What is demucilage in coffee processing?

After a coffee cherry has been pulped - the outer skin mechanically removed - the bean is still coated in a sticky, pectin-rich layer called mucilage. Demucilage is the process of removing it.

Two main approaches: fermentation-based demucilage leaves the pulped coffee in tanks for 12–72 hours while bacteria and enzymes break down the mucilage until it releases cleanly and can be washed away. Mechanical demucilage uses machines that apply friction and water pressure to strip it without fermentation - faster and more consistent, but typically producing a cleaner and sometimes less complex result.

How demucilage happens is a significant flavour variable. A producer who ferments for 36 hours in cool highland conditions at 1,800 masl is making different decisions to one using a mechanical demucilager for two hours. The mucilage deliberately left on the bean in honey processing is the same layer - making the demucilage decision the key variable that distinguishes washed from honey coffees.