Whether you drink decaf for health reasons or just to get a better night's sleep, the decaffeination process will have a major impact on the taste of the beverage you’re consuming. Here's a summary of the main methods used to decaffeinate coffee.
One thing is certain, it is a delicate process. Coffee is very sensitive, and removing the caffeine from it without denaturing it or diminishing its flavour is a huge challenge.
The first commercial decaffeination methods appeared in the early 20th century. The challenge was formidable, as coffee must be denatured without removing its precious aromas. Two types of decaffeination methods exist: natural and chemical. Here's an overview of both!
We use the term ‘natural’ simply to describe methods that don't use chemical solvents. They're also the only ones that can produce certified organic coffee and are also the ones that best preserve the coffee's flavour.
You will hear about SWP the most when discussing methods to decaffeinate coffee. Contrary to the urban legend, this process does not mean rinsing the beans with magical Swiss spring water! Although the method does come from Switzerland. It is one of the most sought-after varieties of decaffeination on the market because: no chemicals are use, and the coffee is 99.9% caffeine-free. Additionally, Swiss Water is a registered trademark, so you can be sure of the quality of the decaf coffee you're drinking when you see its logo. This is what we use for our decaf espresso blend and our decaf filter coffee.
The process:
Soak the green beans in hot water to make them soluble. Both the caffeine and the oils from the beans (which contain most of the flavour) are removed.
This soaking water is then passed through an activated carbon filter, which allows the caffeine to be collected and removed without trapping the oils.
This soaking water now has oils but no caffeine. So, when new beans are soaked in it, they will release their caffeine, but not their oils from the bean! This step uses the same principle of osmosis that we learned in school!
This same soaking water can then be used again and again to decaffeinate batches of beans, one after the other!
One of the advantages of the SWP is the reuse of wastewater and caffeine. Since the water is still saturated with coffee particles, it can be reused; and the caffeine can be used in the pharmaceutical and food industries.
Plus, this method doesn't involve any chemicals and preserves the coffee's flavours much better, however it does take a lot of time (several dozen hours). This is the method that is most often used by micro-roasteries.
It's worth knowing that a similar, however, less common, process also exists: the mountain water method. In this case the soaking water is glacier water, which makes the final product even purer.
The carbon dioxide method is similar to that of chemical solvents. It's also quite expensive if it isn't used for large quantities.
Process
Soak the green beans in tanks of hot water.
Circulate CO2 at high pressure in the tanks. The CO2 bonds to the caffeine, which is removed from the beans in the process.
Filter the beans. The water is then either heated to a high temperature to evaporate the CO2 and preserve the caffeine, or it's passed through an activated carbon filter.
Don't worry! There are strict federal regulations surrounding the decaffeination of coffee. This means that the percentage of chemical solvents remaining on the beans is minimal and poses no risk to your health.
When choosing a chemical process, the indirect method is probably your best option because the beans are never in contact with the chemicals.
Process
Soak the green beans in tanks of very hot water (this removes both the caffeine and the flavourful oils from beans).
Chemical solvent is then added to the soaking water, which is filled with the caffeine and oils. As with the CO2 method, the chemical solvent bonds to the caffeine.
The water is then heated to a high temperature to evaporate the water, along with the caffeine, but retains the oils.
The decaffeinated and tasteless beans are then immersed in new tanks of water, and the oils are then added. Thus, restoring flavour to the beans!
This method is the cheapest and fastest, and therefore, the most popular method amongst decaffeinated coffee companies. The chemical solvent chosen is usually ethyl acetate or methylene chloride.
Process
The beans are steam-treated to be enlarged. The solvent thus has more surface area to decaffeinate the beans.
The coffee is immersed in a tank of water containing the chemical solvent.
The beans are then filtered out and steam treated to remove any remaining water or chemical solvent residue.
Regardless of the method, the coffee is then dried to a normal moisture content at the end of every process. It can then be roasted as per usual!
Careful though, coffee will never be 100% decaffeinated, just like tea or cocoa; legally, the caffeine content of a decaffeinated beverage must be below 0.1%.
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