Washed Process Coffee

Washed process coffee, also called wet-processed coffee, is coffee whose fruit is removed before the beans are dried. The cherries are pulped, the sticky layer left on the beans is fermented loose and washed away, and only then is the coffee dried. It’s the method behind many single-origin and specialty coffees, prized for clean, bright, acidity-led cups.

The short version

• Fruit off first, then dry. The opposite of natural process, where the whole cherry dries.
• Pulp, ferment, wash, dry: fermentation takes about 12–48 hours.
• Dried to about 10–12% moisture before the parchment is hulled off.
• Clean, bright and acidity-led, showing off origin and variety.
• Needs skill, equipment and lots of water.

How is washed coffee processed?

The National Coffee Association sets out the steps:

1. Pulp. A pulper strips off the skin and fruit flesh.
2. Sort. The beans pass through water channels: the lighter, unripe ones float and the heavier, ripe ones sink. Rotating drums then sort them by size.
3. Ferment. The beans sit in water-filled tanks while naturally occurring enzymes break down the mucilage, the sticky layer still clinging to them, for 12 to 48 hours. When it’s done, the beans feel rough to the touch.
4. Wash. The beans are rinsed clean.
5. Dry. They’re spread on drying tables or floors and turned, or dried in large machine tumblers, to about 11% moisture.
6. Hull. Once dry, the papery parchment around each bean is removed.

Wikipedia’s account adds detail. Fermentation can be done under extra water or “dry”, in the fruit’s own juices; underwater fermentation is said to emphasise acidity and aroma. Some mills skip fermentation altogether and scrub the mucilage off by machine, a method called mechanical demucilaging or aquapulping, which uses less water and gives more consistent results, though it doesn’t taste the same.

How long does fermentation take, and how dry is dry?

The sources broadly agree, but not exactly:

Step	National Coffee Association	Wikipedia (Coffee processing)
Fermentation	12–48 hours	About 12–36 hours
Final moisture	About 11%	10–12% (wet basis)

Sources: National Coffee Association; Wikipedia. Fermentation time depends on the temperature, the thickness of the mucilage and the enzymes at work, and has to be watched closely or the coffee turns sour, Wikipedia says. Washed coffee leaves the mill at about 53% moisture; drying it to 10–12% makes it stable and stops the moulds that produce ochratoxin A.

What does washed coffee taste like?

Clean, bright and transparent. The descriptions agree:

Source	Description
National Coffee Association	Clean, with floral, sour or citrus notes; showcases the coffee’s unique characteristics
Coffee Review	The wet method generally intensifies acidity; most of the world’s great coffees are wet-processed
International Trade Centre, via Wikipedia	The most common of the three methods, and often the highest quality

Because the fruit is gone before the coffee dries, the flavour has to come from the bean itself, so the farm, its soil, altitude and the coffee’s variety show more clearly. That’s why many single-origin and specialty coffees are washed, the National Coffee Association says.

In the coffee trade, two of the International Coffee Organization’s four price groups, Colombian milds and other milds, are washed arabicas, Wikipedia notes; the other two are Brazilian and other natural arabicas, and robustas.

What are the downsides of washed processing?

Water and waste. Removing the mucilage is the only stage that needs water, but it’s a lot: small mills have been reported using 2.3 to 23 cubic metres for each tonne of cherry, and the effluent is acidic and heavily loaded with organic matter, Wikipedia says. Using less water doesn’t remove the pollution; it concentrates it. Fermentation also costs the coffee 2–3% of its weight, which machine demucilaging avoids.

What’s between washed and natural?

The honey or pulped natural process. The skin and pulp are removed, as in washed coffee, but some or all of the mucilage is left on the bean while it dries, the National Coffee Association says. The more mucilage remains, the sweeter and more natural-like the cup. Wikipedia describes the grades:

Grade	Mucilage left on	Drying time
Yellow honey	Part, after some is removed by machine	About 8–10 days
Red honey	Roughly half to three quarters	About 12–15 days
Black honey	All of it	About 30 days

Source: Wikipedia, Coffee processing.

Indonesia’s wet-hulled coffee, giling basah, is another in-between method: the parchment comes off while the bean is still wet, so the coffee dries faster in the rainy harvest season.

Washed coffee and other guides

• Natural process coffee: the whole cherry dried first.
• Arabica coffee: the species most washed coffee comes from.
• Coffee in Colombia: home of the “Colombian milds” price group.
• Coffee in Kenya: washed arabica, sold at the Nairobi Coffee Exchange.