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August 24, 2016

As I'm thinking about what to blog about I often think about questions that we get asked at the shop. A more and more common question is about coffee processing so this article touches on some of the terminology that you might see on your bag of coffee or even on the board of your morning coffee shop stop.

Part of the flavour profile of the coffee you drink comes from the processing method of the bean. There are four major categories of coffee processing and this is a ( very brief! )  overview to help you understand some of the coffee terms you might come across when buying your beans.

A coffee bean is actually a seed. It’s planted and bears small fruit that ripen red, called the coffee cherry. Once the cherries are picked they then have to be processed. Processing the cherries is basically removing the skin and pulp of the fruit from the bean and drying it. And it’s the bean inside that we want.

Processing Methods

The wet method sometimes called the ‘washed process’ has the coffee cherries put through a pulping machine to separate the skin and pulp of the fruit from the beans. This leaves the bean wrapped in a protective parchment skin with a layer of what is called mucilage strongly attached to the parchment.

If you've ever tried to get all the flesh off of mango fruit stone you'll know that mucilage layer. It's a bugger to remove. In order to get that layer off the beans are put into water filled containers, where the sugar from mucilage ferments and the mucilage layer falls off.

After this they have to be dried to get the water content of the bean around 11% needed for the next stage. Either they can be sun-dried by spreading them on drying tables or floors, where they are turned regularly, or they can be machine-dried in large tumblers. 

With this wet process the fermentation of the bean is quite controlled which, in turn, means that you will clearly be able to taste inherent qualities of the coffee itself, flavours unique to that origin, in the beans. It can produce a brighter and cleaner cup of coffee with medium to high acidity.

 

 The Dry Method  also called the ‘natural process’ or 'sundried process' is probably the oldest method and an obvious method to be used in countries where water resources are limited. The freshly picked cherries are spread out on huge surfaces to dry in the sun. It’s a time consuming method, not least because In order to avoid moulding or spoiling, the cherries have to be raked and turned throughout the day, then covered at night or during rain to prevent them from getting wet. Depending on the weather, this process can take weeks because the moisture content of the cherries has to drop to around 11% before the beans can move onto the next stage.

With this dry method the fruit acts as a natural casing producing higher fermentation happening in a sealed environment. Expect coffees to be a little sweet, often wine - like, muted acidity and pronounced fruity flavours.  

The Semi - dry method, which is also called ‘pulped natural process’ and ‘honey process’, is probably the most confusing process out there. Quite possibly because we call it 'honey process' and it has nothing to do with actual honey.
This process is very similar to dry process coffee. Except the skin of the fruit is removed leaving the pulp of the fruit covering the bean before it is dried. As you can imagine, this makes for a very sticky / honey-like feel to the beans. These coffees are dried with the skins off. How much pulp is left on and how they're dried varies so it is difficult to group these coffees together flavour wise; but the point is that it creates its own flavour profile, moderately fermented to highlight sweetness and body with muted acidity.

The Wet-hulled method sometimes called 'semi-washed', 'semi-dried' or 'Giling-Basah' is pretty much unique to Indonesia. Like the wet method the cherries are put through a pulping machine to separate the skin and pulp of the fruit from the beans, which are then put into water filled tanks. They are then dried and hulled when the moisture level is around 35% rather than the norm of around 11%  Once hulled they are then dried again to achieve that 11% moisture so they can be stored.

These coffees are often darkly roasting, encouraging the earthy, spicy flavours to fully develop. Muted acidity, big body but with less of the sweetness of the semi - dry method.

Whichever processing method has been used the beans retain some layers that have to be removed. Whether it is the parchment skin of wet-processed coffee, the parchment skin and dried mucilage of semi-dry-processed coffee, or the entire dry, leathery fruit covering of the dry-processed coffee.This is done at a mill with a hulling machine after which they are graded by size and weight before being distributed and the green beans can find a roaster.

I hope that all makes sense, I've written it in the best way that I can, forgive any mistakes!





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