The basics of coffee processing
The term “Coffee Processing” refers to the removal of layers that surround the bean to expose its internal nature. A “Coffee Cherry” is made up of several layers including skin, fruit, mucilage and parchment, all dominant prior to the bean’s processing. Once the bean has been harvest/picked, they need to be processed, removing unwanted layers to release the pure nature of the coffee bean. There are a variety of ways to process a “Coffee Cherry”, each having a significant impact on the cup profile of the coffee.
This method is used most commonly to provoke the inherent flavouring of the bean itself, developed and nurtured in its climate.
The “Washed Process” involves removing all undesired layers of the bean before it’s dried. Whereas natural or honey processing utilises the outer fruit to provide more depth of flavour, washed coffee is almost totally reliant upon the inner core of the bean itself, having gained carbohydrates and flavour throughout its period of growth. This, therefore, means that the bean is affected by environmental factors like climate and terroir, suggesting that the bean becomes environment incarnate. “Washed Process” also means the coffee bean is exposed to operational factors such as fermentation and drying, fundamentally showcasing the coffee’s true flavour.
To begin, harvested coffee is placed through a de-pulper to remove the unwanted skin and fruit. A de-pulper machine can either be manual, requiring a worker to turn the wheels mechanism or electronically powered. Dependent upon the quantity of the coffee and its frequency of purchase, industrialised machines can carry out the de-pulping process much quicker and efficiently. Inside these machines, carefully calculated disks drive the coffee beans out of the fruit. Due to the ripened nature of the “Coffee Cherries”, they break passing through the machine, leaving only the coffee seed (bean) to successfully pass through.
The next stage is to remove the sweet, sticky mucilage that surrounds the bean itself. This is a pretty simple part of the process; the coffee is placed into fermentation tanks for a certain period of time. Typically, the coffee is left to ferment for 12-36 hours, though producers have been known to experiment with the duration of fermentation and assess how it affects the profile of the coffee. Once the fermentation has finished, the coffee is washed with clean water before being left to dry on patios, tables or raised beds.
Rather than removing the outer fruit, as is done with the “Washed Process”, “Natural Process” involves drying the coffee whilst it’s still encased in the fruit and mucilage. Doing this means that the natural sugars & sweetness residing within the “skin”, begin to ferment the core coffee bean and merge. Once harvested coffee has been picked, it’s sorted using flotation and winnowing techniques before the ripe full beans are taken to begin drying. The next stage is tricky and must be managed carefully. What makes this stage so challenging is not only the risk of over fermentation, where the fruit is left to dry for too long but also the development of moulds. These moulds at best diminish the coffee’s flavours and at most cause defective flavours. To avoid the development of moulds, the beans are turned regularly to ensure maximum surface area is exposed to the air, facilitating an even drying. After the agreed drying time when the coffee reaches a set moisture level, all of the outer layers of the dried "Cherries" are removed with a de-pulper.
HONEY/PUPLED NATURAL PROCESSING
Honey or Pulped natural processing are interchangeable terms used regularly. This process, that sits between “Washed Process” and “Natural Process”, are often dictated dependent upon the coffee’s country origin and the producer’s traditions. Coffee’s that maintain these types of processing are often fruit-forward, with a medium sweetness and body, showcasing a unity between both “Washed Process” and “Natural Process”. After the harvested coffee is pushed through a de-pulper, rather than placing into fermentation tanks as is done in the “Washed Process”, the coffee is moved directly into the drying stage with the sticky mucilage still intact. This type of processing allows for a wide range of experimentation, each leaving a different cup profile and colour.
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To find out more about Coffee and the Coffee Industry, watch our SME interview with PS Coffee Roasters below, or transcript here.