How to: Grow Coffee
Here's how coffee is grown and processed. The following describes the "washed" or "wet" process, which is the predominant style of processing coffee in most countries (notable exceptions: Brazil, Indonesia, Ethiopia). For the purpose of this article I've focused on growing and processing and avoided topics like the technical and political aspects of farming and producing.
The Coffee Plant:
Coffea Arabica is the only species of interest for great coffee. It is normally an understory plant - that is, a shrub that grows under taller trees - native to mountainous regions of the tropics. This means a frost-free climate with high rainfall, consistent daytime temperatures around 20-30°C, and (preferably) distinct wet- and dry-seasons. Good volcanic soil is also common to the best growing regions. All of the above amount to very specific environmental requirements! The plants can grow to at least 5 metres in height if left untended, those pictured above (at Mountain Top Estate) are pruned to 3 metres to allow for mechanical harvesting. For manual harvesting they are usually pruned to 2-3 metres in height.
The plants flower after heavy rain, and it then takes several months for the cherries to grow and swell and ripen. Ideally, they become ripe during the dry season so that they can be dried quickly and easily.
Each cherry contains two coffee beans, with their flat sides facing each other, inside a sweet, sticky flesh. Once the coffee is harvested it needs to be delivered to the wet mill.
The Wet Mill (pulping & fermenting):
"Pulping", that is, the separation of the beans from their fruit, needs to happen as soon as possible after harvesting. A pulping machine is used - it works by using motorised drum to squash the cherries (gently), throwing the beans in one direction and the fruit pulp in another. The freshly-pulped coffee beans are covered in a sticky mucilage, which is generally removed by fermentation. The beans are put into a vat, usually but not always immersed in water, and allowed to sit for 12-36 hours. This allows bacteria and enzymes to break down the mucilage. Next the beans are rinsed again, and then dried.
The coffee is called "parchment" at this stage, due to the stiff papery casing that remain on the beans until after drying. Drying is done by laying out the parchment on either concrete "patios" or on raised beds. Once the beans have dried to around 11% moisture, they are often "rested" for up to a month, before being sent to the dry mill to have the parchment removed. Then it's shipping time!
I hope this article illustrates the complex process of getting coffee to you cup! [I will eventually write a follow up to this one with info on the roasting process...]