The delicious flavour of your morning coffee has a great deal to do with the type of bean that was removed from the cherry. The beans are processed differently depending on the country, climate and coffee variety, and the processing methods are quite complicated.
Our coffee embarks on a long journey until it finally ends up as your delicious cup of morning coffee. There are several stages of the journey that have a big influence on flavour of the end product. The roasting and grinding are two of the most important factors. But before any of this can happen, the beloved beans have to be removed from the coffee cherry with as many aromatic substances as possible, which is no mean feat.
The real work begins after the harvest
Coffee can only be stored and transported if it contains as little moisture as possible. Coffee cherries are perishable products just like any other fruit. This is why coffee cannot be transported with the fruit. Natural fermentation sets in immediately after harvesting. If processing is delayed for too long, the fruits rot, which has a negative effect on the flavour of the coffee beans. The cherries are therefore processed within a few hours of being harvested. The aim is to reduce the water content of the coffee as much as possible before transport.
To wash or not to wash – that is the question
In the wet method, also called fully washed, a lot of water is used, as the name implies. It is the most labour-intensive and costly preparation method, and is therefore mainly used for high-quality coffees such as those from Colombia. Almost all Arabica coffee is processed using the wet process, as the fermentation helps the flavours to develop. But more about that later. For hand-picked coffees, the cherries are usually pre-sorted, as only ripe fruits are picked. Alternatively, the cherries are funnelled through immersion channels, where the overripe or damaged cherries are separated from the good ones. In these immersion channels, there are also pits in which stones and dirt gather.
The cherries are then sent to the pulper, where the pulp is removed by rollers that have a rough surface. The beans are then sorted once more in immersion channels before being sent to fermentation tanks, where the mucilage that is stuck to them ferments, is removed from the bean and gradually dissolves. Timing is of the essence here. If coffee beans ferment for too long they can overferment and turn into so-called stinkers. Stinkers have an unpleasant odour and can ruin the flavour of an entire roast.
Because our beans like to be clean, they are washed a second time after fermentation and freed from any residue. However, they are not ready for transport and storage until they have been dried. Drying takes place either in the sun or in mechanical dryers. The final step is to peel the dried parchment skin from the beans. Finally, the spotless stones of the fruit are sorted by size and colour – they are now ready for their trip out into the big wide world.
The golden mean: the semi-washed method
The semi-washed and pulped-natural methods represent the golden mean between wet and dry preparation. In both of these methods, the cherries run through the first phases up to and including the pulper. After this has removed most of the pulp, the remaining pulp is removed with a jet of water in the semi-washed method. The beans are then laid out in the sun for drying or placed in a mechanical dryer.
With the pulped-natural method, the beans are laid out for drying directly after the pulp has been removed. The coffee beans still have some residual pulp at this time. This dries together with the beans and turns into sugar. For this reason, coffee produced using this method is quite sweet.
A dry matter
In areas of low precipitation and in the event of large harvest volumes, dry preparation is the preferred choice. On larger plantations, as can be found in Brazil for instance, the harvest is either carried out with machines or by stripping. The harvest is roughly sorted and stones and twigs are removed. Subsequently, the cherries are laid out before being dried in the sun, either on the floor or on wooden racks. Mechanical drying is also possible with this method, as is a combination of both drying methods.
The coffee cherries need to be turned regularly so that they do not spoil and to avoid the formation of mould. This process takes one to two weeks in most cases. The coffee beans are then de-husked: a roller removes the dried pulp, mucilage and parchment skin. The beans are then sorted by size and colour just like the washed beans.
The drying process needs to be monitored closely. If the coffee dries too quickly, or if the beans contain too much moisture, this can have a negative effect on the chemical processes when roasting. The soil also plays an important role: not every soil is equally well suited. If it absorbs too much heat, the cherries dry out too quickly and unevenly. Some soils can even release toxins into the beans. Concrete and sandstone are most suitable.
So the next time you hear about a “washed Colombian” or a “dried Brazilian”, this has nothing to do with people who are particular hygienic or have a dry sense of humour, but once again has everything to do with our beloved coffee.