Lactic Fermentation
The world of specialty coffee is shifting towards controlled fermentation. While washed, natural, and honey were once the norm, experimental, microbiologically-driven methods are now gaining ground. A prominent example is lactic fermentation, which gives coffee a creamy, sweet, and sometimes yogurt-like flavor profile.
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What is lactic fermentation?
Lactic fermentation is a process where lactic acid bacteria break down sugars and convert them into lactic acid. We are familiar with this process from other food products such as yogurt, kefir, and sauerkraut.
In coffee, this occurs during the post-harvest processing of the coffee cherry, where:
- Sugars and mucilage around the bean are broken down
- Lactic acid is produced instead of, for example, acetic acid
- The pH value decreases in a controlled manner
The result is a softer, rounder acidity compared to other fermentation methods.
How does the process work for coffee?
Although the exact execution varies by producer, lactic fermentation generally follows these steps:
1. Selection of ripe coffee cherries
Only perfectly ripe cherries are used, as they contain the highest sugar concentration — essential for fermentation.
2. Creating an anaerobic environment
The coffee cherries (or pulped coffee) are placed in an oxygen-deprived environment, often in sealed tanks or vessels.
3. Inoculation (optional)
Some producers add specific lactic acid bacteria to guide the process and ensure consistency.
4. Controlled fermentation
- Temperature: often between 15–25°C
- Time: 24 to 96 hours (sometimes longer)
- Monitoring: pH, temperature, and pressure
5. Drying
After fermentation, the beans are dried as in natural or washed processes.
What makes lactic fermentation unique?
The distinction primarily lies in the dominance of lactic acid production rather than other organic acids.
Sensory profile:
Coffees with lactic fermentation are often characterized by:
- Creamy body, almost milky
- Low, soft acidity
- Sweet notes, vanilla, caramel
- Yogurt-like or kefir-like nuances
- Tropical fruit, mango, pineapple
- Less funky than other fermentations
This makes them particularly approachable, even for those who normally struggle with high acidity.