Watermelon co-fermented coffee
- what is it?

Most specialty coffee geeks will know about the most common processing such as washed and natural, but you might scratch your head a little when you hear about our most recent launch Hubba Bubba, which is a watermelon co-fermented nitro anaerobic natural processed coffee. So, here we take a closer look at this new method that adds vibrant and unique flavours to specialty coffee.

Co-fermentation in Specialty Coffee

Co-fermentation is something relatively new in specialty coffee. It draws parallels to winemaking where two or more grape varieties are fermented together. But, co-fermentation in specialty coffee typically adds a fruit or spice that passes its flavour on to the final coffee beans. As an example, in our limited release, Hubba Bubba, the producer has added watermelon to the beans when they are fermenting to create a juicy watermelon flavour.

For more than three years the team at Café Uba has been working on co-fermenting coffee with tropical fruit such as pineapple, passion fruit, orange, mango, banana, coconut among other fruits and aromatic plants. This fermentation technique has allowed them to develop very intense and unique sensory profiles which allow the company to differentiate itself from many coffee producers in the world.

This kind of processing is so new and unique that Universidad de los Andes has carried out research of Café Uba’s coffees. This research looked at the characteristics of fermented coffee which has had a microbial starter culture added.

What is Nitro Fermentation?

Another step that Café Uba adds is creating an anaerobic fermentation environment by using nitrogen to remove oxygen from the fermentation tank. This has several advantages on the final product.

1. It reduces oxidation which in return improves the quality and flavour.
2. Oxygen-free environments can make the performance of certain yeast strains better, potentially creating a more efficient fermentation.
3. Adding nitrogen can help regulate the fermentation rate by limiting the oxygen available, which may be useful for certain fermentation processes.>
4. It can help prevent unwanted compounds forming which may lead to off-flavours in the final product.
5. You get a greater consistency in fermentation across different batches when creating a more controlled environment.  

Using nitrogen to remove oxygen in fermentation is also used by other industries such as beer and wine, so it’s only a natural step that coffee producers are introducing it in their processing to continue to push specialty coffee forward.

So What Actually Happens in a Co-fermentation Nitro Anaerobic Natural Process?

This processing method is a little more complicated than the most common processing: natural or washed, where the cherries are left out to dry after picking, or where they are pulped, fermented, and washed before drying. So what actually happens?

1. Firstly chunks of watermelon are left to ferment for four days. In another process, watermelon juice is also distilled to extract the essential oils. These are both added to the process later on.
2. After picking, the coffee cherries are left in an open tank to ferment for 24-36 hours. This is a spontaneous fermentation with naturally occurring yeasts. After this fermentation, the cherries are pulped and washed.
3. The coffee is then added to a bioreactor. This is essentially a big container which can be sealed to create an environment without oxygen. Along with coffee, the producer also adds a microbial starter culture and the fermented watermelon.
4. The bioreactor is sealed and flushed with nitrogen to remove the oxygen and create an anaerobic environment. It ferments here for an unspecified amount of time until it reaches the desired temperature, fermentation activity, and pH levels. Just before the fermentation is finished, they add the distilled essential oils.
5. When the fermentation is completed, the producer takes it out from the bioreactor and transfers it to dry in the sun first until it reaches 25% humidity. After this, it’s transferred to a mechanical dryer to reduce the humidity to 10-12%.

Fermentation in general in coffee helps develop certain amino acids and compounds which bring out fruity and citrus flavour profiles. It will also help create sweeter tasting notes because of the degradation of sugars, lipids, proteins, and acids into alcohols and acidic compounds, which alter the coffee's aroma and flavour profile.

So, by adding watermelon to the fermentation, you put this development on full max and bring out extreme levels of watermelon flavour in the final cup.

Is Co-fermentation the Future of Specialty Coffee?

Overall, fermentation is a critical step in coffee processing and different techniques and conditions can be strategically used to develop specific desired flavours in coffee. It can greatly enhance the flavour you get in your brew, depending on how the fermentation is managed.

As we’ve discovered above, there are many benefits of co-fermentation. And while many people in the specialty coffee industry often get excited with new developments in coffee, it's important to note that it's still considered an innovative and somewhat controversial technique in the specialty coffee industry.

Traditionalists are somewhat hesitant to embrace new processing methods, viewing them as potentially inauthentic. Some people argue that co-fermented coffees may not meet standards of authenticity, as they can be seen as altered from their natural state. This has led to debates about whether these coffees should be considered genuine specialty coffees.

The Specialty Coffee Association has also recommended that co-fermented coffees are clearly labeled if non-coffee additives are used. This is important for transparency and consumer safety but also adds complexity to labeling requirements.

One thing is clear: it offers very exciting opportunities for innovation in specialty coffee. Its future will depend on how the industry navigates these issues as well as consumer acceptance.

What is your take on this new fermentation process? Explore co-fermentation with Hubba Bubba.