Inoculated fermentation

Selected bacteria or yeasts are introduced during fermentation

Fermentation inoculation, using a starter culture, is relatively inexpensive and easy to implement, and its benefits are great. It reduces fermentation time, increases its efficiency, limits the development of undesirable fungi and increases the final quality of the cup in terms of flavors and aromas.

In addition, the choice of the starting culture makes it possible to guide the development of certain aromas and therefore provides a level of prediction on the quality of the final product [2, 3, 4].

Experiments on the use of the starting culture have been carried out for many years. Farms now have many proven techniques at their disposal that they can implement relatively quickly.

• Using coffee cherry juice

Coffee cherries, when fermented whole, produce juice. This juice contains a high concentration of yeasts and bacteria already present on cherries

This juice can come either from the same batch (for example, during fermentation in humid tanks, the juice produced by the macerating cherries is reintroduced into the same tank) or from a different batch (for example, the juice resulting from the carbonic maceration of a different batch) [5].

• Use of yeasts isolated but already present in the cherry or grain

Certain yeasts naturally present and having an impact on the final quality of the product are isolated and cultured to increase their concentration. This culture will force the spontaneous fermentation of these yeasts, which will make it possible to standardize the process and reduce the acidity of the final product.

• Use of external yeasts, bacteria or fungi

Experiments were carried out using yeasts traditionally used in wine and beer, which results in more fruity, floral coffees with tea notes [6]. Other experiments were carried out using cultures of koji, a fungus traditionally used to make soy sauce and sake. The result is a silkier cup, which may be reminiscent of miso soup [7].

Long fermentation

Fermentation longer than average

The term “long fermentation” will greatly depend on the region of production and the climate when processing the coffee. It is mainly a much longer fermentation than usual. For some regions, this is only more than 36 hours, for others it corresponds to fermentation for more than 96 hours.

The term “long fermentation” can also be ambiguous because the complete pulping process is not always specified: is it an extended anaerobic fermentation in a washed process? or a longer but correctly managed natural process? or a relatively long pre-fermentation before a honey process? or even a colder and longer fermentation?

In any case, a really long fermentation (more than 96 hours) does not always bring relevant results, or can even start to develop defects like fungus (there are obviously experiments which prove the opposite [8] ). Since fermentation is the breakdown of elements into other compounds, once everything has been broken down and transformed, there is nothing left to transform unless other elements are added.

That said, a properly controlled long fermentation can finish transforming the yeasts and bacteria present to achieve more pronounced flavors, closer to red wines or very intense fruits. Unfortunately, the process is not always stable and can present risks for the producer.