Coffee by region, Field trip

Washed coffee in Antigua

The mucilage coating the bean and the skin of the cherry

The mucilage coating the bean and the skin of the cherry

I recently had the good fortune to go to Guatemala for a field trip in the Antigua region. I’ve been in this industry for a good ten years now, so I already knew there’s a huge amount of work behind every cup of specialty coffee served. But to actually see it, to talk to the people doing it, to come face to face with the economic and social challenges involved in producing our favourite drink ... what a shock! Here’s a brief entry to give you the tiniest glimpse of this work process which harnesses tremendous environmental, economic and human potential. I’ll be dealing here with how coffee fruits (cherries) are processed after harvest.

Did you know that after harvesting the coffee cherries, the beans must be extracted from several organic layers (the endocarp), whose main function is to protect the bean and nourish it during germination?  Extraction and drying must be done soon after harvest or the beans will ferment and rot. There are various ways of doing this. The two most familiar methods are wet processing, also called washing, and dry, or natural, processing. Here we’ll be talking mainly about washed coffee.

Fermentation vats

Fermentation vats

In wet processing, the freshly harvested cherries are sent to the pulping machine via a hydraulic siphon system. This crucial step involves immersing the cherries to remove any pebbles and twigs and do an initial sort (since beans of similar density float at the same level). In the pulper, the beans are mechanically extracted from the endocarp (literally, the skin): the fruits are fed through a pair of rollers, carefully adjusted so as not to damage the beans, which are literally expelled under pressure. Next the beans are immersed in big vats of water for 12 to 48 hours. In this operation, the mucilage layer – the flesh of the fruit – is broken down by microbial decomposition. The coffee then moves along water-filled troughs to the drying patios, where it is spread on the ground or on raised trellises and regularly hand-raked to ensure even drying. When it is dry, the green bean must be extracted from the husk or “parchment”, an inner layer that protects the bean. The parchment is removed mechanically in a machine that scrubs the coffee. Then the whole production is moved to pulsating, tilted tables for a second sort. The heaviest (and thus densest) beans end up at the high end of the table while the lighter beans and impurities move to the low end. The beans are then fed by conveyor into a highly sophisticated machine which sorts them individually, rejecting any bean that is substandard in terms of shape, colour or size. At the end of this third sort, the coffee is fed by conveyor into a blower and into silos, from which it will be poured into jute bags for shipping to the four corners of the world. 

Coffee on the patio must be raked regularly to prevent fermentation

Coffee on the patio must be raked regularly to prevent fermentation

The dry, or “natural” method (which will be covered in another article) is much simpler. Basically, after harvesting, the fruits are immediately dried whole. They are then put through a series of rollers that remove the endocarp, and finally through a second pair of rollers to polish the beans and strip off the parchment. From there on, the process is essentially the same as for washed coffee. 

Historically, the choice of method has depended primarily on access to water and infrastructure availability in the producing region. This is why there used to be a lot of dry-processed coffee coming from Ethiopia and Yemen, for instance, where rain is sparse and the development of production mechanisms is limited by lack of resources.

Nowadays, producers can opt for whichever method they consider the best choice to produce a unique coffee with the desired profile.

The processing method does have a major impact on the taste of the final product. Washed coffees, greatly appreciated in the industry for their stability, have more subtle, delicate, balanced aromas. For a long time, natural coffees were shunned for their unpredictability, but they are being showcased now and are highly valued in the specialty coffee industry (and by yours truly) for their unique profile and their more forceful, robust, explosive aromas, very fruity and often with a winey base.

Processing methods raise some other ethical considerations that are currently sparking debate in the industry, notably the issues of water management and the impact of discharging wastewater into the environment, to name just two.

So what’s the final word, natural or washed? Your choice. Be inquisitive, ask for advice, be choosy. After all, you’re drinking it every day!

Simon Fabi
Co-owner, Brûlerie de Café de Québec and Faro Roasting House