‘Ferment’ was considered by many as a defect, in the early 2000’s and before. It was something that stood out, marked an error in the wet or dry process, and would cause a coffee to be recupped or even rejected. Then it became cool, embraced, understood and requested.
The early days of naturals (at least as far as speciality UK/European coffee culture taught us) were exciting and fun. Fruity, jammy coffees abounded and new origins embraced what at the heart of it, is a really old process. We’d gone from clean, washed, Yellow Bourbon or Maragogype to Geishas, fruity natural coffees, to discovering terminology such as maceration, carbonic, anaerobic, inoculated, co-fermented, and infused. Now its augmented, elevated, subverted.
It’s easy to see these as a process development. Manufacturing refinement. A set of rules to follow (especially with inoculation) to provide a given outcome. But in doing so, are we missing one of the biggest factors in coffee itself? Terroir.
A Wider View of Terroir
There is a lot to be said for the Terroir approach. A strict scientific view would be that if you recreate the exact conditions anywhere, then the same result is achievable. Terroir does not, therefore, exist. This is true, but also nonsense. In practice we do not recreate identical environments, and it is in this gap that terroir becomes meaningful.
So what is the ‘there’ that we are referring to? A particular topography gets an extra amount of rain at the right time to swell the beans or set the cherry. A hot wind carries up from the south to provide ideal drying times. The altitude is high enough to allow a change in temperature from the heat of midday to the cool of the evening that perfectly suits the varietals’ requirements. Shade trees extend their benevolence to allow a longer, slower maturation creating a more even, complex fruit. Common parlance refers to terroir as the soil, primarily, and a microclimate. Coffee takes its nutrients from the earth, and that mix of elements in the soil that create the precursors to flavours we associate with the area.
The combination of these can earn recognition through Protected Geographical Indications (PGIs). Protected Denomination of Origin (PDO), a type of PGI, requires not only varietals and processes, but people, methodologies and localisation. The living history of the place. It’s a synergy of what has always been and been allowed to develop over the course of decades. It’s become so embedded in the way of life it is now recognised and rewarded for being so. And perhaps, this understanding allows us to extend the relationship with terroir to not only processes, but what is driving those processes. Yeast. Microbes.
In doing so, we remove the utilisation of fermentation as purely a step in the manufacturing of green coffee and embrace it as a part of the terroir, the inherent character of the coffee. A quality to be embraced and applauded. Because here’s the thing. Yeasts and bacteria are not neutral tools. They are living organisms that grow, respire and feed within the wider ecosystem of the farm. They directly influence the flavour of the coffee that we drink. For most of the year they exist in soil, on plant surfaces and in the surrounding environment. When fermentation begins, the microbes active in the tank reflect the conditions they have adapted to over time.
Microbes as Part of Place
In inoculating a fermentation, often we are not increasing the microbiome, we are reducing it. Way back in 2015, at Re:co in Gothenburg, Master of Wine Isabelle Legeron spoke about the wine industries’ experience and understanding with terroir, including the fermentation process. Part of that includes the globalisation of taste, and with that, the mass introduction of yeast in the 1970’s.
The introduction of yeast was very much behind the growth of the New World wines, and perhaps there is analogy there that is needed in coffee with the unsuitability of much of the coffee growing areas currently with climate change. But what you see a lot in wine now is growth in natural wine, which can be described as being produced with minimal intervention, little to no additives and focussing on native yeast fermentation, to reflect and celebrate the terroir or unique characteristics of the vineyard.
What that suggests here too, is that the fermentation is part of that terroir, not just a process applied to the terroir. A study published back in 2021 in Frontiers in Microbiology, specifically looked at examining how altitude alters microbial composition and metabolic outputs in fermentation. This was accompanied in 2025 by another study comparing microbiomes in two different areas and their effect on flavour too.
What they both showed is that there were environmental variations in the yeasts, microbes and bacteria that we rely on to do the fermentation and therefore impart flavour to the bean. That very variation is what we override when we inoculate a coffee with one strain. That may be for a very good reason – labour management, flavour, innovation. But we are adapting what nature is already doing.
We know from our own work with Daterra the effect light plays on coffee fermentation. Each farm, each region, each country, will have its own subtle variation of light, as it radiates from the sun through clouds, ozone, and daylight hours. Its planetary location is part of the very controlling forces that are creating the flavour of the bean you are drinking. And what is more terroir than that?
Consumer Expectations and the Role of Language
What this points to, and suggests a path forward for, is that rather than fermentation being a manufacturing step, or an opportunity to instil a particular flavour into a bean (itself no bad thing), embracing it as a part of the actual terroir of the coffee is not only more authentic to the story of that bean, but in line with sustainability, provenance, and ethical sourcing demands. Understanding and being able to tell that story is key.
Of course, that does not exclude a competing, opposing viewpoint, that the co-fermented and infused coffees are driving category growth. They are. But these are for a different audience. The beauty in coffee is that there are lots of options and a huge number of consumers with which to find your audience.
Flavoured syrups and whipped cream absolutely drove growth of coffee consumption at the same time that we saw the explosion of third wave coffees and the ‘discovery’ of varietals unique and special. You want iced, blended, coffee with cream on top? Sure! You want washed El Salvador Maragogype? You can have that too!
Perhaps this is where the issue started. Iced, blended, describes steps in the process of making the drink, so why not include washed as a step too? It’s not immediately obvious that washed means fermented, so it becomes easy to treat as hurdle to be overcome in revealing the end product, a green bean. But it was also right next to ‘El Salvador’ the origin. The region, the farm. The terroir.
A Forward Looking View: Fermentation as Terroir
If we accept that fermentation reflects place through living communities shaped by climate, soil, light and practice, then the question is not whether fermentation belongs to terroir, but how deliberately we choose to express it. Inoculation can stabilise outcomes and serve a purpose, yet native fermentations can reveal the signature of origin in a way that standardised inputs cannot.
This approach also raises larger questions about climate change. If temperature, rainfall and ecological shifts alter the composition of microbial communities across coffee landscapes, the flavour signatures associated with these environments may change too. Understanding how these organisms adapt during the wild period outside the tank, and how temperature changes inside tanks favour different mixes of lactic acid bacteria, acetic acid bacteria and yeast, will be essential for safeguarding regional character in the future.
Different audiences will continue to seek different cups. This is healthy. The opportunity is to name that choice, clearly. To recognise fermentation as something shaped by place rather than merely applied to it. To separate menu language that blurs process and place, and to invite consumers to treat microbial expression as part of the geography itself.
