientist of the Max Plan Institute, named Kurt Zosel developed it. It is also known as the Liquid Carbon Dioxide Method and the Supercritical Carbon Dioxide Method. It uses liquid CO2 in place of chemical solvents that acts only on the caffeine and nothing else.
- The beans are placed in a stainless steel container called the extraction vession.
- The vessel is then sealed and liquid CO2 is forced into the coffee at very high pressue.
- The CO2 acts as the solvent to dissolve the caffeine, and thus leaving the flavour molecules behind.
- The caffeine-laden CO2 is then transferred to the absorption chamber where the pressure is released. This returns the CO2 to its gaseous state.
- This process is expensive, and used primarily to decaffeinate large quantities of commercial grade, less-exotic coffees.
It is unfortunately very difficult to make a good cup of decaffeinated coffee, because a lot of the flavour compounds that give coffee its taste are damaged. The decaffeinated beans also roast unevenly. Therefore, if you want the best cup of coffee, it is recommended that you keep the caffeine in, providing you do not have a caffeine sensitivity.