What is lactic fermentation in coffee processing?

Lactic fermentation is a controlled method where the fermentation environment is managed to favour lactic acid bacteria (LAB) over other microorganisms. LAB convert the sugars in coffee mucilage into lactic acid - the same acid found in yoghurt, cheese, and sourdough - rather than the more varied by-products of standard mixed fermentation.

Conditions that promote LAB activity: low oxygen (anaerobic or near-anaerobic environments), lower temperatures, and sufficient moisture. Producers working with lactic fermentation manage these variables precisely, sometimes adding water to create the right substrate for LAB dominance.

The flavour results are distinctive. Where standard anaerobic fermentation tends towards tropical fruit intensity, lactic fermentation typically produces a softer, rounder, creamier cup - mild milky acidity, sometimes described as smooth and clean rather than wild. It's a relatively precise outcome to achieve, which makes it one of the more technically demanding experimental processing methods.