Coffee processing is a generalized term involving a number of post-harvest steps. Significant among them is the fermentation stage. Here, I am exploring processing from the fermentation methods in common use.

This article follows on from an earlier one entitled, The Hidden Science of Flavour Profiles.
 
It is worth noting that processing is unlikely to be something you get involved in (unless when visiting a farm you get a chance to pitch in). However, it will give you greater insight and appreciation for the significant effect processing has on the final cup’s flavour.

As you will see from the illustration here, the coffee berry is in its simplest form comprised of five elements which I will reference in the following descriptions of the various processing methods.

Here’s a breakdown of the most common ones in use, along with rationale behind choosing one over the others:

1. Washed Process (Wet Process)

This is easily the most common method, starting with the sorting of the harvested berries. This is one of a number of quality control steps to ensure only top-quality berries are factoring into a given processing batch.

The berries then undergo a de-pulping to remove the skins and interior pulp. The beans are surrounded by a sticky, mucilage layer which gets removed through fermentation and washing. For greater detail, see my Step-by-Step Guide to the Washed Process.

With the skin, pulp and mucilage removed, the beans are then dried on raised beds or patios.

Factors Influencing the Use of the Washed Process

• High-quality beans
• Clean, bright flavours desired
• Abundant water availability

Commonly Associated Varietals

• Kenyan AA
• Colombian Supremo
• Various Central American coffees

Prevalent Regions

• Central & South America (Colombia, Costa Rica)
• East Africa (Kenya, Rwanda, Burundi)

2. Natural Process (Dry Process)

In this process, whole cherries are first dried on raised beds or patios. This way, the mucilage and pulp dry alongside the beans, influencing flavour in some pretty magical ways. For greater detail, see my Step-by-Step Guide to the Natural Process.

Factors Influencing the Use of the Natural Process

• Limited water resources
• Sweet, fruity, winey flavours desired

Commonly Associated Varietals

• Ethiopian Yirgacheffe
• Brazilian Naturals
• Some Guatemalan coffees

Prevalent Regions

• Ethiopia
• Brazil
• Some parts of Central America

3. Honey Process (Semi-Washed Process)

In this process, pulp is partially removed, leaving some mucilage on the beans. This affords a measure of control over the nuancing of flavour – The more pulp left, the increase in fruitiness. The process is often further categorized as Yellow, Red, or Black Honey Processed. Drying time varies, of course, depending on the amount of mucilage remaining.

Factors Influencing the Use of the Honey Process

• Balancing sweetness and acidity
• Experimenting with u profiles

Associated Varietals

• Many Central American coffees
• Some Ethiopian coffees

Regions

• Central America
• Ethiopia
• Some parts of South America

4. Pulped Natural (Semi-Dry)

Unlike the honey process, all the pulp is removed in the pulped natural process. The beans are then dried with the mucilage still attached.

Factors Influencing the Use of the Pulped Natural Process

• Desire for a flavour balance somewhere between the washed and natural processes

Commonly Associated Varietals

• Some Ethiopian coffees

Prevalent Region

• Ethiopia

5. Anaerobic Processing

Anaerobic processing has become a significant development in coffee processing, offering exciting possibilities for flavour exploration and pushing the boundaries of coffee quality. Driven by the desire to explore new and unique flavour profiles, coffee producers began experimenting with different fermentation techniques, drawing inspiration from winemaking methods like carbonic maceration (see below). The beans are fermented in an oxygen-free environment (e.g., sealed bags).

It established itself producing coffees with distinctive flavour profiles, often characterized by intense fruitiness, winey notes, and reduced acidity. The lack of oxygen during fermentation allows for different microbial activity, leading to the development of unique and complex flavour compounds.

Factors Influencing the Use of Anaerobic Processing

• Experimentation
• A desire for unique flavour profiles (market shaping)

Commonly Associated Varietals

• Various varietals, often experimental

Prevalent Regions

• Growing in popularity worldwide

Lesser Used Methods Worth Mentioning

Carbonic Maceration: This innovative method involves fermenting green coffee beans in a sealed container filled with carbon dioxide. This creates unique and complex flavor profiles, often with fruity and winey notes.

Giling Basah (Wet Hulled): This method is primarily used in Indonesia, particularly Sumatra. The cherries are de-pulped, then hulled while still slightly moist. This results in a unique earthy and savoury flavour profile.

Aquapulping: This is a more recent method that aims to reduce water usage compared to traditional washed processing. It involves a mechanical scrubbing process to remove the mucilage, minimizing water waste.

Other Important Considerations

Climate: Weather conditions greatly influence drying times and the success of each method.

Water Availability: Washed processes require significant water resources, limiting the appropriateness of some methods.

Labor: Natural and honey processes can be more labor-intensive that others, creating another limitation in some regions

Varietal Characteristics: Certain varietals are simply better suited to specific processing methods. So, the limitations of process can also drive the choices farmers make in cultivation.

This information should give you a good overview of the different coffee processing methods. If you haven’t already, be sure to subscribe to The Coffee Authority Weekly where we update this information regularly. Remember that these methods have a significant impact on the final cup profile, so exploring and understanding them will enhance your overall coffee appreciation. As always, be sure to let us know your own experiences in the comments.