Processing

 

Overview

There are many different ways to process cherry before drying. Your localised situation may better suit dry processed, semi-washed, wet processed, or any of an infinite range of subtly different ways of transforming cherries to something ready for milling. We investigate a range of methods in depth elsewhere, but this document is designed to give broad guidelines that will likely improve coffee quality through their understanding, adaption, and implementation in many places. With this in mind, we have chosen to outline the key areas of focus when trying to achieve a clean, safe, simple washed processed coffee with minimal fermentation, and which doesn’t require a lot of new knowledge nor expensive equipment.

Your tools to control fermentation time include exposure to oxygen and the environment temperature. The higher the oxygen exposure or environment temperature, the quicker and more aggressive the fermentation. Lower oxygen exposure or temperature results in longer overall fermentation times required.

 
 
 

RwandaMay2017-4850.jpg

Processing Guidelines

  • Begin your pulping as soon as possible after collection. Do not store the cherry any longer than absolutely necessary.
  • Clean and maintain your pulper, especially the shirt. Be safe: see the BONUS section.
  • Calibrate your pulper to strike a balance between cherries passing through (too wide) and damaging beans (too narrow).
  • Use a screen after the pulper to catch un-pulped cherries, skins, and debris before the beans pass to the fermentation tanks.
  • Ferment in clean non-porous containers if possible, e.g. plastic tanks.
  • Wash beans thoroughly as soon as the mucilage is broken down enough to be removed. The easiest way to know when it is time to wash is to use a Fermaestro. If a Fermaestro isn’t available, you can get reasonable results by grinding a handful of beans together, feeling for the shift from slimy to something akin to grinding river pebbles together.
  • Move to drying beds immediately.
 

Processing Steps

Fenix-6271.jpg

1.

Move your ripe cherries to the pulper. Check the cherries are sorted for ripeness and size and that your mill, screen, and fermentation tank are clean. Pulp the cherries, and sort skins, cherries, and debris out on the way to the fermentation tanks.

2.

With your mucilage covered parchment in the fermentation tanks, set up your Fermaestro. Fill the cone right up to the brim with parchment, put on the cap, and push it down into the fermenting mass until just the cone tip is poking out.

Measure anything you can at this stage and all the way through until washing time: pH, temperature, ambient temperature etc. Do this so you can learn how the things that fluctuate outside of your control change the rate of fermentation. This will make future processing more predictable. Move your fermentation tanks to a more temperature-stable indoors area if possible. Cooler is better. Seal the top of your tanks with one-way valves if this is a possibility.

3.

As you get closer to your expected completion time, check to see if the beans are ready for washing by inspecting your Fermaestro. Lift it out of the tank by the cone tip and drop it 3 times from a height of 3cm onto its base. When the mass inside fills only up to the small ring (i.e. the cone is empty from the small ring up to the tip) it is time to wash the parchment.

If you do not have a Fermaestro, grind a handful of beans between your fingers. You’ll feel the mucilage giving way as the parchment begins to feel like small river stones rubbing together. As soon as this is the case, wash the coffee thoroughly to stop the fermentation and remove all traces of mucilage, using the minimum amount of water you can. Drain and use new water at least three times, or until the water runs clean. Move to drying immediately. Take note of the time and adjust your processing to finish before midday next time taking into account the environmental temperature and size of the mass and the effect these variables have on your fermentation time.

 

Note: There are many ways to lower water usage and reduce the impact on the environment. This is very important, however, this document is focused only on improving coffee quality. Please incorporate good environmental practices that suit your local situation into these processes.