How is coffee decaffeinated?

What process do green beans have to go through to be classed as decaffeinated coffee and are all “decafs” created equal? Get the downlow on decaf here.

Photo : Caffeine Chemical Structure. Source:

What is decaf?
To chemists caffeine is C8H10N4O2; a methylxanthine, central nervous system stimulant and diuretic.

To the rest of us it’s usually simply a morning necessity, the buzz in the cup that we need to wake up and get going. But there are times in our lives when caffeine isn’t our friend and we need to reach for “decaf” a word often spoken with a mix of dread and derision.

Fortunately for anyone who has decided to cut back on the kick in coffee, decaffeination has come a long way.

Decaffeinated coffee is strictly regulated and the international standard requires that 97% of the caffeine be removed for coffee to be labelled “decaf”.

All decaffeinated coffee is processed at the unroasted or “green” stage and follow strict safety standards.



Ludwig Roselius
Photo : Ludwig Roselius. Source:

Who even came up with decaffeination?
The first person to decaffeinate coffee was German coffee merchant Ludwig Roselius.

In 1903, Ludwig and his team were faced with a shipment of green (unroasted) coffee which had been caught in a storm and soaked in brine.

In an admirable attempt to turn lemons into lemonade, Ludwig decided to use this ruined stock in an experiment to remove the caffeine from his salty cargo. He was successful to a degree, using benzene to bond with the caffeine then boiling the bonded solution away.

Unfortunately the flavour boiled away with it, so while it was definitely decaffeinated, it was not particularly drinkable.

It was discovered later that benzene is a carcinogen, so the Roselius Process was abandoned.



green ebans bag vector

So no more chemicals?

Not quite. Ludwig’s work was not for nothing – safe chemicals have been found that are able to do the same job.

The most common solvents used in chemical decaffeination are methylene chloride and ethyl acetate.

To achieve decaffeination, the unroasted coffee is first steamed until soft, before being rinsed repeatedly with the chemical over a period of around ten hours, then steamed again to remove the solvent, and dried until the beans become hard again.

If the decaf you are purchasing doesn’t have a method named, it’s probably been decaffeinated this way.

Sometimes decaf created using ethyl acetate is labelled as “natural decaf” because ethyl acetate occurs in fruit such as apples.

This is a bit of a misnomer however, as the ethyl acetate is nearly always a synthetic version.

Either way, both methods are considered safe by EU, USA and AUS food safety bodies.

Decaf Roadmap

What about water decaffeination?
In our opinion, this is the best method for decaffeination and the decaffeinated green bean Merlo Coffee buys to roast is processed in this way.

Caffeine is water soluble, but so are the aromatics in coffee, so water decaffeination has to be done very carefully to be both low on buzz and high on flavour.

This process can be repeated without wasting any more green bean once the solution has been created, cycling through the filter process with fresh batches of coffee. The caffeine which has been filtered out is often kept for use in energy drinks or cosmetics.



Further reading:

Fun fact – If you’re ever in Bremen you can tour the Ludwig Roselius Musem which houses a fine collection of arts and crafts from the Gothic, Renaissance and Baroque periods.

Go back to Blog