What is Coffee?
Coffee is essentially a fruit and coffee beans are the seeds inside the cherries of an evergreen plant that grows between the tropic of Cancer and the tropic of Capricorn. White blossoms which smell like jasmine give way to red coffee berries. Inside each coffee berry there are one, two or on rare occasions three coffee beans. A coffee plant can grow to a height of 10 or 12 meters and it takes 3 to 5 years for the plants to begin producing, the yield decreases after approx 20 to 25 years.
Arabica V Robusta
There are two main types of coffees Arabica and Robusta. Arabica coffee plants are delicate and prefer higher climates, the elevation causes the coffee bean to mature slowly which in turn leads to a more aromatic and flavourful coffee. Robusta as the name suggests is much more resistant and is grown at sea level. Their characteristics are also very different. Arabica coffee has a very pronounced aroma, is mild, well rounded, and often features a sweet hints of chocolate or caramel, with a pleasing touch of bitterness. Robusta coffees on the other hand, are hard, astringent, not very aromatic and much bitterer to taste, they also contain three times as much caffeine as Arabica coffees.
Harvesting the beans
Harvest times vary according to geographical zone but typically there is only one harvest per year. The vast majority of coffee is harvested by hand, the cherries are placed in large sieves and tossed high into the air to sift out the leaves and twigs and collected in coffee sacks.
Processing the beans
Coffee cherries must be processed soon after harvesting to prevent the pulp from fermenting around the bean, there are two types of processing:
• The dry method
Often referred to as the natural method, where the harvested berries are spread over a concrete surface ideally in sunlight and raked at regular intervals to prevent fermentation. Sun drying the coffees is vital for quality because it promotes a very smooth and natural reduction of moisture. The drying process can take up to 20 days at which time the fruit pulp is dried and you can hear the beans rattling inside, some moisture is still retained. At this point, the dried cherry is removed and the coffee beans are cleaned and sorted according to bean size.
• The wet method
Also known as the washed coffee method. Using a pulping machine the beans are separated from the skin and pulp which are washed away with water. The lighter immature beans are separated from the heavier mature beans through specially designed washing channels or by a pregrader which is a system involving shaking the beans through a strainer into a tank of water. The beans are then stored in fermentation tanks for 12–48 hours. Afterwards the beans are washed again to remove the remaining shell before being spread out to dry in the sun for 4 to 7 days. Sometimes to speed up the drying process tumbler dryers are used.
Coffee that is refined using the wet method will have a sharper more acidic taste than coffee which has been treated to the dry method.
Hulling & Polishing
In wet process coffee, hulling is used to remove the hull or dried parchment layer immediately surrounding the bean. Hulling dry processed coffee refers to removing the husks or whole of the dried outer coverings of the original cherries. Polishing beans is an option process that is not always practiced. During the polishing process, any silver skin that remains on the beans after hulling is removed.
Grading and Sorting
Although coffee beans are of a fairly uniform size and proportion, they are graded first by size and then by density.
The tasting of coffee is referred to as cupping. Ritualistic in form, cupping sessions involve several steps where coffee professionals perform visual examination of the green coffee, and then they roast, smell, and taste each sample. Every step reveals clues about a coffee’s quality and character.
Roasting is the heat treatment which transforms the green beans into the aromatic brown nuggets that we buy whole or ground.
Many changes occur as raw green coffee beans are roasted. As the beans increase in temperature, the water in them turns into steam and expands, their cellular structure begins to rupture and they begin to crackle audibly. Colour rapidly changes from dry green to a more vibrant green as the moisture is forced out, subsequently they become a straw colour progressing to caramel and then to a darker and darker brown.
The colour changes signal the breakdown of starches into simple sugars through the process of carmelisation. The brown bean is initially flat and dull in colour but it quickly becomes flecked with oil. If the bean is removed from the roaster at this stage the oils are reabsorbed as the coffee cools. If the roast is allowed to progress, these oils will remain as a coating on the outside of the beans.
The objective of grinding coffee is to the get the most flavour from the beans. Coffee is ground so that the taste and aroma compounds are more easily transferred into the water.
Coffee beans are roasted ground and mixed with hot water, their concentrated, aromatic flavours are released to make one of the most remarkable and celebrated drinks in the world.