Coffee Drying – Coffee Processing And Drying Process

Vietnamese Coffee Exporter
Coffee Drying
Coffee Drying – Coffee Processing And Drying Process. Regardless of how the coffee is prepared, it will need to be dried at some point. After the cherries have been washed and the mucilage removed, wet-processed coffee is dried.
The drying process begins as soon as some or all of the adhesive remains on the coffee bean in honey processed coffee; in dry-processed coffee, the coffee remains dry with both its pods and mucilage.

There are two main methods for drying coffee. Drying in the sun on a raised bed or drying yard is the first option. The second option is to utilize a specialist coffee dryer. In any case, the moisture level of the coffee beans will be reduced from 60 percent to 10-12 percent.

An overview of the drying process for coffee

Coffee drying (or drying and drying) is a post-harvest technique that preserves rather than improves coffee quality. All processed coffee, whether wet, semi-wet, or natural, must be dried throughout the processing. Temperature and airflow are the two key factors that lead to dry coffee. Heat and air circulation will reduce the moisture content of the green coffee over time.

Coffee Drying

It’s crucial to remember the temperature restrictions for each type of processing procedure for drying:

Coffee beans should not be dried in the husk at temperatures above 40°C (i.e., after wet processing or honey). Do not dry natural shelled coffee above 45°C.
During critical parts of the drying process, coffee should be kept consistently. To avoid mold growth in the beans, humidity must also be regulated. Before drying, the moisture level should be between 40 and 50 percent, then lowered to 11 to 12 percent.
Coffee is usually pre-dried in the sun to some amount when using a mechanical dryer. After that, the dryer will be utilized to finish the procedure more precisely.

Coffee drying is also a critical bottleneck because it is one of the most comprehensive processes in the post-harvest production phase. The length of time it takes for anything to dry depends on various factors, including weather and processing methods. Wet processed coffee will dry faster (6 to 7 days) if exposed just to the sun, followed by semi-wet processed coffee (8 to 9 days) and natural processing (10 to 11 days) (10 to 14 days).

This is why coffee beans are frequently dried on a patio until they achieve a moisture content of 15% before being transported to a mechanical dryer.

Drying – phases of drying

According to Coffee Research, six phases for drying Arabica coffee were documented in a study done in Kenya on the drying stages of Arabica coffee, including:

  • Dry the shell by reducing the moisture content from 55% to about 45%.
  • Humidity ranges from roughly 44% to 33% in the White Stage.
  • Humidity ranges from approximately 32% to 22% on the Soft Black stage.
  • Medium Black, with an approximately 21% to 16% humidity range.
  • Humidity ranges from around 15% to about 12% in the Hard Black stage.
  • The coffee is dehydrated, with only 11-10% humidity left.

Kamau, I. N. — The author of this study demonstrates that third-stage sun-drying of coffee is critical for coffee quality. He also found that as long as the ambient temperature is between 40 and 50 degrees Celsius – that is, the temperature of the coffee beans’ heart is between 35 and 40 degrees Celsius – the quality of the coffee will not be adversely affected throughout the drying phases.

Although temperature and airflow are two of the most critical parameters in drying coffee beans, the key is to concentrate on how moisture might escape from the beans. If dried in a humid environment, it will not lose moisture where moisture cannot escape.

Moisture is a significant worry when drying coffee beans in the sun on a large scale. It can cause a batch of green coffee to take longer to dry and have irregular moisture content.

What are the dangers of sun-dried coffee?

When it comes to sun-dried coffee, the drying surface is crucial. Raised beds and concrete yards are the two most frequent drying systems. The elevated bed has the benefit of allowing more air to circulate the coffee, which aids in even drying. Producers who prefer to dry their coffee on the patio must clean the drying yard. To guarantee uniform drying, they should be flat.

Coffee Drying

When coffee is not dried rapidly enough, microbes break down components inside the coffee, resulting in unpleasant flavors. Coffee beans and animal droppings are harmed by animal contamination, which includes larger species (such as bird droppings in the midst of drying coffee). Finally, if the coffee is not stirred frequently enough, it will develop an uneven temperature and airflow exposure.

When it comes to drying coffee and coffee beans outside, weather fluctuations provide a significant difficulty for farmers. Furthermore, coffee that has been exposed to the open air does not normally dry out (or re-moisturize) at night or in the early hours of the morning. Sun exposure is, in the end, entirely dependent on temperature and humidity stability.

Producers face delays or hazards in terms of coffee quality during periods of heavy rain. On the other hand, coffee risks scorching and losing quality as temps rise, especially if it isn’t stirred frequently.

When drying wet-processed coffee outside, there are a few things to consider

The drying phases of the coffee may need to be different depending on the local climate. However, Alejandro (creator of Caravela Coffee) produced specific recommendations for wet processing coffee drying for South and Central America that you can use as a starting point for reasonable control.

It is advisable to scatter the seed layers extremely thinly, no more than 3 cm, and rake continuously to ensure air passage through the seed block when growing coffee outside. If the seed mass is exposed in a raised bed, the airflow will quickly move through it, reducing moisture loss equally. Wet-processed coffee is slowly dried in three stages over 15 to 20 days if the seed layers are thinly dispersed, the temperature is suitable, and there is good airflow.

At the start of the drying process, wet-processed coffee will have roughly 45 percent moisture. Due to the fragile cellular structure of the coffee beans, a temperature (maximum) of 20°C is preferable at this time. When the coffee is dry, increase the temperature to (full) 35°C. On the other hand, higher temperatures can harm the coffee bean embryo and shatter the husk.
The coffee is recommended to be shaded 40-60% with a ventilation grid for the next ten days. Humidity should be lowered from 25% to 13-14 percent throughout this time.
Although humidity levels of 10 to 12 percent are often regarded as appropriate, however, it is recommended that you allow another two days of sun exposure to obtain a humidity level of 10%.

Wet-processed coffee should be 100% shade-dried for the first three to five days. The humidity will reduce from 45 percent to 25 percent throughout this time. This is the most dangerous stage because coffee is more prone to acquire fungus; thus, it must be completed as soon as possible. Low temperatures can also prevent the husk, the coffee bean’s natural covering, from shattering.

Reduce the risk of mold and oxidation during the coffee drying process

Manufacturers should keep in mind that various nuts should not be put together during the drying process because different types have varying densities and dry at different rates. It’s crucial not to combine dried bean batches from various dates.

They differ in moisture content, but part of that moisture can be transferred from “still wet” to “drier” seeds. As a result, there is a lot of water activity, which promotes oxidation.

Total water activity (aw) is the quantity of water that exists freely in food, unbound by food molecules, and can be used to predict mold risk. (Note that total water activity differs from moisture; aw refers to moisture’s energy rather than its existence.) Water activity is assessed on a scale of 0 to 1; however, for green coffee, the recommended range is 0.5 to 0.6.

The oxidation that occurs during the drying of coffee (mainly in the wet process) impacts lipids, or fat molecules, which are crucial for coffee quality. Green coffee beans’ oxidized lipids create foul-smelling aldehydes and ketones. However, the drying process affects the flavor and aroma of coffee and its shelf life.

According to Alejandro Cadena, green coffee beans can last up to a year, but the coffee flavor can degrade and “age” after only a few months if the drying cycle is done incorrectly.

Using a mechanical drier to dry; an overview

Due to their history of being connected with low-quality commodity coffee, mechanical dryers have been neglected and undervalued. However, the innovative technologies found in modern dryers have provided specialty coffee producers with significant benefits.

Automatic dryers, as a result, are highly valuable for growers with limited space and can also boost overall farm output by saving time, according to Iliana, Azahar Coffee’s Relationship Manager.

Coffee Drying

The drying control system is one of the essential elements of many modern rotary drum (barrel) coffee dryers. These methods allow producers to control the temperature using three different variables: the heat source, the air temperature, and the temperature of the coffee beans.

Drying control systems allow the manufacturer better control over the drying process in this way. Some systems even allow the manufacturer to program a “drying curve” that stops the dryer from reaching the maximum temperature.

Although mechanical dryers require capital inputs in equipment and fuel, the time and money saved in labor can balance these costs. Automatic dryers help producers maintain consistent coffee quality following harvest in the long run. As a result, they’ll be able to maintain relationships with long-term customers who want regular, high-quality coffee.


Finally, while drying coffee in yard beds is still an option for many coffee growers, mechanical dryers provide several advantages. The drying control system technologies give the producer higher accuracy and uniformity throughout the drying process – Mechanical dryers’ consistency is also critical to the drying process—the third wave of coffee quality.

Producing specialty coffees necessitates a never-ending commitment to excellence. Many elements can influence the flavor of a coffee’s final cup, from planting to harvesting, processing to roasting, and extraction. And the drying process is no different.

If a superb coffee is not dried correctly, it will lose points. Coffee that is dried slowly and precisely under the appropriate conditions, on the other hand, will maximize its flavor potential.

Reference source:

  • wwww. A Guide To Coffee Drying
  • wwww. How to Improve Quality When Drying Washed Coffees
  • Coffee Drying

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