A coffee bush lives for roughly 70 years and it produces 2.5 kg of berries giving 500 g of green coffee beans. This represents an annual income per tree of 0.50 Euros in the worst case and at best, 4 Euros. This is the price that must be paid to maintain the plantation, irrigate it, scatter fertilisers and fight diseases.
The coffee shrub – Coffea to botanists – belongs to the Rubiacaea family. Among the 73 existing species, only Coffea Arabica and Coffea canephora (robusta) are commercialised. Each species comprises numerous varieties with organoleptic specificities as well as different rates of production, varying from 3 to 12 tonnes per hectare.
Arabica is autogamous (a single tree can produce its own descendants), whereas canephora is allogamous (two trees are necessary to ensure reproduction). This means cross-breeding is impossible.
A sensorial analysis reveals that Arabica is more fruity and acidic whereas robusta has a smoky, fermented aroma. As is the case for wine, coffees also have “vintages”. The quality depends on several factors: the botanical species and variety, the terrain, the temperature, the altitude, the exposure, the amount of light, irrigation and wind
FLOWERS, LEAVES AND BERRIES
A coffee bush produces its first flowers when it is three years old and its first harvest after five years. Its leaves are persistent; robusta leaves are larger than Arabica leaves.
Coffee flowers look like jasmine – hence the name used in the 17th century, «Arabian jasmine», to describe the tree.
This flower grows into a fruit (drupe or berry) which ripens in 6 to 9 months. Coffee flowers twice a year but depending on the humidity level, it may flower up to 8 times, which explains why fruit at differing stages of ripening can be found on the same branches.
The berries are shiny red and firm when they are ripe, unripe berries give a bitter taste to coffee and over-ripe berries lead to an unpleasant acrid taste.
There are four methods which differ because of their precision and cost:
◦ Stripping: A twig is grasped by hand and everything is torn off in one go – ripe and unripe berries, flowers etc...
◦ Combing: a comb with wide, flexible teeth is drawn along the twig: red berries fall off and the green ones stay where they are.
◦ Mechanical: tractors gather the fruit using brushes, but this also plucks the flowers and leaves. This method is widely used in Brazil and very effective (60 tonnes per day) but it makes planting coffee bushes in the shade impossible and – like stripping – gives poor results from a quality point of view.
◦ Picking: only the ripe berries are picked by hand, one by one.
The harvest is rarely sorted. This has the disadvantage of destroying green berries which could have been left to ripen on the trees.
Once harvested, the two beans have to be extracted from the drupe where they are wrapped in a very sticky mucilaginous substance. To obtain a good quality coffee, this operation must be completed within six hours of the berries being harvested. There are two methods:
◦ The wet method, which produces excellent results because water softens, refines and reduces any defects in the coffee. However, it necessitates a large number of operations (soaking, pulp-removing, floating, fermenting, rinsing and drying) which require a lot of labour and water, which certain producer countries do not always have. This method produces “coffee parchment”.
◦ The dry method consists of spreading the berries out in the sun for 15 to 20 days on concrete, sacks or trays. This produces “husk coffee”.
«PARCHMENT PROCESSING» AND SORTING
This consists of removing the skin of the grain and sorting is necessary to remove all the impurities, defects and waste that are left after the extraction process and it also results in a homogenous coffee “lot” which will be “classed” according to the number of defective grains it contains.
The various sorting methods (measuring grains, density, colour…) are carried out by devices designed for this purpose. Grains may also be sorted by hand.
WRAPPING, STORING AND TRANSPORTING COFFEE
These are delicate operations because once coffee has dried, it has a tendency to absorb ambient humidity and odours. Even though certain natural odours are an advantage (a hint of iodine in Rio or monsoon coffee in India), others must be avoided, especially if the coffee travels with other, highly scented products such as cloves, fertiliser or other substances…
Jute sacks are the most effective means of transporting coffee. “Big bags’ with a capacity of one tonne, loose grains in a container or a tank may cause the coffee to ferment and these methods encourage “parasite” odours. The only two exceptions are Guadeloupe Bonifieur and Blue Mountain which are delivered in wooden barrels.
Diseases that affect coffee bushes are mainly due to fungi such as the hamelia vastatrix. The fungi appeared in the 19th century and destroyed thousands of hectares of Arabica plantations in India and Indonesia. Nowadays, the plants can easily be treated against fungi. “Scolytes” are also a nuisance because they attack the berries and leave the grains full of holes.