How Is Coffee Dried? (Solved & Explained!)

Below are three primary ways in which coffee is dried: 

• Sun-drying. 
• Mechanical Drying.
• Parabolic Drying.

This article will go in-depth on all the ways coffee is dried and the reasons behind it.

How is Coffee Sun-dried?

Sun-drying uses natural Sunlight to lower the humidity content of coffee beans. Here, the Sunlight acts as the source of heat. The method involves spreading coffee beans under the Sun. We use unique drying stations that can be brick patios or raised tables or beds for applying. The latter ones aid the flow of air. Hence they are considered better for the drying process.

How is Coffee Dried Mechanically?

For mechanical drying of coffee, we use specialized mechanical dryers that speed up the drying process and prevent rotting or fermentation. The temperature inside the dryer should be below 40-45°C because high temperature reduces the flavor of coffee and leads to the crystallization of coffee beans. 

Overheating of coffee during mechanical drying is a common problem. To avoid this, adjustable internal thermometers or drying control systems are present inside the modern dryers. People living in high humidity areas often prefer this method for drying coffee. 

How is the Parabolic Method of Drying Coffee Done? 

Parabolic type drying is carried out using the GreenHouse technique. Farmers use pine to build the structure, covered using plastic. This plastic maintains the internal temperature of the dryer to a constant or nearly constant level of about 104 degrees Fahrenheit (40 degrees Celsius.) 

This temperature is ideal because it provides a uniform drying effect to the coffee beans. The plastic cover also insulates the incoming light rays from the sun. Due to this reason, coffee dried by this process is greenish-blue in color while the coffee dried by artificial methods is pale or yellowish. 

Coffee beans are usually washed before parabolic drying. Washing leaves some residual water droplets to stay on beans. Cohesive forces among the water molecules wrap these water drops around the beans uniformly. 

This results in forming a thin layer of water over the bean, which allows the evaporation of water in the form of dew. It excludes the need to apply pressure or increase the temperature to evaporate. Having an optimum temperature of 104 degrees Fahrenheit, we can quickly dry the coffee beans in three to five days by this method. The duration may vary depending upon the season.

Why is Coffee Dried?

Coffee is dried to lower its moisture level. Coffee has 60% moisture, reducing it to about 11-12% by drying. Drying also preserves the quality of Coffee by limiting the growth of molds and yeasts, which can spoil the beans.

What Are the Different Stages of Drying Coffee?

The drying process takes place in the following six stages:

• 1st stage: Moisture content between 55-45% implies skin drying.
• 2nd stage: Moisture level between 44-33% refers to white Stage drying. 
• 3rd stage: Moisture level in the range of 32-22% is the characteristic of the soft black stage.
• 4th Stage: Moisture level varying from  21-16% occurs in the medium black stage. 
• 5th Stage: Moisture content between 15-12% shows the hard black stage.
• 6th Stage: When the coffee is adequately dried, the moisture level is only 11-10%.

Sun drying is necessary for the third stage to retain the quality of coffee. Maintaining a temperature between 104 – 122 degrees Fahrenheit doesn’t pose any severe effects to the quality of Coffee during all drying stages.

How Long Does Coffee Take to Dry?

Coffee takes 1 to 2 weeks on average to dry under the sun. It depends upon weather conditions and processing methods. If we are drying coffee under the sun, time taken by different kinds of coffee varies as given below: 

• Washed Coffee: 6-7 days 
• Semi-washed (Pulped naturals): 8-9 days 
• Dry or honey processed (Natural): 10-14 days.

Which Factors Can Influence Coffee Drying?

Heat, the flow of air, moisture that escapes from the bean, and humidity contribute directly to how coffee dries. Drying coffee in the presence of humidity would be of no use because coffee is not able to lose moisture in such an environment. 

Humidity slows down the drying process and may cause inconsistent levels of moisture within the Coffee.

How do you Dry Coffee Beans?

The best way to dry the coffee beans is to dry under the Sun until they attain a moisture level of 15%. After that, transfer them to mechanical dryers for further Drying. In a mechanical dryer, it takes only six hours to reduce the moisture content of Coffee from 15% to 11% at 40°C.

What are the Methods to Process Coffee?

There are four different methods to process coffee: natural or dry, washed, wet-hulled, and honey processing.

In natural or dry Processing, farmers pick cherries from the coffee plants and separate the ripe ones. They place them under the sun with seeds inside. Fermentation takes place in 3 to 6 weeks. During this time, they rotate or rake the cherries to prevent rotting. 

After that, machines remove the seeds from the cherries, which are coffee beans.

Washed processing involves the removal of cherry seeds before drying, using de-pulping machines. 

These machines remove the outer skin and pulp, excluding the mucilage. This mucilage gets washed off during the washing phase. Farmers use water for washing the seeds. The last step is sun-drying coffee seeds on drying beds or patios. The Washed method of processing coffee is quick and efficient compared to the dry method.

Wet hulled processing is also known as semi-washed processing. Here the de-pulping machines perform the same function during the washed processing. Farmers store the seeds in plastic tanks where fermentation occurs in the presence of left-over mucilage and moisture. 

The mucilage ultimately forms a thick layer that covers the beans. Then, they perform a process called hulling in which they remove the dried mucilage with the help of machines, followed by drying in the presence of sunlight. Wet hulled processing is more common in high humidity regions like Indonesia. Wet hulled coffee like Indonesian Sumatra has a chocolate flavor.

Honey processing is a rare method of coffee processing. It involves both dry and washed methods of processing. Depulping machines remove the coffee seeds, but they don’t undergo the washing process to remove the mucilage. This mucilage sticks to the seeds, which is referred to as honey. The seeds are then dried with the sun afterward.