Over the past decade, there has been growing interest within the specialty coffee industry in experimental processing approaches that seek to manipulate the “fermentation stage” in various ways.
Whether employed to pursue a desirable standard of control and repeatability in coffee processing, or to develop interesting new flavor profiles in the cup, these techniques have been increasingly trendy in recent years, and words such as “anaerobic”, “aerobic”, and “carbonic maceration” have become marketing buzzwords on producer, importer, and roaster coffee descriptions around the world. Among these terms, “anaerobic” is perhaps the most commonly used - often as a description of coffee fermentation that occurs in a sealed container or other low oxygen environment.
Near the start of 2021, as a part of Burundi harvest planning discussions with our friends and partners at the Long Miles Coffee Project, we learned more about the “reduced oxygen process” that the team at Heza washing station was developing. We were interested to pursue a comparative tasting experiment to explore this processing approach, and asked the team at Long Miles if it would be possible to forward-book four bags of coffee from Mutana hill for this purpose. This unique tasting box contains the results of the experiment.
The reduced oxygen process employed by the Long Miles team is a simple variation of traditional wet processing in Burundi. Freshly harvested coffee cherry is delivered to the washing station where it is sorted for ripeness and weighed for farmer payment. The coffee is then de-pulped, at which point the experimental phase begins: rather than undergoing a fermentation stage in an open air tank, the mucilage-coated parchment is placed in a sealed Afri-tank container. The four microlots that Passenger contracted for this experiment were kept sealed in the Afri-tank containers for four different time periods: 36hrs, 48hrs, 60hrs, and 72hrs. When the target fermentation time was reached, the parchment was removed from the tanks, washed in grading channels with fresh water, and then dried on raised beds.
We find each of these experimental lots to be thoroughly enjoyable when brewed individually. And tasting all four of them side by side provides a unique opportunity to assess the impact of differing fermentation times (in a reduced oxygen environment) on eventual cup profile.