COFFEE BEANS: FROM HARVEST TO ROASTING
Coffee and cherry harvest
What we call coffee beans in the UK are fruit seeds like cherries. The coffee trees produce cherries that start with yellow, then become orange and finally red when ripe and ready for harvest.
Coffee cherries grow along the branches of clustered trees. The exocarp is the cherry rind and is bitter and thick. The mesocarp is the fruit below and is intensely sweet, with a texture very similar to that of a grape. The fruit also has the parenchyma: a sticky layer that looks like honey, and this layer helps protect the beans inside the coffee cherry. The beans are covered by the endocarp, a protective parchment covering for green coffee beans, which also has a last membrane called spermoderm or silver skin.
On average, there is a coffee harvest per year, the time of which depends on the geographical area of cultivation. Countries in southern Ecuador tend to harvest their coffee in April and May, while countries in northern Ecuador tend to harvest their coffee at the end of the year starting in September.
Coffee is usually harvested by hand in two ways. All cherries can be removed from the branch one at a time, using the selective harvest method, which ensures that only the ripest cherries are harvested.
Processing of coffee cherry
The coffee should be processed immediately after it is selected. About 45 to 90kg of coffee can be harvested daily, but in the real sense, only 20% of the weight is the coffee bean. There are two major methods of processing the cherries:
Dry process
This is the simplest and cheapest option, where the harvested cherries are left to dry in the sun. They are left in the sun for 7-10 days and are returned and swept periodically. The objective is to reduce the moisture content of coffee cherries to 11%, the peels will turn brown, and the beans will move inside the cherry.
Wet process
The wet process differs from the dry method in that the coffee cherry pulp is removed from the beans within 24 hours of harvesting the coffee. A pulping machine is used to wash the external skin and pulp; the grains are transferred to fermentation tanks, where they can stay anywhere up to two days. Natural enzymes soften the sticky parenchyma of beans, which is then dried in the sunlight or using mechanical dryers.
The dried coffee beans go through another process called peeling, which removes all layers. The coffee beans in the UK are transferred to a conveyor belt and classified in terms of size and density. This can be done manually or mechanically, using an air jet to separate the lighter grains, which are considered inferior. Coffee producing countries send unroasted coffee; this is called green coffee. Around 7 million tonnes of green coffee is shipped worldwide each year.
Roasted coffee
The roasting process of coffee transforms the chemical and physical properties of green coffee beans, and this is where the flavor of the coffee is satisfying.
Large rotary drums are used for the heating of the green coffee beans at a temperature of around 288 ° C. The rotary movement of the drums prevents the beans from burning. Green coffee beans turn yellow at first and are described with a popcorn scent.
The beans "explode" and double in size after about 8 minutes, indicating that they have reached a temperature of 204 ° C, then begin to brown due to the appearance of the essence of coffee (internal oils). Pyrolysis is the name of the chemical reaction that produces the taste and aroma of coffee due to the combination of the heat and essence of coffee. Anywhere between 3 and 5 minutes later, a second "pop" occurs, indicating that the coffee is completely roasted.
Coffee roasting is an art form in itself; roasters use their sense of smell, sight, and sound to check when the coffee beans are perfectly roasted. Time is essential in the coffee roasting process, as it affects the taste and color of the resulting roast.
