Processing

There are two main methods of processing.

• Dry processing

• Wet processing

Dry processing

The dry processing method, also known as natural coffee, is the traditional way of processing coffee beans. It is the most basic method of processing coffee and is mainly used for Robusta varieties around the world. Brazil produces 90% of its Arabica this way, unlike most coffee producing countries that prefer the wet method for Arabica. Coffees that have been processed using the dry method have a full body and mild aroma and can be sweeter and more complex than wet-processed coffees. Rain and humidity can interfere with the drying process and produce inconsistent beans. For this reason, the dry processing method is often used in countries where rainfall is scarce and long dry spells are common as rain and humidity can interfere with the process and produce inconsistent beans.

2. Sorting

The cherries are then sorted with the ripe cherries separated from the unripe and overripe ones.

3. Drying

Cherries are spread out into the sun to dry, either on the ground or on large tables. The cherries are turned three to four times a day to ensure even drying, for up to three weeks. Sometimes hot air machines are used to speed up the process. The cherries must be thoroughly dried or fungus and bacteria may develop which will affect the taste of the coffee.​

4. Raking

The cherries are raked and turned to make sure they dry evenly.

5. Hulling

All the outer layers of the dried cherry are removed in one step by a hulling machine leaving the green coffee bean and its inner layers. The parchment and silver skin layers, which protect the bean from deterioration, are removed just before export. Once all the layers are removed the beans are at the green bean stage.

Wet processing

Wet processing, also known as washed coffee, is the preferred method for most Arabica producers, especially those in Central and South America. Wet processing requires high rainfall and large amounts of water to rinse, soak and wash the fruit to remove the layers around the bean. Wet processing is more expensive and uses more equipment than dry processing, but can command higher prices as the quality of the beans is increased. Wet processed coffees are fruitier and very aromatic but tend to have less body than dry-processed coffee. Acidity is enhanced in washed coffee and can make the coffee seem brighter.

Wet Processing Steps

1. Rinsing and sorting

The coffee cherries are rinsed to remove any dirt or debris after harvesting. Sometimes flotation tanks are used to separate the ripe cherries (which sink) and overripe ones (which float). Unripe green cherries are sorted by hand or by machines.

2. Pulping

Machines remove the skin and pulp from the coffee cherry.

3. Fermentation

The beans are then put into fermentation tanks for up to 36 hours where any remaining outer layers and mucilage are fermented. Fermentation breaks down the remaining layers and makes them easy to remove.

4. Washing

The coffee beans are then washed to remove any fermented or leftover mucilage sticking to the beans. At the end of this stage, the only layers still attached are the parchment and silverskin layers.

5. Drying

The coffee beans are then dried either in the sun or by an air dryer. Drying must be done carefully to ensure the beans are dried evenly and not over-dried.

6. Hulling and polishing

Finally, before being exported, the parchment is removed using a hulling machine and the beans are then polished by another machine to remove the silver skin. The beans are now called green beans and are ready for export and roasting.

Other processing methods

Although the wet and dry methods are the two most common types used there are a couple of others that can be used.