February 22, 2019

How to Improve Quality When Processing Washed Coffees


Wet/washed processed coffees are loved by many specialty coffee consumers, roasters, and buyers, thanks to their reputation for consistency and illuminated acidity. But in the specialty industry, quality is key – and unless producers adhere to best practices, there is no guarantee that wet processing will result in high-quality coffees.

That’s why I reached out to representatives at Cenicafé, the research centre of Colombia’s national coffee association Café de Colombia, to ask for their advice on washed processing.

You might also like: Coffee Processing 101: What Is Washed Coffee & Why Is It So Popular?

coffee producer smiles for the camara in his farm

A coffee producer on his drying patio. Credit: Café de Colombia

What Makes a Coffee High Quality?

Quality: is it the result of good varieties? Strong trees? An ideal farm location? Infrastructure? Harvesting and processing methods? Tree maintenance? Fertilization?

The International Trade Centre says “the quality of a parcel of coffee comes from a combination of the botanical variety, topographical conditions, weather conditions, and the care taken during growing, harvesting, storage, export preparation and transport.

“Botanical variety and topographical conditions are constants and therefore dominate the basic or inherent character of a coffee. Weather conditions are variable and cannot be influenced, resulting in fluctuating quality from one season to another.”

In other words, yes, quality is partly the result of the coffee plants and farm location. Yet the context in which coffee is grown – the weather, the farming methods – also have an impact on quality.

Carlos Oliveros, Principal Investigator at Cenicafé, tells me, “Quality is the result of many factors, not just one… What I can say is that with the new technologies that we have been developing, we have processes that help us to be more consistent with the quality that is expected from Colombia.”

Let’s break down some of these factors.

some coffee trees at a farm covered by some shade trees

Coffee trees are intercropped with pine trees in Colombia. Credit: Café de Colombia

Crop Nutrition

We could easily devote a whole article to crop nutrition, an element that is crucial for coffee quality.

As Cenicafé’s guides say, “For coffee crops, soil analysis is a decision making tool when it comes to fertilization brings economic and environmental benefits”.  

Analysing soil, understanding coffee varieties, and fertilizing appropriately are critical for coffee quality, crop productivity, and reducing the environmental impact. Take nitrogen: it’s key for healthy coffee trees, but you don’t want too much in the later stages of cherry development as this will limit potential growth. The problem is that without knowing the level of nitrogen already in the soil, it becomes impossible to know how much to add when fertilizing. Only soil analysis can provide this answer.

For this reason, it’s important to speak to a specialist before beginning or changing a crop nutrition program.

some coffee cherries still in the tree

Organic coffee cherries ripen slowly on the branch, under shade cover. Credit: Café de Colombia

Cherry Picking

Harvesting ripe, healthy coffee cherries is key: under-ripe or defective beans can have a significant impact on the quality of a lot.

Carlos tells me, “We are always talking about picking ripe fruits, separating them, removing the ones that don’t meet the quality standards…”

Picking and sorting cherries can be an exhaustive process, but it is worth it. Gloria Inés Puerta is a Quality Investigator at Cenicafé. Rather than strip picking, she suggests selective picking, a method which leaves unripe cherries still on the tree to be picked later.

Then after picking comes sorting: the process of removing lower-quality cherries and beans from a lot. This can be repeated multiple times throughout processing and drying. Gloria recommends grouping the cherries and beans by quality so that each lot can be appropriately processed and marketed at a suitable price.

Discover more: How to Improve Coffee Quality in Harvesting & Sorting

ripe coffee cherries in a bascket

Ripe-red, freshly picked coffee cherries in a worker’s basket. Credit: Café de Colombia

Depulping & Mucilage Removal

Gloria stresses the importance of best practices when removing the pulp and mucilage.

“[Pulping] is a mechanical process,” she says, “and then a screen should be used. The screen removes any fruit that wasn’t depulped and any remaining harder fruits.

“Next comes the process of removing the mucilage, which can be done biochemically through fermentation or mechanically with a mucilage remover machine or a piece of technology called Becolsub,” she continues. “With both pieces of technology, the beans must still be washed afterwards.” (A Becolsub is a Cenicafé-produced machine designed to remove mucilage without the use of water, so as to have a reduced environmental impact.)

coffee being depulped by a coffee producer

A producer analyzes coffee cherry quality before depulping them. Credit: Café de Colombia

Fermentation Tanks

Nelson Rodriguez is a Post-Harvest Investigator at Cenicafé. He tells me that three things are necessary for good-quality coffee: clean equipment, clean water, and constant control of fermentation.

Traditionally, he says, the tanks used for washed coffee processing were made of concrete. “The problem with concrete is that it is attacked by the acids generated during the fermentation and washing process,” he tells me. In particular, these acids can damage the lime in the concrete.

He recommends plastic or stainless steel tanks, and emphasizes the importance of daily cleaning. Fermentation, ultimately, is a chemical reaction involving microorganisms. Producers want to make sure that the right microorganisms are involved; other, foreign ones could have a negative effect on the final flavor and quality of the coffee.

producer puts some coffee cherries into tanks of fermentation

Emptying sacks of freshly picked cherries into tanks. Credit: Café de Colombia

Water Quality

For washed coffees, water quality is closely tied to cup quality. Nelson tells me that surface water, coming from streams, rivers, and lakes, is often used for wet processing but that these sources could be contaminated.

“It can create problems in the cup profile and the beverage’s sensory characteristics, when the coffee is processed with poor-quality water…” he says. “[Poor-quality water] can result in pronounced defects, such as chemical and metallic flavors, which are connected to contaminated water.”

While frequent water quality analysis can be costly, Nelson recommends making sure water is odorless, flavorless, and colorless. He also draws my attention to water treatment options. For example, Cenicafé has implemented a system to treat water after it’s been used for fermentation. This can then be used to ferment future lots, reducing the environmental impact while also ensuring quality.

Finally, Nelson suggests using micro and nano filters. “Many of the particles and even microorganisms will be caught in the filter and, in this way, you will have water appropriate for washed coffee,” he says.

coffee pickers ready to sort ripe red cherries

Coffee pickers make their way up the steep farmland to begin their day’s work. Credit: Café de Colombia

Fermentation Times & Temperatures

“We define fermentation as a biochemical process,” Gloria says. “A biochemical process is one in which living organisms, or microorganisms, which are in this case bacteria and yeast… create a biochemical transformation.”

And for this reason, it’s important to have control over all the factors that could affect fermentation. Take temperature, for example. “We can say that there are six or seven processes that occur naturally, depending on the temperature,” Gloria tells me. “At lower temperatures, the process is slower and could take longer… We need to leave enough time so that… the coffee acquires the volatiles and acids that fermentation should produce.”

This leaves producers with options. “If they want to ferment at the ambient temperature of 20–22°C [68–72°C], they can easily do so at this temperature…” Gloria advises, referring specifically to Colombia. “Or if they want to do it at 15°C [59°F], then, they have to lower or control the temperature.”

Producers would do this, she continues, so that certain chemical compounds are produced which would then affect the flavor and quality of the coffee. “Basically, through controlled processes… different flavors can be achieved.”

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However, she stresses that producers need to be willing to invest time and resources into this and that they need to carefully analyze the process. She recommends the Cenicafé-designed Fermaestro and pH readers.

The Fermaestro is a truncated cone that producers insert into a sample of coffee during fermentation to observe the level of mucilage degradation. As for a pH reader, she tells me that it will measure the acids and is “the easiest and most basic” way to determine when the coffee has sufficiently fermented. Producers should look for a reading of 3.7 to 4.1, she advises.

dried coffee in raised beds

Washed coffee dries on raised beds in a greenhouse. Credit: Café de Colombia


Even though fermentation has now finished, the hard work isn’t over. Carlos tells me that the drying phase is still highly risky. The beans can deteriorate and are also vulnerable to bacteria and microorganisms.

Gloria emphasizes that coffee drying should begin as soon as possible. She stresses the importance of an appropriate location, mesh, and parabolic shade to control the amount of sun. Alternatively, she suggests a mechanical dryer.

Carlos tells me that, in Colombia, small farms usually use solar drying but some larger farms use either mechanical dryers or a mixture of the two methods. “That is to say, we begin with sun drying and then, after one or two days, move to mechanical drying. In this way, we achieve quality drying with a significant reduction in energy costs. And finally, we have dry parchment coffee.”

When solar drying coffee, whether on raised beds or a patio, Cenicafé recommends that the beans are dried in a 3.5 cm thick layer and moved at least four times a day until they reach 10–12% moisture content. Depending on the climate, this could take 7–15 days.

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producer inspecting dried coffee in the african beds

A producer examines drying washed coffee; the thermometer allows him to track conditions. Credit: Café de Colombia

Storage & Transportation

Producers cannot start to relax until responsibility for the coffee is legally transferred to the buyer – which, in many cases, is after storage and some degree of transportation.

Nelson tells me that coffee needs to be stored in a ventilated place away from chemical products and odors. Cenicafé guides suggest keeping the beans in fresh, dry environments lower than 20ºC/68ºF and with less than 75% humidity. It’s a good idea to leave a 30 cm gap between the coffee bags and the walls and ceilings. Cenicafé also suggests labeling each bag with a code, to make sure it’s truly traceable.

Equally, if organizing transportation, producers need to pay attention to the temperature, humidity, and degree of light in the truck or boat.

Check out our detailed guide: How to Ensure Green Coffee Quality in Transit & Storage

coffee farmer next to his coffee bags that are going to be exported

A coffee producer transports his harvest to the cooperative. Credit: Café de Colombia

Ultimately, it is the producers’ hands that determine the quality of their coffee. Yes, variety and terroir have an impact – but if poorly farmed and processed, even great varieties farmed on great lands can result in low-quality crops and low prices to match. Alternatively, good production, processing, and drying can highlight the quality of a crop, attracting specialty coffee buyers. Following best practices from picking through to storage is key.

All quotes translated from Spanish.

Please note: This article has been sponsored by Café de Colombia.

Additionally, before implementing the advice in this article, we advise also consulting with a local technical expert, since differences in climate, soil type, varieties, processing methods, and more can affect the best practices for production and processing.

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