During the last few months I have been experimenting with Panya's homegrown coffee beans, trying to process the cherries from the coffee trees into coffee that is ready to drink. To do this I used only tools that were already available.
Turning the fresh fruit into coffee is a lengthy process as the fruit needs to be harvested, de-pulped, fermented, dried, hulled, roasted, ground and brewed before it can be consumed. The methods that I used are time consuming as I did almost everything by hand, and the quality of the roasted coffee might not be optimal as I roasted the beans in the oven having very limited control over temperature and airflow.
In the following text I want to try to retrace the steps I took to process Panya's coffee. I will try to describe all steps in such a way that the process can be replicated successfully and improved upon.
I harvested the fruit in a few batches as the fruit does not ripen simultaneously. I aimed to harvest only fruit that was ripe but I also picked cherries that were part green and part red. I did not harvest any cherries after they had turned black.
At least one coffee tree in Panya is of a different variety that has cherries that are yellow when ripe and that never turn red. These cherries I would harvest when they turned yellow.
Immediately after harvesting the cherries I removed the skin and pulp from the cherry, which left me only a hard, slimy seed.
I de-pulped the cherries by squeezing the cherry until it popped open, or digging into the cherry with my nails. Some cherries are quite firm, and the inside is very sticky and slippery, so de-pulping by hand requires some time and patience. I threw away all seeds that were soft, hollow or shriveled up.
The pulp of the cherries is edible and can be dried and used in tea.
After removing the pulp, there is a second, more persistent layer around the seed that we want to get rid of. This is a mucilage layer that feels slimy and sticky. The easiest way to remove this layer is by letting microorganisms consume it by letting it ferment in water.
I used several different containers for the fermentation, but I always used either ceramic or glass containers that were relatively wide, like a coffeepot or cylindrical bowl. I put the seeds in the bowl, filled it with enough water to rise a few centimeters above all the seeds that sunk to the bottom. I then covered the bowl with a cloth to keep insects out while allowing oxygen in. I changed the water a few times, but not according to any specific schedule. I generally changed the water if it became smelly or very murky, on average about once every two days. I also regularly rubbed a few seeds between my fingers to check the progress: the fermentation is complete when none of the seeds feel slimy, but instead feel rough to the touch like a wet pebble.
After fermentation was completed, I threw the water out, rinsed the seeds with clean water, and spread the seeds in the sun to dry. I used both concrete and metal surfaces to spread the seeds on, and always placed them in spots that were in direct sunlight at least 2/3 of the day. I always stored the seeds inside for the night and spread them outside again the next morning. On most days I would roughly turn the seeds around noon to dry them more evenly. The time it took varied but averaged about one week I think. To be able to store the beans they should be dried to 10% moisture, but I never attempted to measure the moisture level, and just dried them until they seemed as dry as they would get.
If the beans are dried sufficiently it should be possible to store the dried beans for a long time before processing them further.
The next layer that needs to removed is the parchment skin. This dried parchment skin looks a bit like a pistachio's shell, just much softer. I removed the parchment skin by hand by breaking and pealing it off of every individual bean.
Inside each seed's shell are one or two green coffee beans. The beans are covered in a thin light covered layer that is hard to get off. I rubbed the beans between my hands to get most of this skin off. I never got all of this skin off the beans and this never seemed to make any difference except making the roasting process a little bit more challenging.
Roasting the beans was by far the most challenging step in the process for me and the only step that failed a few times. I used Panya's metal, fire heated oven to roast the beans.
Controlling the temperature and timing of the roast is very important in order to get nice tasting coffee. The first time I attempted to roast some beans the fire under the oven was big and blazing and the beans turned black in only a couple of minutes and were completely burned to coal. After that I always tried to keep the fire small and it seemed to work best if I could stick my hand into the oven for about 3 seconds before it felt too hot to leave it.
I spread the green coffee beans on a low baking tray. I always spread them in a single layer with at least about a third of the surface empty. I'd place the tray in the top or middle shelve in the oven, and closed the door. I always tried to keep the fire burning at a stable rate. After a couple of minutes I would open the door to look at the beans. In a successful roasts the beans would be yellow or light brown by now. I would give the beans a quick shake or stir to move them around a bit, and turn the whole tray to a different position in an attempt to roast the beans as evenly as possible. If the beans are still green after two or three minutes in the oven I would quickly try to increase the fire. When the beans were light yellow I would leave them a few minutes again before checking and shaking again. When the beans were turning brown, I would start checking and shaking them every minute or so until they were the color I wanted.