Few have missed the anaerobic coffee trend, producers all over the world have discovered how this method really improves the quality of their coffee, but what exactly is anaerobic fermentation (or Carbonic as it is also called)? And no one has missed how much we at Gringo love this type of tasty, playful and incredibly good coffee.
About anaerobic fermentation (3 min read)
Anaerobic fermentation is a method where the coffee is processed in a completely sealed and oxygen-deprived environment, sometimes barrels are used as for Colombia La Esperanza Geisha Carbonic and sometimes plastic bags; Etiopien Bensa and in case the farm is more sophisticated, stainless tanks; Colombia Honey Granada. These types of coffees are always very labor intensive and experimental, and they are always sold as micro lots.
After selective hand-picking of fully ripe berries, they are placed in pools of water to sort out unripe coffee berries, so-called floaters. The berries are then placed in the airtight environment, which should preferably be as cool as possible, as the fermentation creates heat.
After about 18–24 hours, the anaerobic process has begun to break down the pulp and sugar on the berries, and an accumulation of CO2 - carbon dioxide - is formed and the coffee’s natural lactic acid bacteria begin to work. The process also causes the PH level to drop and the coffee’s acids to change. Slightly simplified, you can say that the pressure forces the flavors from the juicy pulp into the coffee. The pressure is usually released through a one-way valve on the top of the barrel or a gap in the plastic bag. The anaerobic fermentation has many levels and can take from 18-240 hours.
After careful removal from the oxygen-deprived environment, usually with a PH content of around 5.5, the coffee is dried to ensure that the fermentation step is stopped. The types of microbes that can survive and participate in fermentation are limited by the lack of oxygen. The result is often a very expressive flavor profile that often has the character of tropical fruit, cinnamon, banana, bubble gum or ripe pear.
Another concept that is similar to anaerobic fermentation is carbonic fermentation. Sometimes the terms are used to refer to the same thing, sometimes the first mentioned is used for coffee where the berries are peeled from their pulp before fermentation (alternatively Anaerobic Honey). Sometimes Carbonic is used for the coffee where the berry is left intact and fermented as it is (Anaerobic Natural). Carbonic is a term taken from the wine industry, where whole grapes are fermented without pressing the juice. This tends to produce fresh and fruity wines that should be consumed fairly soon after production as they do not age very well.
All this is an exciting new world for producers, coffee roasters and consumers alike. Right now, different fermentation methods are being vigorously experimented on coffee farms around the world, and we can expect many expressive coffees in the next few years. New names for these coffees will certainly appear in parallel with this.