MAY SUBSCRIPTION
Jaime Alvarez — Colombia
We have a pretty different coffee for you this month. It is a fresh release and won't be around long. Each year we decide to buy a coffee that is more experimental in its processing. The main reason for this is to plunge into a different spectrum of flavour, but also to see a wildly differing coffee in our roaster and how it reacts to heat inputs.
We find that processing can take over the inherent varietal/terroir flavour profile and steer the coffee toward a different category of flavours. This leads the coffee away from classically standard quality attributes. Whether this is good or bad, it is for you as the drinker to decide. It is a much-debated topic in the coffee industry.
We are good friends with the owner, Carlos, from Cofinet — an importer and exporter. They have found themselves specialising in these very distinct types of more involved fermentation processes. I think it is nice to break down the following for more understanding. It will outline how and when fermentation happens in the processing of coffee. This will, in turn, help you understand this month's coffee better.
When coffee is picked it starts to decompose. It can ferment at these different stages after being picked.
- In the bags/baskets while the picker is still picking coffee on the farm
- In piles or bags, while it is waiting to be processed at the mill
- In its fruit/mucilage after de-pulping, while it is being moved onto dry beds or water tanks, sometimes purposefully left to ferment (dry-fermentation)
- In the time spent in the water tanks (wet-fermentation)
Here are some of the variables that farmers use to manipulate the ferment.
- Piling the coffee up to create heat and moisture
- Using bags or tanks to minimise oxygen
- Tanks or areas that are temperature controlled
- Water temperature during the wet-fermentation
- Yeast and bacteria additives during any stage
- The time spent within each of these stages
Here are some examples that I have seen happen:
A very clean washed process coffee — A grower/farmer wants their coffee picked, de-pulped and placed in washing tanks 4-5 hours from picking to prevent as much fermentation as possible. When the coffee is in the water tanks it can be washed of its fruit/mucilage quite quickly, in 6-10 hours. It can then be washed again with clean water and laid out to dry. These fast times and freshwater flush will minimise fermentation.
A very clean natural process coffee — The farmer has the coffee laid out on raised beds for drying in the cherry as soon as possible. The cherries are laid in very thin layers so there is good airflow and to minimise heat. It will still ferment mildly and have natural process character, but very little chance of defect and fermentation flavours.
A very winey/fruited washed coffee — The farmer wants to achieve a coffee with a more fermented style acidity but still with good clarity and clean mouthfeel. The cherry is picked and de-pulped relatively quickly, but is left in water tanks without water for 12 hours to heat up and ferment. The water is then added and it's fermented in the tanks for another 48 hours before being pushed through water channels and dried on a patio under shade. The coffee has different stages to ferment and pick up these flavours that the farmer is trying to achieve, with minimal chance of defects because of the washing processes. As long as the drying is done with thin enough layers to achieve adequate airflow it will be free of defects and further fermentation.
An experimental anaerobic washed coffee — A farmer has the coffee de-pulped quickly and placed in stainless steel tanks. They then purge the tanks of oxygen with CO2 and it continues to dry-ferment in the fruit for 24 hours below 20°C. The tanks are then filled with water and acetic acid to break down the fruit on the seed. It is fermented for a further 24 hours and then slowly dried on stacked drying beds with a temperature-controlled fan for airflow. This level of control allows some fermentation types but minimises others, resulting in a distinct 'processed' flavour profile.
How Jaime Alvarez achieved this month's coffee — The coffee was picked and fermented in thin layers to dry off surface moisture for 24 hours. It was then placed in bags inside a temperature-controlled area below 22°C. It spent 90 hours fermenting there in the cherries with almost no oxygen. The lower temperatures and less oxygen reduced the chance of bad fermentation flavours and helped lactic acid build-up, which also helps safeguard against bad fermentation. It is then layered out to dry slowly with great airflow. The result is a natural processed coffee profile with esters created during fermentation that are very strawberry-esque. It also has some remaining lactic acid that impacts mouthfeel too.
I apologise for the long email, but I hope it allows you to better understand the processing labels given to coffee and how processing coffee is in and of itself an art.
Warmest regards,
Ben