Even before the coffee has been processed, the way the fruit is harvested plays a key role to the quality of the final product. Coffee cherries don’t usually ripen at the same time. Therefore, the sugar content must be measured to ensure the fruit has reached the proper ripeness. On many of the big farms, machinery can be used to help with the harvesting (especially in Brazil and plantations in the lower altitudes with flat surface). There are disadvantages to this kind of harvesting. The machinery can cause huge damage to the coffee trees and there is basically no mechanical way to pick only the ripe cherries.
Even when harvesting by hand, it is tempting to pick all the cherries at one time, ripe or not. The pickers are paid by the volume and the cherries can be harvested quickly. However, this method of picking always results in a lower quality coffee. The highest quality coffee requires multiple harvests, picking only the cherries on the peak of ripeness. This is much more costly and time consuming, but produces a superior coffee.
Processing method can very dramatically affect the taste and price of the coffee. Climatic conditions, accessibility of the water, demand, machinery and experience of the farmer are all deciding factors when it comes to choosing the way how coffee will be processed:
Natural ( dry ) processing method
This method is the oldest one and mainly used in regions which have dry climatic conditions during the harvest season or not enough access to water resources. Countries like Ethiopia, Brazil, Yemen, and Indonesia are commonly using natural processing. It doesn´t require almost any additional equipment or machinery and therefore it´s very cost efficient. The dry-process is often used in countries with very little rainfall and long periods of sunshine are available to dry the coffee properly.
In Vietnam almost all arabica growing areas are experiencing heavy rains in the harvest season. Natural processing can be very challenging in these conditions due to high risk of overfermentation and mold. This can easily destroy the whole crop if it´s not done correctly.
During the natural drying process, the cherries are either sun-dried or machine dried with the outer cherry intact until the fruit gets moisture content of around 12%, which can last up to 4 weeks. Coffee beans are still absorbing the nutrients and sugars during the drying stage resulting in the sweeter cup of coffee with heavier body. On larger plantations, machine-drying is sometimes used to speed up the process after the coffee has been pre-dried in the sun for a few days. Fruit has to be regularly turned over to ensure even drying and fermentation.
Introduction of raised beds which are providing more air circulation improved this process quite a lot. But there are still significant challenges to producing top quality coffees using natural processing. In the world, there are people who consider this method as inconsistent and being lower quality. This inconsistency is often the result of unripe fruit drying and turning brown alongside ripe fruits. On the other side there are also many, who believe dry-processing can create the most unique flavors and characteristics.
Tasting notes: You can get a truly sweet taste and dried fruit aroma in the cup of coffee from this method if it is done properly, generally heavier body.
Washed (wet) processing method
This method requires very specific equipment and the highest amounts of water in each step. It will let you taste what is inside of the cherry and not outside, focusing on the bean itself. Fruit covering the seeds is removed and completely washed before drying. It´s essential that coffee bean absorbed enough nutrients and natural sugars during the growing cycle. Wet processing can truly highlight the origin of the coffee but it´s farmers responsibility to avoid contamination with wastewater. It´s the most popular method because it offers most reliability and offers the clean and consistent cup of the coffee.
First step – selection by floating
Harvested cherries go through selection in the water tanks. Good cherries end up on the bottom and under or over ripe ones will be floating with dirt and other foreign matter.
Second step – pulping
Pulping should be done 24 hours at latest after the fruit is harvested. After selection the coffee cherry is removed by pulping which can be done either mechanically or by hand (pulping machine is powered by hand instead of electricity, water or some other method), depends on the size of the farm.
Third step – fermentation
Coffee beans still with the sticky mucilage on them are put to the fermentation tanks where they are carefully monitored. Length of controlled fermentation is usually between 12-36 hours and it depends on the experiences of the farmer and climatic conditions. This step has very big impact on the end result of how coffee will be tasting in the cup and it provides plenty of opportunities to experiment.
After the fermentation, coffee beans with parchment are completely washed to remove remainder of the pulp and dried. Freshly pulped coffee has a moisture content of about 55% and that has to be reduced by drying to 11%. This is the ideal level of moisture content required for proper storage, hulling and roasting. Wet processing requires a lot of skill and water in order to perform correctly. Some of the world’s finest (and often most expensive) coffees are created using this process.
Tasting notes: Washed method produces coffee with more clarity, clean cup, higher acidity and generally lower tea-like body.
Honey processing method
Did you think that this method have something to do with actual honey? The name might suggest it, but the truth is that it comes from the stickiness of the beans during the processing. Coffee cherry skin is removed and with the rest of the mucilage on the bean goes through drying phase. There are few different kinds of honey processing like white, yellow, gold, red or black, but they just simply referring to how much amount of sticky mucilage is left on the beans before drying.
Honey processing is less common than the other two options but definitely increasing in popularity, especially in farms which don´t have access to significant amounts of water. It represents the middle ground because of the less water requirements and also less time for drying than natural process. However, this doesn’t necessarily mean that this process isn’t expensive. Those sticky beans need raking and to be turned over very frequently.
Tasting notes: Honey processed coffees have good clarity and a medium-high acidity (like washed coffees). They also have a heavier body and sweetness (like natural coffees).
So which one is the best?
Technology and coffee processing equipment are constantly moving forward which brings a lot of innovation and experiments to the specialty coffee world. In the end, taste is always very individual and subjective. Everybody has their own preferences and hopefully all these information will help you to choose the best cup of coffee for your taste buds. Exploring the different origins, processing methods and roasting levels is something what truly fascinates me. Each coffee is unique in its own way, information about processing method is essential for highlighting the full potential of green coffee beans during the roasting.