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Processing coffee

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The coffee plant blooms several times a year, possibly with beautiful white flowers and ripening fruit. The fruit of the coffee plant’s a cherry that contains two or more coffee beans, which turn dark red to purple when ripe. The plant can grow up to 13 m high, depending on the variety. The first harvest can be made after two or three years.

Coffee cherries

As mentioned above, the fruit takes the form of a fleshy cherry that contains coffee beans enveloped in pulp. Once peeled, the beans are green in colour and odourless. The actual shapes and size of the bean depends on the given coffee plant and the area where the coffee grew.

Harvesting

One method of harvesting the ripe cherries is to pick them manually, a time-consuming and costly process, but it’s the best means of ensuring the finest quality. This is because only the truly ripe beans are picked and the plant doesn’t sustain any damage. Another method’s known as stripping, when an entire branch is selected and effectively stripped of everything on it. The fruit suffers as a consequence, as does the plant itself. Finally, there’s machine harvesting, which involves removing absolutely everything from the coffee plant, causing the most damage to it. Harvesting constitutes the greatest overhead prior to selling the beans.

At this point, the coffee beans are coated in three layers of wrapping and one layer of pulp, encasing each double and single bean. There various layers around the beans can either be removed via the dry or wet processing technique, both differently affecting the quality and eventual price of the coffee.

Dry Processing

This is a method primarily applied in Central America, Brazil and Arabia, and is the oldest way of processing coffee. However, it’s not practised in regions with high rainfall, as the humidity is too great. The coffee cherries are spread out in the sun, often on large concrete or brick patios. As the cherries dry, they’re raked or turned to ensure they dry to the correct extent and to prevent mildew, which may take up to a month. The cherries turn brown under the influence of the air and sun, becoming rather fragile. The drying operation’s the most important stage of the process, since it affects the final quality of the green coffee. If over-dried, the cherry becomes brittle and produces too many broken beans during hulling (considered defective beans). Whereas, if insufficiently dried, the cherries are too moist and will quickly rot. Almost all Robustas are processed by this method.

Wet Processing

This method’s more expensive than the previous one. However, it benefits from better separation of unripe and damaged beans from the rest. In fact, arabica is sometimes called “washed” coffee, simply because it’s a better quality product and superior beans tend to undergo wet processing. Unlike the dry method, the outer layers of the cherry are removed (hulling) no later than 24 hours after harvest. The reason is that the skin is much harder to take off later, which could also result in damage to the beans. Once separated, the beans are washed in water, a process which filters out any inferior and unripe examples. The green coffee beans are left to ferment in tanks for up to 36 hours, then they are dried in exactly the same way as the dry-processing method.

Both of these procedures greatly influence the taste of the resultant coffee. Dry-processed coffee tends towards a more chocolatey taste, whereas wet processing highlights flowery and fruity tones.

The stage of hulling is when all the outer layers of the dried cherry are stripped off at once by a hulling machine.

After processing, coffee beans are sorted by quality and size, and packed in 60 kg jute sacks. They’re usually transported by ship, the best-known ports in Europe for handling the commodity being Hamburg and Trieste. Coffee’s sold according to variety, amount and quality.

Green beans are still very hard and have no typical coffee smell. The final step is to roast the beans in order to bring out the taste and aroma desired.

Roasting

Green beans are poured into the roaster and turned evenly in a large drum, enabling the entire load to be roasted equally.

During the roasting process the beans increase in size but fall in weight, because the water within them evaporates. Each “roastery” has its own idea of what the ideal temperature for roasting is, but it typically ranges between 200–240°C for a minimum duration of fifteen minutes. The actual length of time is crucial to the eventual flavour of the coffee. A light roast gives are more marked, sour taste. When coffee’s roasted to a medium extent, it’s chocolate tones that are obtained. Longer, darker roasting leads to a more obvious bitter taste.

Subsequently, the roasted coffee has to be left for a while as various gases are still present and these need to be released from the beans. Finally, it’s either sent onto customers as a single variety or the beans are blended with others to create a defined variety. Blends possess a very complex and fine taste profile, whereas single varieties always have a highly specific flavour.


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