Six Common Coffee Processing Methods

Coffee processing is remarkably varied, and there are no fewer than five methods most of us know by name: natural, washed, honey and the rest. We all understand that different processing steps lead to completely different flavors. Before specialty coffee took hold, though, the development of processing methods worldwide served a single purpose, drying coffee beans so they could be stored, and nothing more.

As specialty coffee spread, people gradually realized that processing directly shapes flavor. So many producers stopped choosing a method purely to dry the beans and began choosing one that reaches an ideal flavor while drying. In today's article, FrontStreet Coffee revisits six common processing methods: where they came from, how they work and what sets them apart.

Natural Process

Natural processing always comes first because it is the oldest method. For centuries, all the coffee in the world was processed naturally. Back then it wasn't even called the "natural method"; like drying peanuts, it was simply an ordinary way to dry a crop.

The steps are simple. After the coffee cherries are picked, they are dried in the sun directly. Once the whole fruit is completely dry, machines crush through the skin, pulp and parchment layer to extract the beans, and the process is done. Drying time generally depends on how strong and how long the local sunlight is, and on the specific processing steps. In Ethiopia, for example, sunlight is plentiful, so drying takes about 3-4 weeks. The advantages are obvious: all you need is a spot with long hours of sun. And because the skin and pulp stay around the beans through the whole drying and fermentation period, the resulting coffee develops very rich flavors. Its drawbacks are just as clear. One is a heavy dependence on weather; the other is that fermentation is hard to control, so the share of high-quality beans is relatively small and prices run higher. A customer once asked FrontStreet Coffee why a natural-processed red label costs more than a washed red label. This is one of the reasons.

Natural processing needs nothing but sunlight, yet for most coffee-growing countries that is a difficult requirement to meet, the West Indies among them. When coffee was widely cultivated there, local farmers naturally had to process it. But the humid, rainy weather and short sunshine hours stretched the drying time enormously, and the damp conditions made mold and spoilage far more likely. So by the mid-19th century, the washed method was born.

Washed Process

The biggest difference between washed and natural processing is whether the skin and pulp are removed before drying. Removing them shortens drying time dramatically, to about half of what natural processing needs. The birth of washed processing also owed something to the Industrial Revolution. In 1845, the world's first coffee pulper was invented in Jamaica, and from then on washed processing could take off successfully.

Traditional washed processing is simple yet refined. Before processing proper, flotation is used to screen out defective fruit. Then a pulper removes the skin and pulp from the selected cherries. The beans, still coated in mucilage, go into water tanks to ferment and break down that mucilage. Once fermentation is complete, workers wash the beans to remove any mucilage left on the surface. After washing, the beans are moved to a drying patio. Finally, only the parchment layer remains to be removed, and the washed process is complete.

Because washed processing doesn't let the beans ferment excessively, the final coffee can have a cleaner profile, which lets it better showcase its original character. Washed processing has branched into many variations, and different countries and places work in their own way. Kenya's washed process, for example, is nicknamed K72: the beans are soaked in two washing stages, and the soaking often reaches 72 hours, hence K72, or "Kenya-style 72-hour washed processing." (Click the blue text for details.)

Washed processing is great on every front except one: wastewater. On average, every ton of coffee beans requires 10-20 tons of water, so for countries with limited water resources, washed processing is a luxury. One country was clever about it, though, and invented a method that reaches similar results without using so much water. That country is Brazil, and the method is pulped natural.

Pulped Natural Process

The pulped natural method invented in Brazil, as the name suggests, borrows from both the natural workflow and the washed steps, cutting water use while still shortening drying time significantly. Brazilian natural processing had long been criticized as rough, and the country couldn't spare large amounts of water either, so in 1990 Brazil invented pulped natural processing.

In practice, the harvested cherries are floated, then a pulping machine removes the pulp, skin and part of the mucilage, after which the beans are soaked in water tanks for an hour. Because the soak is short, most of the mucilage stays on the beans. Even so, with the skin and pulp gone, drying takes far less time, greatly reducing the chance of spoilage, and the coffee ends up with a relatively cleaner profile than natural processing. That is exactly why FrontStreet Coffee chose a pulped natural FrontStreet Coffee Brazil Red Bourbon as the Brazilian entry in its regional daily coffee series.

Wet Hulled Process

Many people have asked at FrontStreet Coffee stores whether pulped natural can also be called semi-washed. In theory it can, but in most cases semi-washed refers to wet hulling. Wet hulling is unique to Indonesia. Because the local weather is extremely harsh for coffee, humid, rainy and with very high humidity, drying beans with the parchment on takes a very long time. Indonesia is also a major producer with enormous output, and like Brazil it needed a way to dry beans fast so they could be sold quickly for cash. The methods above were all too slow for Indonesia, so it developed a method of its own: wet hulling.

The first half of wet hulling matches washed processing: float first, remove skin and pulp, then place the beans with their mucilage and parchment in water for 12-36 hours to break down the mucilage. Once that's done, the beans, now carrying only parchment, are spread out in the sun to dry. When moisture drops below 50%, a hulling machine removes the parchment layer. A final drying session brings the beans below 12% moisture and completes the process.

Because removing parchment from high-moisture beans is difficult, the hulling machine works roughly and easily squeezes and damages the beans, producing "elephant beans." Ugly as they look, elephant beans are not counted as defects, though they do raise the risk of contamination. Wet hulling dries Indonesian beans quickly, but the process is cumbersome and imprecise, which makes contamination more likely and leaves the defect rate far higher than in the methods above. That is why hand sorting is necessary. Interestingly, the flavors these factors produce have become the signature aroma of Indonesian coffee. The unique mellow aroma and thick body of FrontStreet Coffee's Indonesia Lindong Mandheling are gifts of the wet hulling process.

Honey Process

This delicious-sounding method originated in Costa Rica. Costa Rica's main method was washed at first, but as the coffee market slumped at the end of the 20th century, local farmers, wanting more income to keep going, stopped selling cherries to the local washed stations and chose to produce and sell on their own to earn more. Honey processing, which doesn't demand heavy investment, was born against that backdrop. It evolved from Brazil's pulped natural, and its biggest difference from pulped natural is that the beans never touch water after flotation. The "honey" in honey processing doesn't describe the sweetness of the coffee; it describes the mucilage coating the beans during processing, which looks like honey. Hence the name.

The steps are straightforward. The harvested cherries are floated, and once impurities and defective fruit are removed, they are depulped with the mucilage retained. The beans then go out into the sun to dry. After drying to the target moisture, hulling extracts the beans and the process is complete. Because the drying time and fermentation degree of honey processing sit between those of natural and washed, honey-processed coffee tends to perform between the two as well. Generally, the flavor leans toward the complexity of natural processing, while the mouthfeel stays closer to the thickness and cleanliness of washed processing.

FrontStreet Coffee also often points out that honey processing divides into four types: yellow honey, red honey, white honey and black honey. Their main difference is how much mucilage is retained. Mucilage contains sugar, which changes color as it oxidizes, so the amount kept during processing directly affects how dark the beans become. More mucilage means more oxidized sugar, a deeper appearance and a more complex flavor.

Anaerobic Process

Methods like carbon dioxide maceration, red wine anaerobic, lactic acid fermentation, alchemist, enzyme and heat/cold shock mostly belong to anaerobic processing. Anaerobic is extremely popular right now. Because most anaerobically processed coffees have flavors unlike anything conventional, the method took off after 2015, when it first appeared on competition stages and won championships, gaining wide recognition.

The exact methods vary from producer to producer, and different estates and regions use different approaches because the combinations are so varied, so FrontStreet Coffee won't go into detailed anaerobic steps here. Most anaerobic processing, though, adds a fermentation stage before or during conventional processing. By placing cherries or beans in an oxygen-free environment to ferment, producers can control how far and in which direction fermentation goes, steering the beans toward the flavors they want. Usually the process is "concentrated" right into the name. Anaerobic natural means anaerobic fermentation was added to natural processing; anaerobic washed adds it to washed processing; double anaerobic natural means the beans ferment twice during natural processing, and so on.

The degree of fermentation determines the intensity of the fermented aroma. The deeper the fermentation, the stronger that aroma, and vice versa. FrontStreet Coffee Ethiopia Santa Venezi, for example, uses anaerobic natural processing, yet it gives almost no fermented aroma when brewed, showing more of a tropical fruit juice character instead. Another bean on FrontStreet Coffee's list, FrontStreet Coffee Orange Oak Barrel (now sold out), threw off a powerful fermented wine aroma. Those are the six common processing methods you'll meet day to day. Which do you prefer?

- END -

FrontStreet Coffee Recommendation

If honey processing caught your attention, FrontStreet Costa Rica Blackberry is the clearest place to start. It uses a black honey process that removes almost no mucilage, so drying stretches out over at least two weeks under covers, keeping strong sun from speeding things up. During that slow dry the beans are turned at intervals to prevent uneven heating and over-fermentation, and the extra care shows in the cup. Medium-light roasted, it releases a rich floral fragrance when ground and drinks with grape, berry and ripe blackberry notes.

For a more inventive honey-style coffee, try FrontStreet Costa Rica Mozart. This one uses a raisin honey process, an adapted version that sits outside the traditional yellow, red and black styles. The cherries are pre-dried on raised beds for at least three days before the skin and pulp are removed and the honey steps continue, retaining 100% of the mucilage, which makes the method harder to control than black honey. The reward is a richer, fruitier sweetness: made as pour-over, cold brew or in a moka pot, FrontStreet Mozart shows osmanthus, pineapple and raisin aromas.