According to the International Coffee Organization (ICO) in London, the world consumed over ten and a half billion kilos of coffee last year alone. With an industry worth billions of dollars, coffee is the most exported product in the world behind crude oil. This week we will be taking a look at the harvesting and processing steps that go into producing this global product. Our journey starts in the fields of coffee plantations around the world where coffee plants are beginning to ripen for harvest.
The coffee bean is actually a seed of the coffee plant encased in multiple layers of fruit and protective film called a cherry. As the coffee cherry matures it changes from a bright green, through yellows and oranges, before finally reaching a uniform deep red color. Once ripe, there are two common harvesting methods to collect the cherries, strip picking and selective picking.
Strip picking involves all the cherries on the branches being pulled off and collected. This saves time and money, because workers can pick faster and it can be done by machine in areas with flat terrain. When strip picked, a majority of the cherries are ripe and the unripe ones are discarded. Most of the coffee that is picked this way is Robusta coffee. Of the two major types of coffee, Robusta is a lower quality species of coffee grown at lower altitudes. Selective picking, also known as handpicking, is more time and resource intensive but yields a higher quality and more consistent product. This method requires workers to pick individual cherries that are ripe and ready to be harvested, leaving unripe fruit on the plant to mature. The coffees we purchase are all Arabica coffee and hand picked to maintain a high quality product. After the cherries are picked, they must be processed and milled into beans before being bagged for export.
A coffee cherry is made up of seven layers as seen in the image. The exterior layers are numbers five through seven and the interior layers are numbers three and four. The first two layers make up the bean we roast into delicious coffee. There are three common ways coffee cherries are processed into the green beans: dry method, wet method and the honey method. The goal of each method is to ferment and remove the exterior layers surrounding the beans.
The dry method is a time-tested and traditional method where whole cherries are spread out to ferment and dry on raised beds/platforms. Using raised drying beds along with scheduled turning and raking to increase airflow around the cherries and prevent mold or spoiling. The cherries are completely dried when they reach about eleven percent hydration and look like raisins. From this point they are sent to be milled and have all the layers up to the silver skin removed.
The wet method which is used by most commercial growers uses water to separate the exterior layers and ferment the interior layers. First the exocarp and mesocarp that make up the skin and pulp are completely removed via a water mill. The beans are then placed into large fermentation areas filled with water, with the mucilage layer still intact. They will rest here for several days while the sugars and alcohols in the mucilage layer ferment, before being washed and continuing the process. Fermentation time can vary depending on each farm, region or country. After the beans are washed they are either laid out in the sun to dry known as patio drying, dried on covered raised platforms similar to the dry method, or machine dried. We mostly buy washed coffee for its purity of flavor.
The last common method of processing coffee cherries into green beans is called the honey method. To begin, the coffee is de-pulped which removes the outer skin (exocarp) and most of the pulp (mesocarp). Some pulp remains on the beans unlike beans processed with wet milling. This excess pulp and mucilage layer is allowed to remain on the beans and ferment during the drying process. The length of drying time determines the color of the fermented pulp on the exterior of the beans, and imparts different flavor characteristics into the finished product. There are three main categories of honey processed coffee: Yellow (fermented for eight days), Red (fermented for twelve days) and Black (fermented for thirty days). Some countries have advanced this process and created new color categories with different drying times, but it varies depending on the region.
When each method is complete, we are left with parchment coffee, green beans with the interior protective layer (endocarp) still intact. If each method yields the same thing, then why does the industry use different methods instead of a universal one? Some coffee cultivating regions have very limited resources and can’t afford to use methods like the wet method that involve large amounts of precious clean water. More importantly, each method of processing coffee will impart different flavor characteristics into the beans. The wet method yields a cleaner tasting and more traditional harvest, because the beans are stripped of all the fruit layers before fermentation and rinsed thoroughly. The dry method introduces a very strong and intense fruit/honey flavor, because the entire fruit is allowed to ferment and lock in flavors. The honey method reaches a middle ground between the other two methods as the flavor is still fruit forward due to the bits of remaining pulp during fermentation, but there is a creaminess that cuts through the intensity when compared to the dry method.
The resulting parchment coffee must be milled before it can be roasted. Milling encompasses three stages: hulling, polishing and grading. This process can be done by hand, machine or often done with both to create a consistent and quality product. Hulling removes the parchment layer of skin (endocarp) that encases the beans. Polishing is an optional process that removes the silver skin (spermoderm) from the beans. It is optional because when this layer is roasted, it becomes chaff and can be easily separated from the beans during the roasting process at a later time. “Grading” is a loosely used term in the industry that can mean categorizing coffee in many different ways. In this situation, grading refers to the sorting of beans by size and weight. Grade is used in the industry as an important way to know the difference of coffees in a similar area.
Depending on the processing method used, the beans may already be graded. For example during the wet method, water channels are used to force the cherries through sorting grates that separate the cherries by size before they enter the fermentation areas. When and how the beans are eventually sorted can vary between methods and depends on how the farmers choose to operate. The beans are then observed one final time for defects such as unacceptable sizes, odd colored beans, over-fermented beans, insect-damaged and non-hulled beans which are then discarded.
The grading process is important because there is generally a strong correlation between bean size and quality. Specialty roasters will often look for coffees within a higher range of sizes, passing on the smaller size beans that are considered cheaper coffee. A consistent grade of beans is also incredibly important, because beans that are all the same size will roast evenly. Beans of varying sizes will make for an inconsistent and hard to control roast. An example of a high grade coffee would be our Colombian Supremo which uses the term “supremo” to indicate the larger bean size and thus higher quality. After the milling process is complete, the green coffee is bagged and exported around the world to be roasted. If you are interested in the roasting process, you can read all about it in our previous post.
If you are interested in the roasting process, you can read all about it in our previous post.
The Art of Roasting