GROWTH AND HARVESTING

Coffee is an evergreen plant, belonging to the family Rubiaceae and the genus coffea. The two most commercially available varieties are the aromatic Arabica and the more full-bodied Robusta. All coffee plants grow best in equatorial regions and at high altitude- between 200m and 2000m. the climate in these regions alternate between dry and damp with moderate temperatures of between15°C and 25°C

Once the coffee beans are ready to harvest, the beans are either picked by hand or stripped from the tree by machine. Picking takes longer and is more expensive, but only the best berries are picked. Machines stripping is cheaper, but damages the trees and some unripe beans are taken into the harvest. Once the beans have been harvested, they are the processed either by the washed wet method or natural-dry method.

The wet-washed process involves cleaning, hulling, fermentation, washing, drying, polishing and sifting- which is time consuming, but produces higher quality coffee. The natural-dry method is and simpler, but a side effect is that the sugar content rises. The natural-dry method is also considered environmentally friendly.

READY TO BE ROASTED

During the roasting process, the beans are exposed to high temperatures and this changes their chemical and physical make up. The green beans swell to nearly double their  original size roasted the lower their caffeine content will be, as the oil given off during roasting contains a large amount of caffeine. There are two methods of roasting coffee- the roasting drum and the fluid layer bed. Both take between 8 and 15 minutes. The roasting drum bring the beans into direct contact with the hot walls of a metal drum, but the fluid layer roasting method roasts the beans using only hot air, which results in better uniformity.

After roasting, the beans are taste-tested for four important qualities:

1. Acidity- the beans should be pleasantly tart, but not sour.
2. Body- the relative sense of heaviness, richness and thickness.
3. Aroma- the fragrance and aftertaste of the coffee.
4. Flavour- whether the coffee is mellow or mild.

The beans must be packed within 48 hours to ensure freshness and maximum flavour. Coffee beans are packed in a vacuum, as any oxygen in the packaging can destroy the quality of the coffee.

GRINDING

After the beans have been roasted, they then move to the gridding phase either in the home or at the factory for ready ground coffee:  There are four ways to grind coffee: burr-grinding, chopping, pounding and roller grinding.   Burr-grinding uses two revolving abrasive elements, between which the beans are crushed or torn. This provides uniform grind that does not clog filters and produces great tasting coffee. Chopping uses blades spinning at 25,000 RMP to grind the coffee and is quick and effective. However, chopping produce heat which changes the flavour of the coffee slightly, it also produces a lot of fine coffee-dust which can clog filters and espresso machines.   Pounding usually takes place in a mortar and pestle, in which the coffee is ground very fine into an almost powdery consitency. This is most often done for Turkish coffee, as the fine coffee would clog filters and espresso machines. Roller grinding is achieved by grinding the beans between pairs of corrugated rollers- this is the most common form of grinding used by large- scale producers.

BREWING

Once the coffee hs been ground, it ia ready to brew:

There are various method used to brew coffee. many of these originated as coffee was introduced to new regions over time. However, all coffee brewing requires hot water to come into contact with the coffee grounds.

One of the oldest method of brewing coffee is’boiling’- a process which, despite the name, requires the grounds to be heated in water, but not actually boiled. A well- known way to make boiled coffee is the ‘cowboy coffee’ method, simply heat coarse grounds in water, then allow them to settle and pour the liquid coffee off to drink. As the name suggests, it was the method originally used by Amerirican cowboys whilst camping.

‘Steeping ‘ is another popular method of brewing coffee, with the french Press being the most notable example. When using a Press, coffee is placed in a glass cylinder and boiling water is then poured on top of it. The coffee is left to stand for few minutes (usually 4-7) and then a plunger with a filter is pushed down, forcing the coffee grounds to the bottom of the  cylinder and leaving high- quality coffee behind. Many connoisseurs still believe this is the finest way to brew coffee as none of the oils and tannins from the grounds are lost.

Using gravity is probably the most common method of coffee brewing. The are a number of machines that allow hot water to fillter down through coffee grounds. the most common of these is probably the Percolator, which uses filter paper to hold a certain amount of cofffee grounds through which water floes. the filter paper stops the grounds from passing through and the coffee is collected in a pot below.

The most modern methods of brewing utilise pressure to force hot water through densely packed coffee grounds. An espresso machine is the most common example of this- using between 800-900 kPa of pressure, water just below boiling point is forced through a’puck’ of finely ground, densely packed coffee.Coffee made using pressure often  has a very strong taste and tends to be fairly low in caffeine as the waater is only in contact with the coffee for a little while.