What even IS Coffee? Processing Methods
Welcome to the third edition of our series where we unearth answers to the question… What even IS Coffee, anyway?
In our last two posts, we covered a general overview of what coffee is, and dug deeper into coffee’s growing regions and harvest protocols. Today, we’re going to explore what happens to the coffee between harvest and export. Strap in, y’all! It’s time to learn about Processing.
After harvest, coffee is typically sorted by hand to remove cherries that are underripe, overripe, or defective, and to remove detritus like sticks, leaves, bugs, etc. Then the coffee moves on to processing.
As a fruit, naturally, coffee has skin. Then there’s the fruit layer, which is so thin it's usually referred to as pulp. Under the pulp is a layer called parchment, that acts as a shell around the seed. Then under the parchment is a thinner protective layer commonly called silverskin or chaff. (The silverskin is the little fragment of gold that stays stuck in the crevice of your coffee beans after roasting.) And finally, the coffee seed itself.
The ultimate goal of processing is to get the coffee seeds free of all those outside layers and dry enough to forestall germination, and there are many ways to achieve this.
The simplest way to process coffee is to simply let the coffee cherries stay on the tree until they’re as dry as raisins. However, this process is risky. The lack of control over ripeness, how much sun or shade each individual cherry is getting, uneven drying, loss due to birds or dropped cherries– the odds of producing specialty-grade coffee with tree-dried cherries are low.
Therefore, many coffee producers will instead opt to pick cherries and spread them out to dry while still whole. Sometimes the fruit will be spread in the sun, and sometimes in the shade. Sometimes it will be dried on raised tables, so that there’s even air flow above and below, and sometimes it will be directly on clean patios.
Coffee that’s processed this way will usually have a full mouthfeel and huge fruity character.
Pulp natural or honey
Another way of processing coffee that reaps the benefits of keeping the coffee fruit in contact with the seed (but with less intensity than natural) is a process called pulp natural or honey process, depending on the region and the specifics of the process.
Basically, only the outermost layer of the coffee fruit is removed, leaving a layer of pulp still on the parchment with the seed inside while drying. Varying amounts of fruit can be taken on or removed, depending on the goals of the person doing the processing. The level of pulp left on the seeds will dry to different colors, giving us the names you may have seen of black, red, or yellow honey processes.
From there, the coffee is again dried on beds or patios. Honey process coffees tend to be fruity and complex, but less intensely so than natural process coffees.
Wet Hull Process
A less common processing method (but one that used to be very popular for Indonesian coffee in particular) is wet hull. For wet hull process, every layer of the coffee is removed down to the silverskin before drying. With most other processing methods, the coffee will be dried while still in parchment to protect the coffee seeds. Wet hull coffees tend to taste really distinctive, oftentimes vegetal and earthy.
We can get even more complicated– For washed process coffee, the cherries are stripped off down to the parchment. But even with the tightest depulping in the world, there’s still going to be a sticky layer of fruit left on the parchment. Enter washed process.
After the fruit is removed, the coffee in parchment is moved to tanks of water. Usually it will soak there for varying amounts of time before being scrubbed, often in moving channels, rinsed, and then finally put out to dry on the aforementioned raised beds or patios. Washed coffees tend to have more subtle fruit characteristics, and lean more toward floral, chocolate, and caramel flavors, (depending on how they're roasted.)
Universally, after drying, the coffee is hulled (taken out of parchment,) bagged, and prepared for sale.
Less Common Processes
At any stage of the process, there are ways to make it more complicated, and coffee producers worldwide are venturing into more experimental processing methods.
Some coffee producers will add their coffee to tanks that are inoculated with specific yeast strains. Sometimes they’ll be sealed to encourage anaerobic fermentation. (Coffees that are labeled anaerobic tend to be on the more adventurous end of the spectrum, and like free jazz, they can vary wildly.)
Fermentation can be induced in coffee that’s whole cherry, parchment, or anywhere in between. If you see a coffee that’s labeled “anaerobic” it’s reasonably likely that it was fermented while whole cherry– however, there are no regulations from country to country, importer to importer, or producer to producer to ensure that everyone is calling the same processes the same things.
However, the end result from all processes is ultimately the same– green coffee seeds, bagged and ready for shipment to your favorite roasters.
Tune in next time as we tackle roasting, the next phase in our series... What even IS coffee?