There are many myths about decaffeinated coffee: unhealthy, tasteless, full of chemicals. This is all outdated news. In this post, I will analyze the different methods of decaffeinating coffee. I hope this will help you get a fairer impression of the impact of decaffeinated coffee on health, coffee taste and the environment.
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The decaffeination process always uses green (unroasted) coffee beans
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The biggest challenge is to separate the caffeine from the coffee beans while leaving the other chemicals at their original concentration
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Since caffeine is a water-soluble substance, water is used in all decaffeination methods
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All decaffeination processes use some form of decaffeination agent (methylene chloride, activated carbon, CO2, ethyl acetate). Additional measures help speed up the decaffeination process and reduce levels of "leaching" (each green coffee bean contains about 1,000 natural chemicals that create what we identify as texture, flavor, aroma, and vitality).
The first commercially successful decaffeination process was invented (1903) and patented (1906) by the German coffee merchant Ludwig Roselius. Once he received a shipment of green coffee soaked in sea water. The story is silent on the details, but one thing is clear: he accidentally discovered that this shipment of coffee wasn't spoiled, it just had a lot less caffeine than usual. Ludwig then went into research and invented what we now call the "Roselius Process". This process involved steaming the coffee beans with brine (ie water saturated with salt) as a solvent to extract the caffeine using the organic chemical compound benzene.
Today, this process is no longer used because benzene is recognized as a carcinogenic substance. However, it is interesting that of the four main methods of decaffeinating coffee used today, two use chemicals (solvents). Let's explore in more detail:
Indirect solvent method
Coffee beans are soaked in near-boiling water for several hours, which helps extract caffeine (as well as other flavorings and oils) from the beans. The water is then separated and transferred to another tank, where the beans are washed with methylene chloride or ethyl acetate for about 10 hours. Chemical solvent molecules selectively bind to caffeine molecules, and the resulting mixture is heated to evaporate the solvent and caffeine. Finally, the beans are poured back into the liquid, where they absorb the un-evaporated coffee oils and flavor elements back into themselves.
Direct solvent method
The beans are steamed for about 30 minutes to open their pores. They are then rinsed with methylene chloride or ethyl acetate for about 10 hours to remove the caffeine. The caffeinated solvent is removed and the beans are re-steamed to evaporate any remaining solvent.
Most often, ethyl acetate is used as a solvent for this method, which is also found in nature (in some fruits). Therefore, despite the fact that all substances used to remove caffeine are synthesized industrially, this method is often called "natural".
Swiss Water Process (SWP)
Also called: SWP method, activated carbon decaffeination, dihydrooxide process.
This chemical-free decaffeination process was invented in 1933. in Switzerland, but commercialized only in 1988. factory near Vancouver, Canada. It differs from the previously discussed methods in that no chemicals are used either directly or indirectly.
First, a batch of beans is soaked in very hot water to dissolve the caffeine. The water is then drained and passed through an activated carbon filter. The porosity of this filter is such that it stops the largest molecules (such as caffeine). All the smaller molecules that give the coffee its taste and thickness pass successfully through it. In one tank we get decaffeinated and flavored beans, and in the other tank we are left with "flavored" decaffeinated water (aka "Green Coffee Extract") that contains all the chemicals needed to create what we identify as coffee. The tasteless decaffeinated beans are discarded, but the flavor-rich water is reused to remove the caffeine from the fresh batch of coffee beans. Since this water is already saturated with flavor ingredients, the flavors of the fresh batch of coffee cannot dissolve in it, so only the caffeine moves from the coffee beans to the water. The result is decaffeination without significant loss of flavor. The process is considered complete when the caffeine level in the coffee beans is no more than 0.1%. It takes 8-10 hours to reach this level.
The SWP method is completely safe for health, retains most of the coffee's flavor characteristics and although there is some loss of coffee, it is considered ecological and sustainable. It is mostly used in the production of single origin and quality decaffeinated coffee.
CO2 process
Also called: carbon dioxide method, liquid carbon dioxide method, supercritical carbon dioxide method.
The carbon dioxide method is the newest of all. In 1967, he developed by Max Planck Institute scientist Kurt Zosel, who used liquefied CO2 instead of chemical solvents. Carbon dioxide gas in liquid form selectively acts on caffeine in coffee beans.
Coffee beans soaked in water are placed in an extraction vessel made of stainless steel. Liquid CO2 is introduced into the coffee at a pressure of ~69 bar. CO2 acts as a solvent that dissolves and extracts the caffeine from the coffee beans, leaving all the flavor components behind. The caffeinated CO2 is transferred to another container called an absorption chamber. Here, the pressure is released, the CO2 returns to its gaseous state, and the caffeine is thus "released". The decaffeinated CO2 gas is pumped back into the pressurized container for reuse.
The CO2 process fully preserves the natural chemical composition of the beans and is completely safe for health. It uses a lot of energy to compress the gas, so it's not the most sustainable, but it's a great option for organic coffee production. Unfortunately, due to its cost, this process is mainly used for larger quantities of coffee, so it is not usually chosen for single-farm coffee decaffeination.
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