After a coffee cherry is picked from the tree, its perilous journey along the path to quality hits an important crossroads. Coffee’s inherent quality is close to its peak during this initial duration of time once it is picked, and the choice in how a coffee bean will be processed is one that is meant to truly showcase the inherent quality of the bean or compliment those raw attributes in a positive way. Coffee is processed differently throughout the world; sometimes this is due to legacy or tradition without an understanding of its influence on the cup, while other times it is a specific choice at the farm level to add or coax out new flavors and experiences in the profile of the coffee.
Within countries, and even within specific farms, several processes can be done. Producers around the world are experimenting with new processing techniques and styles everyday. Sometimes the results are truly astounding, while other experiments result in less than stellar results. As a company that is in the business of developing and uncovering the best coffees in the world, we support our producer partner’s experiments in new processing techniques and separations by committing to purchase the coffee regardless of the cup’s results. In our eyes, this is the only truly sustainable way to nurture and encourage trust and collaboration in this sense on the farm level.
There are several major categories of coffee processing recognized by the coffee industry as a whole. Sometimes these are called different things depending on what country you are in, but the general principles remain the same. Below you will find some information on the main processing techniques used around the world: fully washed, natural, pulped natural, and wet hulled.
Washed coffee is distinguished by the clarity of the flavors and attributes that it can achieve. This clarity need not suggest timidity, as the best washed coffees combine nuance and complexity with great intensity. Clarity should also not be regarded merely as simplicity. Rather, it is exactly the transparency of wet processed coffees that allows for perception of the remarkable complexity of acids and other compounds present in the coffee beverage- complexity that is frequently masked in alternately processed coffees.
During this process, the sugars present in the mucilage are removed through natural fermentation or mechanical scrubbing. Fermentation can be done by stacking the coffee outside or placing them under water and allowing nature to take its course. After the sugars are removed, the beans then can be taken through a secondary washing to remove any additional debris, or taken immediately to the patios or beds for drying.
“During wet processing, the pulp (i.e.the exocarp and a part of the mesocarp) is removed mechanically. The remaining mesocarp, called mucilage, sticks to the parchment and is also removed before drying. Hulling of dry parchment coffee leads to green coffee. The wet process is used for most Arabicas… and only for a small percentage of Robustas, although the trend to wet process Robustas is increasing.” (Wintgens 611)
“Mucilage is insoluble in water and clings to parchment too strongly to be removed by simple washing. Mucilage can be removed by fermentation followed by washing or by strong friction in machines called mucilage removers. Fermentation may be natural or accelerated by chemicals or enzymes. Mechanical mucilage removers operate by rubbing parchment beans against each other and against the mobile and static parts of the machines.” (Wintgens 645)
“Fermented coffee can be washed manually in the [fermentation] tank itself or in channels, by centrifugal pumps or by several types of specific machines.” (Wintgens 647)
Natural coffees frequently carry a flavor similar to that of the coffee cherry itself. While this flavor profile is a limiting factor in scoring washed coffee, it is characteristic of the dry process and as such is assessed for its relative quality and integration in the coffee beverage. At its most simple, Naturally processed coffee is coffee that is dried with the cherry remaining on the bean and parchment throughout the drying process and will often remain on until just before the time of export. Naturally processed coffee can be categorized as “special prep”, meaning ripe cherries are picked and dried, or it can be coffee cherries that dried on the tree and finished on the patios or drying beds.
“Dry processing implies that the whole cherry is dried together (exocarp, mesocarp and endosperm, i.e.. pulp, parchment and bean). The whole hull (dried pulp and parchment) is then removed mechanically to obtain green coffee. The dry process is used for more than 80% of Brazilian, Ethiopian and Yemen Arabicas, and for almost all Robusta coffees in the world.” (Wintgens 610)
Pulped Natural/Semi-dry/Honey Process
Outside of Brazil the pulped natural process is frequently referred to as the honey process, with producers leaving various amounts of mucilage adhering to the parchment as well as employing different depths of the coffee layer in drying, both resulting in unique profiles that span and even expand the range from dry to wet process. There can also be varying levels of honey processed coffee, typically referred to as black, red, or yellow honey. This is where it gets a bit complicated. In some regions, the level of honey is determined by the frequency of turning the parchment while drying, with the black end of the spectrum being turned least often. Not turning the coffee often allows the sugars to caramelize quickly on the outside of the parchment, leaving it stained a dark maroon or “black” color. In other places, the degree of honey is determined by the amount of mucilage left on the parchment after being passed through a mechanical demucilaginator or quick fermentation. In this scenario, the black end of the spectrum has the most mucilage left on, while the yellow has the least. There are no hard and fast rules with terminology for honeys as there is currently no global processing standards (one day?!), but having this basic understanding will be a great start.
Because of the in-between nature and large profile range of pulped natural coffees, assessment is difficult to codify. In our lab, we label pulped naturals with an H (honey) and ask our panelists to assess basis our natural standard, though without considering a lack of coffee cherry character as a limiting factor in scoring as it would be for a naturally processed coffee.
“In the semi-dry process, that Brazilians call the pulped natural process, the mucilage is not fully removed after pulping, and parchment is dried together with most or all its mucilage. Green coffee is obtained by hulling dry parchment with dried mucilage adhering to it. The semi-dry process, originally used in Brazil, is now being introduced in other countries too.” (Wintgens 611)
Wet Hulled/Semi-washed/Giling Basah
The assessment of wet hulled coffees is challenging, to say the least. The potential range of coffee flavors, process flavors and environmentally imparted off flavors is dramatic. In general these coffees occupy a range from earthy to vegetative. Scoring relies heavily on discerning between sweeter and “cleaner” (e.g.. clean earth vs compost or roasted pepper vs raw) versions of each. Despite the frequent assertion that wet hulled coffees are low acid, we’ve found that carefully processed coffees can display significant and vibrant fruit acidity, integrated with the wilder flavors imparted by the process itself.
This process is common practice in some areas of Indonesia. This likely is a result of legacy, but the resulting cup profile is something that has become distinctly indicative of the region. Wet hulled coffees are pulped at the farm level, and without any additional formal processing, the wet beans in parchment and mucilage are usually sold to a nominated processing facility. Here, they actually remove the parchment (still covered in mucilage), and dry the coffee beans completely exposed to the elements.
“Most small-scale farmers on Sulawesi, Sumatra, Flores, and Papua use a unique process, called ‘giling basah’, which literally means ‘wet grinding’ in Bahasa Indonesia. The industry also uses the terms wet hulling, semi washed and semi dried for this method. To avoid confusion, SCAI is encouraging the term ‘giling basah’.
In this technique, the outer skin is removed from the cherries mechanically, using rustic pulping machines, called ‘luwak’. The coffee beans, still coated with mucilage, are then stored for up to a day. Following this waiting period, the mucilage is washed off and the coffee is partially dried for sale (to 30% to 35% moisture).
Processors then hull the coffee in a semi-wet state, which gives the beans a unique bluish green appearance. This process reduces acidity and increases body, resulting in the classic Indonesian cup profile.” (SCAI)