Agricultural and botanical aspects The two most important species of coffee are Coffea arabica (Arabica coffee) (over 70% of world production) - and Coffea canephora (Robusta coffee). Two other species which are grown on a much smaller scale are Coffea liberica (Liberica coffee) and Coffea dewevrei (Excelsa coffee).
Arabica (Coffea arabica) This is a shrub or small tree with relatively small glossy leaves and small fragrant white flowers. Arabica coffee usually receives a premium for its superior flavour and aroma. Arabica is more suited to higher cooler climates (600-2000m altitude and 15-20°C).
Robusta (Coffea canephora) There are many different Robusta varieties. In general, they can thrive in hotter lowland areas (below 900m altitude and over 20°C). Robusta coffee is preferred for instant coffee production since the yield of soluble solids is relatively high.
Liberica (Coffea liberica) This is a larger tree with large leaves and berries. It can tolerate hot and wet conditions. Liberica coffee is grown in Malaysia and in West Africa, but only very small quantities are traded as demand for its flavour characteristics is low.
Harvesting Selecting seeds Good coffee cannot be made from poorly harvested coffee cherries. Only large and fully ripe berries from disease-free, pest-free and high-yielding trees should be selected. The coffee cherries should be picked when they are bright red all over. At this stage, the bean can be squeezed out from the pulp by applying light pressure between finger and thumb. Small shrivelled, lightweight and abnormal berries or dry, over-ripe berries should not be used.
Processing There are two ways coffee can be processed - dry ('natural') processing and wet ('fermented and washed') processing. Wet processing is regarded as producing a higher quality product. The dry process, also known as unwashed or natural coffee, is the oldest method of processing coffee but it is now limited to regions where water or infrastructure for machinery is scarce.
Dry processing Drying The entire cherry after harvest can be placed in the sun for 10-14 days to dry on tables or in thin layers on concrete drying areas. Once the skin is dry, the pulp and parchment are removed from the bean. The bed depth should be around 3 cm and the cherries should be raked frequently to prevent mould-growth, fermentation or discoloration. However, contamination by dust and dirt blown onto the produce is a problem, and rain can soak the produce very quickly.