Coffee Processing: from the cherry to the cup
Many coffee drinkers, even coffee lovers, have no idea what a coffee bean actually is. I’ve had numerous conversations with people that think a roasted coffee bean is it’s original form. This is far from the truth. There is A LOT that happens to a coffee bean before it makes it into the bag that you purchase.
Let’s starting from the beginning. A coffee bean, in food terms, is not actually a bean. It is a seed that is found inside a coffee cherry.
Coffee cherries, indeed, look like cherries hence the name. But they grow in clusters much like grapes. Each cherry itself is much like a normal cherry. It has a skin, fruit/mucilage, hull, silver skin (think of the thin skin layer around a peanut), and the seed. Most cherries contain two seeds with the flat sides facing each other like two sides of a brain.
After the coffee is picked and sorted, and the real meat of this blog post, is the different types of processing. You’ve probably heard terms like “washed”, “natural”, and “honey” processing. There is much much more science behind these processes than I will get into right now but here is a general breakdown.
- WASHED -
In this process, the coffee cherries are first sent through a hulling mill to strip off the skin and the bulk of the mucilage. The beans are then sent through a series of water tanks that contain fermentation microbes that eat the remaining mucilage outside of the hull. They are then spread out on large drying racks and, once dried, sent through another mill to strip off the hull and silver skin before bagging. This process tends to yield a very clean tasting cup of coffee with more separation of recognizable flavor notes.
- NATURAL -
In this process, immediately after sorting, the cherries are laid out on drying racks and dried with the beans inside. Through this process, fermentation happens and much of the natural sugars and flavor compounds from the fruit get absorbed into the bean. After drying, the cherries are sent through a hulling mill to separate the beans from the skin, dried mucilage, and the hull. This process often leaves much of the silver skin attached to the beans that will separate when roasted. Roasters refer to this as “chaff”. You may see some chaff in a bag of natural processed coffee but don’t worry. Chaff is completely tasteless and once it goes through a grinder with the beans, you won’t even know it was there. The natural process tends to yield a sweeter and often very fruit forward cup. Many Ethiopian coffees, for example, are naturally processed and often will have strong flavors of blueberry, strawberry, passion fruit, and green apple. Naturals won’t have the clarity of washed coffees, but many coffee enthusiasts love the bold sweet flavors that they contain.
- HONEY -
First off… no, honey processed coffees do not contain honey. They actually have nothing to do with actual honey. The term “honey” is used colloquially referring to the sweetness of the mucilage of the cherries. Honey processing is sort of a mix of washed and natural. The cherries are first sent through the hulling mill to remove the skin and some of the mucilage. They are then laid out to dry on beds like natural processing with much of the mucilage still attached to the beans. This process yields some of the clarity of a washed but also with slightly bolder flavors. In my experience, honey processed coffees are closer to a washed than a natural but mileage may vary.
- WET HULLED -
Lastly, there is a niche process that is mostly exclusive to Indonesia called wet hulling. The cherries are milled to remove skin and mucilage and then washed to remove the remaining mucilage. Then they are immediately run through a mill to remove the hull before drying. Because the hull is a protective layer, the drying process is very hard on the beans and prone to undesired fermentation and even mold. Also, without the hull, the beans can absorb flavors from the environment very quickly often making them taste very earthy depending on the quality and placement of the drying beds. Some taste bright and clean, others taste like moldy dirt. Often importers that are buying wet hulled beans for specialty roasting will do a lot of sample tasting to pluck out the good ones.
Similarly, there are newer experimental processes that use yeast strains to further ferment the beans to bring out and create unique and funky flavors.
In summary, if you’re new to specialty coffee, I would encourage you to try coffees that use different processes and see what you like. You may find you prefer one process over another. I personally tend to prefer washed coffees as a “daily driver” but many of the naturals I’ve had have been truly mind blowing and have stretched my belief in what is possible.