So, there's a lot of talk about fermentation within the coffee industry. Its impact on flavour is just one aspect.
I'm Phil, P&R Head of Coffee. I'm in a fortunate position to be able to taste coffee from all around the globe, various varietals and coffees that have been processed in all manner of ways. Some methods challenge the perception of what coffee can taste like.
Importantly, I find myself forced not to be biased by preconceived notions of what to expect from particular coffee regions and varietals.
Recently, I spent some time in Kenya attending the Fermentation Training Camp (FTC). I've put together this article with the aim of unpacking "fermentation" and its impact on coffee.
What is a Fermentation Training Camp
Fermentation Training Camp (FTC) is designed to provide coffee professionals with in-depth knowledge and practical skills in coffee processing, focusing particularly on the role of fermentation. It combines expert-led sessions with hands-on experimentation to allow students to refine their craft. This course is aimed at coffee professionals who wish to learn more about coffee processing and specifically, coffee fermentation.
Why fermentation?
Fermentation in coffee is inevitable. It starts as soon as the coffee cherry is removed from the tree. It only stops when all the source food (sugar) is gone, there is minimal moisture, or the temperature conditions are not suitable (too hot/too cold). This gives us our parameters to work within.
So, is fermentation in coffee good? It can be very good! It can also be detrimental, which is why it’s important to understand and control it.
Diving deeper into fermentation
What can we actually control? It depends on what equipment and setup we are working with. We learned at the fermentation camp to work with what we have and to be consistent with each process. For example, If we can’t get to the de-pulping of the cherries as soon as they are delivered it’s best to store them somewhere cool and dry (this slows down fermentation). This step also needs to be considered and planned for future lots when trying to yield consistent results. Submerging the coffee (pulped or whole cherry) in water (during the fermentation stage) is also a great way of controlling the intensity of fermentation. This provides the best way to homogenise the environment. It’s more temperature-stable and easier to ensure all the good yeast and bacteria can get to all the available food to create that flavour we are after.
We can also control the fermentation by selecting the yeast and bacteria that are pivotal to the flavour and characteristic outcome. At FTC, Lucia Solis educated us on a few ways to do this.
Different protocols
One protocol we learned was called the “naked process”. This is not so much about controlling the fermentation as it is about removing the mucilage from the de-pulped coffee (limiting fermentation) in preparation for drying. This protocol is used as a “mechanical” way to remove mucilage. It’s a way to understand the coffee’s characteristics with limited interaction with the mill's normal protocols. It is important to identify the kind of impact the fermentation is having. It’s entirely possible that the fermentation is having a limited impact or even a negative impact. There could be steps in the protocol that are unnecessary, overly complicated and therefore draining valuable time and resources for no additional benefit. The naked process is an accessible way to create a “control” lot (i.e. benchmark coffee lot) to better understand other steps during the processing.
Another protocol we tested was the lactic process (Lactic Acid Bacteria). This involves using a salt solution (2%) dissolved into the submersion water. While a lot of washed coffees go through this process (submerged fermentation), usually it’s up to chance as to which microbes are available and dominant in the fermentation. So, how does Lactic Acid Bacteria (LAB) survive in these conditions? Well, LAB is salt-tolerant or halophilic, whereas many of the other competing microbes aren’t so keen on salt. This provides the perfect environment for lactic fermentation. But what’s all the fuss about lactic fermentation in coffee? It’s a great bacterial strain that creates a lot of delicious flavours we enjoy in coffee. It makes the coffee creamy, sweet and fruity. Unfortunately, we don’t always know if it’s available in the environment, but if it is, you’re in luck!
The last two protocols we were shown were inoculations or controlled fermentations, which allow precise manipulation of flavour profiles by introducing specific, well-studied microbes to dominate the fermentation process. This is where we provide the coffee with specific yeasts and/or bacteria that we would like to be dominant in the fermentation. The first was a Saccharomyces yeast strain Intenso™ from Lal Cafe, and the second was a Pichia yeast and lactic bacteria combination Smartbev™ by Chr. Hansen. These yeasts and bacteria are specially selected and tested over many different coffee lots to create characteristics in coffee that are sought after. The Saccharomyces needed to be rehydrated and fed until we were ready to add it to the tank. This was a careful process of using hot water at the right temperature to help activate the yeast while making sure not to let it die before adding it to the tank by feeding it. One important thing Lucia noted here is to make sure the temperature differential between the yeast slurry and coffee is not too great, as this could shock the yeast and you’ll end up with lacklustre fermentation.
The Pichia yeast with bacteria was already activated and only needed to be added to the fermentation tank. This yeast, however, needs to be stored below a certain temperature to keep it alive before adding to the tank, making it a little more complicated.
Starting
So where do we start when thinking about fermentation and inoculation? We start by asking some questions.
How is the coffee without a specific fermentation? What do I need the fermentation to achieve? How much coffee volume do I need to ferment? Is it scalable? Do I have the tools and tanks to successfully complete the fermentation? And most importantly - Do I have a market to sell this to?
FTC wasn’t just about learning different ways to manipulate or control the fermentation in coffee. It was a holistic course outlining everything from identifying when to harvest cherries to creating a drying plan and managing it to work with the volume of coffee and space you have. It was also a chance to meet many people from all over the coffee industry and world to exchange ideas and learn from each other.
For anyone interested in attending one of these courses I highly recommend it. It’s an interesting part of coffee processing and I believe a big part in the future of flavour development for coffee. You can find out more details here.
At Pablo & Rusty’s, we source and roast exceptional single-origin coffees.
We'll frequently offer coffee that showcase unique fermentation methods as part of their processing. You can explore our current Single Origin collection to taste the results for yourself. Happy brewing!
