Posted March 7, 2013 by Matt in General Information
 
 

The Coffee Plant and Bean

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he coffee plant is in the Coffea family, which again is under the large family Rubiaceae. The coffee plant is really an evergreen small tree or shrub, which originates from the tropical and south Africa. Today the coffee plant is grown and cultivated in South-America, Africa and Asia.

The two main types of coffee which is commercially cultivated are Coffea canephora and Coffea arabica. These trees have an average height of 5 to 10 meters (15-30 ft.) with glossy dark green leaves. The white flowers grow in clusters and have a sweet fragrance, almost like perfume. When a coffee tree is blooming all the flowers bloom at the same time and it can be as many as 30,000 of white flowers. Just after 24- 36 hours after the blooming the fruits start to develop.

The coffee bean

Ripe berries from arabica coffee plant

Ripe berries from Arabica coffee plant.

The fruits, which are called “cherries”, are really drupes. A drupe is a fruit with a fleshy outer layer and a stone (seed) inside, like a peach. The drupe on the coffee plant is much smaller than a peach though, it is just a 1.5 cm (0.6 in) oval fruit. The cherries are green when they are immature and grow in cluster as the flowers. As the cherries ripen they turn first yellow, then red and finally they get a dark red or purple color. The ripening process of the cherries takes from seven to nine months.

A coffee tree doesn’t start to bear fruits before it is 3-4 years old and will continue to bear fruits for at least the next 10 to 20 years. How long the tree will bear fruits depends on the type and climate. A Coffea arabica tree can produce coffee beans for 50 to 60 years.

The “coffee beans”, which is not really beans, are seeds inside the cherry. Inside each cherry there is normally two “beans”, but in about 5-10% of the cherries there is only a single bean. The single bean is called a peaberry, which is smaller and rounder than a normal coffee bean. The peaberry is usually removed from the normal coffee beans and either sold separately or discarded.

Coffee plants on a plantation

Coffee plantation in Colombia.

Habitat and cultivation

The planting of coffee have been traditionally done by putting about 20 seeds in each hole in the beginning of the rainy season. A more efficient way of growing coffee, which is commonly used in Brazil, is to grow seedlings in nurseries. After 6 to 12 months, the seedlings are planted outside and often with other crops, like rice, corn or beans for the first few years. The coffee tree is planted in rows with several feet apart, often with other fruit trees around or on hill sides. This is due the coffee plant need specific conditions to thrive when it comes to climate and soil.

In the subtropical regions the wet season marks the beginning of the flowering while the ripening happens in the colder and dryer autumn or winter. Climate with frequent rain with no clear seasons, like you will find in the equatorial regions, results in continuous flowering and two or more harvesting seasons. The main harvesting season comes after the wettest period of the year while the second harvest is determined by the period with least rainfall. In these areas with moist climate and frequent rainfall, artificial drying might be necessary to grow coffee. On Java Island in Indonesia, coffee trees are planted at all times of the year and coffee can therefore be harvested all year.

The temperature is an important factor for the quality and flavor of the coffee bean. Large temperature fluctuations between day and nighttime improves the flavor of the fruit and also the seed. Too large temperature fluctuation is not good either, if it is too hot during the day the photosynthesis will be slowed and frost during the night will damage the crops.

World map of coffee production

Map of coffee production r: cultivation of Coffea robusta m: cultivation of Coffea robusta and Coffea arabica. a: cultivation of Coffea arabica.

Coffea canephora is grown in relatively hot climates with a temperature range between 24-30ºC while Coffea arabica is grown in a cooler climate and light shade. We find Coffea arabica in the region between the Tropic of Cancer and Capricorn with an optimum temperature range of 15-24ºC and often cultivated as high as 1500 meters above sea level (4500 feet).

The coffee tree has often a tendency to produce too many cherries which can lead to damage to the tree, like breaking of branches. This does not only affect the same year’s harvest, but can also affect harvest the following year as the flavour of the cherries is determined by the tree’s health. It is therefore important that the coffee farmer prune and trim the trees to prevent any damage to the trees.

It is important to pick the cherries as they ripen to get the best flavor and as the coffee cherries do not ripen at the same time they are often hand picked. When the majority of the cherries are ripe sometimes the whole coffee tree is harvested by shaking the cherries off onto mats. The unripe and ripe cherries then have to be sorted afterwards. The method is fast and efficient, but to a cost because the unripe cherries have to be discarded. A tree can produce anywhere from 0.5 to 5 kg of dried beans which depends on the tree itself and weather of the season. As you might understand there are a lot of factors to consider when growing coffee.

Coffea canephora

Coffea canephora is better known as Robusta and is the second most produced coffee. Even though it is the second most popular type of coffee it has only approximately 20% of the market share. Robusta originates from the central and western sub-Saharan area in Africa, but is today mostly grown in Vietnam. You can find the Robusta on plantations in Africa and South-America as well, where it is better known as “conillon“.

The Robusta flowers irregularly and its cherries takes about 10 to 11 months to ripen. The crop yield is greater compared to Coffea arabica and is also easier to grow and more resistance against diseases. With a caffeine level of 2.7%, Robusta contains almost twice as much caffeine than arabica.

The Robusta coffee bean has a strong earthy and bitter flavour which is desirable in espresso. Robusta coffee makes a thin layer of foam at the top of the espresso cup, which is called crema. Robusta coffee is also used as a filler in cheap coffee blends and instant coffee.

Coffea arabica

Coffea arabica is by far the most popular type of coffee due to its smooth taste. Almost 80% of all coffee produced in the world is arabica. Coffea arabica originates from the southwestern highlands of Ethiopia and southeastern Sudan. From Africa it was brought to Arabia by Yemeni traders, where it got its name Coffea arabica. Today arabica is cultivated in Latin-America, eastern Africa, Arabia and Asia.

Flowers on an arabica bush

Coffea arabica flowers.

The small white flowers of the Coffea arabica tree have a sweet fragrant which resembles the smell of jasmine flowers. Even though the tree can be as high as 10 meters it usually only grow to 5 meters and even as low as 2 meters on plantations. This is due to the farmer frequently trim the trees to make the harvest easier.

The flavor of the coffee can vary greatly even though it is of the same type. This is because the flavour depends on the soil and climate where it is grown. Coffee from Indonesian, such as Sumatran and Java, have a heavy body and low acidity while coffee from Latin America and east Africa have a high acidity. Coffee from Colombia is usually mild and used in gourmet coffee blends where only high quality and mild varieties are desired.

Processing and roasting

Drying coffee beans in the sun

Traditional drying of coffee in Panama.

The picked cherries are first sorted by ripeness and then the flesh around the coffee bean is removed. The flesh is usually removed by a machine before the coffee bean is washed in fresh water. Before the roasting process can happen the beans have to be dried. This is either done by the coffee beans are spread across drying tables or a concrete patio.

When the the green coffee beans have been dried the next step of process is roasting. The beans are heated up and when the temperature inside the beans reach roughly 200 °C (392 °F) a caramelization of the sugars occurs and the aromatic oils start to seep out. The starches in the bean are changed into simple sugars which change the color and flavor of the bean. A darker roast is bolder and have a more sugary flavour, while lighter roast have a stronger and more aromatic taste.