The Ultimate Coffee Glossary


What does Fermentation mean?

In coffee cultivation and processing, fermentation is a crucial step in the wet process of coffee fruit. It involves the breakdown of the fruit layer, or mucilage, that covers the coffee seed, allowing it to be washed off. Fermentation is typically done soon after picking the cherry from the tree, and can last 12 to 24 hours depending on various factors, including temperature. Once the mucilage layer feels slimy and the parchment layer feels rough like sandpaper, the coffee is ready to be washed. Good fermentation and subsequent drying can lead to the cleanest coffee flavours in wet-process lots.
It's important to note that coffee seeds themselves are not fermented, as that would result in defective coffee. Instead, it's the fruit coating the outer parchment skin that is broken down through the action of peptic enzymes in the coffee. Fermentation must be carefully monitored to ensure the right balance of enzymes and acids are present, which can vary depending on factors such as altitude, temperature, and time. If fermentation is not done properly, it can result in off-flavours and defects in the final cup.
Proper fermentation is crucial for producing high-quality coffee. Under-fermentation can result in coffee that is difficult to wash and dry, while over-fermentation can result in off-flavours and negative effects on the final cup quality. Factors such as temperature, time, water quality, and the microbial population of the fermentation tank can all have an impact on the fermentation process.
Additionally, the method and duration of washing the coffee after fermentation can also influence the final cup quality. Finally, it's worth noting that the wet process of coffee production, which involves fermentation, is just one of several methods used to process coffee, each with its own unique characteristics and effects on cup quality.
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