Coffee: the plant

There are several coffee tree species, but only two are cultivated: Coffea arabica, known as Arabica coffee, and Coffea canephora, or Robusta coffee. They are grown in tropical and subtropical regions, between the Tropics of Cancer and Capricorn.

Arabica is usually found at altitudes from 1,000 to 2,000m above sea level. It has a lower crop yield than Robusta, and a lower caffeine content, but it is superior in terms of taste and accounts for 70-80% of world coffee production.

Robusta is found at lower altitudes, from sea level to about 1,000m, has more robust beans, higher crop yields and higher caffeine content. However, it produces inferior beverage and accounts for about 20-30% of world production.

A few years after a coffee tree is planted, it will produce sweetly smelling white flowers.

After pollination, a fruit - called a coffee cherry - will grow and change in colour from green to red (in some cases to yellow) in about 30-35 weeks after flowering. Each fruit will usually contain two seeds - coffee beans.

COFFEE HARVESTING AND PROCESSING

Coffee is harvested when the cherries are bright red and firm, either by hand or by using a harvesting machine (mainly on big farms in South America).

After picking, coffee is processed in one of the three ways:

Dry (or natural) method: harvested cherries are spread out to dry in sunshine, until their moisture content has fallen to about 11% and the outer shell of the cherry turns brown and dry. Coffee processed this way is usually heavy in body, sweet, smooth and complex.

Wet method: the pulp of the cherry is removed from the beans within 24 hours of harvesting by washing and pulping. The beans are then put into fermentation tanks for 12 to 48 hours, and are dried afterwards either by the sun or in mechanical driers. Coffee processed this way is usually cleaner, brighter and fruitier, retaining more acidity.

Pulped natural method: coffee is pulped but fermentation stage is omitted and the beans are dried quickly instead, while still covered in sweet mucilage. These coffees have characteristics of both dry- and wet-processed coffee: they are usually sweeter than wet-processed coffees, have some of the body of dry-processed coffee, and also retain some of the acidity of the wet-processed coffee.

Once the beans are dried, all of the remaining outer layers are removed from the beans in the process of hulling. Beans are then graded and sorted, by size and by density.

Coffee is shipped as green coffee, usually in jute or sisal bags. From every 100kg of coffee cherries harvested, about 12 to 20kg of export-ready green coffee will be produced.

Back to Coffee essentials in the Learning section.

(Photos © Mercanta Ltd)