Dry or natural method processing of coffee

There are four main methods used to process coffee: Washed Process, Natural (or Dry) Process, Wet hulled and Honey Process.

Dry process is a method of processing coffee beans to remove the fruit of the cherry and dry the bean. In the dry method, the usual objective is to harvest all cherries simultaneously with the least percentage of unripe ones.

The ideal situation is to harvest all fresh, ripe cherries with the least possible damage to the tree, irrespective of the processing system to be used. The cherries are picked ripe, which is important since the fruit itself imparts flavor during this process. They are sorted and weighed before moving to the drying area.

In this method, the coffee cherries are laid out in the sun on a concrete drying patio, or raised beds. Raised beds are preferred because they increase the airflow around the whole fruit to enable more even drying. The coffee is shifted every 30-40 minutes.

Throughout the course of 3-6 weeks, the coffees will ferment, as producers rake these cherries and rotate them to prevent spoiling. During this time, the sugars and mucilage (that sticky substance that coats the seed) will latch onto the seeds, which develop flavors and make them sweeter.

Raking also prevents bruising on the fruit where it’s in contact with the patio or tarp on which it’s resting. Producers are vigilant about avoiding bruising because it can cause flavor defects.

Coffee must be dried from approximately 60% moisture content to 11-12% moisture content. After a period of 3 - 6 weeks, the husk of the dried cherry is removed mechanically. The resulting coffee is often referred to as unwashed. This is the oldest method of processing coffee and is more ecologically friendly, as it does not require water.

Natural sundried, also called “natural process” or “dry process,” means drying coffee cherries whole without the intervention of water or machines to remove any of the fruit. Drying should be uniform to obtain acceptable color, size along with the removal of pests for a longer safe storage. Since coffee production is seasonal, traditional sun drying is quite tough.

This method is widely used in Brazil, but less widely used in Guatemala or Costa Rica where the coffee is more often piled perpendicularly to the old piles.
Dry or natural method processing of coffee

Green Coffee Processing: Dry Method

Green Coffee Processing: Dry Method
Ideally in this process the coffee berries should be uniformly ripened, but often in practice they are harvested by stripping all the berries at once from the trees and collecting them on the ground beneath.

The berries are gathered from the ground and spread out in the sun where they are raked so that they are evenly exposed.

Initially the microorganisms and the enzymes inherent in the coffee berry after the pulp and mucilage. Then the red skin, pulp, mucilage and parchment fuse to produce a thick hull as they dry out.

The coffee is called “pergamino” at this stage.

This hull is removed in a hulling machine that simultaneously polishes off most of the silverskin layer.

Both Arabica and Robusta coffees can be processed in this way, but an additional step is necessary for the Robusta beans which have a particularly tough silverskin.

Before the tough silverskin can be removed, the beans must be soaked in water. The moistened silverskin can then be removed mechanically and the beans are dried again before storage and shipping.

The dry method produces green coffee beans much less expensively than the wet method. A high proportion of Brazilian Arabica coffee is processed in this way and almost all Robusta coffees are treated in this way.

The final beverage produced from dry processed coffee has a full flavor that is often described as hard and sometimes is characteristic of a region, for example Rio coffees.

The dry method is generally the less controlled of the two main methods. The stages where extra care could be introduced after harvesting are where the coffee berries may be washed and sorted by flotation before being dried and during then drying itself.

The risk of fungal damage to the berries and consequently to the beans is vey high if the berries are too heaped.

They need to be spread out very thinly, to be frequently raked and not resoaked by rainfall.
Green Coffee Processing: Dry Method