Coffee is one of life's great gastronomic pleasures. The flavours, the aroma and the body combine to produce a drink that, to its devotees, is deeply and utterly satisfying. Like wine, also made from the fruit of a plant, the exact taste experience is determined by a whole series of variables, of which variety, country of origin, post-harvest preparation and roasting are perhaps the key elements. Care and skill are needed at all stages.
Where
It is widely agreed that the Horn of Africa, in the area of modern-day Ethiopia, is the origin of Coffee Arabica. The first written record of coffee is in the 10th century and widespread cultivation spread to the Yemen in the fifteenth century. From here it was exported throughout the Arab world via the port of Moccha, the name of which is now firmly associated with coffee. Its popularity didn't sweep through Europe, via the Levant and Venice, until the seventeenth century. It was about this time that the first viable seed was taken - probably illicitly - to start cultivation in India and then the Dutch East Indies and thus spread coffee growing throughout the tropics.
Coffee is now one of the world's most valuable primary products in the international commodity markets and it is estimated that it provides an income for tens of millions of people. It is produced in over 50 countries which, since it is a tropical plant, are grouped on either side of the Equator between 25°N and 25°S. The eight largest exporters are, in descending order:
Brazil, Vietnam, Colombia, Indonesia, Guatemala, Peru, India and Ethiopia.
There are two main groups of coffee, robusta and Arabica, within which there is a wide range of varieties and qualities. Robusta is higher yielding and grows well in hotter and more humid conditions and is generally found at lower levels, below 800 metres. It is generally considered a coffee for use in mass blends although it is often used in small quantities to provide a particular note within an espresso blend. It has a higher caffeine level (see later).
Arabica flourishes best at altitudes of up to 2000 metres and it is generally held that the higher the altitude, the finer the coffee. It is these origins which provide the speciality and top quality coffees, often traceable to a single farm or estate, from which home-roasters will make their selection.
Despite these broad generalisations, it is worth remembering that within the confines of the tropical belt, coffee will grow in different climates, altitudes, and soils. These wide variations are the primary reason for the infinite variety of beans and the brew they make.
How
The coffee tree is an evergreen which can grow to over 10 metres high. However, it is normally pruned to a height of 2-4 metres to aid harvesting and to make it possible to grow in the shade of other trees such as bananas. This mixed cropping is typical of smaller family holdings and is referred to as "shade grown" although much high quality coffee is grown in open coffee gardens.
The tree starts to bear fruit after four or five years. This is heralded by the appearance of fragrant white blossom, followed by the appearance of green cherries which start to ripen towards a deep red. Each cherry consists of a soft and sugary pulp within which are two seeds which are the coffee beans.
Like the lemon, the tree can bear flowers and cherries at the same time and the cherries ripen at different times throughout the year. This means that for quality hand-picked coffees, the same tree must be visited regularly through the year in order to pick at just the right time. Since one kilo of roast coffee requires about 5000 berries, it is salutary to realise how much labour is required.
Processing
There are two traditional routes to preparation of the ripe beans which will eventually produce the ready-to-roast green beans offered by Green Coffee Ltd:
In the dry method (also called the "natural method"), the cherries are placed on terraces or patios (or sometimes on racks which allow air to circulate) to dry in the sun and wind. They are turned several times a day to ensure even drying and covered in the evening to protect against moisture. When they are eventually so dry that the beans rattle inside the dried cherry, they are mechanically separated. They are generally regarded as producing a sweet coffee from the prolonged contact with the sweet pulp during drying.
The wet (or "washed") method is only possible where copious clean water is available. The outer pulp is first removed mechanically and the undried beans are then steeped in fermentation tanks for up to 36 hours. This process changes the acid structure of the beans and needs to be tightly controlled to produce exactly the required enhancement of taste. It is stopped at the right moment by washing and drying in the sun. This method produces a pleasant acidity to the coffee.
A third method, the "pulped natural", is a relatively new hybrid method, used mainly in Brazil. The outer pulp is removed, as in the wet method, but the underlying silverskin is left on and the beans are not fermented. They are then dried with the silverskin on and this results in a cup that delivers a balance between the characteristics of the two more-widely used methods.
Coffee Roasting
Roasting is a process where heat triggers a series of physical and chemical changes to a green bean that starts off as neutral as wet cardboard and is transformed into a headily aromatic and flavoursome delight.
The first part is the drying phase. The green bean has a moisture content of up to 14% and its presence helps to conduct heat to the centre of the bean. As the temperature exceeds 100°C, the water is driven off and the cell structure starts to become hollow.
As the bean temperature rises to 130°C, the colour starts to change from green to yellow and how quickly and evenly this happens is very variable from type to type. At this point the first aroma develops, similar to toast or popcorn.
The volume of the bean also starts to increase, largely caused by the internal pressure of the water evaporating. The centre cut opens and the beans eventually start cracking from the release of tension. This point is called "first crack" and it is audible as a sort of clicking sound even above the airstream noise of the i-Roast home roaster.
At around this time, as the temperature reaches 140°C, carbon dioxide is produced in the bean. It is this gas, held within the structure of the unground bean, that partly accounts for the better keeping quality of whole roast beans over ground.
At around 150°C, the beans start to darken further. Sugars start to caramelize and aroma development speeds up. Acids, of which thirty-four have been identified, are generally reduced by roasting but some increase up to a medium roast. At around 170°C, volatile oils start developing. Although only a tiny fraction of the total weight, they are major contributors to the character of coffee and have been shown to have more than 800 constituents.
At over 190°C, there is the likelihood of a "second crack" as pressure in the bean again builds up. You may find that you prefer a lighter roast that, with some beans, may need to be finished before second crack. It is now that you will have to use your judgement as to the optimum roast that you are targeting for that particular coffee. Smoke can be seen and at 210°C the beans will start to carbonize and the coffee oils will migrate to the surface giving a shiny appearance which is characteristic of Naples-style roasts. Much further along this road will lead to a roast which kills any of the subtle flavours to be found in high quality beans.
The roasting needs to be finished with a cooling phase in order to prevent continued and uncontrolled roasting from retained heat: this is automatically included in the programme of the i-Roast.
The coffee can be drunk immediately after roasting but a further 24 hours of resting allows the flavours to develop and settle down.
The Perfect Cup
The method for making the perfect cup is the one that you prefer. We find that the humble cafetière is the method that best allows the coffee to express its personality but recognise the intense devotion of espresso makers.
We would only add that the right grind is important. While whirly-blade cutters do the job, they produce a widely variable particle size within a single batch. A decent burr grinder is a worthwhile investment to provide a consistent texture to get the best out of your method of coffee preparation.
 | Hearthware i-Roast
Home Coffee Roaster |
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 | Dualit Conical Burr
Coffee Grinder |
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| + + 3 | packs of green beans |
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