|
The coffee plant is a tree that belongs to the gender Coffea. There are more than 60
different varieties of coffee, but for trade purposes the Coffea Arabica (Arabica) and
Coffea Canephora (Robusta) are the most important.
Appearance
In some parts of Africa, the coffee tree still grows in the wilderness, mainly at the
Ivory Coast, Uganda and Zaire. Depending on the type, the coffee tree can reach a height
of 10 to 15 metres. On the plantations, however, continual pruning prevents the trees from
growing taller than 1.5 to 3 metres. This ensures a high yield and makes harvesting
easier.
The tree's leaves are broad, dark green and shiny, similar to those of a camellia bush.
The blossoms are white, star-shaped flowers and resemble the flowers of the Jasmine tree
in fragrance, colour and appearance.
Harvest
Trees blossom over a six- to eight-week period in countries such as Brazil and Mexico. But
in countries located along the equator, such as Kenya and Colombia, a coffee tree can have
blossoms, ripening fruit and mature berries (called cherries) on the same branch at the
same time. Pickers must go over the trees again and again to pick only perfectly ripe
berries. Because harvesting is so labour-intensive, it's one of the most expensive steps
in coffee processing.
The time span between the blossom and the harvest generally covers eight to nine
months, depending on the altitude and prevailing weather conditions. Coffee trees produce
for about 20 to 25 years, yielding about 2.000 beans a year, which is about one kilogram
of raw coffee per year. With modern cultivation methods the harvest in a good year lies
between 3,000 and 4,000 kg per hectare.
Green coffee
The coffee bean is the seed of the berry. It resembles a cranberry and has a sweet pulp,
protected by a membrane called parchment and a silky thin membrane called silverskin.
Coffee beans are actually the two flat-sided seeds inside the cherry. Unprocessed coffee
is called green coffee.
Coffee grows exclusively in tropical and sub-tropical regions. The present
coffee-producing belt around the globe comprises about 70 countries involved in
cultivation, and lies between the latitudes of 23 degrees north and 25 degrees south. The
ideal growing conditions for coffee trees are an average of 17 degrees Celsius to 23
degrees Celsius as well as abundant precipitation and fertile soil.
Countries
Brazil is the world's largest coffee producer. On average it produces around 28 percent of
the total world output. Colombia follows second with about 16 percent, third lies
Indonesia with around seven percent, and fourth Mexico with about four percent. After that
a number of countries follow that only contribute between three percent and less than one
percent to world coffee production.
Altitudes
The altitude at which a coffee is grown plays a major role in determining the quality of
the bean. Because there is less oxygen, coffees grown at higher altitudes take longer to
mature than plants grown at lower altitudes. This allows the flavours to develop more
fully and produces beans that are delicate and flavourful. Higher-grown coffee beans
usually have a higher density than low-grown beans, which enhances the complexity of the
coffee flavour profile.
Most Central American coffees are graded by altitude.
Altitude Bean Type:
- above 1.600 metres Strictly Hard Bean
- 1.350 - 1.600 metres Hard Bean
- 1.200 - 1.350 metres Semi Hard Bean
- 1.000 - 1.200 metres Extra Prime Washed
- above 600 metres Prime Washed
Growing conditions
The coffee plant is selective about growing conditions. Coffee trees can't tolerate
weather that is too hot or cold, or too wet or dry. They need direct sunlight, but only
for a few hours a day - about two hours a day is ideal.
Wild coffee in Ethiopia grows in rain-forest mountains where taller trees shelter it
from the sun's burning rays and low-growing plants serve as mulch. Farmers try to mimic
those conditions by planting fruit trees between coffee trees to provide shade, mulch and
an alternative crop. Other growers build protective trellises or plant their groves on
hillsides that only receive a few hours of sun per day. Coffee plants thrive in fertile
well-drained soil.
Enemies
The most feared enemy of the coffee plant is leaf rust; a mould that infects the leaf and
makes it turn brown and black and eventually fall off. Other enemies are insects: lice and
caterpillars. Another constant threat comes from the weather conditions: hail, storm,
heavy rainfall, drought and frost can be fatal.
The various types of coffee are distinguished by the variety and origin (highland or
lowland), the flavour and the aroma. Arabica is a well-flavoured, aromatic coffee with
less caffeine than Robusta, which has a somewhat unrefined, earthier taste.
Highland and lowland coffee
Highland coffees have a particularly fine aroma and are cultivated on plantations at an
altitude of 600 to 1,800 metres above sea level. Lowland coffees have a different flavour
and originate from plantations at lower altitude. In general the higher the altitude, the
more superior the quality of coffee produced. However, this is not always the case, since
plantations at lower altitude can also produce very good quality coffee.
Arabica coffee
Arabica is the oldest species of bean and is the most widely cultivated, accounting for 74
percent of the beans grown in the world. Arabica beans grow at altitudes between 600 and
1,800 metres above sea level and take six to nine months to mature.
The Arabica beans command a higher price on the coffee market because growing coffees at
higher altitudes is more expensive and labour-intensive. Arabica beans fall to the ground
soon after they ripen, so they must be harvested as soon as they are ripe to prevent them
from spoiling or absorbing flavour taints from the ground. High-grown coffees are also at
risk of frost damage, so farmers tend to build plant replacement costs into their prices.
Production costs are higher since most Arabicas, especially those grown at the highest
altitudes, are hand-picked and processed in the more expensive wet method.
Robusta coffee
The Robusta plant was discovered in the 1870s, growing wild in the Congo. About 26 percent
of the world coffee trade consists of Robusta beans. Robusta today is mainly cultivated in
West Africa and Southeast Asia. Robusta trees are very hearty plants that grow at lower
altitudes (sea level to 600 metres) and are more cold- and moisture-tolerant and
disease-resistant than the delicate Arabicas. Robustas mature in about half the time
of Arabicas and yield almost twice as many berries.
Unlike Arabica beans, Robusta beans do not fall off the tree when they become ripe, so
they don't need immediate harvesting. Robustas are also used for commercial, canned and
instant coffees. Because they are cheaper to produce, Robustas are sometimes combined with
Arabicas to make a low-cost blend with some of the flavour characteristics of the more
expensive Arabica beans.
The cultivation, care and harvesting of coffee is extremely labourintensive.
It begins with the sowing. Coffee seeds will only germinate if sown within the eight
weeks following the harvest. They are sown one to two cm deep in specially constructed
beds.
After five to eight weeks the tiny plants reach the surface. As soon as the first pair
of leaves appear, sometimes even sooner, the seedlings are transplanted to special foil
planting bags, so called polycovers, or often to peat pots. They are then set 20 to 25 cm
apart in large, predominantly shaded beds.
Six months later the young plants are 30 to 50 cm tall. At this stage they are
transplanted to their final place in the coffee plantation, now at a distance of one to
three metres apart. Here, the plants are usually protected by Guamos, trees which shade
the plants from intense sunlight.
The newer varieties of coffee tree begin to bear fruit from the third or fourth year
and go on to produce an optimal crop for ten years. Older varieties produce their first
harvest after five years, but continue to produce maximum crops for 25 years.
Around nine months after the flowers appear, the berries are ripe and can be harvested.
Harvesting is mainly carried out by hand.
The main harvesting season lasts around four months for Arabica coffee, and for Robusta
coffee a little longer. In some countries, however, there is no standard harvesting season
because of the significant climatic and geographical differences. In Colombia for example,
harvesting continues throughout the year.
There are two reasons for the length of the main harvest of Arabica coffee, which can
last for up to four months. Firstly, the speed at which the coffee berries ripen varies
from tree to tree. And secondly, the coffee tree is unusual in that blossom, unripe and
ripe berries can all be found on the same branch.
There are three methods of picking:
- Hand-picking (also called selective picking)
- Strip-picking
- Mechanical harvesting
Hand-picking
Higher quality Arabica beans are almost always hand-picked. Allthough this is a more
expensive method of harvesting, it ensures that only ripe, high quality berries are
picked. The workers go between the trees and selectively pick only the cherries that are
at the peak of maturity. Hand-picking is the most labour-intensive harvesting method.
Coffee cherries are at their peak for only a few days before they turn overripe, so
workers must go over each tree many times. On a single day a coffee picker harvests
on average between 50 and 100 kg of coffee berries.
Strip-picking
In Brazil, and for the Robusta coffees cultivated in Africa and Indonesia, the coffee
berries are not picked individually. Here, the pickers strip the branch of all the
berries, both ripe and unripe, with one sweep of the hand. The berries, together with torn
leaves and twigs, fall on the ground beneath the trees, onto large cloths, from which the
harvest is later gathered. This method of harvesting is used for cheaper, commercial
Robusta beans and causes some of the flavour taints associated with lower quality coffees.
Mechanical harvesting
On large plantations in Brazil harvesting machines are sometimes used, which shake all the
berries from the tree.
The two coffee beans make up only one third of the coffee berry, the rest consisting of
fruit flesh (also known as pulp), skin and husk, all of which must be removed so that only
the green beans remain.
Two different methods of processing the coffee beans have now been adopted worldwide:
wet processing and dry processing.
- Wet processing
Wet processing, whereby the beans are washed, is mainly employed in Central America
and parts of Africa (notably Kenya). This process is relatively expensive, but is
beneficial to the quality of the coffee. The berries are first fed through a water channel
to soak them and to remove any impurities. The unripe berries sink to the bottom, leaving
the ripe fruit to float to the top. The ripe berries can then be processed further. The
fruit flesh of the berries is removed with the help of a 'de-pulper', a machine that has a
roller with a roughened surface. This scours away the fruit flesh (pulp) from the berries
under a stream of water. Previously, the remaining pulp was treated as waste, but nowadays
it is blended with minerals and turned into fertiliser.
In the second stage of wet processing the coffee beans are fermented in large water
containers. The object of the fermentation process is not only to dissolve any
remaining fruit flesh, but also to remove the sticky film surrounding the coffee beans,
which is not water soluble. This part of the procedure, which lasts approximately
two days, is very important. The long period of fermentation is what first gives the
coffee its rich aroma and special flavour.
Washing
On completion of the fermentation process the coffee beans have to be washed. At this
stage, the beans are still surrounded by their parchment husk, and for this reason the
coffee is also referred to as 'parchment coffee'.
Drying
The washed parchment coffee is then spread out on concrete slabs or drying racks and left
out in the sun. To ensure that the beans dry evenly they are turned over several times a
day. Depending on the weather conditions, this process takes five or six days. Cultivators
operating on a medium to large scale make use of drying machines, huge metal drums inside
which hot air circulates. Again, to ensure that the beans dry evenly the drums rotate
continually. In the drums the drying process lasts about 24 hours. Dried parchment coffee
has an attractive golden yellow colour and is known as pergamino coffee.
At this stage the work of the coffee cultivators is largely at an end. The producer parts
with his product, selling it to a wholesale distributor and/or an exporter.
Hulling
Next the pergamino is stored in bags, before being mechanically hulled by special
machines. These peeling machines have grooved cast iron cylinders, inside which the husk
of the coffee beans is scoured away as they rub against one another.
At the end of this process the beans are generally olive green in colour. Some varieties
even have blue beans; these are the high quality so-called 'blue' coffees.
Sorting and grading
First the coffee beans are sieved to remove any foreign objects and damaged beans.
Next they are mechanically graded according to size and shape. This is followed by a
further selection process, this time carried out by trained workers. The coffee is sorted
by eye as it passes in front of them on a conveyor belt into the different quality grades.
There are also machines now that can perform this selection work.
- Dry processing
In Brazil and across a large part of Africa, dry processing is used for lower quality
Arabica and Robusta berries, a simple technique which is less labourintensive than wet
processing. However, cheaper production costs must be offset against a loss in quality,
since the length of the process (the drying of the berries) is dependent on the
unpredictable climate. Once all twigs, leaves, stones and other foreign objects have
been sieved out, dry processing can begin. Drying
The berries are spread out in the sun on cement or brick slabs in layers five to six cm
deep. To ensure that the beans dry evenly, the berries are turned regularly for a period
of two to three weeks. On smaller plantations drying mats made of wire netting are often
used.
Hulling
Once the beans are completely dry, hulling begins. In a peeling machine similar to that
used during wet processing, the dried fruit flesh (the pulp), the parchment skin and a
part of the husk that surrounds the coffee bean are removed.
Cleaning and selecting
Finally, the beans are cleaned and then sorted according to size by mechanically operating
vibrating sieves. The beans are then measured into sacks of a standard size (usually 60
kg).
The sorted coffee is packed in sisal bags each holding 60 kg (70 kg in Colombia). The
final stage in the process is inspecting the coffee. A sample is taken from a large number
of sacks. These samples are then examined, roasted, ground and separately numbered by
expert inspectors before being brewed. After the experts have examined and tasted the
samples, they deliver their verdict. The bags are given a quality seal and can then be
exported.
Grading standards
Each producing country sets its own standards for grading, and the criteria used for
grading vary from country to country. The governments of many coffee-growing countries
impose strict grading standards to maintain consistent quality and preserve the reputation
of coffees grown in those countries.
In addition, coffee is sometimes graded by the number of imperfections (stones, broken
or deformed beans, twigs, etc.) per kilogram. Less than 20 percent of beans are of high
enough quality to be considered speciality coffee.
Bulk transport
The majority of the coffee is shipped direct from the country of origin to the country of
consumption. Previously, the sacks were piled up one by one in the ship's hold, but
nowadays container transport is used. The newest form of transport is that of bulk
transport, whereby the coffee is stored loose in the container.
Storage periods
Once dried, the green coffee can be stored for about a year without appreciable
deterioration in quality. Green coffee of up to a year old is designated 'current crop'.
Longer storage times alter the quality of the coffee, as the beans become drier. They are
then marketed as 'past crop' or 'old crop'.
source: Douwe Egberts |
