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Methods of processing coffee beans

29 03 24Rivershop Work

What is coffee processing?

Simply put, coffee processing is the removal of the layers of the berry that surround the coffee bean.

Coffee "cherry" consists of several layers, which include cascara, pulp, parchment, silverskin. After the berries are picked, they need processing that removes these layers and cleans the grain. This can be done in a number of ways, each of which creates a different flavor profile for the cup.

Below we will look at the four most common coffee processing processes in more detail!


The process of washing the beans involves removing each layer of the coffee berry before it is dried.

To begin with, the coffee berries undergo sorting, during which they are separated into immature berries and floaters. Floaters (or "floaters") are light defective coffee berries that rise to the surface of the water during processing. This is an important step as floaters tend to affect the taste of the coffee. Therefore, their separation before depulping allows you to preserve the quality of the coffee.

The harvested coffee is then passed through a depulper to remove the skin and pulp. These machines can be either manual, where workers turn a wheel-mechanism, or electric. Huge industrial machines can peel coffee much faster and more efficiently.

Inside these machines are disks (holes) that push the coffee beans out of the fruit itself. Because the ripe coffee berries are soft, they are crushed when passing through these machines, and only the coffee bean passes through them. Unripe "cherries" and garbage are also separated in the process.

The next stage of coffee processing is the removal of the sweet, sticky mucus that surrounds the coffee bean. For this, coffee is placed in tanks with water for fermentation for a certain time. This is usually between 12 and 36 hours, but producers often experiment with different fermentation times to influence the flavor profile of the coffee. After fermentation, the coffee is washed with clean water and then dried on patios, tables or dense nets raised in the air. The coffee is then placed in warehouses in order to equalize the average humidity in the bags and stabilize the water activity. After that, the green coffee beans are ready for the final stage of peeling from the parchment cover, which served as a kind of protection tool for the bean. The final stage is export from the country of cultivation to the customer.

Washed is one of the most popular coffee processing processes. It gives the grain a clean and medium-bodied profile, as well as a more playful acidity than in the natural way.


Natural processing of coffee is the oldest and riskiest process.

Instead of removing the outer layers, as in washed processing, natural processing involves drying the coffee beans in the pulp and mucilage that envelops the beans. This means that the fructose, sweetness and aromatics contained in the coffee "cherry" begin to ferment and are absorbed by the bean during drying.

The harvested coffee is sorted by flotation and sieving to remove defective berries, after which they enter the drying chamber. They are then laid out on a surface in the yard in the sun, on a table or raised "African bed" and left to dry.

Natural processing of fruit is complicated not only by the risk of over-fermentation when the fruit is left to dry for a long time, but also by the development of mold and rot. Mold fungi at best weaken the aroma of coffee, and at worst - cause taste defects. To avoid this, the coffee should be turned and stirred frequently, ensuring maximum air access to each of them, which contributes to uniform drying. After a certain amount of time, when the coffee reaches a given moisture level, all the outer layers of the dried cherry are removed in one step. This process is called "hulling" and used to be done manually. Now there are special devices for this - hallers, with the help of which the grain is rubbed and cleaned.

This coffee processing method tends to produce a very bright, lively and full-bodied cup, mostly with a high sweetness and a thick body.


In a broad sense, this is a coffee processing process that is between washed and natural.

This coffee often has a fruity aroma, but with a medium sweetness and body, having the taste characteristics of both washed and natural processing methods.

After the harvested coffee is sorted and pushed through the depulper, instead of placing the coffee in fermentation tanks as in washed processing, the coffee is moved directly to the drying area, leaving only the beans in the sweet mucilage. Makers often experiment with leaving different amounts of it on the bean to achieve different cup profiles and colors. After drying the coffee beans and mixing them, they are sent for aging. After that, they will go through the peeling stage and will be sent to containers for export. This final stage should preferably be carried out in all processing methods. The period of coffee beans in the patch during rest is intended for ripening and development of their taste and aroma.


The most popular experimental methods of coffee processing are anaerobic fermentation (fermentation of coffee without access to air). This process can be performed according to one of the processing methods indicated above. On some farms, particularly knowledgeable technologists may use a combination of different processing technologies with the addition of anaerobic processing, thereby expanding the flavor potential of classic Arabica varieties.

During coffee fermentation, the temperature is controlled (in the range of 18 - 20 °C), and the sugar level (Brix) and pH are constantly measured. As carbon dioxide (CO2) is produced during fermentation, the pressure in the tank increases, so a valve is needed to release the CO2 and keep oxygen out.

Another advantage of the anaerobic fermentation method is that at each farm or each batch, the primary processor can add some selective yeasts or bacteria to create a specific aroma.

With traditional fermentation methods (with washed or natural processing methods), bacteria and yeast are not controlled.

In anaerobic fermentation, as a rule, the processor-experimenter already has training and knowledge about which microorganisms can form which complexes and compounds.

The most typical example is the addition of Lactobacillus bacteria during coffee fermentation to promote lactic acid production.

Saccharomyces fungi/yeasts are also often used as they are among the most common fungi and yeasts used in beer, wine or bread production.

The most common taste profiles of anaerobic grain are tropical and alcoholic (for example, a red wine descriptor). However, some also have a yogurty, spicy and somewhat "musky" smell. Such coffee has high sweetness and a pleasant aftertaste.

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