The Truth About Double Anaerobic Coffee Processing (and Why BomBón Shows What’s Possible)
At Torque, we’re obsessed with coffees that express sweetness, clarity, and identity — and few processing methods shape flavor as dramatically as double anaerobic fermentation. For coffee aficionados curious about how this method works (and why it inspires both excitement and controversy), here’s a clear look at the science, the risks, and the payoff.
What Double Anaerobic Processing Actually Is
Double anaerobic processing is a two-stage, oxygen-free fermentation that uses naturally occurring yeasts and bacteria to transform the flavor precursors already inside the coffee cherry. It does not add fruit, flavorings, or external ingredients of any kind. Instead, the microbes metabolize the cherry’s sugars and mucilage, creating esters, acids, and aromatics that magnify the coffee’s inherent fruit notes.
It’s fundamentally different from co-fermented coffees, where producers intentionally add fruit or other adjuncts during fermentation to infuse extra flavors. Double anaerobic coffees rely entirely on microbial metabolism — nothing added, nothing artificial.
How the Process Works
Every producer’s approach varies, but a true double anaerobic method includes three key stages:
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Anaerobic Whole-Cherry Fermentation
Cherries go into a sealed, oxygen-free tank. Temperature, pH, and microbial activity are monitored closely. This first stage begins breaking down fruit sugars and developing early fermentation compounds. -
Depulping + Second Anaerobic Fermentation
After depulping, the beans undergo a second, longer fermentation in another sealed tank. This phase is where complex esters and aromatic compounds really begin to build. -
Careful Drying
The coffee must be dried slowly and consistently — often with mechanical dryers or dehumidifiers — to preserve the delicate volatiles created during fermentation.
The entire process requires scientific precision. A few hours too long, a small temperature swing, or the wrong microbial balance can push the fermentation into boozy, vinegary, or unpleasant territory.
Why Producers Take the Risk
Double anaerobic processing is expensive and risky for producers:
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It requires specialized tanks, valves, and monitoring tools.
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It takes more labor than washed or natural coffees.
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It’s difficult to replicate consistently.
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A single misstep can ruin the batch.
But when everything goes right, the coffee becomes more expressive, more aromatic, and more valuable. Producers who master the technique can command higher prices — especially from roasters like us who champion innovative, intentional coffees.
What It Means for Flavor
Done well, double anaerobic coffees often show:
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heightened fruit intensity
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sparkling, wine-like acidity
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juicy texture
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candy-like aromatics
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layered tropical or floral complexity
These flavors don’t come from added ingredients — they come from chemistry. Yeasts and bacteria convert sugars into esters and volatile compounds that amplify the coffee’s natural character.
BomBón: A Prime Example of Double Anaerobic Mastery
One of the best expressions I’ve tasted is BomBón from Jhon Vergara — a double anaerobic marvel from producers who have mastered the fine line between control and creativity.
BomBón undergoes:
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72 hours of anaerobic fermentation in whole cherry,
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a second anaerobic fermentation after depulping,
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and slow, controlled drying to lock in aromatics.
The result is a cup bursting with pineapple candy, lychee, pink guava, and silky sweetness. It’s nuanced, it’s complex, and it’s proof that double anaerobic processing — when done with skill and intention — can elevate a coffee into something truly unforgettable.
You can explore it here:
BomBón – Jhon Vergara, Colombia
https://torque.coffee/products/bonbom-jhon-vergara-colombia
Why It Matters to Us at Torque
We champion producers who take real risks to push coffee forward. Double anaerobic processing isn’t a shortcut — it’s craftsmanship, science, and courage. When we feature coffees like BomBón, we’re celebrating the modern coffee heroes safeguarding coffee’s future through innovation.
