Do you drink coffee because you love the taste or because it gives you energy? Do you drink it to wake up? Perhaps you drink it because it allows you to take a break and relax for a minute.
What if you drank it for other reasons? Do you, like me, want to know as much as possible about the coffee you’re consuming? Do you want to know the process?
Are you that person who wonders what all these hipster baristas are on about? Natural process, typica varietal, sun dried… what does it all mean? After reading this, you’ll know more about coffee and be able to share your knowledge with others.
We take into account numerous factors when choosing the coffees you drink every day, but it might be something of a mystery to you.
This text is discussing all things related to green beans. In my first blog about green beans, I’m going to start by explaining some of the factors involved in your daily cup.
Coffee processing methods
All about the ‘green bean’
Pick up one of our Single Origin information cards and you’ll see ‘Process’ followed by ‘Fully Washed’ or ‘Natural’ or something else written on there; these are general descriptions of what process the coffee cherry has been through to be exported to us as seeds, or, as we know them, ‘green beans’.
A coffee cherry has an outer skin just like a regular cherry when it is picked. The coffee bean has a fleshy part called mucilage, a thin layer of skin called silver skin, and a seed. The part that we all love, the green bean, is inside this shell.
Removing the layers before exporting is called ‘processing’.
Let’s get one simple thing out of the way. Bunches of ripe, deep red coffee cherries are picked by workers.
The varietal of the grape may result in a yellow or orange cherry-looking fruit, or the farmer may allow the grape to darken to a purple (or even darker) to increase the sugar content.
The coffee cherry can have its outer skin removed in several ways. Let’s take a look at each.
1. Washing
The most common practice is washing, accounting for approximately 50% of all coffee produced. The term “washing” is used to describe the process of removing the fruit from the parchment before it is dried.
The cherry must be fermented to help it fall from the parchment. First, the cherries will undergo a de-pulping process that will remove the outer layer and some of the mucilage.
Then, the fruit is placed in fermentation tanks. There are two forms of fermentation: wet fermentation and dry fermentation. Wet fermentation is when the yeast is mixed with the must, and dry fermentation is when the yeast is added to the grape juice once it has been pressed.
A coffee that has been washed often tastes citrusy or like apples, and has clean finishes that can be floral and aromatic, as well as smooth in texture. The acidity in this vinegary product is usually more intense than what you’ll find in other types of vinegar.
In wet fermentation, fruit is covered with water and left to sit. This process can take between 12-18 hours. The producer will be looking for when the fruit starts to peel away from the parchment paper easily.
When they rub a handful of the fruit in their hands, the sound it makes is similar to rubbing marbles together.
The fruit is left to ferment in the dry fermentation tank. The process is riskier as you can over ferment the coffee more easily.
An over fermented coffee might taste like alcohol to some people, but others might not mind the taste. The producer sticks a stick through the middle of the bed of coffee beans to check the process.
If the hole caves in, it’s not ready. If the hole in the bean stays, it is ready for the next process. Once fermented, they are washed to remove the fruit. The coffee beans are then sent to be dried, which I’ll explain in more detail later.
While wet fermented coffees produce a cleaner flavor, dry fermented coffees can provide a sweeter complexity with a bit more body.
2. Dry processed coffee
It is called dry processed because the coffee beans are dried with the cherry intact. The coffee beans are dried with the cherry intact in the dry processed coffee method. Cherries are typically laid onto concrete patios or raised beds after they are picked. This style is usually referred to as “African beds” because it originated in Africa.
Cherries are typically grown in elevated beds made of hessian or a similar material that allows for air circulation. The producer needs to decide how quickly to dry the cherries in both of these methods.
Some of the variables in this process include letting the cherries sit in thick layers or bags in a warehouse first to warm them up and allow for some fermentation, and then spreading them thinly. Some regions simply lay them thinly straight away.
There are also varying degrees of sun exposure to consider, as well as shade from nearby buildings or trees. In some cases, there may be added air circulation from fans or a closed side pergola. You should rake your leaves regularly to keep them from getting too compacted.
The fruit is dried and hard. The producer uses a machine that cracks the fruit layer from the parchment.
Coffees that have been dried naturally tend to be richer in body, with intense flavors of dried fruit or sticky fruit, like stone fruits or berries. Because no water is used, the flavors are usually stronger, but the liquid is usually less clear.
The acidity of the wine can vary, and sometimes it can be inconsistent, but it can often be amazing and easy to distinguish. Natural coffees also cut through milk more easily.
3. Honey processed
The honey process is a middle ground between the washed process and dry process. Honey processed coffee is coffee that has had the sticky texture of the mucilage left on the honey during drying.
In pulped natural processing, the fruit of the coffee cherry is removed first (just like wet processing) and then left to dry, much like natural processed coffee. Although the coffee cherry has sticky mucilage on it during the drying process, it will eventually go away.
This “honey” mucilage changes during honey processing. The honey-like bean is turned frequently to ensure more even drying.
The beans dry and ferment to become red and finally black honey due to oxidation. Red and black honeys are turned less often.
Sometimes the beans aren’t left to ferment for as long, which leaves them yellow or white in color. You can fermented beans to different colors depending on your preferences. They don’t have to be left that long.
Honey processed coffee is less fruity than natural processed coffees, but more complex and sweeter than washed coffees. The lack of acidity is due to the dry fermentation process.
Honey processed coffees are very sweet, like apple juice.
Honey processing can only be done in areas with low humidity, because the drying process is similar to what happens in nature. Drier climates prevent the mucilage from fermenting too much.
Brazil is especially known for the honey process. Ethiopian coffees are also sometimes processed using the honey process instead of the dry process. This is because the honey process doesn’t require much water. There are also coffees from Tanzania and Costa Rica that are made using the pulped natural process.
4. Wet hulled
Don’t confuse wet hulling with washed coffees! This rarer method of coffee processing, which is common in Sumatra, creates a unique flavor that is not very acidic.
After running through the depulper, the beans are then soaked in water for 12 to 48 hours. After the coffee cherries are run through a hand-cranked machine called a depulper, which removes the skin and some of the fruit flesh, the beans are then soaked in water for 12 to 48 hours. The mucilage is then fermented and washed off.
In the wet hulling process, coffee beans that have been depulped and fermented dry for a matter of hours, as opposed to being left to dry for a week like in the washed process.
Coffees that are processed wet are dried until their moisture content reaches around 10%, but in wet hulling, coffee beans are dried to about 50%. The coffee beans will still be swollen when taken off the coffee parchment they’re left to dry on.
These coffee beans will be sold quickly, rather than left to store like natural processed coffee.
Once the roaster or other intermediary has bought the beans, they will be dried again until they reach a moisture content of about 25-35%.
After the coffee beans are roasted, a machine called a wet-huller is used to remove any leftover parchment. The final step is to air-dry the beans again to reduce the moisture content to 12%.
This coffee processing method produces specialty coffee that is known for its body, but without the acidity that wet coffee beans are known for. This coffee has an earthy flavor, but is also bright, and might have notes of herbs, tobacco, or cedar.
The wet hulling method for processing coffee is primarily used in Indonesia on the islands of Sumatra and Sulawesi. The local name, giling basah, means that the coffee beans are ground while they are still wet, referencing the wet-huller machine. For coffee lovers, giling basah coffee beans produce coffee with a fuller body, earthier taste, and less acidity.
5. Fermented coffee
Most coffee processing methods require fermentation, of course. There are also coffee processing methods that involve fermentation.
First, let’s get a couple things straight. There are two basic types of coffee fermentation: aerobic and anaerobic:
Aerobic
Aerobic fermentation takes place when oxygen is present. The coffee beans are dried by air in the shade, which results in a stronger coffee due to the slow aerobic fermentation process.
Anaerobic
Anaerobic fermentation takes place in oxygen-deprived environments, typically occurring in fermentation tanks during the coffee roasting process.
6. Carbonic maceration processing
A popular type of anaerobic fermentation is carbonic maceration. Whole coffee fruit are placed in a steel tank and carbon dioxide is pumped through in the process of carbonic maceration.
When carbon dioxide enters the water, it pushes oxygen out and starts to damage the sticky substance that coats the plant. The process can take as long as months.
The coffee cherries/beans are monitored and when the time is right, the green coffee beans are soaked in water to halt the fermentation process. Then the typical coffee drying process occurs.
Other anaerobic fermentation processes usually work in a similar way, but don’t involve carbon dioxide and take less time.
Carbonic maceration is a process where the fruit flesh is left whole before fermenting. This is sometimes considered part of the washed process, even though the fruit is not washed here.
The pressure in the tank during carbonic maceration and anaerobic fermentation creates more intense flavors.
The coffee beans used in this process can create fruity flavors, similar to wine. This is because many wines go through a process called carbonic maceration. Coffee beans that have been treated anaerobically tend to be bright.
Anaerobic fermentation gives you the opportunity to infuse other flavors into the drying cherry/coffee bean. Additions such as cinnamon, licorice, bananas, pears, etc. can be made to the coffee beans in the tank in order to impart their flavors to the coffee beans/resulting coffee.
It’s one way to get flavored gourmet coffees.
7. Other methods
We’ve talked about the main ways to process coffee, but there are some more advanced methods you might hear about in the future.
These processes are specific to one farm or group of farms, and many are variations of carbonic maceration/anaerobic fermentation.
Lactic processing
The La Palma y El Tucan coffee plantation in Colombia is using anaerobic fermentation with lactic acid to produce coffee beans.
Finca Kilimanjaro’s experimental processing
This coffee farm is known for its flavor-infused and wet fermentation experiments.
One experiment from Finca Kilimanjaro is cascara fermentation
The coffee beans are soaked in a tisane made from cascara for 12 hours before they are dried.
Post coffee processing
After all of the effort to clean the beans, what do you do with them? Those bad boys are prepped for roasting.
After the coffee beans have been harvested and sorted, they undergo a final cleaning, polishing, and sorting (grading) in the dry mill. In the grading process, defected coffee beans are removed.
The best beans will be packaged in bulk, stored, and sold to exporters or sold directly to coffee roasters. Roasting is its own science, which is beyond the scope of this text.
In other words, green coffee beans are roasted to create the desired level of darkness, and then they undergo a decaffeination process. Different coffee beans from different farms and regions are sometimes blended together to create unique roasts.
After the coffee beans have been roasted, they are sold to either coffee shops or consumers. If everything goes well, the coffee that is brewed from these beans will be delicious!