Decaffeination, a brief history of technique

January 21, 2019

At the end of the nineteenth century the concept of removing the alkaloid component known as caffeine from coffee, began to gather momentum. A German chemist realised that using a solvent would essentially dissolve caffeine to an inert state, losing its impact as a stimulant. It wasn’t however, until an actual coffee merchant in the city of Bremen in North Germany suggested swelling the raw green beans by 100% using water and steam in order to enable penetration of the created solvent. The decaffeinated coffee bean was thus born and sold exclusively in German in the early 1920s by the wonderfully named Kaffee HAG. 

Since this discovery chemical solvents have moved on considerably and one such development is referred to the use of supercritical carbon dioxide. This method sees CO2 heated and pressurised to a degree where it is converted to a fluid state. This fluid form is able to dissolve caffeine but with the added advantage of targeting the caffeine only without any removal of flavour or aroma.

Other non solvent and chemical free methods for creating decaf coffee became available by 1979. SWP, commonly known as the Swiss Water Technique was such a technique. This method uses an extract from the raw green coffee, combines it with the green coffee destined for decaf, then adds temperature and more water to remove traces of caffeine. The solution used for removal is then reused for the next batch. Although this method is considered chemical free, it has the contentious claims that some flavour also gets removed.

Decaf (raw green on left) is usually considered tricky to roast. This can be attributed to a few reasons such as the caffeine (raw green on right) extraction slightly degrading the cellular make up of the bean meaning they are more susceptible to taking on heat during the roast. The processing methods also remove the silverskin (outer bean layer) which is more commonly known as chaff. This layer restricts or protects a bean from taking on excess heat during the roast. The chaff then peals off and is expelled from the skin as the bean expands rapidly to double its green size.

the images below show our roasted seasonal decaf on the left when compared with a roasted caffeinated sample on the right. You can see that for the decaf roast, there is no colouring of the chaff remaining on the inner fold of the bean. This is because the chaff has mostly degraded and  removed due to the water processing required to extract caffeine during processing whilst in its raw state. We like a challenge here at Cotswold Coffee Roasters and this is exactly what we get when roasting our seasonal decaf choices .... and we love it.

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