Washed/Wet Processing¶
Washed Processing (Wet Processing, Fully Washed) A coffee processing method where the fruit is removed from the bean before drying. Produces clean, bright, acidic coffees that showcase the bean's intrinsic characteristics. Most common processing method globally. Pulping The mechanical removal of the skin and most of the pulp from coffee cherries. Done with a pulping machine (pulper) within 24 hours of harvest to prevent fermentation. Leaves beans coated in mucilage. Pulper A mechanical device that removes the skin and pulp from coffee cherries. Works by pressing cherries between a rotating drum and a fixed surface, squeezing the beans out while retaining the fruit layers. Fermentation The process where naturally occurring microorganisms (yeasts and bacteria) break down the mucilage layer surrounding parchment coffee. Typically 12-48 hours in fermentation tanks. Critical for developing acidity and removing mucilage. Fermentation Tank Concrete, tile, or plastic tank where parchment coffee sits in water (wet fermentation) or without water (dry fermentation) to break down mucilage. Temperature and time carefully monitored to prevent over-fermentation. Dry Fermentation Fermentation without added water, relying on the moisture in the mucilage itself. Often considered to produce more complex flavors. Common in East Africa. Wet Fermentation Fermentation with added water covering the parchment coffee. Water can be changed during process. Common in Central America. Washing Channels Water channels or tanks where fermented coffee is washed to remove loosened mucilage and grade beans by density. Lighter (lower quality) beans float, denser (higher quality) beans sink. Grading Channels Inclined channels filled with flowing water where coffee is sorted by density as it moves through. Heavier, denser beans sink and move slowly; lighter defective beans float and wash away quickly. Soaking A final clean water soak (12-24 hours) after washing, common in East Africa (Kenya, Rwanda, Burundi). Believed to improve cup clarity and develop acidity further. Demucilaging Mechanical removal of mucilage using machines (aquapulpers, mechanical demucilagers) instead of fermentation. Faster than fermentation, uses less water, but may produce different cup profiles. Common in Central America. Aquapulper A machine that uses water pressure and friction to mechanically remove mucilage without fermentation. Invented in Brazil, now common in Central America. Allows for water recycling and faster processing. Parchment Coffee (Pergamino) Coffee beans still enclosed in the parchment layer after washing and drying. This is how washed coffee is stored and transported before hulling for export. Drying The process of reducing moisture content from ~60% (after washing) to 10-12% for storage. Done on patios, raised beds, or mechanical dryers over 7-21 days depending on climate and method. Raised Drying Beds (African Beds) Elevated mesh or slatted tables where parchment coffee dries in thin layers with air circulation from below. Produces more even drying and higher quality than patio drying. Standard in East Africa. Patio Drying Traditional drying method where coffee is spread on concrete, brick, or clay patios and sun-dried. Requires regular raking/turning for even drying. Common in Latin America. Mechanical Dryer (Guardian Dryer) Machines that dry coffee using controlled heat and air circulation. Useful in humid climates or rainy seasons. Must be carefully managed to avoid over-drying or damaging beans. Over-fermentation When fermentation continues too long, creating vinegary, sour, or unpleasant flavors. A processing defect that ruins cup quality. Under-fermentation Insufficient fermentation time, leaving mucilage residue that creates processing defects and off-flavors.
Related Notes: - Coffee Terminology MoC