Growing coffee beans from seed to harvest is just one part of the entire process of delivering a specialty cup of coffee to the consumer. After harvesting the coffee plant, the real work within the coffee industry begins with processing. It is the process of removing the unnecessary layers of skin, mucilage, pulp, and parchment around the coffee bean. How growers choose to process the coffee will have a substantial impact on how that coffee will taste.
Coffee processors are actually growers who have the right equipment to process coffee. Sometimes, it can be a collective effort among growers, processors, and the entire coffee supply chain, where each group provides some equipment and gains access to the processing at a site of their choosing.
Since consumers can choose among coffee products that have been processed with different methods, we are going to cover all of them and see how they affect the flavor. We will cover the main processing techniques that most growers and processors use, even though there are countless variations of each technique.
Processing of the Coffee Cherry
After it is picked from the tree, the coffee bean needs to be processed. In the specialty coffee industry, a great deal of effort, science, and technology goes into creating various coffee flavor profiles. What inspires the ongoing development and innovation of new processes are the passionate farmers (seeking to improve quality), conscientious consumers (seeking new experiences), and attentive roasters.
At harvest, what surrounds the green coffee bean is the pulp and husk of the coffee cherry. Before preparing the beans for export or distribution, this must be removed. The two methods currently used to remove the pulp and husk from ripe coffee cherries are the dry and wet methods. When ripe coffee cherries have been picked, processing should begin as quickly as possible to prevent coffee bean spoilage.
Dry (Natural) Method
With the natural or dry method, the coffee cherries are spread out on a large surface (e.g., a mat, raised beds, or patio) in the sun and often raked to ensure even drying (until the pulp and husk are dried enough to be removed by hand). At night or during rain, the coffee cherries are covered to prevent them from getting wet. This is one of the oldest techniques of processing coffee and is used to this day in countries with limited water resources. The entire process might continue for a few weeks (depending on the weather) for each batch of coffee cherries, until their moisture content drops to 11%.
Before drying, coffee cherries are cleaned and sorted to separate the damaged, overripe, and unripe cherries and remove leaves, twigs, soil, and dirt. The ripe coffee cherries can be separated by flotation, using washing channels next to the drying areas. Also, it can be done by winnowing, using a large sieve. Unwanted coffee cherries and other materials that don’t get winnowed away are picked out from the top of the sieve.
The most important stage of the entire coffee-producing process is the drying operation because it affects the final quality of the green coffee bean. Overly dried coffee becomes brittle and is easily damaged during conveying and hulling (broken beans aren’t used because they are considered defective). On the other hand, insufficiently dried coffee is too moist and prone to bacteria and fungi that cause rapid deterioration.
When red coffee cherries dry, they are removed from the coffee bean in a depulping machine. Dry-processed coffees tend to be very intense and fruitier. A great example of classic, dry-processed coffee is coffee that comes from Ethiopia, which works wonderfully with espresso machines. Roasting the same coffee beans on different roasters or with roasting processes can produce different effects. For example, different coffee roasters apply heat differently, so even if the final roasted coffee beans look the same from each coffee roaster, the complexity, body, and acidity are altered based on how it is roasted.
The dried coffee cherries are stored in special silos, where they wait to be sent to the mill where the hulling, sorting, grading, and packaging take place. The dry method is used for producing most of the coffees that come from Brazil, Paraguay, Indonesia, Yemen, and Haiti, as well as for some Arabicas produced in Ecuador and India. When it comes to Robustas, almost all of them are processed by the dry (natural) method.
In rainy regions where the atmospheric humidity is too high, or regions where it often rains during coffee harvesting, the dry method is not practical.
The Wine Process is a variation of the Dry Process. With such processed coffee, the cherries are allowed to over-ripen on the shrub (instead of being harvested at the peak of harvest), which gives them a slightly fermented flavor and a higher concentration of sugar.
With the Wet Process, the coffee cherries are first softened in vats of water and then processed through a machine to remove the pulp and husk. The fruit and skin layer of the cherry is commonly used for cascara. The mucilage is usually left on the parchment, and then the coffee bean is inserted into fermentation tanks (large vats of water). The time varies (depending on the farmer’s direction with the coffee), but it generally takes about 48 hours.
After fermentation, the coffee requires further washing to clean up the bean and remove mucilage residue. At this point, the coffee is ready for drying. The wet processing method is rarely seen in dry areas due to a lack of running water. For about 1-3 months, the coffee matures in the parchment in warehouses, and then gets sorted, graded, scored, packaged, and shipped.
Semi-Dried (Honey, Pulped Natural Processing) Method
This method bridges the gap between natural and washed coffees because it typically produces some of the sweetness and body of a natural while retaining some of the acidity of a washed coffee.
In the honey processing method, only the skin of the cherry is removed, while most of the fruit remains on the coffee. The coffee beans are often covered with plastic and left to dry on a patio or raised beds. Some growers use hot air machines to force drying under the tables, which gives them more control over cup taste and profile. During the drying process, the coffee beans need to be moved constantly to prevent fungal and mold infections. They are usually racked about 2-3 times every hour. Most smaller coffee farmers in Papua, Flores, Sulawesi, and Sumatra use this method.
Depending on the amount of pulp left on the coffee, honeyed coffee can be classified as:
- White: Almost completely washed with a fraction of ferment concentration
- Yellow, Orange, and Red: Somewhere in between White and Black
- Black: Almost fully natural with a bit more complexity, restraint, and elegance
Black Winey Process
After being picked, the ripe red coffee cherry is placed into a polystyrene bag. Then, it’s left to turn black and develop winey traits. It is then put on raised beds and left to dry to approximately 11% moisture content. When rested for four weeks, the enzymes have enough time to settle down and balance. At that point, the coffee is sorted, graded, scored, and packaged. Coffee processed with a black winey processing method has low acidity and a well-balanced ferment, which gives it exceptional enhanced sweetness.
The process of decaffeination is performed on green beans. It starts with steaming of the coffee beans that are then rinsed with a special solvent that extracts the caffeine (but leaves other constituents unaffected). This process is repeated about 8-12 times, until 97% (U.S. standard), or 99.9% (EU standard) of the caffeine content is removed from the coffee bean.
Trying to separate the caffeine while leaving other chemicals (such as proteins, cellulose, sucrose, tartaric acid, citric acid, and formic acid) at their original concentrations is the greatest challenge of the decaffeination process. Most decaffeination processes use ethyl acetate, CO2, activated charcoal, and methylene chloride as decaffeinating agents. In the natural type, the most used decaffeination process uses sCO2 (supercritical carbon dioxide). The process is advantageous because it avoids the use of harmful substances, but because it is costly, it is mostly used to decaffeinate large amounts of commercial-grade types of coffee).
Using the right conveyor system in quality coffee processing plants and sites is necessary, especially for dried coffee, which is prone to damage due to being brittle. Cablevey’s tubular cable and disc technology is used in countries across the world because it prevents coffee bean breakage, enhances cleanliness, and gently transports the materials. Our conveyors can be designed to fit the spatial requirements of any facility and minimize financial losses resulting from coffee bean degradation and breakage.