Understanding how coffee fermentation affects flavor
Many people are not aware of this fact, but all coffee is fermented in some way or another - either in water, under the sun or with the juices of their own fruit. Fermentation occurs when yeasts accumulate and break down the sticky mucilage that clings to the coffee bean.
New ways of developing flavor and removing fruit from coffee seeds seem to be emerging every day. Here is a run down of some of the major coffee fermentation methods that you have probably tasted in your cup of coffee without even knowing.
Natural/Dry Fermentation
Also known as natural or dry processing, is the oldest and most traditional method of coffee processing. In this method, the freshly picked coffee cherries are spread out on large drying beds or patios and left to dry in the sun for several weeks. During this time, the natural yeasts and bacteria present on the surface of the cherries begin to ferment the sugars inside the fruit. As the cherries dry, they turn dark and shrivel up, and the fermentation process produces a range of fruity and wine-like flavors in the coffee beans.
Dry fermentation can result in a wide variety of flavor profiles depending on the specific microorganisms present in the fermentation process. Some dry-processed coffees are known for their bright, fruity notes, while others have a deeper, more complex flavor profile.
Washed/Wet Fermentation
Also known as washed processing, wet fermentation is a newer method of coffee processing that was developed in response to concerns about quality and consistency in dry-processed coffees. In this method, the cherries are sorted and then pulped to remove the fruit and mucilage from the bean. The beans are then soaked in water tanks for up to 2 days to remove the remaining fruit, mucilage and parchment from the beans. During this soaking period, the beans undergo a controlled fermentation process that helps to break down the sugars and remove any unwanted flavors.
Wet fermentation is known for producing coffees with a cleaner, more uniform flavor profile than dry fermentation. The process removes any unwanted flavors from the beans, resulting in a brighter, more acidic cup of coffee.
Honey/Semi-Washed Fermentation
Semi-washed fermentation, also known as honey processing, is a newer method that combines elements of both dry and wet fermentation. In this method, the skin and most of the pulp are removed from the cherries, but some of the fruit is left on the bean to ferment and dry. The mucilage is usually left on as well. The beans are then dried on patios or raised beds, with frequent turning to ensure even drying. This method is called "honey" processing because the remaining fruit on the bean gives it a sticky, honey-like texture.
Semi-washed fermentation produces a wide range of flavor profiles depending on the level of fermentation and drying. It can result in coffees with a syrupy sweetness and a range of fruit and floral notes.
Anaerobic or Carbonic Fermentation
In addition to the traditional methods of coffee fermentation, there is a newer method that has gained popularity in recent years called anaerobic fermentation. Instead of exposing the coffee beans to oxygen during the fermentation process, anaerobic fermentation requires keeping the beans in an oxygen-free environment.
Anaerobic fermentation is known for producing coffee beans with a sweeter, more complex flavor profile. Without oxygen, the bacteria and yeasts that grow during fermentation are different, leading to a different flavor profile. The process is often used for low-altitude coffees, where the warmer temperatures and lower humidity make anaerobic fermentation more feasible. The primary difference between anaerobic fermentation and carbonic maceration is whether or not the coffee is pulped, so you may hear these terms used interchangeably.
In Conclusion
The type of fermentation used in coffee processing has a significant impact on the flavor and aroma of the beans. Dry fermentation often produces complex, fruity flavors, while wet fermentation can produce a cleaner, more uniform flavor profile, while semi-washed fermentation offers a balance between the two. Whether you prefer a bright and acidic cup or a more complex and fruity flavor, there is a coffee fermentation method that will suit your taste.