Coffee is a tropical plant which grows between the latitudes of 25° N. and 25° S. but requires very specific environmental conditions for commercial cultivation. Temperature, rainfall, sunlight, wind and soils are all important, but requirements vary according to the varieties grown.
Ideal average temperatures range between 15 – 24° C. for arabica coffee and 24 – 30° C. for robusta, which can take hotter, drier conditions but does not tolerate temperatures much below 15°, as arabica can for short periods. All coffee is easily damaged by frost, a danger either in southern Brazil or, closer to the Equator, at altitudes around 2000 metres.
In general, coffee needs an annual rainfall of 1500 to 3000 mm., arabica needing less than other species. The pattern of rainy and dry periods is important for growth, budding and flowering. Rainfall requirements depend on the retention properties of the soil, atmospheric humidity and cloud cover, as well as cultivation practices.
Whereas robusta coffee can be grown between sea-level and about 800 metres, arabica does best at higher altitudes and is often grown in hilly areas. As altitude relates to temperature, arabica can be grown at lower levels further from the Equator, until limited by frost. All coffee needs good drainage, but it can grow on soils of different depths, pH and mineral content, given suitable applications of fertilizer.
Wind-breaks are sometimes planted to protect coffee plantations; shade trees, which may be economic crops such as bananas, are a common feature and mimic the natural habitat of coffee.
All food products possess characteristics which are related to their state, aspect or appearance such as weight, volume, size, shape, colour, solubility, moisture content, texture, etc. Coffee is no exception. From the tree to the cup, the various physical characteristics of coffee in its different forms play an important part in the way it is treated and in the design of equipment to process it. Coffee is harvested when its red colour indicates that the appropriate maturity has been reached. Later on, colour is a guide to the degree of roast of the beans. Flotation or winnowing is used to physically separate defective cherries on the basis of density and to remove twigs and stones. Size, shape and colour are used to grade beans after they have been dried to an even moisture content for storage. Because coffee beans have a porous, spongey texture, they can easily be contaminated by microscopic fungi, giving rise to off-flavours, or pick up strong odours, and deteriorate rapidly if allowed to become too moist.
Coffee is a natural product and therefore variable, but some typical physical properties of coffee are listed below:
|Wet green beans||
|Dry beans or pergamino||
|Light roast beans||
|Dark roast beans||
|Coarse ground coffee||
|Fine ground coffee||
Wet process: 550lb fresh cherry – 225lb wet pergamino – 120lb dry pergamino – 100lb dry polished coffee
Dry process: 550lb fresh cherry – 200lb dry cherry – lOOlb dry polished coffee
Roasting causes on average a 16% loss in weight and an increase in bean volume of 50-80%.
Fresh cherry: 50%
Green bean: 8-13%
Roast coffee: < 7% (depending on humidity)
Soluble powder: < 4%
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