In my last post about Guatemala, I gave a little overview of the Volcafé way and how Genuine Origin / Volcafe was working with farmers in Guatemala to help them become more profitable. While we were in Guatemala, we also spent a lot of time visiting farms, wet mills, dry mills and basically getting a close-up view of every step in coffee processing.
If you’ve ever attended one of our coffee brewing classes, you’re familiar with the difference between a washed process coffee and a natural process coffee. Pretty much all of the coffee we got to see was washed process coffee. There’s a little bit of natural process coffee being done in Guatemala, but not a lot.
Why “Processing” Coffee?
Coffee is a cherry. It grows on a tree. The bean that we roast is the seed inside of the cherry. Typically there are 2 seeds in each cherry. Processing is what is done to a coffee cherry to remove the pulp and other parts outside of the coffee cherry in order to get to the seed.
First Step – Get The Coffee To the Mill
Most coffee farmers don’t have the equipment on their farm to process their coffee cherries. So they need to take the cherries to a co-op or a processing facility of some kind. Obviously, larger farmers are going to use a truck, but sometimes, it’s whatever works!
Processing facilities sometimes have receiving locations spread out around a particular region in order to make it easier for farmers to get their cherries processed. The processor will then consolidate the cherries from several farms and bring them to their main facility.
This is also important because this is the point where farmers are often paid for their coffee cherries.
Step 2 – Remove the Pulp and Mucilage
Once they get to the main facility, coffee cherries are dumped out of the truck into hoppers that feed the coffee into a big milling machine. This machine crushes the coffee cherry between two cylinders so the pulp and mucilage is removed from the seed. There’s still a good bit of sticky, sugary mucilage on the outside of the seed when this process is done. Most of that will be removed in the next steps.
The pulp and skins of the coffee cherry is separated off by water and is used for compost in most cases.
Step 3 – Fermentation
It’s not as fun as it sounds….
Once the pulp has been removed from the coffee seed, they leave the seeds sitting in fermentation tanks. The sugars in the mucilage ferment and break down. This makes it easier to remove the remaining mucilage from the seed. The coffee is allowed to ferment overnight or up to about 24 hours.
Fermentation is an optional step in coffee processing. It’s done a majority of the time, but not always. Fermentation, if it’s not carefully monitored, can impart some off flavors to coffee that can be evident in the final roasted product.
Step 4 – Washing
After the coffee rests in the fermentation tanks, it’s pushed down these long water troughs. While it travels down the trough, the water washes the remaining mucilage off of the seed.
Step 5 – Drying
There’s still a lot of moisture in the coffee seed, so they lay the seeds out on huge patios to dry in the sun. They turn the seeds over every 20 minutes so there’s no mold or mildew building up on the seeds. The seeds will sit out on these patios for about 8 days until they go from 60% moisture content down to about 12% moisture content.
Step 6 – Sorting
Coffee is sorted and graded by size and defects. When it’s sorted by size, they use vibrating gravity tables and screens to separate out the different sizes of coffee beans. Once they are sorted by size, they need to separate out any defective beans.
There are a couple of different ways to separate out defective coffee beans. One of the facilities we had the opportunity to visit sorted everything manually. During the harvest season, they hire mostly women from the surrounding area to come in, sit at desks and sort coffee to separate out all of the defects. This is a highly effective way of sorting coffee and yields very few defects in the bag. On average, they can sort about 1-2 bags of coffee per hour using this method (60 kg or 132.25 pounds of coffee).
A More Modern Sorting Facility
The other facility we had the opportunity to visit is much more automated. In addition to the gravity tables, they use a computer controlled system that takes pictures of the coffee as it goes by and uses a small puff of air to blow any discolored coffee down a separate chute. They can sort about 80 bags of coffee an hour this way. It’s very fast but not nearly as accurate as the manual sorting method.
Beans are first sorted by size through a screen filtering system.
Then, they’re run through a machine that sorts by color. It’s amazingly fast – like 80 bags per hour vs. one bag per hour sorted manually. A computer takes a photo of the bean as it goes past. If the bean is discolored, it is pushed out of the path by a small puff of air. The down side of this method is that it is not able to sort out mis-shapen beans or damaged beans.
All this just to get some coffee to you! We haven’t even touched on the part where it has to go to port, get put on a ship and make it’s way to you! We’ll talk about that someday. Probably in a post called “Planes, Trains and Automobiles”.