Coffee Processing: What Is It?

Long before coffee graces our mornings with its rich and aromatic scent—a fragrance we’re intimately familiar with—it begins its journey in a form quite surprising: a cherry. These bright red or yellow fruits of the coffee plant, through a meticulous and transformative process, yield tiny seeds that undergo several stages before they’re ready for roasting.

This initial stage, known as coffee processing, plays a crucial role in shaping the flavours, characteristics, and overall quality of your morning cup. Whether you’re a seasoned coffee enthusiast or new to the world of coffee, understanding this often-overlooked aspect of coffee production is key to appreciating the complexity and craft behind every brewed cup.

In this blog post, we’re going to break down this step and explore some of the most common methods producers use to process coffee, but let’s first define:

What is coffee processing?

Simply put, coffee processing is the journey that coffee cherries undertake to prepare them for roasting. Producers use several methods, sometimes in combination, to achieve this transformation. To start, we will cover the three main methods: washed, natural, and honey. Additionally, we will briefly explore some newer and experimental techniques that are expanding the boundaries of traditional coffee processing.

Washed Process

Also commonly referred to as the Wet Process, the Washed process is the most widely used coffee processing method worldwide. It consists of the following steps:

1. Depulping: After harvesting, ripe cherries are fed into a depulping machine which removes the skin, leaving a thin layer of fruit, known as mucilage, still attached to the seed.
2. Fermentation: The seeds, now with mucilage, are soaked in clean water for typically 48 to 72 hours. During this time, natural fermentation occurs where microorganisms in the water begin to break down the mucilage.
3. Washing: Post-fermentation, the beans are thoroughly washed in clean water to remove any remaining mucilage. This step also often includes grading the beans for size and sorting them for quality.
4. Drying: The washed seeds are then spread out on large patios to dry in the sun, reaching a moisture content of about 10-12%.
5. Milling: Once dry, the seeds’ outer layer of parchment is removed using milling machines.
6. Resting: Post-milling, the seeds are stored in grain-pro bags to rest for a period. This stabilises them before they are finally ready for roasting.

Taste profile: Washed coffee typically exhibits a cleaner flavour profile with great clarity of flavours. It will usually highlight acidity but have a low-medium body.

Natural Process

Also known as the Dry Process, the Natural Process is a traditional method widely utilised in Ethiopia. Contrary to the washed process, no water or depulping is required. Here’s how it unfolds:

1. Drying: Immediately after harvesting, ripe cherries are spread out on raised beds or patios where they are left to sun dry, reaching the ideal moisture content of about 10-12%.
2. Turning: To ensure even drying and prevent bacterial growth, the cherries are regularly turned throughout the day.
3. Hulling: After the cherries have dried to a brown, shrivelled appearance, reminiscent of dates, they are processed through a hulling machine to remove the dried fruit layer surrounding the seeds.
4. Resting: Post-hulling, the seeds are stored in grain-pro bags to rest for a period. This stabilises them before they are finally ready for roasting.

Typical taste profile: Naturally processed coffee typically exhibits a heavier body with more fruity undertones.

Honey Process

Also commonly referred to as the pulped natural or semi-washed process, the Honey Process is a hybrid method that combines elements of both the washed and natural processes. It involves the following steps:

1. Depulping: After harvesting, ripe cherries are processed through a depulping machine which removes the skin but leaves a sticky layer of fruit, known as mucilage, attached to the seed. This mucilage, resembling honey in its texture and colour, gives the Honey Process its name.
2. Drying: Unlike the washed process, these seeds are not fermented or washed but instead are sun-dried with the mucilage still attached on raised patios. The amount of mucilage left on the seed can vary, affeceting flavour profile. The seeds dry to the ideal moisture content of 10-12%.
3. Turning: Because the seeds are coated with sticky mucilage, they need to be turned every 1-2 hours to prevent bacterial infestation and ensure even drying.
4. Milling: Once dry, the outer layers of mucilage and parchment are removed using milling machines.
5. Resting: After milling, the seeds are stored in grain-pro bags to rest for a period. This stabilises them before they are finally ready for roasting.

Typical taste profile: Honey processed coffee usually sits somewhere in between washed and naturally processed coffee. It can take on qualities from both with a slightly elevated sweetness.

Why Process Differently?

The processing methods used by producers vary vastly around the world, largely dictated by the resources available to them. Each method involves certain costs and yields different potential revenues, factors that heavily dictate a producer’s choice. For instance, in Ethiopia, where access to clean water can be both challenging and expensive, many farmers opt for the natural process.

Moreover, market demand plays a crucial role in determining the processing method. The washed, natural, and honey processes each produce distinct flavour profiles, allowing producers to cater to specific preferences and trends in the coffee market.

Due to the high cost of processing facilities, it’s also common for farmers to collaborate with or sell their cherries to cooperatives. These cooperatives often have the necessary infrastructure, enabling farmers to process their harvested cherries more efficiently and effectively. This collective approach not only helps manage costs but also supports farmers in achieving a higher standard of quality and consistency in their coffee production.

New and experimental processing METHODS

As the demand for high-end, exotic specialty coffees continues to climb, producers are innovating their processing techniques to enhance cup quality and garner premium prices. Over the past decade, several novel processing methods have emerged, enabling producers to not only increase revenue, but achieve higher acclaim and win prestigious awards like the Cup of Excellence.

These methods often require additional steps and, occasionally, sophisticated equipment, which may not be accessible to all farmers. However, these innovations serve as valuable strategies for producers looking to increase profits and distinguish their products in a competitive market. Below are some methods making a splash in the market.

Anaerobic Fermentation

Anaerobic fermentation is an extra step that producers can integrate into their processing to significantly enhance flavour development. It involves enclosing the cherries or freshly pulped seeds in an oxygen-free environment. Here’s how it works:

1. Sealing: Immediately after harvesting, ripe cherries or freshly depulped seeds are placed in a container, which is then sealed. Overtime, carbon dioxide will build up, and oxygen is forced out through a one-way valve, creating an anaerobic (oxygen-free) environment.
2. Fermentation: This stage typically lasts between 24 to 72 hours, although some producers opt for extended fermentation periods, sometimes exceeding 500 hours. Producers may also add specific yeasts to accelerate or initiate the process.
3. Flavour Development: During fermentation, microorganisms consume the sugars in the coffee cherry, converting them into simple acids and other organic compounds. This transformation can drastically alter the flavour profile of the coffee, often enhancing sweetness and fruitiness. Extended fermentation periods can also introduce a boozy or funky undertone, a result of increased ethanol production.

Anaerobic fermentation allows producers to experiment with flavours, offering coffee lovers like you and I new and exciting taste experiences.

Lactic Fermentation

Lactic fermentation, like anaerobic fermentation, involves placing coffee cherries or freshly pulped seeds in an oxygen-free environment. The key distinction, however, lies in the initiation of fermentation: instead of adding yeast, conditions are adjusted (often through the controlled addition of a salty water solution) to favour the growth of lactic acid bacteria.

During this process, microorganisms consume the sugars present in the coffee, but unlike typical fermentations where ethanol is the primary by-product, lactic fermentation produces lactic acid as the dominant by-product. This shift results in a distinctive environment that significantly influences the flavour outcome.

Lactic fermentation is known for enhancing the body and complexity of coffee, introducing unique flavour notes that can range from a mild, yogurt-like tanginess to strong fruity or floral overtones. This technique is especially prized for its ability to craft complex and nuanced cup profiles.

Carbonic Maceration

Carbonic maceration is an advanced processing technique adapted from the wine industry, used to ferment coffee in a highly controlled environment. This method involves placing coffee cherries or depulped seeds in pressurised containers filled with carbon dioxide. Essentially, it is a form of anaerobic fermentation, with the main distinction being the use of specialised equipment that allows for precise control over variables like temperature, oxygen levels, pH, etc…

This enhanced control enables producers to fine-tune the fermentation, leading to a more predictable and refined outcome. Carbonic maceration typically results in a coffee with distinct, enhanced flavours that are not achievable through traditional fermentation methods.

Despite its benefits, the sophisticated equipment required for carbonic maceration is costly and expensive to operate. Consequently, only a limited number of producers are able to implement this technique, making coffees produced via carbonic maceration rare and often sought after in the specialty coffee market.

Thermoshock

Thermoshock, or thermal shock is an innovative technique often applied prior to or immediately after fermentation that can help boost a coffee’s flavour profile even further. This method involves subjecting coffee cherries or depulped seeds to rapid temperature fluctuations in water baths, with temperatures ranging from 0 degrees Celsius to 90 degrees Celsius. Such dramatic shifts alter the cellular structure of the coffee cherry, facilitating deeper flavour development throughout the subsequent processing stages.

We have found that Thermoshock can notably increase the perceived sweetness and enhance the body of the coffee. During an origin trip to Pillcocaja, Ecuador, we conducted our own Thermoshock experiments. We subjected a Typica variety to Thermoshock followed by carbonic maceration for 120 hours. When compared to the same coffee processed naturally, the results were strikingly distinct, showcasing a profound transformation in flavour and aroma. You can actually taste this unique coffee and observe the remarkable differences for yourself, shop it here.