What is coffee processing? A living document covering all things coffee fermentation.

What is coffee processing? 

That’s a great question but it’s also a little more complex than it would seem at first glance. To start, coffee is an agricultural product and is grown on trees. What we think of as a “coffee bean” is actually a seed found within a coffee cherry. Coffee plants are known for being grown at high altitudes, typically nestled around the equator, and require very specific conditions, temperatures and microclimates in order to thrive. These microclimates coupled with the variety of coffee grown are in part what help produce desirable traits in your end cup. The other major factor is the processing of the coffee.

Coffee processing refers to the type of intentional fermentation the coffee underwent before it was then dried. In some cases the seed is extracted from the fruit while in other cases it’s left inside. Now let’s dig into the different types of coffee processing:

Core Coffee Processing:

Washed Processing:

Washed processing involves de-pulping the coffee cherry. A bladed tool is used to cut open the cherries, extract the seeds and discard the empty fruit. The coffee is then soaked in water to soften the seed and typically is left to ferment for 12 to 72 hours. Afterwards the coffee is washed clean of any remaining fruit, mucilage and silverskin before it’s finally dried. 

Fun fact: Washed coffees are the most common processed coffees you’ll see!

Natural Processing: 

Natural (or sundried) processing is the most traditional processing method for coffee! In Natural processing the whole cherry is left on the coffee and is placed on flat raised beds or patios to fully dry out (think turning the coffee cherries into little coffee raisins!). While natural processing can take longer than some other processing methods it can be a more accessible processing method for smaller producers while still having those complex fruity notes.

Honey Processing:

Honey (or pulped natural) process is a hybrid processing method that combines elements of both Natural and Washed techniques. In Honey processing coffee is depulped but allowed to dry first before washing. Unlike Natural process where most, if not all of the fruit is left on the coffee, only some fruit is left! 

Fun fact: The reason  “honey processing” gets its name is because while most of the cherry is gone, the remaining fruit becomes golden and the sticky mucilage is reminiscent of honey! 

Innovations in processing:

Anaerobic Processing:

Anaerobic fermentation is a coffee processing method where coffee cherries are fermented in an environment where the coffee is deprived of oxygen during the fermentation stage! Deprivation of oxygen can happen within a bag, vat, or other container that limits oxygen’s ability to reach the coffee as it ferments. The oxygen is then released via a one-way valve, or specifically pushed out by forcing carbon dioxide into the container being used. This allows for a longer fermentation phase to occur without the risks of over fermentation!

Aerobic fermentation:

Aerobic fermentation in coffee processing involves exposing freshly picked coffee cherries to oxygen for a set period to break down their sugary mucilage, removing the sticky layer and creating unique flavor compounds through the action of natural yeasts and bacteria. Unlike anaerobic methods that occur in oxygen-free environments, aerobic fermentation relies on time, temperature, and the availability of oxygen to control the process, resulting in distinct flavor profiles that can range from fruity and floral to earthy

Co-fermentation:

Co-fermentation is a trend popping up within coffee processing, where fruits or spices are added alongside the coffee during the fermentation phase.This is not a new practice producers in some regions have been adding cinnamon to fermentation tanks for years! However, this new trend of applying different additives, like grapes, lychee, cardamom, etc., to fermentation or drying has taken off over the last couple of years. 

Bio Innovation:

The simple definition is a carefully crafted fermentation process but the more in-depth answer is a little complicated. Farmers cultivate a substrate to ferment coffee cherries in, using a microscope to purposefully select the microorganisms allowed to interact with the coffee. They place the full cherries in clay pots for approximately 100 hours with 50% of the substrate, then depulp the coffee and place them in an aerobic environment with the remaining 50% for 24 hours. This meticulous process allows the regional characteristics to shine through in every sip.

Chilled Cherry:

Chilled Cherry processing is a variant of anaerobic natural processing. After leaving the tanks, the coffee is dried with the coffee cherry still intact. This creates a sweet and fruity taste that’s perfect for those who prefer a lighter, more refreshing coffee. Temperatures range between 20° to 35° Celsius and for this reason, they are able to create a process where they could extend the fermentation period without damaging the embryo and avoiding alcoholic boozy notes. The tanks are lined with jackets that enable the flow of cool water, so the cherries are kept at a stable, cool temperature. 

Mossto or Culture fermentation:

Coffee is picked and delivered to the processing yard where it is allowed to ferment in-cherry until the next morning when it is pulped and then fermented a second time, in-parchment. The second fermentation took place in mossto (juice made by compressing coffee cherries) before being mechanically washed and then carefully dried.

Limited Oxygen:

The Limited Oxygen Fermentation process starts with ripe cherries, which are placed in float tanks to remove lower-density fruit, leaving only the highest density cherries. Unlike typical Natural processes, these cherries undergo a critical fermentation step in an oxygen-controlled environment. This “Limited Oxygen Fermentation” is influenced by naturally occurring environmental yeasts enhancing clarity, fruit notes, and sweetness.. The cherries are fermenting in this environment for approximately 24 hours, dependent on variables such as temperatures and weather. After fermentation, the cherries dry slowly on open-air tables under mesh canopies.

Dynamic Cherry:

In this process, cherries are spread out on a warm patio for two days prior to undergoing fermentation. This step helps reduce the moisture content of the coffee seed so that there isn’t enough water available to promote bacteriological reactions outside of the seed, but leaves enough moisture to aid enzymatic reactions within the coffee. The purpose of this is to decrease the risk of fungal development in those first few days of fermentation, and also serves to prolong the fermentation process considerably. 

There are so many different innovations in coffee processing than we could discuss in this post, but we hope that the ones we did go over have helped give you a deeper understanding of what coffee processing is and why they're so vital to the industry as a whole. This will be a living document that we add to as we carry different coffee processes here at Little Bear so be sure to come back to this page if you’re ever unsure of a processing method you’ve never seen before.