In this blog post we explain some of the most common processing terms that you might come across and how the way your coffee is processed could change how it tastes in the cup.
It’s a long one, so we recommend sticking the kettle on and making sure you’ve got your favourite brew to hand before getting stuck in.
What do we mean when we say coffee processing?
In coffee we talk a lot about different processing methods.
In short, these are the journey that coffee makes from being a bright red coffee cherry (a fruit) to a green bean ready for roasting. Just like origin, roast profile, soil climate and varietal, how a coffee is processed has a huge impact on the final taste of the coffee in the cup and how the quality of the coffee is judged.
Most speciality coffee is priced according to quality. Coffees of a higher quality, with few defects and complex, interesting flavours score higher when graded and therefore fetch a higher price. Usually, this price is far higher than organic or Fairtrade premiums. Speciality coffee producers and mills therefore take great care in harvesting, sorting and processing their coffee to reach the highest possible score at grading.
What is coffee sorting?
Specialty coffee growers are meticulous about the sorting of their coffee. Farmers will pay a premium to skilled pickers who can ensure that only perfectly ripe red cherries are harvested.
Higher quality coffee with few defects can be sold for much higher premiums, so investing in harvesting and sorting will impact the final score and price that a grower can expect for their coffee.
Once harvested the coffee is sorted. This can be done by hand, or sometimes density in flotation tanks where poor quality cherries float to the surface and are removed from the lot.
Below are some pictures from trips we've made to visit some of our coffee growers. Here, you can see coffee being sorted by hand by farm workers at Cauvery Peak coffee estate in India, and and coffee being sorted in flotation tanks at the Mutira Coop in Kenya.
Women sorting coffee beans by hand at Cauvery Peak, India.
Coffee in flotation tanks being sorted by weight at Mutira Cooperative in Kenya.
Once coffee has been harvested and sorted it will be processed.
What is washed process coffee?
The washed or fully washed method is the most common way of processing coffee. It’s also the most water intensive. Ripe red cherries are picked and then sorted. This can be done by hand or by density on flotation tanks. The sorted cherries are pulped to remove the skins from the cherry, then washed to remove the sticky mucilage from around the bean. Finally the coffee is dried. This could be in mechanical dryers, on tarpaulin or patios on the ground or on African raised beds.
Some producers add a fermentation step into the washed process, fermenting the coffee cherries in fermentation tanks before removing the fruit of the cherry. We go into more detail about the different types of fermentation that a producer might use later on in the blog post.
The photo below was taken by Dan and Ben from Extract when the visited Chania Coffee Estate in Kenya and shows washed coffee beans.
Washed coffee photographed at Chania estate in Kenya.
What is honey process coffee?
In the honey process, the coffee cherries are picked and sorted (either by hand or by density in water). The cherries are pulped to remove the skins, leaving behind the sticky mucilage around the coffee bean.
Instead of washing the fruit of the cherry off the bean, the coffee is left to dry with the fruit intact. This can be on raised beds, on patios or in mechanical dryers. As it does so it imparts sweet fruit flavours into the coffee (this is where the name honey process comes from). During the drying process the coffee is turned or raked over to ensure even drying and to control the humidity of the coffee as it dries.
Once dried, the coffee is dry-milled to remove any remaining fruit or parchment from the beans. The final step is sorting and grading the processed coffee.
In this photo, from Finca Santa Teresa in Panama, you can really see the golden colour of this honey process coffee as it dries.
Honey process coffee at Finca Santa Teresa in Panama.
What is natural process coffee?
Natural process coffee is the least water intensive method. Ripe cherries are picked and sorted, then left to dry usually on patios, tarpaulins or African raised beds but sometimes they could be dried in kilns or mechanical driers.
The fruit of the coffee cherry dries, it ferments around the coffee bean, imparting intense fruit flavours and sweetness as it does so. The fermentation process may also impart a boozy note into the final taste of the coffee - so it’s not unusual to see natural coffees with flavours like brandy or sherry in the flavour notes.
The humidity of the coffee is monitored closely as it dries. Coffees are turned and raked over throughout the process. Any sign of mould or over-fermentation could be disastrous and result in the producer losing the entire lot. However the complex flavours which are added as a result of natural processing can have a huge impact on the score the coffee receives in grading - so it’s a case of the coffee grower or mill balancing the risk with the reward.
Natural coffees can be divisive, not everyone enjoys the intense fruit flavours that come with coffees processed in this way!
At Extract Coffee Roasters we set ourselves a challenge each summer to find the funkiest natural coffee we can for our summer espresso, Funka. We carefully choose an accessible roast profile which will mean the coffee tastes delicious with and without milk in the hope that we can introduce coffee drinkers to natural process coffees.
In the photographs below from Finca Santa Petrona in El Salvador you can see the coffee cherries intact as they begin the drying process. The second photograph shows coffee a little further along in the drying process on raised beds at the Chania coffee estate in Kenya.
Natural processed coffee cherries at Finca Santa Petrona in El Salvador.
Natural processed coffee on African raised beds at Chania estate in Kenya.
What about other types of coffee processing?
There has been an increasing amount of words added to the "processing' section of in competitions, on coffee bags and cafe menus over the past few years. Words like maceration, anaerobic, carbonic, extended fermentation and thermal shock are all becoming increasingly common.
The team at Extract Coffee Roasters are still trying to understand what they all mean in practice. Whether these new terms and processing methods are adding to the experience for drinkers, for baristas and roasters and if they actually add value to the producers.
We asked Extract’s Head of Product, Dan Lacey what these actually mean and how they differ from the three main coffee processing methods. This is what he told us:
Some of the terms used to describe coffee processing are borrowed from other industries - wine in particular which uses fermentation to influence a fruity drink so the connection is logical, even if the results aren't.
Few people have been able to succinctly explain what each term means and the results are somewhat inconsistent. This isn't surprising as each farmer will be doing their own version based on experimentation, advice and feedback and these are all influenced by the coffee they start with as well as naturally occurring microorganisms and the environment they work in. A lot of variables.
I'm not a vinter, nor a microbiologist so I can't give you all the answers but I'll try and get you a little closer with the little I've learned so far.
Ripe fruit contains sugars and sugars can be manipulated by bacteria, yeast, oxygen and heat in particular. The newer processing methods use these four elements to affect the flavour and complexity of the coffee by speeding up or slowing down fermentation process. Here's how this works.
Bacteria consumes sugar, breaking down the pectins and leaving acidic secretions.
Yeast also consumes sugar, and different yeasts eat different sugars at different rates. Some sugars are inedible to certain yeasts (think lactose in beer, milk stout remains sweet rather than fermenting into more alcohol or Co2). Yeast secretes alcohol and carbon dioxide.
Oxygen allows both bacteria and yeast to live and so by restricting it, you restrict its growth and outputs. Like us, without any they will die.
Heat has an impact on both bacteria & yeast which have ideal operating temperatures. Too low they will mostly go dormant, but not die. Too hot and they will die. Different heats will have different preferred temperatures and growth will become rapid as well as producing different types/flavours of alcohols.
Now that we've got these basic principles covered, let's dive into some of the more experimental processing methods.
What is anaerobic or semi anaerobic coffee processing?
Anaerobic fermentation refers to coffee which has been processed without oxygen. Typically the coffee cherries are pulped to remove their skins and then placed in an airtight sealed tank to ferment. (how long is decided by the coffee producer).
Semi-anaerobic fermentation follows a similar process but in this case oxygen is present, but in a reduced supply.
Without little or no access to oxygen there are only a few, very specific microbes which can survive during the coffee's fermentation process. The result is that coffees processed in this way develop unique and complex flavour profiles.
For example earlier in 2022 Extract roasted a semi-anaerobic fermentation filter coffee, Finca Capri with notes of black jelly babies, papaya and plum. These complex flavours help the coffees score highly in grading and make them popular in coffee competitions too!
What is maceration coffee processing?
Maceration, often Carbonic Maceration, in wine means leaving skins in contact with the fruit, which is usually crushed to release the juice. This allows the tannins and colour pigments, anthocyanins, to combine with the juice.
In coffee we are seeing some producers leave cherries intact, no crushing, but others lightly crushing or loosely pulping the cherries and then leaving the skins in contact, similar to how some pulped natural coffees are processed in Brazil.
The carbonic part can be caused by the naturally occurring CO2 being trapped or by introducing bottled CO2 much like we do with Nitrogen in our bags.This is done to reduce the rate of fermentation (starving the bacteria & yeast of oxygen) Grain pro bags, plastic barrels and tarpaulin covered fermentation tanks are all being used.
What is extended fermentation coffee processing?
Extended fermentation is one of the more common techniques used in coffee processing to add complexity to the flavour of the coffee.
Extended fermentation loosely means pushing the fermentation longer than usual, and usual will vary hugely from farm to farm, mill to mill.
The producer manipulates and is all impacted by the local conditions for bacteria, yeast, heat, oxygen to slow down the fermentation process. It is thought to develop more complex fruity flavours without allowing off flavours to develop. Some of Extract's oldest coffee partners, for example Veracruz coffee farm in Colombia, use an extended fermentation process to give their coffees such a unique flavour.
In the photos below you can see coffee in a fermentation tank at Cauvery Peak in India, and a washed coffee which has undergone extended fermentation drying on raised beds at Veracruz, Colombia.
Coffee fermentation tanks at Cauvery Peak coffee estate in India.
Washed coffee which has undergone extended fermentation drying on raised beds at Veracruz in Colombia.
What is controlled yeast coffee processing?
Controlled yeast has been used in alcohol production for most of the 21st century to, well, control which yeast is able to grow and ultimately control its impact on flavour.
Historically this wasn't the case and the resurgence of 'natural wines' is bringing back the diversity of local yeasts to the world. For those who have tried them you will know how variable they can be. This is where we are at with all coffee but especially natural coffees.
There are a small number of coffee producers now using a controlled yeast which will outgrow any locally occurring ones and with a little temperature and moisture control enable the producer to replicate the same levels of fermentation (in washed, honey or natural) coffees again and again - as long as they buy the same control yeast again.
What is thermal shock coffee processing?
Thermal shock coffee processes uses hot and/or cold water, sometimes in succession at various temperatures, to halt and limit the growth of the yeast or bacteria, slowing down and fermented flavour development and allowing the coffee to remain at that level for prolonged periods.
This happens naturally in every coffee farm every night - hot days cool nights - and coffee is picked throughout the day, processed in the afternoon and often ferments slowly overnight anyway. What isn't usually controlled is how warm it gets the following day.
Coffee processing? Completed it mate!
You made it! A huge thank you to all of the coffee lovers who stayed with us to the very end of this blog post. We hope this helps you to understand some of the terms being used and why.
It seems to us that the variety of processing methods now available is good for coffee drinkers, baristas and enthusiasts - creating interesting flavours in the cup, but also for coffee growers, who benefit from less spoilage, higher scores and prices for their coffee at grading and a reputation for innovative coffee production.
All that reading left you thirsty?
Check out our latest selection of coffees available to buy online.