120-hour anaerobic fermentation is an advanced, ultra-extended coffee processing technique where coffee cherries (or depulped beans) are sealed inside airtight, oxygen-free tanks for exactly 120 hours (5 days) before drying.By completely blocking oxygen, producers restrict the types of microbes that can survive, forcing a slow metabolic shift that breaks down natural fruit sugars into complex organic acids, alcohols, and esters. While standard fermentation typically lasts only 12 to 36 hours, stretching the window to 120 hours pushes the boundaries of a coffee's sensory limits. When combined with a light roast profile, this extended contact time unlocks maximum sweetness and structural clarity while avoiding heavy, over-fermented bitterness