Anaerobic coffee: what it is and how to specify a green lot

Anaerobic coffee vs natural: what is the difference?

A traditional natural is whole cherry dried in open air; fermentation happens on the patio or bed, with oxygen present. An anaerobic natural first ferments the whole cherry in a sealed tank for a defined time, then dries it as a natural.

In the cup, anaerobic naturals tend toward concentrated tropical fruit and a liqueur-like finish, while a clean traditional natural usually reads as ripe fruit with less fermentation character. Both depend heavily on ripeness selection and drying. Anaerobic washed and anaerobic honey lots keep more of the clarity associated with those methods while adding fermentation intensity.

Cup profiles you can expect

Anaerobic lots are commonly described with wild and red fruit, wine-like notes, dense body and lingering sweetness; double anaerobic lots push intensity and complexity further. Altitude and variety still shape the result: a Geisha at 2,000 MASL will not cup like a Caturra at 1,600 MASL with the same protocol.

Research supports the idea that time is a lever. In a 2023 study of self-induced anaerobic fermentation, all samples scored 84 or above, and 48- and 72-hour fermentations gave more complex, intense cups than 24 hours. That is one study under specific conditions, not a recipe.

Quality risks: where anaerobic coffee goes wrong

Cenicafé notes that anaerobic fermentation carries the risk of being either insufficient or excessive, and that higher temperatures shorten fermentation but raise the risk of over-fermentation. Overripe fruit increases the risk of the "fermento" defect. When you cup, look for these signals:

• Vinegar or excessive volatile acidity.
• Solvent, nail-polish or overly alcoholic notes.
• Rotten fruit, onion or dirty finish.
• Harsh, astringent or woody aftertaste.
• Cup-to-cup inconsistency within the same sample.
• Profile fading between offer, pre-shipment and arrival samples.

How do you specify an anaerobic lot when buying?

Write the specification before you request samples. It makes offers comparable and gives you grounds to reject a lot that does not match.

• Process detail: substrate (cherry or mucilage), single or double phase, hours per phase, temperature range, inoculum if any, pH at end.
• Drying method and final moisture; the ICO programme bars exports below 8% or above 12.5%.
• Water activity below 0.70 aw (SCA specialty standard); ask for the actual reading.
• Target profile and fermentation intensity: clean and fruity, or overtly winey.
• Minimum cup score, cupping form used and who cupped.
• Volume, bag count and packaging (hermetic liners are common for fermented lots).
• Offer, pre-shipment and arrival samples, with the right to reject on deviation.

Sourcing anaerobic coffee through our network

Today our network has one verified producer, in Cauca, offering single and double anaerobic lots at 1,800–2,100 MASL that cup at 87–91 points, from micro-lots to container volume. The producer runs on-farm microbiology and quality labs, and its lots include national champions and coffees used by World Brewers Cup competitors. Identity is shared only with verified buyers after a discovery call, and buyers pay nothing for the introduction.

If you are also evaluating thermal shock, the same producer offers it, so you can compare both profiles side by side before you commit volume. If you are looking for another origin, tell us which one.