The Life Cycle Of Coffee; Processing

Wet Processing in Kenya!

After coffee cherries are ripe and ready for harvest, they must undergo serious changes to prime them for roasting. These following steps are what are referred to as Coffee Processing. To begin, diligent farmers scavenge the plantations for only the ripest cherries. Unripe cherries produce a lower quality cup and are therefore sorted out during the picking and sorting stage of processing. After being sorted there are three methods that are  most common for processing coffee. Before we talk about these methods it is important to understand the anatomy of a coffee cherry given its different parts are what drive the different processes.

Cherry Anatomy

The cherry is protected by its red outer skin. Directly underneath the skin the fruit pulp is present, this is packed with redolent aromas of the coffee blossom.  Below the pulp is a thin layer of pectin that envelopes the beans. This is followed by the parchment, and directly attached to the beans is a thin membrane or “silver skin.” Hidden underneath all of these protective layers lie the seeds of the coffee plant.

Washed Processing

It is important to note that the processing of coffee, specifically washed coffee, varies notoriously from region to region. But lets cover the basics:  The cherries are sunk into water to continue sorting, ripe cherries will sink to the bottom while unripe cherries will float facilitating their elimination. Afterwards the cherries are pulped, which contrary to its name is the process of removing the “cascara” or red skin. To facilitate the removal of the mucilage the coffee fruit is fermented. This is where the most variety exists. In Latin America, fermentation happens over night, in Kenya fermentation can take up to 3 days, and in Ethiopia it happens under water. These variations in technique come from climate and tradition and are monumental in the flavors of coffee. These flavor affecting techniques could benefit from controlled studies and research given there is much we don’t know about what is happening at this stage of processing. The fermentation process must be closely monitored or else taste of ferment will be present in the cup. But to continue; the fermented cherries are washed to remove their pulp, this happens by running the cherries through streams of water while raking the cherries.  The second mucilage removal method is machine facilitated, meaning the cherries are sent through machinery that polishes the beans until the entirety of the pulp is removed. Although similar, many farms have different washing equipment. Given every step of processing from seed to cup is present in the final extraction, it is interesting to see how washed methods of even same varieties and regions can vary from farm to farm. After the beans have been removed of its fruity companions they must be dried and become parchment coffee or in “pergamino”. Beans are either dried on raised beds, patios (in the past clay patios where fashionable, recently concrete patios have yielded better results), or commercial dryers. The drying stage is very important; it is crucial to let the beans hold on to an exact amount of humidity that preps them for roasting. This processing method results in a very clean cup and is by and far the most common. The washed method tends to use about 2000 L of water per 50 lb bag of green beans.

Natural Processing

Dry processing was the first method used to process coffee. As specialty coffee grew as an industry and roasters were finding cleaner cups with washed coffees, this method faded. Brazil being a very large producer of coffee, was still processing coffee in the dry manner. Almost as an advertising campaign, it was the Brazilians who coined the term “Natural” for dry processing. For this method cherries are harvested then sorted up to 3 or 4 times. The ripe cherries are then allowed to rest on either raised beds or patios to dry out in the sun. This process takes anywhere from 1 to 4 weeks depending on cherry humidity and climate. Throughout this process producers rake or rearrange the cherries to promote even drying. The cherries are allowed to dry until they reach a humidity level of around 11%. Then the cherries are removed of their pulp and parchment. This method is more common where potable water is scarce. It is also a great way for small cultivations to start their operation given it operates at much lower cost. This method does not result in a cup as clean as the washed method but can have heightened sweetness and more fruit notes found in the cup.

Pulped Natural

This method is a kind of hybrid. Cherries are pulped, and then the exposed fruit is allowed to dry onto the bean. Then the dried fruit is removed from the bean.


Parchment coffee is then sent to the mill, or milled on site if facilities permit to remove parchment. After parchment is removed we are left with what we call “green beans.”


After processing the beans must be sorted by two different methods. First by weight and size, which is either done by a set of sieves or in an air operated machine that separates sizes of beans from each other and also removes any products that are not beans, such as small rocks. Defective beans may be the same size and weight than high quality beans so after initial sorting color sorting separates the odd ones out. Color sorting is predominantly done by hand, although large commercial coffee producers employ laser machines to carry on color sorting.


Not all coffee is aged. Aged coffee has a fun story behind it. It is said that coffee producing countries started aging coffee because of its roots as a trade commodity. When coffee was only cultivated in Mocha and Java, it had to travel long distances by boat to arrive at its destination. The humidity and temperature on the boats provided an environment for the beans to age. Consumers, used to this aged flavor, who then became producers elsewhere tried to replicate this process.

After processing the beans are packaged in burlap bags, or more increasingly vacuum sealed bags (called pro grain bags), and then shipped to their destination. Once they arrive…

[pic from gimme!coffee]


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