Coffee bean fermentation is an important step in the production of coffee beans from coffee cherries. Fermentation’s primary purpose is to remove the sticky mucilage that surrounds the coffee beans. If not removed, this polysaccharide-based mucilage can impede drying and increase mould growth.
After the coffee cherries are plucked, the fermentation process begins. The cherries are placed in water tanks or on the ground, and naturally occurring yeasts and bacteria in the environment begin to break down the mucilage. Fermentation normally takes 12 to 48 hours, but this might vary depending on ambient circumstances.
The fermenting duration has an effect on the flavour of the coffee beans. A coffee with a shorter fermentation time will have a more acidic flavour, whereas a coffee with a longer fermentation time will have a more mellow flavour. The type of microorganisms present during fermentation will also have an impact on the flavour of the coffee. Different microbes create different chemicals, resulting in distinct flavour characteristics.
Fermentation has several impacts on coffee beans besides eliminating mucilage. It can help to develop the flavour of the beans while also improving their quality by making them more resistant to mould growth.
Wet fermentation, natural fermentation, and semi-dry fermentation are the three basic types of coffee bean fermentation. The most prevalent process is wet fermentation, which is used to generate coffees with a fruity or winey flavour profile. Natural fermentation is a more traditional approach for producing coffees with earthy or nutty flavour profiles. Semi-dry fermentation is a hybrid of wet and natural fermentation, and it is used to create coffees with a balanced flavour profile of fruity and earthy notes.
The technique of fermentation utilised will be determined by the type of coffee being produced, the climate in which the coffee is grown, and the coffee producer’s preferences.
Fermentation is a critical step in the coffee bean processing process. It can have a major impact on the flavour of the coffee, as well as help to improve the bean quality.
Fermentation types:
Wet fermentation:
This is the most prevalent method of fermenting coffee beans. Coffee cherries are placed in water tanks and fermented for 12 to 48 hours. Naturally occurring yeasts and bacteria aid in the fermentation process.
The water in the tanks aids in the dissolution of mucilage, a sticky covering that surrounds the coffee beans. The yeasts and bacteria then break down the mucilage into simpler molecules that the beans can absorb.
Wet fermentation is a reasonably quick process that is usually completed in 48 hours. This makes it an excellent choice for coffee growers who need to process big amounts of coffee beans.
Wet fermentation has the disadvantage of producing coffees with a more acidic flavour. This is due to the fermentation process breaking down part of the sugars in the beans.
Natural fermentation:
This method of fermenting coffee beans is also known as “dry processing.” The coffee cherries are not placed in water tanks but rather ferment on the ground. This fermentation process is more popular in arid locations where the water in the mucilage evaporates faster.
Natural fermentation takes longer than wet fermentation and can take up to ten days to complete. This provides the yeasts and bacteria more time to break down the mucilage, resulting in more mellow-flavoured coffees.
The disadvantage of natural fermentation is that it is more prone to mould formation. This is due to the fact that the coffee cherries are not protected from the environment and can become tainted.
Semi-dry fermentation:
This is a hybrid of wet and natural fermentation methods for coffee beans. The coffee cherries are first placed in water tanks for a brief amount of time before fermenting on the ground.
This fermentation method combines the benefits of both wet and fermentation. The water in the tanks aids in the rapid dissolution of mucilage, while fermentation on the ground permits the coffee beans to produce a more mellow flavour.
Semi-dry fermentation is an excellent choice for coffee growers seeking a blend of fruity and earthy characteristics.
The technique of fermentation utilised will be determined by the type of coffee being produced, the climate in which the coffee is grown, and the coffee producer’s preferences.
Tasting notes associated with different types of coffee bean fermentation:
- Wet fermentation: This type of fermentation often produces coffees with fruity, winey, or floral flavours. Some of the tasting notes that can be found in wet-fermented coffees include:
- Fruity: Pineapple, raspberry, strawberry, peach, apricot, mango
- Winey: Red wine, white wine, champagne, port
- Floral: Jasmine, rose, lavender, violet
- Natural fermentation: This type of fermentation often produces coffee with earthy, nutty, or chocolatey flavours. Some of the tasting notes that can be found in natural-fermented coffees include:
- Earthy: Mushroom, forest floor, dirt
- Nutty: Hazelnut, walnut, almond
- Chocolatey: Dark chocolate, milk chocolate, cocoa
- Semi-dry fermentation: This type of fermentation often produces coffees with a balance of fruity and earthy flavours. Some of the tasting notes that can be found in semi-dry-fermented coffees include:
- Fruity: Grapefruit, orange, lemon, apple
- Earthy: Tobacco, leather, cedar
- Other: Caramel, honey, spice
Fermentation is a critical step
It can have a major impact on the flavour of the coffee, as well as help to improve the bean quality. The type of fermentation employed will be determined by the type of coffee being produced, the climate in which the coffee is grown, and the coffee producer’s preferences.
It is crucial to note that the flavour notes associated with various forms of coffee bean fermentation are only broad strokes. The flavour of a coffee is determined by several factors, including the type of coffee, the growth conditions, and the roasting technique.