Ferments coffee with oxygen reduced or excluded, in sealed tanks or bags, favoring lactic acid over alcohol.
Anaerobic fermentation ferments coffee with oxygen reduced or excluded, in sealed tanks where air is gradually replaced by carbon dioxide, or in sealed sacks or bags. It is applied to whole cherry or to pulped beans in their mucilage, commonly for about 3 to 5 days in single-phase versions. Sources say it encourages lactic acid over alcohol, with reported flavors including tropical fruit, spice and yogurt-like tartness. Wrong microorganisms or careless practice can produce unpleasant flavors.
How it worksCoffee ferments with reduced oxygen, in tanks where air is gradually replaced by carbon dioxide or in sealed sacks or bags, which encourages lactic acid formation rather than alcohol. It is applied to whole cherry (anaerobic naturals) or to pulped beans still in their mucilage.
Step by step
- 01
Whole cherry or pulped beans are loaded into a sealed tank or bag.
- 02
Oxygen is excluded, with the air replaced by carbon dioxide or the container sealed.
- 03
The coffee ferments sealed.
- 04
It is then washed or dried, depending on the finish.
Timing · Roughly 3 to 5 days in sealed tanks for single-phase. Two-phase runs about 2 days as whole fruit then 3 days after skin removal
Field notes
- i
The Indonesian Labu method seals pulped fruit into polypropylene bags with as much air expelled as possible.
- ii
The lactic-acid character is compared to fermented foods like yogurt, kimchee and sauerkraut.
Our notes on Anaerobic Fermentation are still being checked against their sources, so for now this page shows only the facts we can stand behind.
What can go wrong
- Wrong microorganisms or careless practices can give unpleasant to repulsive flavors.
In the cup, according to guides
- Tropical fruitOften notedDescriptors reported include tropical fruit such as mango and papaya, spices and lactic-acid tartness.
Variants
At the same stage
Sources · 3 Every sentence here was checked against a source we read. Taste notes are what guides describe, not promises about your bag. Last revised 2026-09-30. Some details here are less settled than others.
- Coffee Report: Anaerobic Fermentation and Other Processing Experiments · Coffee Review
- Coffee basics: A guide to anaerobic fermentation · Mtpak Coffee
- Coffee processing · Wikimedia Foundation