The processing of coffee beans starts with the initial collection of the coffee cherries off the plants branches either hand picked or mechanically picked. They are then taken to the separation tanks which discards unripe cherries and foreign matter and then to the chosen processing method.
As you will read below the varying processing methods have an influence on the final flavour of the coffee even though it is from the same estate and origin. This is why our "Bean Talk" programme is very important. We strongly recommend you try at least one of our Bean Talk offerings by purchasing online or having a cup at one of our partnering espresso bars.
The hand picked process is labour intensive and usually found in mountainous terrain where mechanical harvesting equipment is restricted. This process is more gentle on the plants as only the ripe cherries are collected and minimal damage is done to the branches. Coffee pickers regularly attend to their plants and collect only the ripest cherries which are deposited in baskets and then emptied into the bulk collecting bins where the growers volume is recorded for payment purposes.
The coffee trees are planted at calculated distances between rows to allow access for the large mechanical harvesting machines. The harvester is a huge catamaran type vehicle which has two vertically positioned roller brushes similar to the old street sweepers. The vehicle drives over the row of coffee plants and the brushes agitate the branches causing the cherries to fall into the collecting pan. Any leaves and twigs collected are discarded via vacuum chute and dropped back onto the ground for decomposing. The cherries are then driven to the processing station.
The coffee cherries are poured into the receiving bays which feeds the cherries into the separating tanks. These tanks work with water and separate unripe cherries and twigs from the ripe cherries via gravity. The unripe cherries and twigs float into the discarded bay whilst the ripe cherries are more dense and are channeled into the ripe cherry bay. From here, the coffee is taken to the chosen processing section.
The washed process generally high lights the acidity of the coffee and gives the coffee a more fresh citric aroma.
Before we start don 't let the word fermentation scare you away, it is purely the process by which the proteins, sugars and acids are excited and transformed to develop the coffee, just like with wine, beer, breads, and other foods.
The cherries are transported with water into the pulping separator which removes the fruit off the beans leaving the sticky mucilage on the green (raw) beans. The fruit is collected and used for fertilising the soils as it is still rich in nutrients. The green beans are again washed and placed into fermentation tanks for 8 - 24 hours depending on the mill and other factors such as temperature , ripeness of the cherries e.t.c. The mucilage is generally removed during the fermentation. Once the right amount of fermentation is achieved, the coffee is washed thoroughly to remove any left over fermented mucilage residue. The clean wet coffee beans (parchment) is now ready for drying to stop the fermentation process.
The Sun dried process relies purely on the heat and surrounding weather conditions to dry the coffee. The coffee is evenly spread over clean concrete beds and agitated via raking either by hand in smaller estates or with a with a floating rake connected to a tractor in larger estates. The coffee is continually agitated to avoid any uneven wet spots and spoiling until it reaches the desired moisture content of around 11 - 12% before it is screened and bagged.
Flat or Pan Bed Mechanical Drying
The wet parchment is placed onto large vats with mesh bottoms to dry via mechanically produced heat whereby hot air is circulated through the coffee. Even with this process, the parchment must be turned at regular intervals to avoid wet spots and ensure a uniform moisture content and can take up to 20 hours depending on weather conditions.
Rotary Drum Dryers
The wet parchment is poured into huge perforated cylindrical rotating drums. Hot air is circulated inside the drums. The parchment here is mechanically turned by the rotating action of the drum. The temperature is controlled with sophisticated equipment to prevent over heating and spoiling of the coffee. Each Estate owner has their own preferred temperatures as I experienced when I visited a few Brazilian estates. One estate was running the dryers at 40 degrees whilst another preferred 60 degrees. We purchase both their coffees and although they are different they both come up very good in the cup.
Pulped natural "Honey Process"
The pulped natural process gives a balance between the acidity and sweetness of the coffee. The character isn't as bright or acidic as the fully washed process, but a more complex sweeter flavour is produced.
With the Pulped Natural process, the coffee cherries have been pulped and washed, but the sticky sweet mucilage is left on the parchment coffee and then dried with the mucilage intact. This process produces different flavours within the coffee as there are different sugars, proteins (acids) coming into play and developing inside and on the surface of the actual coffee bean.
This process tends to increase the finish or length of the coffee. Quite labour intensive, but very worth while.
Coffee is naturally dried in the sun on purpose built raised beds. The parchment is evenly distributed throughout the beds and hand raked at intervals to ensure even drying and moisture content. During the drying process, hand pickers also remove any debris, foreign matter and defective coffee beans.
The natural process adds more complexity, character and a sweetness to the coffee. It seems to bring out a nice deep even flavour without too many irregular high notes.
This process involves the whole cherry being collected and dried in any of the above mentioned processes. It is predominately used in estates where water is scarce. The coffee enveloped in the cherry has extensive contact during the fermentation of the fruit sugars and proteins and results in a more complex flavour. The Natural process is one of Mocha Coffees favourite for Brazilian coffee.
This process is open to opinion for the exact term. The cherries are pulped and the mucilage is removed mechanically with a demucilager rather than relying on the water in the fermentation tanks to remove the mucilage. The coffee is then dried in a chosen method above. However, in Indonesia their process for semi-washed coffee is as follows, the parchment and mucilage is placed in baskets or bags and left overnight to ferment.