Processing coffee cherries

Cultivation

After around 5 years of maturing, a coffee plant begins to produce cherries. Generally, the cherries are ripe once they have changed colour from green through to red and are then ready for harvesting.

Shade grown

In the wild, coffee trees grow naturally underneath the forest canopy and not in direct sunlight so coffee can be planted and cultivated beneath shade-trees which helps to promote diversity, habitats and wildlife. However, coffee can also be grown without shade as many newer varietals can withstand full sun exposure. This method is increasingly seen as less beneficial to the overall sustainability of the landscape in which coffee is grown.

Harvest

The annual coffee harvest, particularly with the steep terrain involved, is a labour intensive but vital process.

There are three main ways in which the crop is harvested.

• Strip picked
• Selectively, hand picked
• Machine picked

Strip picked

When the entire crop is primarily harvested at once by hand. Basically all the cherries are stripped off the branch in a single visit. The disadvantage to this method of harvesting is that unripe or overly ripe cherries (bad ones) are picked along with the ripe ones (good ones). If good sorting equipment is not available, then the coffee is pretty much guaranteed to be of poor to average quality.

Selectively, hand picked

When only the ripe cherries are harvested; this process is done by hand only. It may involve several re-visits to the same sections of the farm because coffee cherries don’t always ripen simultaneously. This is a much more expensive to achieve as it is highly labour intensive. The very best farms will often check the quality of cherries harvested before they are processed.

Machine picked

Uses equipment that removes cherries from the coffee trees. This can be much more cost effective after the initial investments as much less labour is required. However, it is rare that the landscape is suitable for using such equipment (we’ve seen this in Brazil where there is also the machinery to sort the good and bad cherries after harvesting).

Processing

The 2 main methods of processing the harvested coffee cherries are dry processing and wet processing.

Dry natural coffees

The dry process is used to produce natural coffees and is the most traditional method of processing coffee. After harvest and selection, the whole coffee cherries are first cleaned and then placed in the sun to dry. It may take up to 4 weeks before the cherries are dried to the optimum moisture content, depending on the weather conditions. The coffee beans are then removed from the dried cherry.

Ethiopian Harar and Yemeni Mocca are two examples of classic natural coffees.

Washed coffees

The wet process is an alternative means of completely separating the coffee beans from the rest of the cherry and in most cases produces the finest results in terms of taste. The downside is that it requires large volumes of fresh water, which is why it is traditionally associated with regions with more abundant rainfall.

Firstly, the coffee cherries are washed in clean, fresh water and are pulped to remove the skins and outer flesh from the beans. However, the beans are still covered in the sticky pulp or mucilage that must be completely removed before drying the coffee beans.

To do this, the pulped beans are put into fermentation tanks so that the mucilage is fermented for approximately 24-48 hours (depending upon conditions), essentially breaking it down so that it can be washed clear of the bean with clean water. Washing channels are used to help achieve this.

The wet processing generally imparts cleaner, fruitier and more acidic flavours to the coffee and results in classic fully washed coffees.

Semi-washed coffees

These are the result of pulping the cherries and then using alternative techniques to separate the coffee bean from the mucilage or to dry successfully the coffee. They can often use much less, or very little water to assist processing and do not involve the full fermentation process of a fully washed coffee.

De-mucilaged coffees

These rely on mechanical removal of the mucilage from the bean using specialized equipment before drying the coffee and are particularly common on ecologically conscious farms wishing to reduce water usage.

Pulped natural coffees

Are the great semi-washed coffees of Brazil where much of the sweet, sticky mucilage is left on the coffee bean as it dries in the sun, imparting sweeter more rounded flavours. It works here because of climatic conditions being suitable. If it was too cool or humid, the coffee would not dry rapidly or consistently enough and the beans (and flavours) would be irreversibly damaged.

Drying the coffee

Regardless of the method of drying, the coffee must be spread in a fairly thin, even layer in order to dry evenly and consistently and be regularly raked and turned.

Drying coffee on earth patios

This is usually done by the poorest, smallest farmers who will pick and dry all of their coffee at once on their own smallholding. The coffee is dried in the cherry on the bare earth. Used for a lot of Robusta and lesser quality Arabica, the coffees tend to have good, full body and low acidity but the earthiness imparted on the coffee tends to be over-powering and make the coffee taste "dirty". Not recommended for speciality coffee.

Drying coffee on concrete or ceramic patios

This is one of the best ‘traditional’ methods for coffee drying. These surfaces are cleaner by nature and so the coffee picks up fewer negative elements or heavy earthiness. It’s important that the patio is kept in good condition for consistent drying.

Patio drying in the sun is better than artificial drying as the drying is much steadier – it might take up to 10 days for a washed coffee or longer still for ‘dry natural’ coffees. Drying too quickly prematurely ages the coffee and can damage the taste and aromas.

The coffee is brought in and stored at night during the days of drying, and it’s vital to gather and cover it at the first sign of rain.

Artificial (drum) drying

Most larger farms and mills will have drum dryers to ensure that all of their crop is successfully dried – often there is not enough patio space for all of the coffee and it also guarantees against bad weather. The problem with drum drying is that if it’s not controlled carefully, it can end up damaging the quality of the coffee. It’s also bad if the dryer burns firewood from the local forest – eco-conscious farms would use specialised dryers that burn coffee husk or wood from the annual pruning of the coffee trees as it’s more sustainable.

Even if a farm has a dryer, their highest quality coffees would usually be sun-dried on the patios and the lesser quality coffees in the dryers unless absolutely necessary. However, some farms are located in regions (areas of Costa Rica spring to mind) that are wet and humid even during the harvest season and patios are of no use here.

Screen drying / raised bed drying

Wooden, raised screens and beds have been popular in some coffee regions, including parts of East Africa. The benefit is that air can more easily circulate around the coffee for more even drying and there is much less chance of the coffee being tainted by the ground or floor surface.

Modern, raised screens involve investment from the farmer (we’ve seen a number of these on BSCA farms in Brazil) but are great for ensuring quality in the flavours of the coffee. Where farmers can afford the technology, this is the way forward for the drying of quality coffee and they can protect the coffee immediately if it rains as the screens have curtains that can be pulled quickly across if the weather turns.

Dry milling the coffee

Once fully dried and separated from the coffee cherry, the coffee beans are still encapsulated in their parchment. At this point, the coffee is rested before final processing at the dry mill.

Here the beans must be removed from the parchment (hulled), density sorted, colour sorted, hand sorted and screened to ensure the consistency, size and quality of the varying grades of coffees. The very best export grades (speciality coffees) will be denser, consistent in size and have all defective beans removed and will have been cupped by professional tasters before final selection.

The beans are then bagged into jute sacks (unless vacuum packing) and transported to Grumpy Mule HQ via container and ship (we do not support the use of air freight for coffee).