Coffee beans have caffeine naturally in them. How is the caffeine removed from them to create decaffeinated coffee?
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Hot water and co2 goes into the coffee, caffeine leaks out.
Hot water is used to remove caffeine from one batch of the coffee bean, it’s filtered through charcoal filters, they then take another batch of the coffee and soak it in that filtered bean juice, it keeps the flavour in the coffee but the caffeine moves out of the beans and into the water.
There’s a few more ways but these are the two main ones used.
You can’t for the same reason you can’t toast your toast.
But seriously, it’s called the Swiss Water method, if you want to look for the details
This may not answer your question buy decaf was originally discovered by the Sanka brothers.
A ship of theirs carrying coffee beans to the US sank in sea water. They recovered the beans from the hold on that ship and processed them. After trying the coffee made from them, they found that the coffee was almost caffeine free. So, they marketed that load as caffeine free coffee.
So it would seem that sea water was able to draw out the caffeine.
Source: A placard on my table at a Dennys when I was a kid.
Addendum: I looked up how they do it in modern times. This was the most common answer:
The most-common methods of decaffeination involve chemical solvents, usually ethyl acetate or methylene chloride.
In the direct method, the coffee beans are steamed and then rinsed
repeatedly with the chemical solvent to flush away the caffeine.
Green beans are steamed to open pores. Then the beans are soaked in a solvent. The solvent can be Ethyl Acetate, Methyl Chloride, supercritical CO2 or water. This solvent is pre-loaded with all disolvable coffee components, the caffeine migrates from the bean to the solvent. Then the caffeine is removed from the solvent and the solvent is reused to remove more caffeine from beans. The caffeine gets removed from the solvent by phase change (solvent evaporates and caffeine crystalizes), or is being absorbed in activated carbon.
They put a supercritital fluid (hot high pressure co2 that is too hot to be a liquid but under too much pressure to be a gas), which selectively dissolves the caffiene with the help of a little water and leaves the odor compounds and flavenoids behind in the bean. Mostly (some change still happens to the taste, it’s not perfectly selecting the caffeine only)
Pretty cool.
https://www.futurelearn.com/info/courses/everyday-chemistry/0/steps/22338
https://www.scientificamerican.com/article/how-is-caffeine-removed-t/
“There are three main decaffeination processes currently in use. They have some basic similarities. In all three approaches, the green or roasted beans are first moistened, making the caffeine soluble so that it can be drawn out. Also, they all decaffeinate green coffee at moderate temperatures, typically ranging from 70 to 100 degrees Celsius (160 to 210 degrees Fahrenheit).
“One method is water processing. As you might expect, this process employs water as the solvent to remove caffeine from the green coffee beans. Typically a battery extraction process using eight to 12 vessels is employed; each vessel contains green coffee at a different stage of decaffeination.
“A mixture of water and green-coffee extract that has already been reduced in caffeine is circulated around the coffee beans within the extraction battery (oils in the coffee extract aid in the decaffeination process). After a predetermined time, the vessel that has been exposed to the low-caffeine extract is isolated and emptied. The decaffeinated coffee beans are then rinsed and dried, and a vessel containing fresh green coffee is put on stream. The caffeine-rich extract that was drawn off from the vessel containing the fresh, green coffee is passed through a bed of activated charcoal, which absorbs the caffeine. This charcoal has been pretreated with a carbohydrate, typically sucrose, that helps it absorb caffeine without removing other compounds that contribute to the flavor of the coffee. The sucrose blocks carbon sites that would normally absorb sugars from the liquid, green-coffee extract. The caffeine-reduced extract can then be reused to begin the process anew. The water process is natural (that is, it does not involve any chemicals), but it is not very specific for caffeine; it removes 94 to 96 percent of the caffeine.
“A second decaffeination method is the direct solvent method. These days this technique usually employs methylene chloride (used predominately in Europe), coffee oil or ethyl acetate to dissolve the caffeine and extract it from the coffee. Ethyl acetate is an ester that is found naturally in fruits and vegetables such as bananas, apples and coffee. The liquid solvent is circulated through a bed of moist, green coffee beans, removing some of the caffeine; the solvent is then recaptured in an evaporator, and the beans are washed with water. Residues of the solvent are removed from the coffee to trace levels by steaming the beans. Often this process utilizes batch processing–that is, solvent is added to the vessel, circulated and emptied several times until the coffee has been decaffeinated to the desired level. Solvents are used because they are generally more precisely targeted to caffeine than is charcoal, leaving behind nearly all the noncaffeine solids. The more caffeine-specific solvents, such as methylene chlorides, can extract 96 to 97 percent of the caffeine.
“The third approach, supercritical carbon dioxide decaffeination, is very similar to the direct solvent methods, except that in this case the solvent is carbon dioxide. High-pressure vessels (operating at roughly 250 to 300 times atmospheric pressure) are employed to circulate the carbon dioxide through a bed of premoistened, green coffee beans. At such pressures, carbon dioxide takes on unique, ‘supercritical’ properties that enhance its usefulness as a solvent. Supercritical carbon dioxide has a density like that of a liquid, but its viscosity and diffusivity are similar to those of a gas. These attributes significantly lower its pumping costs. Carbon dioxide is a popular solvent because it has a relatively low pressure critical point, and it is naturally abundant. The caffeine-rich carbon dioxide exiting the extraction vessel is either channeled through a bed of activated charcoal or through a water ‘bath’ tower to absorb the caffeine. The carbon dioxide is then recirculated back to the extraction vessel. Supercritical carbon dioxide decaffeination is capital-cost intensive, but it offers very good yields. It typically can extract 96 to 98 percent of the caffeine originally present in the beans.”
They wash the caffeine out with a solvent that won’t get rid of the coffee’s flavor. They’ve done this with pressurized carbon dioxide, methylene chloride, and water that’s already saturated with coffee flavor.
The chemical method is not used as commonly anymore most places use the swiss water method.
You take a bunch of green beans and soak them in hot water so they release all of their flavour and caffeine.
You then pass that water through a filter that catches the caffeine but doesn’t catch the flavour.
You then throw the beans away and put more beans in the same water. The water is saturated with flavour molecules so the beans retain their flavour but the caffeine is pulled out.
Think of it like this:
You have a bunch of M&Ms. You want to eat all the M&Ms, but you only want to eat the chocolate part, not the candy shell. So, you take a bunch of M&Ms and put them in a bowl, and then you pour hot water over them. The hot water melts the candy shell, but not the chocolate part. So, you pour off the water (with the candy shell in it) and you’re left with just the chocolate.
Caffeine is like the candy shell – it’s a coating on the coffee bean. When you remove the caffeine, you’re just left with the coffee bean.
Another good analogy is to think of it like peeling an apple. The skin is the caffeine and the apple is the coffee bean. When you peel the apple, you’re just left with the apple.
Now, to get into more detail, sometimes a solvents is used to remove the caffeine. But, more often, the coffee beans are soaked in water. The caffeine dissolves in the water, but the coffee beans don’t. So, the water with the caffeine in it is drained off, and you’re left with just the coffee beans.
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