Coffee drying – Before becoming a cup of coffee that you can enjoy, as we know, coffee requires a long journey. Starting from harvesting, cherry coffee picking, long coffee processing, drying, and roasting. There are many processes that must be gone through just to serve a cup of coffee.
Each process is important and requires attention, surely, to maintain the quality and characteristics of the coffee beans. As we mentioned before in our articles, coffee processing is one of the longest stage in coffee production. But, just like coffee processing, drying process also requires a lot of time and things to be considered.
No matter how the coffee is processed, at some point, the coffee beans need to be dried. Will the different processing methods affect the drying method? Yes, it’s affect the drying process as well. The difference between the processing methods can also be seen from the order in which the coffee is drying.
What is the coffee drying process? What are its use and what should we pay attention to? Want to learn more? Then let’s dig in into today’s topics, drying process!
What is Coffee Drying Process?
So, what is drying process? Coffee drying is a post-harvest process that generally preserves coffee quality rather than improving it. Washed, natural, and honey processed coffees must all be dried at some stage of processing.
For washed coffee, drying is done after the cherries are peeled and mucus removed. For honey-processed coffee, drying occurs when some or all of the mucus is still on the parchment. Meanwhile, drying with natural ingredients is even done when the coffee is still fruit and has not been separated from the mucus.
Coffee drying is also one of the longest processes in the post-harvest stage of production, and as a result, it is a major bottleneck point. Drying timelines change depending on a number of factors, including weather conditions and processing method.
How Coffee Is Dried
Quoting from coffeeresearch.org it is said that prior to shipment, coffee is dried and a coffee moisture meter is used to measure the coffee bean’s moisture. Coffee must be dried from approximately 60% moisture content to 11-12% moisture content. There are two main factors that contribute to how a coffee dries: temperature and airflow. Over time, these reduce the moisture within the green coffee.
As we mentioned before that drying coffee process can be different according to the processing method. But, quoting from perfectdailygrind.com, coffee is dried in two main ways. The first is by spreading beans out under the sun on raised beds or patios. The second is by using dedicated mechanical coffee dryers.
As the main factors, temperature really need to be considered. During the drying process, it is important to pay attention to the temperature limits for each type of processing method; Parchment coffee should not be dried at a temperature higher than 40°C, while natural coffee should not be dried above 45°C. It is also recommended that the producer keeps temperatures a constant level for certain periods of the drying phase.
When drying coffee using mechanical dryers, the coffee is usually dried in the sun to a certain extent. The use of a dryer is to complete the process with more precision and accuracy. When dry only in the sun, washed and semi-washed coffee will take less time to dry (6-9 days) while natural coffee and honey processed coffee will take longer (10-14 days).
What Are the Other Important Factor Besides Temperature and Airflow?
While temperature and airflow are two of the main factors affecting how coffee is dried, it’s also important to focus on how well moisture can escape the beans. Bruno Riberio from Pinhalense, reported on the perfectdailygrind.com site stated that if coffee drying is done in a humid / humid environment where moisture cannot come out, the coffee will not lose its moisture.
When coffee beans dry out in the sun on a large scale, humidity is a significant concern. This can delay the drying process and cause inconsistent moisture levels in a batch of green beans. However, the use of a coffee dryer is still effective at micro-scale drying.
Coffee Drying Stage
Several studies have attempted to identify the stages of the long drying process of coffee. One of the studies, quoting from coffeeresearch.org is the Kamau Report from Kenya which identifies that there are 6 stages of coffee drying, namely:
- Skin drying. Moisture 55-45%.
- White Stage drying. Moisture 44-33%.
- Soft Black stage. Moisture 32-22%.
- Medium Black Stage. Moisture 21-16%
- Hard Black Stage. Moisture 15-12%
- Fully dry coffee and conditioning. 11-10%.
This study found that sun drying coffee for stage three is mandatory for coffee quality. It’s also reports that as long as the temperature was between 40-50°C–which means a bean temperature of 35°C–then the coffee quality will not be seriously compromised during the other coffee drying stages. The final two coffee drying stages (15-11% moisture) take just six hours at 40°C in a mechanical dryer.
Sun Drying Vs. Mechanical Drying
As mentioned before, coffee is dried by two main ways: under the sun and mechanical drying. Here we’re gonna talk about advantages and disadvantages of two main way of coffee drying process.
Coffee Drying: Under the Sun
Risks of coffee drying in the sun include uncontrolled fermentation, animal contamination, improper manual drying, and bad weather conditions, all of which can have a major impact on coffee quality.
Quoting from the site perfectdailygrind.com, uncontrolled fermentation can occur when coffee is not dried fast enough, because microorganisms break down the compounds in the coffee and produce unwanted flavors. Animal contamination includes larger wild animals that cause physical damage to the seeds and animal waste (such as from birds) that fall between dry coffees.
Finally, improper manual drying occurs when the coffee is not dispersed properly, resulting in exposure to uneven temperature and airflow
Coffee Drying: Mechanical Drying
The three main advantages of drying coffee using a mechanical dryer over drying coffee in the sun are that it eliminates uncontrolled environmental variables that can affect coffee quality, increases accuracy and minimizes delays. One of them is the factor that is often worried about coffee farmers / producers, namely unpredictable weather.
One of the most important features of many modern coffee dryers is the drying control system. This system offers coffee producers / growers the ability to adjust the drying temperature via three separate variables: heat source, air, and coffee. Thus, the drying control system offers greater control during the drying process. Some systems even allow manufacturers to create a “drying curve” that interrupts the dryer before it reaches the specified maximum temperature.
In conclusion, this two main way of coffee drying can be more good if we can combine them. As coffee producer, it’s important to know what best coffee drying method for their coffee. This process also gonna affect the characteristic as well as the quality of coffee beans, that’s why as producer we need to choose wisely.
Quoted from perfectdailygrind.com, it is said that while drying coffees on raised patio beds may still be a suitable option for many coffee producers, mechanical dryers offer a number of different advantages. Technologies such as drying control systems provide the producer with more accuracy and precision throughout the drying process.
CV. Buah Berdikari is an active coffee trading and exporting company that is based in North Sumatera, Indonesia. Our domain of expertise lays on sourcing Arabica green beans from North Sumatera and Aceh origins. We will help you finding the perfect fits for your coffee needs.