COLOMBIA TROPICAL CASTILLO
Coffee (aerobic and/or anaerobic) fermentation: What is it and how can it improve coffee quality?
So, what actually is fermentation? How can it be used to improve coffee quality? And is it even possible to process coffee without it?
Fermentation is a natural change that happens when you put sugar and water together – and coffee cherries are full of both. And so, just after the cherries are picked, the fermentation process will start.
The thing is, fermentation can improve a coffee’s flavor or ruin it. It’s just a matter of how a coffee producer deals with it.
Fermentation is a key part of post-harvest coffee processing. It can happen in one of two ways:
• Aerobic: This is what happens when oxygen is available. Engineering this kind of fermentation is simple: just leave the recently picked cherries in a tank or a container and let the microorganisms work. Monitor the time and temperature to help you control and analyze it.
• Anaerobic: In this case, coffee cherries are laid in a tank (before or after pulping) and covered in water. That allows different microorganisms to work.
So, what’s the difference?
The anaerobic processes are more homogeneous and easier to monitor, and the aerobics are more heterogeneous and more complex to monitor.
Since fermentation is so complex, there are many different potential outcomes. Poor, uncontrolled fermentation can lead to moldy or even chemical flavors in coffee – which is why it’s so important that the producer understands the process, monitors it, and works according to best practices.
Because when fermentation is successful, it can enhance a coffee’s best attributes. Basically refining the sweetness, acidity, and body of these coffees, and also adding distinguished sensorial notes, like fruits, caramel, chocolate, and others.
For all fermentation conditions, aerobic, anaerobic, and mixed, the time can vary from 16 to 25 hours, in which we consider the process done when we have a brix reading [indication of probable sugar content] of 8°Bx (8 grams of sucrose per 100 grams of sample) and controlling the pH to approximately 4.5, not allowing this value to be lower than that.
It’s important to highlight that it’s not only about the grade; the complexity of these coffees is also enhanced. The sensorial description of these coffees become richer and more complex.
But great coffee isn’t just high-quality: it’s also consistently high-quality. This adds security for coffee buyers and roasters as well as for producers.
And after all, fermentation is inevitable. It’s simply a matter of choosing whether to limit it or embrace it.
Written by Ivan Petrich, Thanks to O’Coffee.