Lactic acid processing is a [[coffee]] fermentation method where ripe, [[Sugar|high-sugar]] cherries are placed in **sealed anaerobic tanks** to create ideal conditions for **[[Lactobacillus|lactobacillus]]** cultures — the same bacteria used in dairy production. Without oxygen, these bacteria dominate the fermentation, converting the sugars in the mucilage into lactic acid, ethanol, and CO₂ over a minimum of ~80 hours. Producers carefully monitor pH, temperature, and moisture throughout. The process is risky: long fermentation times can lead to phenol development, fungus, or over-fermentation that results in overwhelming bitterness. High-altitude cherries are preferred for their higher mucilage content. When executed well, lactic-processed coffees have a **very sweet cup** with **medium-high body**, **strong lactic acidity**, and **tropical fruit** flavours — often recalling papaya or pineapple yogurt. Pioneers of the method include [[La Palma y El Tucan]] in [[Colombia]], who developed it through extensive experimentation at their wet mill.