Coffee processing is the transformation of the coffee cherry into the coffee beans we all know and love. The way in which this is done has a dramatic effect on the flavour of the coffee. Think about grapes vs sultanas. Same fruit, different flavour. There are endless possibilities with processing, but there are three main categories; washed, semi-washed and unwashed.
This week we will focus on unwashed processing. Also known as natural or dry processing. This is the first part in a three part series.
This is the simplest of all methods and is great for areas that have no access to clean water. The basic steps of the unwashed process are; fruit picking, drying, hulling, cleaning and grading.
Once ripe coffee cherries have been picked, they are dried with the fruit intact. This method gives the coffee more time to absorb all the flavours of the fruit. This method can only be done in areas where the weather, specifically humidity, allows the cherries to dry slowly without going mouldy.
When the coffee has reached it's desired dryness, usually 10-12% moisture content, the fruit layer can be removed. This hardened fruit is removed by a 'huller' or 'dry mill'. This is a perforated, spinning cylinder that sits in a housing. The gap between the spinning cylinder and its housing is adjustable, which enables the processor to choose the right gap for the right bean size and density. The parchment coffee is fed in between the spinning cylinder and its housing, which separates the fruit from the bean. The coffee might have to be passed through this machine multiple times to get a good result without damage.
The coffee beans are then cleaned and sorted to be sold to different coffee buyers around the world. The grading systems differ for each producing country, just to add another layer of confusion. You might of heard of a 'Grade 1' coffee, 'AA' or 'Fancy'. These are all examples of different size and quality grading systems.
Each seemingly simple part of the process can ruin coffee. If under or over-ripe cherries are picked, the rest is pointless. If the coffee is not dried evenly in good weather conditions, the coffee will taste fermented. If the beans are damaged by the huller, the grade will be lower. The more we understand about the coffee process, the more we appreciate good quality coffee when we get it. It doesn’t happen by mistake!