As coffees are being dried on the patio, one important element of the process is monitoring the moisture content. Monitoring the moisture content of the parchment is significant in determining when each batch on the patio is able to be 1). piled and covered; 2). entered into the mechanical dryer; or 3). bagged and brought into the warehouse to rest.
Each of these steps in the drying process, are indicated when the coffee reaches certain moisture contents. For example, coffees entering the mechanical dryers should not have a moisture content greater than 40%, nor should coffees entering the warehouse, have a moisture content above 12%.
The reason for this, is due to the fact that, too much moisture in a coffee, can damage, limit the quality, or cause fermentation in a coffee, if it is not handled properly. Moisture in coffee parchment is not negative, it is normal, considering that every coffee must be processed by washing, (one way or the other), and therefore, realistically contains moisture. Managing that moisture is what matters in coffee processing.
For example, when piling and covering coffees on the patios for the night, to maintain the heat of the sun, is a common practice, however, if it is performed with too much moisture in the parchment, it can cause fermentation. Likewise, drying with machines is also common, and beneficial to the processing of a coffee, however, if coffees are added to the dryers with a moisture content greater than 40%, quality can be jeopardized.
This can be caused by a couple factors. First, if the coffees entering the mechanical dryer, still contain surface moisture, it is likely that the coffees can become stuck within the cylinder of the dryer, either against the surface of the walls, or to other coffees, and thereby cause damage to the batch by restricting the flow of the coffees. Secondly, having a high moisture content can influence the internal development of the coffee, throughout the drying process, since the development of the temperatures and airflow within the dryer, are diagramed according the moisture content. Greater moisture content, means more time in the dryer, which can influence the flavor in the cup.
Also, as coffees are being dried within a mechanical dryer, the process of measuring moisture is extremely important, as the parchment may not drop below 10% moisture. At Beneficio El Manzano, coffees are dried to a moisture level between 11 & 12%; and the final ten hours within that drying process are important in order to ascertain that the coffees are not over cooked within the dryer. This is accomplished by developing profiles for coffees within the dryers, very similar to that of a roast profile.
As coffees enter the mechanical dryer, they are slowly heated, allowing them to develop within the rising temperatures. A drying profile is a bell curve, meaning temperatures are elevated slowly, where coffees will dry for the maximum amount of time, however; once coffees reach 20% internal moisture, the temperatures or likewise slowly decreased, to make sure that they can be monitored closely, during the final hours within the dryer.