Foul, sour, spoiled, rotten, brackish, acrid – all are words we hope to never use on a cupping form. As roasters, we know we can’t roast these qualities out. The solution to eliminating these descriptors is good water during processing.
To talk about water in processing effectively, we should go back in time—a time before water was ever used to process coffee. Processing started with the ‘Natural Process.’
Natural coffee processing – No water. Also, very slow. This does not mean that coffee would never turn out sour, spoiled, or rotten; it just means that some other processing or harvesting mistake caused the off-flavors. Fermentation does happen inside the skin while drying, and sometimes bacteria can get into split cherries.
In order to speed up processing time, the ‘Wet Process’ was invented. Attributed to the British in Jamaica around 1850, they used what was referred to as the West Indies Method to speed up the processing of coffee. As in all manufacturing, time is money. Not to mention that the rainfall in Jamaica made it difficult to pull off good Natural Processing. By pulping the coffee first, getting rid of the mucilage, and then drying the coffee, processing time was cut in half.
Water then becomes a central tool, byproduct, and variable in the Wet Processing facility. Careful management of this resource is crucial to a successful operation.
Water is used to move coffee from place to place. Clean water should be used to start these transports and recognize that mucilage-rich water comes out the other end. Water can also be used as a tool in mechanical demucilagers, which is highly efficient and reduces water consumption vs. regular fermentation tanks.
Post-fermentation water is now tainted and must be dealt with. The solution is a wastewater treatment strategy. This strategy requires different filtering systems of tanks and ponds to capture the solid waste, purify the effluent and then return the water to service either on the farm or to the stream.
Water is also a key variable in the wet processing method in determining manufacturing speed and product quality. The key factors in the variable are the quantity of water available and the purity of the water.
If you have enough water for several washing tanks and moving the product from place to place, you start your work. If you are light on water or attempting to use as little as possible, then you might choose a couple of strategies. You can recirculate water through a mechanical demucilager and send the parchment to dry without ever using a fermentation tank. That saves a ton of water but can change taste characteristics.
Another choice is reusing water in fermentation tanks. Usually, you can use part of the water from one tank as a ‘starter’ for the next tank, thereby using a little less water but speeding up the process vs. fresh water each time.
With good water and good practices, we will get good coffee.