Drying Characteristics: Natural (Dry) Process: Ayutepeque Acaia – Four Way Process Experiment


Source: El Salvador Specialty Coffee
Natural processing is the oldest and most traditional way of producing coffee. In many parts of the world, it is still the most common; where, after harvesting, the coffee cherries are spread immediately onto patios or raised beds to dry.
Drying coffee in this manner requires the greatest amount of time, since the external fruit itself must dry, before the internal bean can effectively dry, and thereby reach the desired moisture content.
In most cases, coffees are taken directly from the farm to the patios.  Before drying the however, we put the cherries through a mechanical syphon.
This being the case, cherries are rinsed and sorted into the categories of sinkers and floaters, prior to drying, there is a uniformity / consistency in the cherries, and thereby can complete the drying process at approximately the same time. Were cherries not sorted into categories of ripeness and quality, it suffices to say that there would likely be drastic inconsistencies in the drying time for the batch of coffee, since some cherries were at maximum ripeness, while others are sometimes dried on the tree, or still unripe at the time of harvesting.
Sorting coffees into qualities of ripeness, is what enables the natural process to remain consistent throughout the drying process.
In this experiment, we washed, and introduced the cherries to the raised bed, at approximately 7:30 PM, on a Monday evening. While the other process methods completed the drying cycle in just over one week, the natural process required nearly two weeks time, before reaching a moisture content around 12%.
In our observations, cherries maintained much of their red color for three to four days of drying. In this time, the skins of the cherry maintain much of the moisture, and as they become wrinkled, maintain a soft semiliquid feel.   Upon reaching the fifth day however, they quickly turned a deep purple, which they remained for the rest of the drying cycle; until reaching near 12% moisture, at which point, the external cherry is hardened, and takes on a clean, smooth textured feel.
The cherries were removed from the raised beds at 8:00 AM on a Monday morning, exactly 13 and one-half days after being sorted and spread, a total of 324 hours. This amount of time was just over the average amount of days that we were expecting, however within the parameters of normal drying time for a natural process, which we find to usually take 10 – 14 days.
With the natural off of the raised beds, we have hulled and roasted the four samples; and now begin to set the table for what will be an exciting cupping.
Cherries, after 12 hours of drying on a raised bed.

Cherries, after 12 hours of drying on a raised bed.

Cherries after 36 hours of drying on a raised bed.

Cherries after 36 hours of drying on a raised bed.

Cherries after 60 hours of drying on a raised bed.

Cherries after 60 hours of drying on a raised bed.

Cherries after 84 hours of drying on a raised bed.

Cherries after 84 hours of drying on a raised bed.

Cherries after almost 180 hours of drying on a raised bed.

Cherries after almost 180 hours of drying on a raised bed.

Cherries after almost 300 hours of drying on a raised bed.

Cherries after almost 300 hours of drying on a raised bed.

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