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Coffee – Coffea arabica, Coffea canephora



COFFEE TAXONOMY

Coffee is a member of the Rubiaceae or Madder family. Coffee is by far the most economically important species, but a number of ornamentals derive from the family, notably gardenia (Gardenia), madder (Rubia), patridgeberry (Mitchella), and ixora (Ixora). Of the 25-100 species in the genus Coffea (the number is still debated), two main species are used in production: C. arabica L., generally called “arabica” coffee, and C. canephora Pierre ex Froehner, called “robusta” coffee. About 70% of the world’s coffee is derived from C. arabica, considered to have higher quality than robusta.

Coffee fruit is largely harvested by hand. The coffee seed is easily squeezed out of the fruit with a pinch of the fingers after the fruit turns from green to bright red (the ripening process takes about two weeks). The seed from the coffee fruit is what you know of as a dried coffee “bean.” What you see in the picture is the natural color of two dried coffee “beans.” It is only after roasting that they take on their familiar brown and black colors.

Cultivars
Cultivars of Coffea arabica were derived from two botanical varieties, bourbon and typica (syn. arabica). Bourbon is more slender in habit than typica, has smaller beans but higher yield, resists coffee berry disease better, and lacks the bronze cast of the new foliage. Today, a plethora of modern cultivars, derived from typica and bourbon, are now grown in greater quantities than the originals, and the botanical variety designation lacks utility outside of breeding.
Similar to arabica, there are two botanical forms of C. canephora: robusta, an upright growing form, and nganda (also called Kouillou), a spreading form. Once again, the utility of retaining these botanical form designations is questionable, as 90% of cultivars grown today are erect forms stemming from robusta.

ORIGIN OF COFFEA ARABICA AND COFFEA CANEPHORA, HISTORY OF CULTIVATION

Coffee is an understory shrub or small tree native to tropical Africa. C. arabica is native to the highlands of southwestern Ethiopia, whereas C. canephora is native to the lowland forests from Liberia east and south to Kenya and the Congo basin. The word “coffee” may be a corruption of Kaffa, the province of Ethiopia where C. arabica originated and may have been domesticated. Coffee fruit may have been eaten in the native area, but the beverage was a much more recent invention. Coffee seeds were transported to southern Arabia (modern day Yemen) as slaves were taken from the Sudan region to Arabia around 600 AD. The Arabs are credited with the discovery of the beverage coffee from roasted seeds as we know it today, although it is unclear how far in advance of the 15th century that this occurred. Today, coffee is grown by an estimated 25 million small farming families in many tropical countries worldwide. In some countries, coffee receipts account for 80% of foreign trade earnings.

WORLD AND UNITED STATES COFFEE PRODUCTION

World (2004 FAO) – 7,719,600 MT or 17.0 billion pounds of dried, green (not roasted) coffee beans. Coffee is produced commercially in 82 countries worldwide on over 25 million acres. Average yields are 684 lbs/acre.

 

Top 10 Countries
(% of world production)
1. Brazil (25%) 6. Mexico (4%)
2. Colombia (9%) 7. Ethiopia (3%)
3. Vietnam (9%) 8. Uganda (3%)
4. Indonesia (8%) 9. Cote d’Ivoire (3%)
5. India (4%) 10. Honduras (2%)

Coffee is the 2nd most traded commodity in the world after oil. Since the early 1990s, the retail value of the coffee industry has more than doubled to US$70 billion, while the export earnings of coffee producing countries has been cut in half, to only $5.5 billion in 2004. Four countries – the USA, Germany, France, and Japan – consume over half of the world’s coffee.

United States (2004 USDA) – 3954 MT or 8.7 million pounds. All coffee is grown in Hawaii on about 5900 acres. The industry value is $23.5 million, as Hawaiian growers enjoy prices several-fold above the world average at $2-3/lb. Yields are double the world average at 1500 lbs/acre.

For the most up to date statistical data on United States and World production numbers please refer to the following two websites:

World: The Food and Agriculture Organization of the United Nations Statistics Division (FAOSTAT). FAOSTAT

United States: The United States Department of Agriculture National Agricultural Statistics Service (USDA Ag Stats). USDA Ag Stats

BOTANICAL DESCRIPTION

Plant
A small, evergreen tree, reaching 30 ft in the wild, but generally maintained 6-8 ft in cultivation. Leaves are ovate, 3-8″ long, dark green, prominently veined with interveinal areas raised, waxy and smooth with entire margins. Leaves are arranged oppositely on stems and decussate, with successive pairs of leaves arising at 90° angles from each other around the stem. Leaves live about 1-2 years.   

Flowers
Flowers are white, fragrant, ½ – 1″ across, with 5 linear petals fused into a slender tube at their base. The ovary is inferior, bicarpellate, and capable of producing 2 seeds. There are 5 stamens and a 2-lobed stigma extending beyond the floral tube. Flowers are borne in highly compressed, head-like racemes of 2-4 flowers each. Up to 20 individual flowers form per axil, yielding a profuse, white cluster of flowers at each node. C. arabica flowers only on previous-season’s growth, whereas C. canephora flowers on current season’s growth.

Pollination
Coffea arabica is self-pollinating, whereas C. canephora is self-incompatible and must be cross pollinated. Flowers of both species are wind and insect pollinated.

Fruit
An epigynous berry. Coffee fruit are often called “cherries” and erroneously considered to be drupes. Fruit are ½ – 3/4″ long, ovoid, and borne axillary in clusters on growth from the previous season (arabica) or current season (robusta). Two ovoid seeds are found in each fruit, with flat sides facing each other; seeds occupy the bulk of the fruit volume. Single-seeded fruit occur, and are called peaberries. Fruit mature in 6-11 months, depending on species, cultivar and climate.


GENERAL CULTURE

Soils and Climate

Soils – coarse volcanic sands to loamy alluvial soils, light textured, well-drained volcanic soils with slightly acid pH (5.0-6.0) are best, cannot tolerate flooding, and develops nutrient deficiencies at extremes of pH.
Climate – both arabica and robusta are killed or severely injured by light frost. Neither require any chilling

One of the unique aspects of coffee is its cultivation with some degree of shade, stemming from its origins as an understory plant. Almost all other fruit crops are grown in full sunlight (cacao is also shade-grown). However, coffee can be grown in full sunlight, and often is in large plantations where the focus is on high yield. Sun-grown coffee will out-yield shade-grown if fertilized more heavily. Small coffee growers who lack access to such inputs achieve moderate yields with minimal chemical fertilizers, but must maintain the shade crop as well as the coffee. Measurements have shown that shade trees reduce evapotranspiration (hence water use) of coffee by 25-50%, while intercepting only 3-13% of incident rainfall. Shade coffee is regarded as more sustainable by some, and promotes greater on-farm biodiversity.

Shade grown coffee. Eucalyptus trees used for shade in a planting near Buenos Aires, Costa Rica.

Sun grown coffee in Costa Rica. A planting near Turrialba that had Erythrina shade trees, but was converted to a full sun plantation by severely pruning the Erythrina.

 

Propagation

Arabica is generally seed propagated; cuttings are used for robusta propagation. Scions of arabica or robusta can be wedge grafted onto robusta seedling rootstocks when both are just recently germinated, prior to cotyledon expansion

Rootstocks
When used, rootstocks are generally a robusta cultivar since this species is more resistant to nematodes and disease.

Planting Design, Training, Pruning
Planting Design – Arabica coffee 4-8 ft in rows 8-10 ft apart, yielding plant densities of 500-1300 trees/acre; dwarf cultivars 2000 trees/acre, particularly in high-input systems. Robusta coffee 6-8 ft x 12-13 ft (about 350 trees/acre). Terrain is often hilly in highland areas suited to arabica coffee, and rows are thus laid out on contours. Shade trees may be planted in regular rows, periodically within every other or every third coffee row, or scattered throughout the planting. Leguminous trees are most frequently used since they fix nitrogen. Trees are pruned severely every 4-7 years to renew fruiting wood and keep height down.

COFFEE HARVEST, POSTHARVEST HANDLING

Maturity
Individual fruit turn from green to completely bright red and glossy over a period of 1-2 weeks when mature. The seeds are easily squeezed from mature fruit by moderate finger pressure.

Harvest Method
Coffee is largely hand harvested.

Postharvest Handling – Dried coffee “beans” are obtained from the fruit by either dry or wet processing.

Dry Processing. In the dry method, seeds are dried while still in the fruit, which is why under- and over-ripe fruit can be accommodated. Harvested fruit are sun-dried on benches or on concrete coffee yards, and later hulled by machine.

Wet Processing. Ripe fruit are dumped into a tank of water, where debris is removed and poor quality fruit is floated off. The good fruit sinks and is moved by a stream of water to a pulping machine. Pulping machines rub off the skin and some of the mesocarp by forcing fruit between a rubber strip and a perforated rotating drum. The expelled fruit still have mucilagenous pulp adhering to the endocarp around the seeds. The pulp is dried and used as mulch or animal feed. The next step is termed “fermentation”, but is actually just enzymatic degredation of the pectinaceaous mucilage. Beans are carried in a stream of water to a tank, where they undergo this process for 12-48 hrs, depending on temperature. Beans are either washed during fermentation or afterwards to prevent staining. Beans are then dumped from wash tanks to the coffee yard, still inside the endocarp or “in parchment”, for sun drying. Drying takes 10-15 days in dry weather. Parchment coffee is generally bagged and taken to a plant which dehulls and polishes the beans.

 

Storage
Properly dried, coffee can be stored for years under optimal conditions. Storage is best at 40°F and 55% humidity, where coffee keeps for several years, but will keep 3-4 years even at room temperature.

COFFEE’S CONTRIBUTION TO DIET

Virtually all coffee is used to make the familiar beverage, but small amounts are used to flavor ice cream, confectionary products, and liqueurs such as kalhua. Per capita consumption of coffee is about 10 lbs of beans per year, roughly what it was in 1980.
Decaffeination of coffee was accomplished as early as 1820. Three basic methods are used: solvent extraction, supercritical gas extraction, and water extraction. All of the methods are at least 97% efficient, reducing caffeine levels from 100 mg per cup in normal coffee down to 1-5 mg per cup in decaf.

Dietary value, per 100 gram edible portion
[Note: an 8 oz cup of coffee weighs about 230 grams, so multiply the amounts below by 2.3 to yield amounts per cup.]

 Black coffee
Water (%) 99
Calories 4
Protein (%) 0.2
Fat (%) 0
Carbohydrates (%) 0.7
Crude Fiber (%) 0
% of US RDA*
Vitamin A 0
Thiamin, B1 0
Riboflavin, B2 0
Niacin 0
Vitamin C 0
Calcium 0.5
Phosphorus 0.5
Iron 5.0
Sodium <0.1
Potassium 0.3

* Percent of recommended daily allowance set by FDA, assuming a 154 lb male adult, 2700 calories per day.