A Primer on Processing Methods 101
At 49th Parallel we love coffees of all kinds, and seek out the best of the best from coffee growing countries around the world. It is no secret that the majority of our coffees are of the traditional Washed (“Wet Process”) method, as we have long had an inclination for juicy, sweet and floral, or citrusy and bright, coffees no matter the origin. When produced to the highest standards, these are arguably the best representations of varietal and terroir, laying bare the uniqueness of say a Honduran Pacas, Panamanian Geisha or Ethiopian Heirloom.
This isn’t to say however that we are not also taken by Natural (“Dry Process”) coffees, and we have experienced many mind blowing dried in the cherry profiles over the years. The reality is that we are experiencing a renaissance in Natural and Controlled Process methods and as a result 49th is offering more of these innovative coffees than ever before.
Below is a primer on the most common processing methods, along with innovative fermentation techniques that are changing the landscape of the coffee world today.
Primary Processing Methods
At the heart of all processing methods is this - The coffee “beans” that we know and love are actually “endosperms” within coffee cherries, and in order to access the beans it is necessary to first remove multiple layers of the fruit around them. This is done in one of three ways, commonly referred to as the Natural, Honey and Washed Processes. These processing styles are accompanied by drying – by the sun or machines - to produce “green coffee” ready to be transformed.
Natural “Dry Process”
This is the original way coffee was processed, until the 1800s when depulpers and the resulting Washed method emerged. Natural processed coffee is also called “Dry Process” coffee because it uses relatively little or no water. It makes some sense that in coffee’s birthplace, Ethiopia, where the climate is arid, and access to water is relatively limited, coffee would have traditionally been processed without the use of water. In this straightforward (and rustic) version of things, coffee is simply harvested and laid out to dry in the cherry, with very little sorting or separation. It is only after the coffee is fully dry that the cherry (skin and pulp) along with the parchment (hard inner shell or endocarp) are removed and we are left with the green bean. If the coffee isn’t cleaned and sorted prior to drying however, quality can be very low.
There are many variations of the dry process that actually use some water as a means to separate ripe cherries from over-ripe or defective cherries, in an effort to improve quality. By floating cherries in water the coffee is both cleaned and separated by levels of density – the ripest cherries sinking to the bottom and the defects floating to the top, where they are skimmed off and separated. Coffees that pass through this stage tend to be more uniform and of higher quality. Floating is used in almost all processing methods, as it is an easy and effective way to achieve higher quality. Almost without exception, the producers 49th Parallel partners with would use some sort of separation method, in addition to the very important practice of harvesting only ripe cherries. “Selective harvesting”, as this is called, is one of the key elements of coffee quality and on smaller farms where investment in expensive sorting equipment is not an option, is the most cost effective way to boost cup quality.
Drying of Natural coffees is most typically done on cement patios or raised beds, though mechanical dryers can also be used.
While for many years Washed coffees were seen as superior to Natural coffees, this was largely because the dry process utilized in many countries did not adequately separate ripe coffee from under-ripe or defective coffee. This has changed in the past 20 years as expectations, techniques and technology have evolved. Today quality minded producers from Ethiopia to Panama have made Natural coffees some of the most prized and valuable coffees in the world.
Honey “Semi-Washed Process”
This process is an evolution of the Natural process, and came into being in the 1990s. It was developed to solve for a persistent problem with floating coffee as a means of separating – while floating removed defective “floater” coffee, it combined both ripe and underripe “sinker” beans together. The issue with this is that under-ripes dried along with ripes creates a lower quality cup (green beans are astringent and can have off, vegetal flavors), and hand sorting out underripe cherries or investing in sensors is costly. The Honey Process improves on this by first floating the coffee, and then passing the ripe and underripe “sinkers” through a sieve at high pressure. In doing so, only the soft ripe cherries are pulped and pass through the sieve where they are then separated from the pulp. The firmer green cherries remain stuck on the outside of the sieve and are diverted to dry separately from the ripes.
At this point Honey process coffee is left to dry with some or all of its mucilage - the sweet sticky part of the cherry just under the skin - still intact. As it dries it glistens as though it has been covered in honey, and when it is fully dry, the oxidized sugars give it the appearance of the popular 1980s cereal Honey Smacks.
While developed as a way for large, commercial producers in countries like Brazil to efficiently produce higher quality coffee, the Honey Process has been embraced by the specialty coffee industry because it can result in a unique cup character that falls somewhere between fruity Natural and clean/floral Washed process coffees.
Washed “Wet Process”
What constitutes a Washed coffee can get bogged down in the details and endless variations, and as we have seen water is often used in both the Natural and Honey processes, but for sake of clarity let’s say that beyond using some water, Washed coffees have as a characteristic the removal of some or all of the mucilage – the sticky layer that covers the hard shell (parchment) surrounding the bean - either through fermentation or mechanical scrubbing. How does this work?
After floating, cherries are sent to a depulper to remove the outer skin and some of the mucilage. These pulped cherries are then either sent to a tank where they ferment for a period of time until the mucilage falls free from the parchment, or to an “eco-pulper” where they pass through mechanical scrubbers that remove the mucilage without fermentation. Fermented coffees are then washed with clean water to stop fermentation, while mechanically de-mucilaged coffees skip this step, having scrubbed off the mucilage in one step. The differences here are a matter of great debate in the coffee world, with many coffee purists preferring coffee traditionally fermented over mechanically de-mucilaged, the argument being that bypassing the process of fermentation decreases quality. We will not get into that today, as a lot has been written about the benefits of both, but suffice it to say that in our experience either process can produce excellent coffees.
One important note is that mechanical “eco-pulpers” emerged as a way to decrease environmental pollution from coffee processing byproducts, simply by using significantly less water. When allowed to reach rivers and other sources of freshwater, coffee processing byproducts can destroy sensitive habitats. This isn’t to say that traditional fermentation methods have to be problematic, because local regulations have become much more strict in most coffee producing countries, and it is now expected that wastewater is treated before going into water ways. Responsible producers understand they have a legal obligation to environmental stewardship, and that with a little planning the byproducts of coffee processing can be converted into valuable natural compost as well as animal feed. When visiting our producer partners one of the top questions we ask is about their byproduct management systems, seeking to support them to make improvements when necessary.
Another interesting note is that “eco-pulpers” are often used today to produce Honey coffees, simply by setting the scrubbers to remove less mucilage.
Once de-mucilaged, Washed coffee is dried on patios, raised beds or mechanical driers, roughly the same as Natural and Honey coffee.
“Controlled Process” Fermentation Techniques
In addition to the three primary processing methods there are a number of innovative techniques being employed that specifically play with how coffee is fermented. The impact of these “Controlled Process” fermentations on flavor can be dramatic and they have therefore generated a lot of attention in the coffee world – drawn in large part from similar conversations in the beer and wine worlds. While very much a dynamic field, there is some agreement about terminology which we will discuss here.
If we consider that “Traditional Fermentation” (in Natural, Honey or Washed methods) can be called “Aerobic Fermentation” because it occurs in a relatively open environment where oxygen is present (aerobic), Anaerobic Fermentation is simply fermentation that occurs in an environment where there is limited or no oxygen. This is normally achieved by putting either pulped or whole cherry coffee in a sealed container with a one way valve to let gas out without letting oxygen in. The impact on flavor is dramatic because the types of microbes responsible for fermentation that are able to survive in this environment are totally different that in an oxygen rich environment. It also tends to take longer for fermentation to occur for this very reason. Anaerobic Fermentation can be with or without water.
It is similar or in some cases interchangeable with Anaerobic Fermentation, but for sake of differentiation, Carbonic Maceration is an Anaerobic Fermentation in which the coffee cherries are not pulped. Carbonic Maceration comes from the wine industry,
and those wines are known for being juicy and fruity, which roughly translates to the cup character of coffees fermented in this way. Many in the coffee industry prefer to skip the use of the term Carbonic Maceration altogether, and you will commonly see the description of “Natural Anaerobic” coffees in which the coffee cherry is left intact through some or all of the processing. In any event, in Carbonic Maceration, because the coffee is not pulped the fermentation process tends to take much longer as the cherries slowly break down, and the cup character as already noted is unique.
Yeast Added Fermentation
Although the vast majority of coffee is fermented using wild, native yeasts, producers have started to experiment with adding yeasts to their coffee while it is fermenting in an attempt to control and manipulate the fermentation process. This is both radical and logical – radical because coffee fermentation has always been presented as something that just happened spontaneously and somewhat mysteriously; and logical because in the beer and wine industries, with a few exceptions, yeasts are carefully selected and employed to achieve a desired outcome. It would be considered crazy to leave it to chance. Adding yeast to the fermentation process in coffee can be combined with the above methods to change the course of the process and impact flavor profiles in unique and sometimes stunning ways.
There are many combinations of the above fermentation techniques, making the world of coffee processing endlessly complex, dynamic and fascinating. As we head into 2021 look for a diverse offering of intriguing Controlled Process coffees in addition to 49th’s reliable stable of meticulously processed Washed coffees.