Welcome to part 2 of my series of articles looking at the way that coffee develops so many unique flavours on its journey from crop to cup. If you haven’t read it already, I recommend you start with Growing Coffee although I do hope this article will stand on its own if you are just interested in the processing of coffee beans.
When you first start to taste coffee it can be an eye opening experience. It’s amazing that a single drink can have such varied and complex flavour, but it really does. I am going to have a go at explaining some of the reasons why.
What is Processing?
Good question, before I get to answering though. I’m going to start by explaining that coffee beans are in fact the seeds of the cherries which grow on coffee plants. Now this might be stating the obvious, or it might not, but I have learned over the years to assume as little as possible, so those who knew this already will have to forgive me.
To ready a coffee crop for export and eventual roasting into the tasty bean we all love, we need to remove the outer layers of the cherry and get to the seed inside, then dry out that seed to keep it fresh during transport. The methods used to do this are called coffee processing. But before we can get to using them there is one more important step.
Once you have your harvest of coffee cherries picked, the first major step is to sort any unripened fruit from the ripe fruit that you want to process, unripened coffee cherries do not make for good coffee. This can be and often is, done by hand, a labour and time intensive process aided by winnowing (passing through specially designed sieves) or by flotation, (using tanks of water to seperate unripened cherries which float to the surface and can be removed) and make no mistake this sorting is hard work. Once the cherries have been sorted it’s time to remove and dry the coffee beans, and this is where it gets complicated.
Ways to get to the Bean
As with so many parts of the coffee journey there are multiple methods to achieve the goal here, and each possible method can and will change the flavour of the green beans (a term used for coffee ready to transport before roasting, due to the natural colour of a processed and dried coffee bean). I am going to take each of the four most common coffee processing methods and discuss how they work and their impact on the coffee.
Natural Process Coffee: Back to Basics
I’ll start with “Natural Processing”. This method, most likely the oldest, certainly the simplest, and arguably the most traditional of the processes used, consists of laying out the ripe cherries and allowing the fruit to dry “naturally” hence the name. As long as the cherries are watched and regularly turned to avoid the development of mold, the natural process of fermentation will dry out the various layers of the fruit.
The resulting raisin-like product can then be “hulled” (the outer layers removed from the seed) and fully dried leaving the green beans needed for export and roasting. Natural processing emphasises the intense and fruity aspects of coffee and is known for producing some exceptional and complex flavour profiles, your humble scribe is a big fan of this sort of coffee, though for some it can taste a bit “not coffee like”.
The natural process allows for many variables, accounting for the complexity of flavour, but equally it opens the door to many potential problems along the way. These include mold and insect infestation, as a result natural processing is sometimes avoided in favour of more consistent and modern processing methods, this is often the case when large commercial batches of coffee crop are being processed. Lately specialty coffee growers have embraced natural processing and many great coffees of this type are found on the market.
Washed Process Coffee: The Search for Consistency
In the “Washed Process” the coffee cherries are first “depulped” (some of the outer layers removed) in a wet mill, this can be done with or without mechanical assistance, and then fermented for up to 24 hours to remove the last of the inner part of the fruit, called the Mucilage. Finally they are dried on exposed beds, taking up to 25 days before they are ready to export. This period can be reduced to about 3 days through the use of industrial drying machinery, but doing so can have an adverse effect on the flavours of the coffee produced.
Washed coffee is known for having an excellent level of uniformity in bean colour, size and moisture content, all of which are watched and measured during processing. Washed coffee tends towards clean and above all consistent flavours, very desirable qualities in many parts of the industry. Interestingly adjusting drying times will also change the complexity of the cup from the coffee, with a shorter dry likely to result in a clean distinct flavour, while a longer dry can add layers of subtle undertone to the drink. Washed processing has been very much in vogue for some time and is unlikely to become otherwise, producing some excellent coffees throughout the world and critically providing a strong level of consistency.
Honey Process Coffee: The New Kid on the Block
Recently coffee drinkers are seeing more and more of the “Honey Processed” bean. This method is actually many methods under one name, I’ll come back to this later. It’s a fascinating hybrid of natural and washed processing, and centred on the use of the cherry’s mucilage, remember that from earlier? as a flavour enhancer.
Time to get a tiny bit technical so bear with me if you will. The coffee cherry has multiple layers all of which are removed during processing. First we have the outer skin of the fruit, then the pulp, both of these are removed during processing. Beneath these we reach the mucilage a syrupy layer of pulp which is also traditionally removed, but in honey processing the idea is to control the washing of the beans so as to leave some of this layer on the seed before drying and hulling. Why is this desirable? The answer lies once again in coffees natural absorbance of flavour from factors it’s exposed to. As it breaks down, the mucilage of the cherry develops a strong sweet flavour, and during fermentation this sweetness, akin to honey in taste (hence calling it the Honey Process, which is frankly a lot more appealing as a name than the Mucilage Process) makes its way into the seed and alters the flavour. By deliberately controlling the amount of mucilage left before drying, the farmer can even impart a particular degree of sweetness into the bean. This process can produce some really interesting coffees and is becoming more common in coffee farming.
Different names like Yellow, Red, White, or Black Honey are used to refer to the amount of mucilage left and the degree of sweetness added, arguably each of these is a process unto itself, but they fall under the banner of honey processing for everyone’s sanity. Honey processed coffee beans are a fascinating innovation with real potential for amazing flavour profiles, but the mucilage left on during drying increases the potential for mold growth or insect attack and so, just like natural processing, it is more time and work intensive than a washed coffee.
Semi-Washed Process Coffee: Tradition Kept Alive
In any article on coffee processing I would be remiss to miss out Semi-Washed or Wet Hulled Processing more properly called Giling Basah (Wet Grinding). Any journey into coffee tasting will doubtless expose you to this term eventually. This traditional process is native to Indonesia and like Honey Processing, is something of a hybrid.
Giling Basah coffee is depulped and then laid out to dry as in Washed Processing, but part way through the drying process the farmer will hull the partially dried beans, before returning them to complete drying. This early hulling is thought to emphasise earthy flavours in the coffee, and the change in the chemical reactions within the process produces a recognisable blueish tint in the final bean. While in many cases this could be considered a sign of a defect in the bean, caused by excessive and risky exposure to environmental factors and insects, the careful use of this technique produces some very desirable flavours.
In particular Sumatran Giling Basah coffees are famed for their unique and intense cupping notes. While never likely to be a common process, GIling Basah coffee is well worth seeking out, the flavours are quite unique, and the traditional nature of the process holds its own appeal for many.
More before roasting
Ok so I confess I said this article would cover coffee processing and it has, but I need to address a few other concepts before I end. Remember how I’m always pointing out how complex coffee is? Well here we go again, you see before we get to the next article and the roasting stage, other factors can have an impact on favour. Beyond the main process used in getting to the bean, other factors and methods many of them truly creative ideas, can be used to alter flavour.
A good example is “Monsooning” a process used to produce the famous Monsoon Malabar coffee beans. On the Malabar Coast (it’s in the Karnataka and Kerala regions of India, for non geography buffs) coffee beans are laid out in partially exposed warehouses for 12-16 weeks during monsoon season, the resulting exposure to the moisture laden monsoon winds adds a particular and distinctive essence to the final flavour. Ironically, the development of this process owes itself to the desire to replicate a flavour lost to us through modern advances in the transportation of coffee beans.
Historically the coffees grown in these regions were transported on sailing ships, and during their six month journey to market the green beans would swell and mature developing a yellowish colour with exposure to the moisture and winds of sea travel. This of course changed the flavour of the ever adaptable coffee bean and the particular heavy body and pleasantly musty note added to the taste of the coffee was greatly enjoyed, even prized in European coffee houses.
With changes to the methods of transport and the speed at which the beans could reach the shores of europe, this natural change in flavour was lost, and so some very clever farmer came up with a plan to recover the historical flavours of this great coffee, human ingenuity recovering something lost, to… human ingenuity. Never let it be said that the coffee industry doesn’t have a romantic tone, or a sense of humour.
There are other examples of this sort of flavour enhancement, old java coffee in Indonesia is left to age in moist caves, beans can as we have seen gain flavour from the strangest of sources and the industry is filled with creative people who find new ways to use this fact. Once more as you taste your coffee and read the information on the packet of beans, you might take a little time to appreciate the intense complexity involved in growing and preparing the product you love to consume.
Next time the flavour journey will take us into the world of roasting coffee…
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Thanks, – Bear