Coffee seeds take weeks to germinate, months to grow into seedlings that can withstand transplanting, and years to bear fruit. Each season, a fleeting flowering of the coffee plants releases an intoxicating fragrance and starts a nine-month countdown to the harvest, which transpires slowly over a period of several months. But when the ripe cherry is pried from its stem by a gentle twist of the picker’s hand, the patient process of coffee production enters a final phase that is, by comparison, frenzied. This phase, disproportionately important in determining a coffee’s quality and durability, consists of a series of successive processes through which coffee is transformed from a ripe fruit to a shelf-stable seed in a matter of weeks. During this time the coffee undergoes many biological and chemical changes that are endlessly complex, only just beginning to be fully understood, and filled with both opportunities and pitfalls for growers.
Most of our coffee is harvested the old-fashioned way: by hand. Why? There are two key reasons. The first is a practical one; most of the world’s finest coffees are grown on remote highland farms in rugged terrain where mechanization isn’t an option.
The second has everything to do with quality. Much like wine grapes, the ripeness of the coffee cherry is essential to quality. But unlike wine grapes, all the coffee cherries in a given cluster do not mature at the same time. That’s why we ask our Direct Trade partners to harvest cherries only at peak ripeness -- a task that requires a discerning eye, sensitive touch and skill that only well-practiced farmers or workers possess.
The labor-intensive process of manual harvesting involves millions of workers who fan out on steep hillsides across the coffeelands of Africa, Asia and the Americas for weeks and months on end. . They gently twist each cherry from its stem, but only those that have reached their peak maturity. The rest they leave to ripen. They repeat this selective process as many as six times over the course of a single harvest season, until the trees are bare.
The length of the harvest can vary from one country to the next and one crop year to the next, but it is generally divided into three phases: early harvest, peak harvest and late harvest.
When picking thousands of cherries a day, even the most discriminating and experienced farm workers will miss the mark on occasion. Since the last part of the coffee cherry to ripen is the area around the cherry’s stem, which faces the shrub’s trunk and is not visible to the picker, even cherries that appear ready from one side can still be underripe. That’s why even the most meticulous manual harvesting is sometimes complemented with manual sorting by color before further processing. This includes cherry separation, the removal of overripe and underripe cherries, as well as the removal of leaves and twigs inadvertently collected during harvesting.
Many farms also put their selected cherries into flotation tanks, which allows them to eliminate cherries with defects not visible to the naked eye. Cherries that have developed properly will sink to the bottom of the tanks, while those with malformed or damaged seeds have lower density and will float to the top, where they can be skimmed and set aside for separate processing.
During the immediate post-harvest milling process, ripe red coffee cherry is transformed to the green coffee seed that we eventually roast and brew. Coffee can travel different paths after picking, and the choices made during milling impact flavor in powerful ways, leading to distinct outcomes. The product of each process has a different name. The wet process produces washed coffee, the dry process produces natural coffee, and the semi-washed process yields coffees that go by the name honey or pulped-natural.
Wet Processing: Washed Coffee
Washed coffee is the product of the wet-milling process. Within hours of being picked, wet-milled coffee cherries are fed into a machine that squeezes them firmly to separate the seeds from the skins. This is often referred to as depulping. The seeds are covered with sweet, sticky mucilage and usually undergo a short fermentation period followed by agitation or soaking in water to remove any residual pulp, or mesocarp.
Washing coffee highlights its intrinsic flavor attributes with an emphasis on clarity and detail. It is a process that allows coffee’s inner beauty to be experienced in high-definition, where the nuances and delicate taste attributes of the individual coffees are presented transparently. Most specialty coffee is washed, and there is good reason for this: washing coffees showcases the unique differences in coffees that come about as a result of the intersection of variety, environment, and plant husbandry. The organic fruit acids and other compounds that contribute to complexity and are on full display.
Dry Processing: Natural Coffee
Dry-processing is the oldest approach to post-harvest handling of coffee. The fruit is picked, sorted and set out to dry in the sun until it shrinks, like a grape being turned into a raisin. It dries completely within its skin, and the seed is not removed until just before export.
Natural coffees offer a much different character than their washed counterparts — they tend to taste more overtly fruity and sweet, in ways that we often associate with port wines. Often the perceived acidity is diminished because the delicate organic acid tastes are overpowered by more dominant flavors that suggest red wines and dried cherries. The aromatics are distinctly fruit-like and can be very intense. Compared with washed coffees, naturals are like photographs that have been layered over with a vivid color filter, obscuring some detail while elevating the dramatic impact. The extended contact time between the cherry skin, pulp and seed imparts tastes that are not found in washed coffee, developed as a by-product of the particular kinds of fermentation that take place.
Semi-Washed Processing: Honey Process / Pulped Natural
Between the two dominant post-harvest processes of wet and dry processing is an alternative, middle path that incorporates elements from both. This approach is very common in Brazil and has recently become popular as an alternative style in other parts of Latin America, most especially in Costa Rica.
A clever amalgam of elements of the wet and dry processes that produce a coffee of an altogether different profile than either. The terms Honey and pulped natural both get used to describe a process in which the skin is mechanically removed and the coffee seeds are allowed to dry with some or all of their mucilage still attached. It yields coffees that have much of the clarity we associate with washed coffees but with a tendency towards soft, sweet fruit character.
During fermentation naturally occurring microorganisms interact with sugars in the mucilage in complex ways that can have both subtle and dramatic impacts on flavor. Fermentation in coffee production has long been employed by farmers as a pragmatic means of breaking down pectins to allow the mucilage to be removed before washing or drying. There are numerous chemical changes that take place during fermentation, and many byproducts of the process that can lead to distinct flavor outcomes. There is still much to be studied and learned about the manipulation of fermentation parameters and how the complex flavors in coffee can be both preserved and altered by the application of more deliberate and precise control during this stage of processing. With natural coffees, fermentation takes place while the coffee cherries dry. Since the complex microbiology is transpiring inside the fruit and cannot be easily observed, farmers have less control over fermentation in the dry process than the wet process.
In wet milling, coffee covered with sticky mucilage rests in tanks for periods of 12-36 hours or more as the mucilage breaks down. Growers may choose to ferment in wet or in the open air. The duration of the process depends greatly on ambient environmental conditions, especially temperature. The fermentation process ends when the coffee is washed with water and agitated to remove the remaining mucilage from the seed. Some growers will also subject their coffee to underwater soaking for a period of time after washing, to give the coffee time to rest before drying and to ensure that every last bit of mucilage is removed.
Each region tends to have a single dominant drying process that evolved in response to a blend of influences, including history, culture, climate and geography. In much of Latin America, drying coffee on concrete, stone, or brick patios is normal, although many farmers without access to patio space still dry coffee on plastic tarps or on rooftops, and some have adopted the raised bed approach that is standard in most of East Africa.
Raised bed technology is simple — waist-high wooden table frames with screens on which wet parchment or fresh cherry is spread out to dry — and often yields the best results. These elevated beds give farmers the ability to regulate drying rates more effectively than they can when coffee is resting on concrete patios or other surfaces that retain heat and don’t allow for good air circulation.
There are an endless number of variations on these basic drying technologies that involve permanent and temporary structures for shade, racks for portable drying beds, greenhouses with vents or electric fans to regulate airflow and ambient temperature, even buildings with drying racks in the rafters and roofs on tracked wheels that open and close to regulate the coffee’s exposure to sun.
There are also a range of mechanical drying processes. Some of these, like the Guardiola-style drums fired by wood, gas or by-products of the coffee milling process, are fairly common at larger farms and mills with a high volume of throughput. They are also used most often in places where the environmental conditions are particularly humid and make outdoor drying difficult to execute consistently. Others, fabulously varied, are homespun innovations.
Regardless of how our coffees are processed and dried, they must all be dry milled before they can be exported. At minimum, the dry milling process involves hulling the parchment shell from the green seed within, and some degree of sorting to eliminate defects and separate coffees by grade. Usually these separations happen in three stages: first by size, then density, and finally by color. These days the final separation by color is typically done using optical electronic color sorting machines, although there are still many places where coffees are sorted by mechanically or even by hand, bean by bean. The precision with which coffees are milled varies a lot depending on the desired result. For top quality lots, an especially rigorous standard is applied and often can mean a substantial reduction in volume, which adds to the cost of the coffee. Sorted and hulled coffee is stored in GrainPro bags or vacuum-packed to preserve its quality during its long trip to our Roasting Works.