Anaerobic coffee is coffee whose cherries or beans are fermented in sealed tanks with little or no oxygen. Producers place the coffee in an airtight tank, often fitted with a one-way valve, and let it ferment for anywhere from about a day to a week or more before drying it. Without oxygen, different microbes and acids take over, creating bold, intense flavors: tropical fruit, red wine, berries, cinnamon and sometimes a boozy or yogurt-like tang. Anaerobic coffees are popular in specialty coffee, usually cost more, and can taste very different from a classic cup.
| What it is | Coffee fermented in a sealed, low-oxygen tank |
| Fermentation time | Usually about 24 hours to several days; some lots much longer |
| Main styles | Anaerobic natural, anaerobic washed, carbonic maceration |
| Typical flavor | Intense fruit, winey, sweet, sometimes spicy or boozy; heavier body |
| Became popular | Mid-2010s, after it featured in barista competitions |
| Price | Usually higher than regular specialty coffee |
How Fermentation Works in Coffee
Almost all coffee ferments a little during processing. After the cherries are picked, yeasts and bacteria feed on the sugars in the fruit and the sticky mucilage around the beans, producing acids, alcohols and aroma compounds. In a traditional washed or natural process, this happens in open tanks or on drying beds, exposed to air. It helps develop flavor, but if it runs too long or too hot it creates sour, rotten or vinegary defects.
Anaerobic processing takes oxygen out of the picture. In a sealed tank, the oxygen is quickly used up and replaced by carbon dioxide from the fermentation. That favors different microbes, especially lactic acid bacteria, and slows the process down, so producers can ferment longer and steer the flavor more precisely by watching the temperature, sugar levels and pH.
How Anaerobic Coffee Is Made
- Pick and sort. Only ripe, sound cherries are used, because any defects get amplified by long fermentation.
- Load the tank. Whole cherries (for an anaerobic natural) or pulped beans with their mucilage (for an anaerobic washed or honey) go into a sealed stainless steel or food-grade plastic tank.
- Remove the oxygen. The tank is sealed with a one-way valve that lets carbon dioxide out but no air in. Some producers also flush the tank with CO2.
- Ferment and monitor. The coffee ferments for anywhere from about 24 hours to several days, while the producer tracks temperature, pH and sugar levels and stops it at the right moment.
- Dry. The coffee is then dried on patios or raised beds, often slowly, before milling and export.
Types of Anaerobic Coffee
| Style | How it is made | Typical cup |
|---|---|---|
| Anaerobic natural | Whole cherries fermented in a sealed tank, then dried in the fruit | The most intense: jammy, tropical, winey, sometimes boozy |
| Anaerobic washed | Pulped beans fermented in their mucilage in a sealed tank, then washed and dried | Cleaner and brighter, with clear fruit and sweetness |
| Anaerobic honey | Pulped beans fermented sealed, then dried with some mucilage left on | In between: sweet, fruity, syrupy |
| Carbonic maceration | Whole cherries in a tank flushed with CO2, a method borrowed from winemaking | Very aromatic, often red fruit, cinnamon and wine-like notes |
| Co-fermented or “infused” | Fruit, spices, yeasts or other ingredients added to the tank | Flavors like cinnamon, mango or rum; should be labeled clearly |
Producers and roasters use these names loosely, so check the bag description. See our guide to honey-processed coffee.
Anaerobic fermentation became famous in 2015, when Australian barista Saša Šestić won the World Barista Championship with a carbonic maceration coffee from Colombia. Since then, farms in Colombia, Costa Rica, Panama, Ethiopia, Brazil and elsewhere have developed their own anaerobic and experimental fermentations. Our guide to Colombian coffee covers one of the countries leading the trend.
What Does Anaerobic Coffee Taste Like?
Anaerobic coffees are usually bolder and fruitier than regular coffees from the same farm. Common tasting notes include pineapple, mango, passion fruit, strawberry, cherry liqueur, red wine, cinnamon, dark chocolate and a creamy, yogurt-like acidity from the lactic acid. The body is often heavier and the sweetness more syrupy. Some lots taste clean and juicy; others are funky, boozy or almost fermented-tasting.
That intensity divides opinion. Fans love the big, exotic flavors. Critics argue that heavy fermentation can mask the character of the farm, variety and origin, so that very different coffees end up tasting alike. If you are used to classic nutty, chocolatey coffee, start with an anaerobic washed coffee, which is usually more restrained than an anaerobic natural.
Why Is Anaerobic Coffee More Expensive?
- Equipment: sealed tanks, valves and monitoring tools cost money.
- Labor and skill: each batch needs careful sorting and close monitoring.
- Risk: a fermentation that goes too far can ruin a whole lot.
- Small lots: most anaerobic coffees are made in small, experimental batches for specialty buyers.
There is no evidence that anaerobic coffee is healthier than regular coffee; the health benefits of coffee apply to both. People buy it for the flavor.
How to Brew Anaerobic Coffee
- Brew it as filter coffee. A pour-over such as a V60 shows off its fruit and aroma best.
- Start with the basics: 1:16, water at 200 to 205°F and about 3 minutes. If a very funky lot tastes harsh, try slightly cooler water or a slightly coarser grind.
- Let it cool a little. The fruit and sweetness often open up as the cup cools.
- Taste it side by side with a washed coffee from the same country to see what the process adds. Our coffee cupping guide shows how.
- Check the label. Look for the process, the fermentation time and whether anything was added. Our guide to reading coffee bag labels helps.
Anaerobic coffee is not for everyone, but if you enjoy fruity, adventurous coffees, it is worth trying at least once. Look for it from specialty roasters, or browse a few options below.
Former roastery owner and coffee tour operator. Steve spent five years roasting coffee for his own shop and wholesale customers. More about Steve