It doesn’t matter how good you are at roasting coffee, if your raw product isn’t already the highest quality, then your end product is never going to be. Any good chef will tell you the same. If the quality of their ingredients is sub par then the food they serve on the plate is never going to earn them a Michelin Star. With this in mind, we only buy the highest quality, ethically secure green coffee. Bought from trusted friends and partners – relationships we’ve made over many years; we are not only purchasing coffee, we are supporting whole communities who invest their lives in growing the product we ultimately end up drinking. They sow the seed, we are rewarded with beautiful coffees and in turn they reap the reward of premium prices for their premium product. First, let’s briefly talk about bit more about green coffee and how it’s processed.

What exactly is coffee?

Coffee is a fruit! Once a coffee plant has finished flowering, a cherry will form. This cherry usually contains 2 seeds (some contain one – known as a peaberry), and these seeds eventually become coffee beans. Each cherry is made up of a number of different layers – the outer skin (pulp), the mucilage (a sticky layer that helps with the sweetness of a coffee), the parchment and the silverskin (a membrane which covers the two seeds). In processing coffee we are basically removing these layers of fruit.

Most arabica coffee is grown at high altitude (over 1000 metres above sea level – masl – but often over 2000 masl), which makes it difficult to harvest. Therefore, almost all harvesting, at the higher altitudes, is completed by hand! This is obviously very labour intensive and takes time, but it is also better for us as only the ripe cherries are picked, leaving the unripe cherries on the tree to mature for a bit longer. Harvesting can take up to 3 months from start to finish.

Once picked, the cherries head straight for processing. There are now a number of ways to process coffee for roasting, but to keep this simple I’ll just talk about the main two: Washed and unwashed (natural). Other ways of processing are really just variances on these main two. Between harvesting and roasting (or storage), the fruit needs to be removed and the beans need to dry to the correct level. A washed coffee has had the skin and the mucilage removed leaving only the parchment and the silverskin behind.

Stages in washed processing

(1) The first stage in processing is sorting – this removes any defective or unripe cherries that have crept in there by mistake. Generally they are put into water, and any that float are removed. (Higher quality coffees are denser than water as they have properly formed seeds within them). Lower quality cherries aren’t necessarily thrown out, just separated and sold to a less discerning market.

(2) Next, is pulping – removing the skin of the cherry. This is usually achieved through the use of a machine called a depulper. (Below you can see the depulper in action high up in the Sierra Madre mountains in Mexico, on Venceslao’s farm (which is part of the El Jaguar cooperative we buy from directly).

(3) Fermentation is next. This usually takes anything from 12-36 hours, but in some cases it can take longer (depending on the farm. Although care needs to be taken as over fermentation can lead to poor tasting coffee). During the time in the fermentation tank, microorganisms in the beans create enzymes which, in turn, break down the mucilage. In Kenya, double fermentation is common – basically the coffee is soaked in water twice, using a lot of water, but resulting in very clean coffee! One of the criticisms of the washed process is it’s high water usage. I’ll chat more about this shortly.

(4) The last stage is drying. Smaller farms (like El Jaguar in Mexico) are totally reliant on the sun to dry their coffee, whereas some larger farms (for example in Brazil) are turning to mechanical driers to achieve the correct moisture level. Some farms also use a combination of the two – starting it off on patios in the sun and then finishing in the mechanical drier. However, any use of a mechanical drier increases costs and fuel use for a farm/ washing station. This is one of the affects of climate change that we are seeing more and more. When Gregg and I were in Guatemala in 2018, we heard that mechanical driers were never needed until 10/15 years ago – the weather was always so predictable that they weren’t needed! Now, it often doesn’t rain when they need it to (during growing) and it rains when they don’t (during drying).

Natural process

This leads us to Naturally processed coffee. Originating in Ethiopia, it’s a process that uses a lot less water and is often used in areas where water is scarce. Although many farms are now experimenting with it to appeal to western coffee roasters. The fruit remains on the coffee beans and dries. Needing a lot less labour than washed coffee, it still requires certain conditions to ensure the fruit and seed dry in time.

Once picked the cherries are laid to dry in the sun (either on patios or on raised beds – which is done mostly in Africa). They need to be turned regularly to reduce the risk of mould growth (think of any fruit left out in the hot sun!) The cherry is dried with all the layers intact which means there is some natural fermentation that occurs – enzymes are absored from the mucilage into the bean which leads to really distinct flavour profiles. Onced dried the cherries will look like raisins – then it is hulled to remove all the outer layers and then sorted in a ‘dry mill’ (removing any defective beans) for shipment.

In both washed and naturally processed coffees, the moisture content is at 11% before being bagged and exported to the roaster. At Ristretto, we roast washed coffees, natural coffees and anything in between!

In Part 2, we’ll step away from the science and delve into exactly where we buy our coffee from.

Thanks for reading.

JS