We're very pleased to bring this Costa Rican bombshell back for the fourth year in a row from Cordillera de Fuego in the Alajuela region. Yet another great example of using specifically designed and controlled anaerobic fermentation to achieve some extraordinary flavour characteristics.

The Cordillera de Fuego mill (beneficio) started in 2015 by two families, headed by their patrons Don Luis Campos (L in pic below) and Don Jose Fransisco de Jesus Fernandez Arias (Coco for short), with over 100 years of family history in coffee production between them. Their ‘signature’ coffee is this Anaerobic Natural that we buy, but of course that’s not all they do. They have another more intense fermentation they call ‘Thermic’ as well as washed, naturals and honeys that go to different market-places. An early lesson learned which re-enforced knowledge from previous trips is that every coffee has a home: the high quality, high scoring lots, the ‘good’ standard coffees and the not so good stuff. At its core, coffee production is agriculture and everything that gets harvested has a market. 10% of their production goes to the speciality market, the remainder is washed and goes to the commercial market.

Don Luis is the fermentation expert, having started experimenting back in 2006 with Anaerobics and then Carbonic Maceration in 2012. Measuring CO2, brix, pressure, pH, and temperature and then they built their own ‘fermentation machine’ (which we were not allowed to see). As well as production from their own farm, they buy cherry from 200 producers. For their signature anaerobic and thermic coffees they buy Caturra-Catuai from 6 high altitude (over 1600m) high quality farms in the Tarrazu region . They are processed as separate lots, but the really clever thing is that they use a mix of mucilage from all 6 farms to add to each fermentation for each lot. This means that micro-organisms on the skin and in the mucilage across the 6 farms creates a homogenised fermentation pot of goodness.

It took 6 years to master this twist on an anaerobic fermentation process which began with considering some fundamental principles: the coffee cherry is a fruit and the mucilage is the juice. The flavour of the fruits is concentrated in the juice and not the seeds. The mucilage will have differing levels of sugars according to the ripeness of the cherry, its variety, the time of year and the nutrients available in the soil, and therefore the mucilage across a ‘lot’ of coffee will have several flavours.

Their particular process uses a mucilage 'gel' donor. Intriguing eh ! This is how it works.

Cherries are harvested at 26 Brix and then placed inside stainless steels fermentation tanks. An additional selection is made for the coffees that will be the donors of the mucilage and these also have to be very ripe with a Brix reading close to 26. The mucilage donor cherries are pulped and the parchment is then passed through the demucilagination machine, tightly packed to create a mucilage ‘gel’.

This gel is then added into the fermentation tanks with the amount of gel enough to cover the entire mass of parchment, and mixed thoroughly to ensure homogeneity. Then the fermentation begins and is monitored and controlled by the temperature and pH (different yeasts and bacteria have their own favoured temperature range for active metabolism). Typically the process lasts between 18 and 23 hours.

One of the successful elements of any fermentation is to stop it once all the sugars of the mucilage have been consumed, but before alcohol is produced. During the fermentation the release of CO2 produced in the sealed tanks exerts a very high pressure and facilitates the flavour pre-cursors of the fermentation as well as the more volatile flavour components of the actual juice to be forced into the seeds themselves.

Once the measurement and the fermentation has reached the optimum level the tanks are opened very carefully (due to the high pressure), drained, and the coffee removed and taken directly to the drying beds in the sun for a minimum of 4 hours. This is a crucial and necessary step which must be carefully coordinated with the available daylight to ensure the fermentation is stopped. Otherwise the desirable flavours could be destroyed if fermentation is allowed to continue.

The result is quite something. Sweet, syrupy and very boozy. Yup - it's a whole mouthful of flavour.