If you are a regular coffee drinker, you’ve probably tasted a few different types of coffee. It’s natural to explore the different coffee bean varieties and ways of processing them.
That curiosity leads to the discovery of rare coffees and coffee processing methods such as fermentation.
You may only think of yogurt, wine, or kombucha when you think of fermentation, but it occurs in the coffee industry too.
It’s part of the production process of coffee that makes it easier for coffee producers to extract beans from coffee cherries.
What is Coffee Fermentation?
Fermentation is the process of breaking down the sugars in food into simpler substances. It happens when you expose coffee cherries to micro – organisms such as bacteria and yeast.
The bacteria, yeast, and other microorganisms used in fermentation break down the organic matter in coffee cherries. They leave behind compounds such as carbon dioxide, acid, and ethyl alcohol that give fermented coffee a unique flavor, depending on their variety.
Although you can ferment coffee after it is brewed, the most common fermentation processes are performed on coffee cherries. They are fermented through wet or dry processes to remove the pulp and mucous layers around the coffee bean.
The rate of coffee fermentation is faster in hot than wet areas. Therefore, although it takes a minimum of 18 hours to ferment coffee, it may take longer depending on where it is fermented.
Different Traditional Ways of Fermenting Coffee
The coffee fermentation process adds flavor to coffee beans by improving their acid content and flavor. Here are four coffee fermentation processes you should know about.
1. Dry Fermentation
The dry fermentation process is usually done under the sun in places with little water. These are dry regions such as Ethiopia, where coffee is grown in arid areas.
Dry fermentation is also referred to as a natural fermentation process because nothing is done to the cherries to encourage fermentation apart from washing them.
The sun’s heat softens the coffee cherries making it easier to separate the coffee beans from the pulp. Dry fermentation gives coffee beans a fruity, wine-like flavor.
2. Wet Fermentation
There is also the wet fermentation process where the coffee cherries are de-pulped and the beans soaked in a water tank for 12 to 48 hours to ferment. It is mainly done in coffee-producing regions with a predominantly humid climate.
Wet fermentation aids in the removal of a mucilaginous layer attached to the skin of the coffee bean. The mucilage falls off during the fermentation process leaving behind coffee beans that are washed and put out to dry.
Wet fermentation improves the acidic content of coffee beans giving them a pleasant mouth – feel. It also brings out their individual flavor notes.
3. Honey Fermentation Process
Coffee can also be fermented through the honey method, which is a bit complicated when compared to the dry or wet fermentation processes.
During honey fermentation, the coffee processors remove a little of the pulp in a coffee cherry leaving behind a part known as the “honey” covering the coffee bean.
The honey is left to ferment on the coffee bean for 18 -25 days. Honey fermented coffee beans are characterized by floral, sweet notes.
4. Anaerobic – Environment Fermentation Process
Some coffee producers also use the anaerobic – environment process to ferment coffee cherries. During this process, coffee cherries are fermented in a vessel stripped of all its oxygen.
Anaerobic fermentation produces coffee beans with a special flavor and acids such as lactic acid.
Modern Coffee Fermentation Processes
There are also those coffee beans that are fermented through what you would call modern processes. That refers to the vessels they are fermented in and the substances used to enhance their fermentation. Here are some examples.
1. Kopi Luwak Coffee
Kopi Luwak coffee is a type of coffee collected from the poop of Asian Palm Civet cats. The civet cats eat coffee cherries that ferment in their bellies, imparting a distinctive flavor to them.
Once the Civet cats poop, coffee producers collect the fermented coffee beans from their poop, wash, and dry them before roasting.
Kopi Luwak coffee is said to be of high quality because Civet cats only eat the best coffee cherries from the coffee plant. And because it undergoes some form of digestion in their bellies, it is less acidic and is packed with amino acids.
2. Green Coffee Fermentation
Green coffee fermentation is another unique coffee processing method. This process involves the fermentation of dried green coffee beans by exposing them to special microorganisms that give the coffee beans a pleasant flavor.
You could say green coffee fermentation involves double fermentation. The coffee beans are first fermented during the process of depulping to expose the green coffee beans. These beans are then dried and put through a second fermentation process.
Green fermented coffee beans are also referred to as cultured coffee beans. They are low in caffeine and have a bold, sweet flavor. They are also gentler on the digestive system due to the second process of fermentation they undergo that leaves some gut-friendly bacteria on them.
3. Barrel Fermentation
Some coffee producers also ferment their coffee in barrels previously used to store liquor or wine. That creates coffees like whisky barrel-aged coffee that’s fermented in whiskey barrels for a month or two.
The moisture in the liquor or wine oak barrels hastens the fermentation process and gives coffee an interesting aroma. Barrel fermented coffee beans make excellent pour-over coffee and cold brews.
Those are three unique processes of fermenting coffee that are used to create specialty coffee. Other forms of coffee fermentation you may be unaware of are Jaggery fermentation, fruit juice fermentation, and milk and honey fermentation.
You can buy these fermented coffees from specialty coffee stores or online from gourmet coffee vendors. Some popular vendors are Corridor Seven Roasters and Blue Tokai Coffee Roasters.
Does Fermentation Make Coffee Beans Better
There is no doubt that fermentation enhances the taste of coffee beans. It reduces their sugar content, balances acidity, and gives it amazing body. That’s why it’s an integral part of processing coffee cherries.
However, any probiotics produced during the fermentation of coffee cherries are lost during the roasting process. Only green fermented coffee and coffees fermented after the roasting process contain gut-friendly bacteria such as probiotics. That’s why home fermentation is such a popular process these days.
How to Ferment Coffee at Home
All you need to ferment coffee at home is a culture starter with some bacteria or yeast that can kick start the fermentation process. These culture starters are called SCOBYs.
Here’s how to ferment coffee at home using a culture starter.
7 cups of brewed coffee
I kombucha SCOBY mix of bacteria and yeast
A large mason jar
A rubber band
- Stir the sugar into the brewed coffee until it dissolves.
- Pour in the Kombucha mix and cover the jar with the cheesecloth.
- Secure the cheesecloth around the jar with a rubber band and keep it in a cool, dark place for fermentation.
- Leave the coffee to ferment for 3 – 7 days. Make sure you taste it in between the fermentation process to check how the flavors are developing.
- If it’s too bitter, add some sugar and let it ferment for longer. In case the coffee gets rancid, pour it out and start the process again.
- Once you are satisfied with the flavor of your fermented coffee, keep it in the fridge to cool before drinking.
Although fermentation occurs the same way in coffee cherries by breaking down their sugars, the resulting coffee beans don’t taste the same. The coffee variety used in the fermentation process will determine the flavor of the coffee bean you get.
Other steps added to the fermentation process, such as soaking the coffee cherries in water, removing oxygen from the fermentation vessel, and leaving some pulp on the coffee beans, give coffee beans a special flavor.
You may try the different types of fermented coffee beans in the market to find out how they taste. Approach a coffee roaster for assistance, and they will be able to sell you a batch of beans produced using one of these coffee fermentation processes.