Green Coffee Processes

What is a green coffee "process" anyway?

Coffee beans are the seeds of the cherries of the coffee tree. Normally there are two beans inside each cherry whose flat sides are face to face. When a ripe cherry is picked and the beans are removed, the beans are covered with a sticky mucilage. They need to be cleaned and dried (not necessarily in that order) to make them ready for roasting.

KEY POINT

The green coffee process refers to the method used for getting from a coffee cherry on the tree to a clean dry bean ready for roasting.

There are a number of ways of doing this, and the farmers choose their preferred method based firstly on their local climate and environmental conditions. The process also has an impact on the aromatic and flavour characteristics that will come through in the cup, so this is also a factor that farmers may take into account when choosing what process to use. A farmer might decide to use more than one process to be able to offer different coffee profiles to their buyers.

There are two main processes used: Washed and Natural, sometimes also referred to as Wet (Washed) and Dry (Natural). These days we now see a range of other process names appearing on coffee packaging too, such as Semi-washed, Honey (Red, Yellow or Black), Pulpled Natural or Anaerobic. It can be confusing but these are essentially just variants of the washed and natural methods: a hybrid between the two, or a more elaborate process with additional step or technique added, such as fermentation under specific conditions.

Coffee cherries on the tree
Ripe coffee cherries
Green beans from inside the cherry, covered with a sticky, shiny "mucilage"
Dried green coffee beans, ready for roasting

Washed Coffees

The cherries are first de-pulped, a rough mechanical process which lightly crushes them, squeezing out the beans and thereby separating them from the fruit pulp. At this stage the beans still have their sticky mucilage coating.

The beans with their mucilage are then put in a tank, with or without water, for anything from a few hours to a couple of days. Here they are lightly fermented, which softens the mucilage and makes it easier to wash off. They are then washed by rinsing them in water until there is no more mucilage and they are completely clean.

Finally the clean beans are laid out on drying beds until their moisture content drops to the right level, generally about 10% – 12% humidity. This might take 4 to 10 days.

Washed coffee processing - a 6 minute video by Café Imports

KEY POINT

With a “washed” process, the beans are removed from the fruit and washed before going through the long drying stage

Where is this method used?

This method requires certain climatic and environmental conditions such as an abundant water supply, good sun exposure during the day and low humidity. Countries in which it is common include Ethiopia, Kenya, Rwanda, El Salvador, Columbia and Panama

How does it affect the coffee in the cup?

KEY POINT

Compared to a naturally processed coffee (see below), washed coffees have a more refined profile – cleaner, purer notes, perhaps with less body and sweetness but with a brighter, more well-defined acidity

Natural Coffees

The first step of the natural process is to lay the cherries, freshly picked of the tree, out on beds to dry. This process takes a long time, between 10 and 30 days – longer than the drying process for wash coffees because it is the whole fruit being dried, not just the bean. 

After drying, the cherries are run through a hulling machine which mechanically removes the outer layers such as the fruit pulp and mucilage, to leave the green bean.

Sometimes the hulling might be done before the drying process is complete, for example when the moisture content has dropped from around 70% to 15% – 30%. In this case, there will then be a final drying stage for the beans that are now removed from the fruit.

Natural processing - a 5 minute video by Café Imports

KEY POINT

With a natural process, the beans are still in the fruit when they go through the long drying stage.

Where is this method used?

This is the oldest method that exists and can be used anywhere, but particularly in climates which are dry, warm and sunny, without much humidity or cloud cover. It is used in Brazil (where it was developed), Ethiopie, Panama and Costa Rica, among other countries.

How does it affect the coffee in the cup?

KEY POINT

The contact of the bean with the fruit throughout the drying process leads to more powerful fruit flavours, more like preserved fruits than fresh fruits, and a creamy body. Compared to washed coffees, naturals can be richer and even “winey”, but have lighter acidity and less “clean” or refined aroma profiles.

Other Processes

Honey, or Pulped Natural

These are two names for essentially the same thing. It is a hybrid process, between washed and natural.

The cherries are firstly de-pulped – squeezing the beans out of the cherry – as they are in the washed process, but then the step to remove the mucilage prior to drying is reduced or skipped altogether. With the mucilage left on, the beans are sticky, like honey. They are dried in that state, and only when they are dry is the mucilage removed through mechanical hulling.

Sometimes not all the mucilage is left on, and this gives rise to the different honey variants, according to the percentage of mucilage that is left on the bean during drying:

  • Yellow: 25-50%
  • Red: 50 – 95%
  • Black: 95 – 100%

 

In terms of taste characteristics, the yellow are the most similar to washed coffees (milder, cleaner, more acidity), the red are sweeter (bigger fruit aromas with a more syrupy body), and the black are the most similar to a natural (jammy, full fruit aromas and creamy body)

KEY POINT

In the honey process, the beans have been removed from the fruit but still have some or all of the sticky mucilage layer on when they go through the long drying stage. 

Because of this, honey coffees tend to have similar tasting characteristics to natural coffees but  are sweeter and cleaner.

Semi-washed

The semi-washed process is not very common, used mainly in Indonesia.

To explain this process we need to understand that, underneath the mucilage, there is another very thin layer around the bean called the parchment. In other processes, this is normally removed right at the end, after the beans are fully dried and just before they are bagged.

The semi-washed process starts off like the washed process, with the beans put out to dry after the pulp and mucilage is removed. Here, though,the drying is only partially completed before the beans are taken off and put through a hulling process to remove the parchment as well. They are then put out to dry again, and without the parchment they dry much more quickly.

This is done because the high humidity in Indonesia makes normal drying difficult. It gives rise to coffee with lots of body but low acidity.

Anaerobic

Fermentation is present in all coffee processes, whether it is in tanks before drying for a washed process (mainly to help remove the mucilage), or while the full coffee cherries are out on the drying beds for a natural process.

An anaerobic process is one that includes a specific fermentation stage, before the beans are removed from the cherries and before they are put out to dry. he contact with air is limited by putting the cherries in closed container or bags. Sometimes the process goes one step further, eliminating all contact with air by replacing it with CO2. The absence of air means that the fermentation can be more closely controlled, since air itself contains bacteria and other compounds that affect fermentation.

Anaerobic coffees can have the intensity and big fruitiness of naturals but with more complex aromatic attributes, depending on the exact fermentation process used.