The world's favourite drink

by Peter L. E. Jones

Foxy, stinker, earthy, pulping, liquoring... These strange expressions are just a few of the many fascinating terms used by coffee growers and producers all over the world. There is a good chance that you drink and enjoy coffee every day, but what do you really know about the world's favourite drink?

Arabica coffee trees, the first variety known to man, were originally discovered by travelling Arabs on the cool high plateaus of Ethiopia (Abyssinia). These produce a much soughtafter, mild-tasting drink. Robusta, on the other hand, is a native of the hot humid forests of western Africa. It is, as the name suggests, a more robust coffee containing a much higher cluantity of caffeine than Arabica. Robusta is used mainly for instant coffee. Nowadays, both types of tree are cultivated woridwide - in the Americas, Africa, Asia and Oceania.

Wild coffee trees can grow up to ten metres tall but most cultivated trees are pruned to grow no more than head height. Any taller, and picking the ripe clusters of bright red cherries at harvest wouid prove difficult. The sight of an Arabica coffee plantation at flowering time is one that is never to be forgotten. The trces, which are evergreens, are laden with white blossom and the air is filled with the perfume of jasmine. In most places where coffee is grown, harvesting the cherries is a family affair with neighbours also helping to gather the crop. Children are often excused from school to help with the cherry picking.

Pulping is the first of many processes to which the coffee bean will be subjected before becoming the fragrant and aromatic drink that so many people enjoy. This is carried out on the estates by machines dmigned to remove the sweet, pulpy substance found inside the cherries. What remains is two seeds, although these do not yet resemble the coffee beans that most of us are familiar with. Two more skins have to be removed, but first, the seeds have to be dried. This is done on long drying tables which can be seen set up around the houses in the mountainous villages where Arabica coffee is grown. The golden coffee beans are spread out to, dry in the sunlight, before the onset of '' the rainy season. Over a period of several days, the beans lose most of their moisture and the golden outer casing becomes loose and brittle, like parchment in both colour and texture: hence the term parchment coffee which is used to describe the dried beans at this stage.

Some coffee farmers prefer to pulp their own cherries at home on a small hand or engine-driven drum pulper. Others take their crop to a central pulpery. This will use a much larger disc pulper which is usually owned by a cooperative group formed and run by the farmers themselves.

Ideally, the cherries shouid be pulped on the same day they are picked. Failure to do so can produce a smelly, fermented coffee bean known as a stinker. A professionai coffee taster, known as a liquarer, wouid detect the presence of a stinker in a brow immediately. Only one stinker in a whole sack of perfect beans is enough to contaminate the batch. As stinkers adversely affect the taste and smell of the final cup of coffee, they have the effect of greatly reducing the price offered to the farmer at the coffee auction.

The drying complete, the coffee farmer can now arrange for his parchment coffee to be sent to the factory for milling. This is usually done by lorry with the vehicles often having to negotiate difficult roads. In many areas, the heavy tropical rains will have bequn, making the journey even more hazardous. Once delivered to the mill, the parchment coffee will be weighed, recorded and stacked, awaiting the milling process.

If you grind a handful of parchment beans in your hands, the 'parchment' comes away easily. You will then see that the beans are covered with yet another skin - this time, a fine, transparent membrane - which isn't so easy to remove. This is called the silverskin. The main purpose of the milling process is to remove the parchment casing and the si~verskin membrane.

Later, the same factory will grade the newly-milled coffee beans according to their size and weight.

Broadly speaking, the larger and heavier the bean, the better the price it will make at auction. Before the milling process can begin, however, the parchment coffee has to be cleaned by special machines that remove all 'foreign' matter. Stones, nails, string and even pieces of metal can mysteriously find their way into the sacks - making them weigh heavier when delivered to the coffee mill weighbridge!

Once cleaned, the coffee beans are ready to be hulled - the process whereby the parchment casing is removed. This is done by centrifugally impacting the beans inside a machine rotating at high speed. The casings are discharged like flying cornflakes, blown from the mill by huge fans. Utilising friction, a machine called a polisher is then employed to rub off the silverskins. What then emerges is the familiar 'naked' coffee bean, now referred to as green coffee. Good quality green coffee has an intense green-khaki lustre. It is very hard to bite and has a bitter taste.

Grading - from ‘elephant' to 'peaberry'

The beans are then graded according to size, a process which involves passing them over vibrating or rotating screens and allowing them to fall through holes of differing size. There are five categories: 'E' which stands for elephant followed by 'A', 'B' and 'C' in order of diminishing size. The fifth grade is 'PB' which stands for peaberry. A peaberry is a misshapen coffee bean in which the two seeds appear to have grown together. They are, nonetheless, capable of producing a fine cup of coffee.

The final stage at the milling factory is where the coffee beans are graded according to their weight. The principle is elementary. A simple machine allows the coffee beans to work their way along an angled and rapidly vibrating surface known as a gravity table. Due to their weight, the heavier beans vibrate up the table and fall through a collecting duct at the top. Medium weight beans follow in the same direction but, unable to make it to the top, they fall off to be collected at the mid point. The lighter beans move downwards to be collected at the bottom of the gravity table. The graded beans are collected and transferred by three conveyors to large storage silos.

Buying orders based on sample coffee sent to the auctions follow shortly afterwards. Specified lots of green coffee are then bagged as ordered, ready for export overseas. Sometimes, a buyer will ask the factory to bulk together different grades of beans before bagging them, to meet a specific customer's requirements.

Every coffee mill has a quality control department known as the liquoring room. Here, samples of coffee are roasted and ground to be infused into a black, sugarless brew. This is tasted (and spat out) by professional liquorers who are responsible for determining its quality.

Most coffee mills do not undertake the commercial roasting and grinding of coffee beans. Generally, the green coffee is exported for further processing at a factory in a different country.

In the international commodity league tables, coffee comes second only to oil. Throughout the world, the industry employs more than 20 million people. And more than four million tonnes of coffee is consumed every year - proving that coffee is still the world's favourite drink. P.L.E.J.