← Coffee guide

Co-fermentation and added flavours in coffee - the speciality controversy

Coffee that tastes clearly of cinnamon, strawberry or passionfruit - so strongly that it is hard to believe it is still coffee? Behind such profiles stands co-fermentation: fermenting coffee beans together with fruit, spices or other additions. It is one of the most controversial novelties in the world of speciality, dividing the industry into two camps. Some see in it creativity and new flavours, others a betrayal of the idea that good coffee should give the clean voice of origin. The line between co-fermentation and plain flavouring is often thin, and the key becomes transparency. Here is a guide to co-fermentation: what it is, where the flavours come from, how it differs from infusion and why it stirs such hot debate about honesty and terroir.

What co-fermentation is

Co-fermentation is a processing of coffee that consists of fermenting the beans together with additions - fruit, spices or other ingredients. During active fermentation, when microbes process the sugars in the mucilage, fruit or spices, for example, are added to the tank. The coffee then absorbs the volatile compounds from these additions, which build into its flavour profile. The result is intense, unconventional flavours, far from classic coffee: cinnamon, strawberry, blueberry, passionfruit, ginger or vanilla. It is an extension of the idea of experimental fermentation, but with an ingredient from outside added. The key word is together: the additions are present during the fermentation, not thrown into the finished coffee. Understanding that co-fermentation introduces a foreign ingredient into the fermentation process is the starting point for the whole controversy. We cover fermentation without additions more in anaerobic fermentation.

Where the intense flavours come from

The intense flavours of co-fermented coffees come from two sources at once. First, the fermentation itself, often anaerobic, builds fruity and winey notes, as in classic experimental processing. Second, to this are added the volatile compounds from the added fruit or spices, which the coffee absorbs during fermentation. This is why the profile is often so clear and specific - the taste of cinnamon or strawberry here is not a subtle suggestion but a dominant note. Unlike ordinary fermentation, where the flavours arise only from the transformations in the mucilage, here part of the character comes directly from the added ingredient. It is precisely this directness that raises questions: how much is this still the flavour of coffee, and how much the flavour of the addition. The line between natural absorption and plain flavouring becomes key here, and often unclear.

Co-fermentation versus infusion

It is important to tell co-fermentation from infusion, though in practice they are often confused and mixed. Co-fermentation is the addition of ingredients during active fermentation - the coffee absorbs their compounds in a natural microbial process. Infusion, by contrast, is the addition of flavour after fermentation, or even the soaking of the beans in flavourings or extracts. The difference is significant: one is fermentation with an ingredient, the other is seasoning a finished bean. The problem is that the line is often blurred, and some roasters admit that not only fruit but also powdered additions or flavour extracts end up in the tank. Then it is hard to speak of pure co-fermentation. This is why transparency becomes so important: whether the producer honestly says what they added and when. Without this transparency the consumer does not know whether they are drinking fermented or simply flavoured coffee.

A table: three approaches

Let us gather the three approaches in one place:

The table shows where the dispute lies: classic fermentation is undisputed, infusion is open flavouring, and co-fermentation lies in between - and it is precisely this grey zone that stirs the most emotion.

The purist debate

Co-fermentation strikes at the foundation of the philosophy of speciality, hence the sharp opposition of purists. For decades speciality has bet on the clean voice of origin and variety - terroir, that is the expression of place, soil and climate in the flavour. Co-fermentation reverses this approach: instead of highlighting the natural character of the coffee, it lays a flavour from outside upon it. Traditionalists argue that such methods stray from the natural terroir and can cover the inherent qualities of the coffee. An extreme example is the famous incident at the world championship in 2017, when a coffee tasted so strongly of cinnamon that it caused a storm and a debate about the limits of processing, later named cinnamongate. For purists it is a sign that co-fermentation blurs what is most precious in speciality coffee: the truth of place. It is a dispute about the very essence of what good coffee is meant to be.

The supporters arguments

The other side, though, has its own strong arguments. Supporters see in co-fermentation creativity and a widening of the boundaries of flavour - coffee becomes a field of experiment, like cooking or winemaking. They stress that new, attractive profiles draw in new consumers and can raise the value of coffee from lesser-known regions, giving farmers a better price. These are real economic benefits for producers. They also argue that since it is done deliberately and openly, and the coffee tastes good, there is nothing wrong with it - what counts is the result and honesty, not the dogma of purity. For them co-fermentation is simply another tool, not a betrayal. The dispute is therefore not black and white: it is about whether coffee should be a faithful record of place or also a field of creative play with flavour. Both values make sense.

The key: transparency and the label

In the whole dispute transparency turns out to be the most important. Most of the criticism comes not from the adding of flavours itself but from hiding it from the consumer. If a coffee is co-fermented or flavoured, and is sold as a natural coffee of a wonderfully fruity profile, that misleads. This is why the industry increasingly loudly demands transparent labelling: a clear distinction of whether we are dealing with pure processing, co-fermentation or flavouring. At barista competitions full transparency of the process is required of the producer. An honest label lets the consumer choose deliberately - some will love a cinnamon coffee, others will avoid it, but everyone has the right to know what they are drinking. Transparency resolves most of the dispute: the problem is not that flavours are added, but whether it is stated outright. Transparency is the foundation of trust.

How to sense it in the cup

You will often recognise a co-fermented coffee by an unnaturally clear, specific flavour of the addition. If a coffee smells and tastes exactly of cinnamon, strawberry, passionfruit or fruit gum - so unambiguously that it is hard to attribute to the coffee itself - that is a good clue that it is co-fermentation or flavouring. A classic, even very fruity coffee has flavours more complex and less literal. A co-fermented profile is often downright candy-like and one-dimensional in its intensity. It is worth reading the label and description - an honest producer will state that the coffee is co-fermented and with what. Compare such a coffee with a classic washed one from the same region, to feel the difference. Over time you will start to recognise the added flavour and decide whether it suits you. We cover classic processing more in natural processing.

The essentials in brief

Let us gather it up. Co-fermentation is fermenting coffee beans together with fruit, spices or other additions, whose volatile compounds the coffee absorbs, giving intense flavours like cinnamon or strawberry. It differs from infusion, that is seasoning the coffee after fermentation, but the line is often blurred. The method divides the industry: purists see in it a betrayal of terroir and the purity of origin, and supporters creativity, new flavours and a better price for farmers. An extreme example of the dispute is cinnamongate from the 2017 championship. The key to a resolution is transparency: the problem is not the adding of flavours itself, but hiding it from the consumer. An honest label lets you choose deliberately. Now you know where these flavours come from, how co-fermentation differs from flavouring and why it so divides the world of coffee.

Note every coffee in GustoNote - including the processing and the added notes you sense. Over time you will start to recognise co-fermentation and decide whether you prefer the clean voice of origin or a creative experiment.