This is the most intensive style of coffee processing, comprising of several steps that result in a coffee expressive of both terroir and varietal. Most coffee in the world is processed in this fashion.
After the coffee fruit (or cherry) is harvested, the flesh is removed and separated using a machine called a pulper. What remains is a bean covered in a thin, sweet layer of sugary mucilage. There are two ways of removing the mucilage: via fermentation or mechanical separation. For fermentation, the coffee is poured into a clean tank where it rests in its own juices as naturally present bacteria and enzymes (mostly pectinase) break down the mucilage layer. This can be accomplished with or without the use of water and requires 6 – 72 hours for completion depending on the volume of coffee, amount of mucilage on the beans, temperature, humidity and desired results. Once the mucilage can be easily rubbed off by hand, the coffee is then rinsed free and clean of any residuals.
At this phase the coffee is commonly referred to as parchment, which describes the remaining protective layer covering the green bean, and it is dried in one of several ways. Once the proper moisture content of 10% – 12% is achieved the parchment is set to rest. After sufficient resting, the parchment layer is removed using a dry miller resulting in a clean, polished green bean ready for the roaster.
While overall the washed process seems pretty straight-forward, fermentation is regarded as a craft. There are numerous subtleties in this technique that dramatically affect the cup. Skillfully manipulating these variables helps create beautiful coffee.
This processing method follows a similar path as washing except the mucilage is not removed but instead left to dry on the parchment layer. Not all honey coffees skip mucilage removal entirely. Some are fermented just a little bit, lightly rinsed and laid out to dry. Others nearly complete fermentation and dry with maybe 10% mucilage remaining. Semi-washed is perhaps a more accurate term to describe this approach since it implies a wide spectrum of variability in the amount of mucilage intact while drying.
Just like fermentation, a well-done honey process requires observation and mastery because the mucilage layer plays a crucial role in creating cup character. The tricky part is drying. Once the beans pass through the pulper, special care has to be taken so the coffee dries quickly enough to prevent fermentation and stave off fungal or bacterial growth but not too quickly. And the weather needs to be just right. The beans must be agitated or raked 2 – 3 times per hour until they are dry enough not to stick to a down-turned palm, usually 6 – 8 hours. More raking than average is often required beyond this point to ensure nothing rots nor ferments. Once dried to the proper moisture, the coffee, with parchment and dried mucilage still attached, is set to rest and then finally dry milled just like a washed coffee before moving to the roaster.
Honey processing bridges the gap between washed and natural coffees as it generally possesses some of the body and sweetness of a natural while retaining some of the acidity of a washed. Honey coffees often have a syrupy body with enhanced sweetness, round acidity and earthy undertones.
At this point, you may be asking yourself, “How was coffee processed before all of this machinery and equipment was available?” Naturally, of course! In this method, the cherry is harvested and then dried fully intact as a whole fruit. What results is quite expected: a very fruity, often exotic, coffee that is generally sweeter and fuller in body than its counterparts.
While honey coffees require extensive care in the short term as they dry, naturals demand long term care and attention to detail. It takes roughly 2–4 weeks to reach 10%–12% moisture, and during that time any number of fungal or bacterial growths can emerge to create rot and nasty flavors. The coffee needs to be hand-sorted to ensure the crop remains clean and free of mold. Once dry, the coffee remains fully encased in its fruit leather-like flesh during the resting phase.
Naturals are generally more inconsistent in quality given that every bean is its own closed environment of varying levels of sugars and alcohols. To work with those variables in certain parameters is time-consuming and labor-intensive. This is one of the reasons why consistent, exquisite naturals are often highly revered.
As benign as this stage may seem, drying is an extremely important step in processing. The key is consistent, gradual and gentle moisture wicking, ideally in low light conditions. Too much heat tends to dry the coffee unevenly and the cells on the exterior of the bean crystalize and harden which traps internal moisture. If there’s too little heat, too much humidity, poor air circulation or too many beans piled together, drying time can take too long and encourage mold growth or rot. A meticulous approach yields a coffee that maintains a long shelf life of high quality and reacts appropriately during the roasting process to provide great cup quality and consistency.
Once appropriately dry, coffee benefits greatly from a period of resting in a cool, stable and ventilated environment. This phase is crucial because it stabilizes moisture, strengthens cellular structure, extends shelf life and facilitates consistent results in the roasting process. If this is not done, the coffee tends to age more rapidly and quality diminishes significantly. Unstable storage conditions with fluctuations in temperature and humidity can result in moisture loss or gain, which can damage the beans and produce undesirable consequences.
Ideally, coffee is rested within the protective parchment layer (or all layers in the case of naturals) for a period of 30 – 90 days. This is much more difficult than it appears. For starters, most farmers are in need of income. After fertilizing, harvesting and processing much of the year, waiting an additional 1 – 3 months can be very financially strenuous. But waiting isn’t the only financial constraint. Providing a stable storage facility to maintain the 10% – 12% moisture for proper resting can also be very expensive. The best storage conditions maintain an environment with consistent humidity and temperature combined with steady airflow, in addition to security from pests or thieves. This is no small feat, particularly in lieu of thousands of pounds of coffee. So the process of resting is itself an issue of balancing the needs of the coffee with environmental conditions and financial/logistical capacities of the producer.