FROM THE CHERRY TO THE GREEN COFFEE
There are three methods used to transform the coffee cherries into beans and these have a direct impact on the cost and quality of a coffee. The methods involve removing the waste from the crop and removing the layers of the cherry to reveal the bean. This is how the green coffee is obtained, which is the generic term given to coffee after it is processed and before it is roasted. The wet method favoured by Nespresso, which requires more investment and care, results in coffee with a more complex aromatic profile.
The wet method
The wet method intensifies the aromatic flavours of the coffee, and reduces its bitterness. Coffees processed using the wet method are described as ‘washed’. They are almost always hand-picked Arabicas, and washed Arabicas are also referred to by the name ‘Milds’.
• The beans are submerged in a water bath for 16 to 36 hours until they have expanded and softened.
• A machine separates the bean from the pulp using friction.
• The beans are placed into concrete water tanks to ferment for up to 36 hours. The fermentation process breaks down any viscous substances remaining on the beans after depulping.
• The coffee beans are forced against a water current to free them from any remaining pulp or impurities. The ripest beans are the heaviest beans. They sink to the bottom of the water tanks where they can be collected easily by the sorters.
• At this stage the coffee is known as "parchment coffee". It is dried in the sun for up to three weeks either on huge racks on rails that can be closed quickly in case of rain or spread over large tables made of fine-mesh wire netting.
• The remaining outer layers of the bean are then removed by the hulling process. We are left with green coffee that is now ready to be put into sacks and exported.
The dry method
Coffees processed with the dry method are referred to as "unwashed" or "Natural" coffees. Dry processing is a much quicker, easier and less expensive method than wet processing. The dry method consists of drying the cherries on large surfaces in the fresh air for three weeks to a month.
• With this method the pulp isn't removed before drying. The coffee cherries left to dry are regularly turned over using a rake to prevent their fermentation. This technique leads to a loss of aromas and the migration of sugary substances from the pulp into the bean. The result in the cup is milder and less aromatic than the wet method.
• The dry cherries are then hulled: the outer layers of the coffee beans are removed.
• The beans are then sorted by size, shape and density. Beans that are deemed to be defective can be removed either manually or mechanically. In addition to screens and strainers, the human hand is still the most accurate method of sorting.
The semi-dry method
A hybrid of the wet and dry methods, if performed correctly, maintains the balance between the coffee’s body and acidity.
• The ripe cherries are separated from the unripe cherries by using a small amount of water.
• The pulp is then removed mechanically.
• Lastly, the coffee beans, still covered with mucilage are dried in "raised beds" to avoid being contaminated by the ground.
View the film about the processing of coffee cherries on the Nespresso Experts website.