While coffee enthusiasts frequently discuss the roast type and country of origin, the processing method is often overlooked despite its significant impact on the final flavor of the bean.
With dozens of different coffee processing procedures, understanding them is essential if you want to grasp coffee at a more fundamental level.
In recent years, a “processing revolution” has taken place in the specialty coffee market, with farmers, exporters, and roasters experimenting with new techniques.
It is increasingly evident that the difference between good coffee and excellent coffee lies in the processing.
In this post, we will explore coffee processing and its role in shaping the unique flavor profiles of coffee cherries.
COFFEE BEAN 101
But before we get into processing, let’s have a nano-sized biology lesson.
See, the coffee bean technically isn’t a bean. In reality, it’s a seed, and this seed is developed inside what we call a ‘coffee cherry.’
Technically, coffee farming is fruit farming.
Processing is all about turning that fruit into a stable and homogenized product ready for export, where it will eventually be roasted.
It usually goes down the way described below.
Stages from cherry to coffee bean
- Plant: The coffee cherry changes from green to red and matures slowly as harvest season approaches.
- Picking: During harvest season, pickers will visit all coffee trees. Ideally, they’ll only pick the ripe cherries.
- Processing: After the cherries have been collected they will be processed. In its essence, the processing is all about removing the pulp and drying the seed without creating mold or fermentation problems. There are three main ways to process coffee:
- Washing (aka wet processing)
- The Natural method (aka dry processing)
- The honey process
- Dry milling: The last step of processing is to remove a protective layer called ‘the parchment’ that sits outside the bean. It’s a thin but hard shell.
- Green bean: This is the finished agricultural product that is ready for export. The moisture level should be around 10-12 %. It should be stored carefully.
- Roasting: The green bean is bought by the coffee roaster, where it can be stored for up to a year. The roaster will usually be located in the country of consumption.
THE 3 MAIN PROCESSING METHODS
When you go into the more delicate subtleties, there are countless ways to process coffee, but generally speaking, they fall into three main categories: Washed, natural, and honey.
Each processing method results in different flavors, and this is important to note if you’re looking for particular characteristics in your coffee.
In the following sections, I’ll go in-depth with the finer details.
tHE natural process
The oldest method for processing coffee beans is the natural processing method. You may have heard it called ‘dry processing’ as well.
Typical Notes: Strawberry, Blueberry, Raisin, Pineapple, Jackfruit, White Wine
Originated in: Ethiopia and Yemen.
Flavor Profile: During the drying process, the coffee beans absorb the fruit’s flavors, allowing for a more intense, sweet flavor. You might experience a strawberry or blueberry note. It’s common to get fermented almost winy flavors with natural processed coffees. Regions with a long tradition for eating pickled and fermented food will often favor naturals. In places like Taiwan and Korea, you’ll find many natural processed coffees in the coffee shops.
Method: This kind of processing is very crude and basic in its most simple form. The cherry is harvested and placed on raised mats, beds, or patios to be dried in the sun.
Once the cherry has reached the correct right moisture level, the coffee will be hulled to remove the coffee cherry’s skin and the pulp. Typically this will take 2-4 weeks.
Historically, natural processed coffee was considered low-grade since it doesn’t remove defective cherries the same way washing does.
Many things can go wrong during the drying process, so the farmers need to pay constant attention to the cherries to avoid mold or over-fermentation.
tHE washed process
The washed process is the most common and also the most consistent coffee processing method.
Typical Notes: Chocolate, nuts, lemon, florals, stonefruit
Originated in: Latin America
Flavor Profile: Washed coffee is what most people recognize as ‘normal coffee.’ Compared to the other main types of processing, it tends to increase the acidity and clarity of the coffee bean.
With this method, you typically end up with a refined and balanced coffee. The best washed coffees have complex notes, a medium body, and a pronounced acidity while still being sweet. They are great for being brewed in a typical coffee machine.
Method: The washed process is the most consistent method for quality. Washing takes place at a dedicated wet mill. There is typically a washing station at the larger farms in Latin America. In Africa, it is more common for smallholder farmers to bring their cherries to local washing stations owned by coops.
First, the freshly picked coffee cherries are put in water. This is a way to sort out unripe cherries or have some other defect. The green or defect cherries will often rise to the surface. They are called ‘floaters.’
The cherries then go through a de-pulper to remove the outer skin and pulp.
A layer of slime, called mucilage, will be left on the seed. It can be compared to the sticky layer that coats the stone of a peach.
The seeds will have to ferment in water tanks for 8-50 hours to eliminate this slimy layer. The time the seeds are allowed to soak depends on the equipment, climate, and the producer’s preference.
After that, beans will be floated and rinsed once again. The beans are then dried on concrete patios or raised beds until they reach a 10-12 % moisture content.
tHE honey process
This processing method emerged in Costa Rica around 15 years ago. However, the traditional Brazilian way of processing coffee bears many similarities.
Typical Notes: Cane sugar, dates, caramel, apricot, fig, low acidity
Originated in: Brazil and Costa Rica
Flavor Profile: Because the coffee cherry is stripped of its skin, but the pulp remains intact while it dries, this process brings out the sweetness and body of the coffee flavor.
Depending on how much pulp remains, it influences how the end product will taste.
Some are closer to the natural and have flavors similar to dried fruits, while others are more forward and acidic. Usually, they are very sweet and pleasant though.
Method: The beans are de-pulped and laid out to dry with the slimy outer layer (called mucilage) remaining.
In spite of the name honey, processing has nothing to do with actual honey. The name originated from Costa Rica, where coffee farmers would compare the sticky and sweet mucilage stuck to the bean with honey – “miel” in Spanish. Ironically, this coffee tends to be very sweet and fruity, so the name somehow makes sense. In recent years honey processing has become popular with coffee snobs in all parts of the world because it tends to combine the best aspects of both the washed and natural processes.
YELLOW, RED, AND BLACK HONEY
As mentioned above, some coffee producers have started to label their coffee as either yellow, red, or black honey.
These colors refer to what the coffee will look like when it’s being dried. Depending on how much of the pulp is left on the bean, different colors will develop.
- Yellow Honey goes through a semi-washing process that is designed to leave less mucilage around the coffee bean. This leads to a cleaner and sweeter tasting coffee more similar to the washed method. The drying process is usually faster than the red and black.
- Red Honey is also rinsed a bit but it has more mucilage intact and will take on more color when dried.
- Black Honey is often said to have all the mucilage intact.
THE DIFFERENCE BETWEEN PULPED NATURALS & HONEYS
While natural and washed coffee is easy to understand, the definitions can become somewhat murky when we talk about the honey process. Especially because some coffee regions have used different terminology to describe what is essentially the same.
The pulped naturals of Brazil could also be called ‘honey’ or maybe more precisely ‘red honey’, as the process is similar.
Sometimes you’ll also hear the term semi-washed, which can again be compared to yellow honey.
It seems that the specialty coffee industry has taken a liking to the term ‘honey’, so this will most likely prevail in the future – maybe except when it comes to Brazil.
Other processing methods
Even though the vast majority of the coffee produced in the world reasonably could be said to fit within one of the three methods outlined above, there are other processing styles out there that are worth a closer look.
Some are historical relics that still have a small but loyal fan base, while others are new and cutting-edge methods that aim to modulate flavor notes or fermentation even more.
While processing has been more of an afterthought in the last century and before, there’s no doubt that it will be an area of massive focus for future generations of coffee farmers.
We have already seen techniques from the wine industry move into coffee processing, and there is no doubt that this is just the beginning.
The carbonic maceration method emerged in Costa Rica around 15 years ago. However, the traditional Brazilian way of processing coffee bears many similarities.
Sasa Sestic, a world-champion barista, is known to use the so-called ‘Washed Carbonic Maceration’ to process coffee. The process starts with the coffee cherries being harvested and washed.
Once they’re washed, they’re sealed in a stainless steel container that gets carbon dioxide pumped in to remove all of the oxygen from the sealed container.
Once the oxygen is out, the coffee beans will sit in water that is carefully monitored for temperature. These stainless steel containers are then put into greenhouses where the temperature is kept around 24 degrees Celsius. This process allows the beans to macerate in a carefully controlled environment to ensure that the finished product has a very distinct flavor. It also makes it easier to duplicate the same flavors over and over again.
Acetic & Lactic processing
This innovative kind of processing is all about controlling fermentation to modulate the flavor profile.
The innovative Colombian Farm, ‘La Palma y El Tucan’ has created two different signature processing methods called ‘acetic’ and ‘lactic’ processing.
Both are variations of the traditional Colombian wash process, but with some key differences. The pulped beans are fermented in special anaerobic tanks, where the oxygen flow and pH level can be controlled. This promotes the growth of certain strains of bacteria that will create either lactic or acetic acid. After the fermentation, the coffee is dried in two stages. First on drying beds and afterward in a mechanical dryer.
The typical Kenyan processing method creates amazingly clean-tasting coffee.
Kenyan coffees are famed worldwide due to their high acidity, clean flavors, and unique notes of apple, blackberry, and tomato. Part of this is down to the unique Kenyan coffee varietals SL28 and SL32, but another reason is the special almost all coffees are processed in this country.
The Kenyan method is often called double fermentation. The beans are first soaked for 12 to 46 hours to remove any pulping residue. Then they are washed and rinsed off. But then they are put in a second fermentation tank, where the process repeats itself for 12-24 hours – this time with significantly less sugar. Again, a wash and soaking follow.
After that, the beans are laid out to dry in two stages. A rapid one and a slower one. When the coffee has reached 11-12 percent moisture content is ready to be milled.
Wet hulled & gilling basah
Much of Indonesian coffee’s unique flavor is derived from this crude and unusual processing method.
Wet hulling, called ‘giling basah’ in the local language, is the main processing method on the islands of Sulawesi and Sumatra, which are the biggest coffee regions in Indonesia.
You could be forgiven for thinking that wet hulling and the washed method have many similarities, but in fact, their flavor profiles couldn’t be more different.
In the world of specialty coffee, this kind of processing is frowned upon. It’s a bit like taking a nice piece of Kobe steak and then smothering it with ketchup.
Smallholder farmers carry out the first step themselves. It involves de-pulping the cherry and then fermenting the beans by letting them soak in whatever kind of tub, tank, plastic bag, or container they have around in their backyard.
Once they’ve soaked for a day, the beans get washed in order to remove any mucilage left. Then the beans are sundried for two to three days until the moisture content is between 20 and 24 percent.
At this point, the farmers will sell the beans to a middleman, who will wet-hull them right away with a machine that is specially designed to handle semi-dry parchment. Hence the name; wet-hulling. These machines are very powerful and they can easily damage the beans.
MONSOONED MALABAR COFFEE
Monsooned Malabar coffee is a rather old-fashioned processing technique that doesn’t get much love from the specialty coffee community. However, once in a while you still see this particular bean show up in an espresso blend.
The Malabar Monsooned coffee process originated on the Malabar coast of India, where it took several months to ship coffee beans to Europe. During the journey, the beans were exposed to various weather conditions, including monsoons, which gave them a distinct flavor. However, as transportation improved and the journey became shorter, customers began to complain about the lack of the unique “monsoon” flavor. To replicate the old flavor, a new processing method was developed.
The process involves picking coffee beans, sun-drying them in large barbecues, and grading them into two piles – ‘A’ and ‘AA’. From June to September, the beans are then exposed to constant monsoon moisture in well-ventilated warehouses, where they are turned and raked multiple times. The constant moisture exposure causes the beans to swell and turn pale gold in color.
However, due to the low pH level resulting from the moisture exposure, most specialty coffee customers tend to avoid this type of coffee.
Processing in the future
Historically, the washed process has been seen as superior to other processing methods. Partly, because it had a taste that was considered more ‘clean’, but also because it was efficient at sorting out unripe cherries or other defects.
This is about to change. Specialty coffee consumers, as well as the ’emerging’ coffee markets in Asia, are looking for novel flavors, and this demand is met by innovative farmers, who are able to integrate agricultural science into their processing methods. This enables them to create interesting and complex lots without the risks inherent to dry-processed coffee in the past.
This trend can also be observed at competitions such as the World Brewers Cup, where three consecutive winners from 2015 to 2017 all opted for natural-processed coffee.
In 2018 the winner used a bean that had undergone carbonic maceration. Clearly, there’s an increased awareness about processing all levels of specialty coffee today.
Like there are different categories for wine; red, white, and rosé, we’ll probably also start to think about coffee in terms of processing in the future.