Coffee is becoming increasingly complicated. And I’m not talking about knowing the difference between an American cappuccino (obnoxiously oversized, like a bowl of fettuccine Alfredo from the Cheesecake Factory) and the Italians’ daintier original (who are generally horrified by both our bastardisation and willingness to drink one at any time of day.) However, I digress.
Consider the term “green coffee” (coffee that has not been roasted). Even the colour of standard commodity beans – the world’s second most traded commodity after crude oil – can vary by several shades. Green coffee is a term that refers to the colour of beans prior to roasting. Its hues range from dark raisin to dried chickpea, and its flavour profiles, for those sensitive to them, can also be quite varied.
This wide range of colour is due to the processing and fermentation methods used in various regions, which vary according to their climate and resource availability. It should come as no surprise to those familiar with winemaking that this other carefully cultivated fruit also requires some chemistry application.
What does processing entail? Despite its negative connotations in the food world, processing freshly picked cherries refers to the necessary steps, which include some degree of fermentation (yeasts and bacteria break down the sugars in the mucilage to produce acids and fruit notes), to remove the three layers surrounding the seed in preparation for shipping, and later, roasting. The outer fruit or pulp is the first layer, followed by the sticky mucilage that surrounds the seed, and finally by the parchment, or thin layer that surrounds the seed and is named for its resemblance to parchment paper when dry.
As consumer palates have evolved, speciality coffee producers have begun to experiment with processing methods. Whether it’s emphasising fruit notes, emphasising or softening acidity, or fattening or lifting the body, this helps differentiate products. Consider wine for a moment. Grapes that are left on the vine longer develop more sugar, which results in more alcohol, a larger body, and riper fruits. Early-harvest grapes have a higher acidity, lower alcohol content, a leaner profile, and tarter fruits. While this is not an exact comparison, the point is to demonstrate that, from a producer’s perspective, coffee processing decisions, along with terroir (e.g., a cool, coastal site in Sonoma vs. a warm valley site in Napa) and tree variety (e.g., Pinot Noir vs. Cabernet Sauvignon), all affect the sensory properties of the final drink.
While experimentation continues, the three most common processing methods are dry or natural (labour intensive), washed or wet (water intensive), and a newer hybrid called honey or semi-dry.
Natural or dried
Natural is the original method – or, more precisely, nature’s method – because in this case, the coffee cherries are simply picked and allowed to dry, frequently up to the point of export. This increases the risk of mould and the possibility of over-fermentation into boozy flavours (sounds better than it tastes), takes weeks, requires almost no water, and allows the fruit to influence the taste. Certain naturally processed coffees may give you the impression of blueberry pancakes in your cup (tastes as good as it sounds). It is especially prevalent in Brazil, accounting for roughly 80% of the country’s production, as well as in arid countries such as Ethiopia, the birthplace of coffee, where water is scarce. Some of Panama’s finest geishas are naturally processed.