It may seem that it’s easy to grow coffee but its path from the field to the cup on the table is very long. A lot of factors influence the quality of the coffee we drink, from the genetic properties of the species we use in blends and the conditions and manners of cultivation to the production process and packaging.

Know-how and experience of coffee growers are key elements for the quality of coffee and the production of coffee is in fact an entire philosophy.

Botanic

The coffee plant (genus: Coffea, family: Rubiaceae, same as gardenia) grows as a bush or as a tree. Natural mutations and genetic techniques created new variants and interspecies hybrids.

In regard to quality and financial aspect, only two species matter: Coffea Arabica (varieties: Typica, Maragogype, Mocha, Caturra, etc.) and Coffea Canephora (varieties: Robusta, Kouilou, Conillon, Niaouli, etc.)

Genetics

Genetic properties of the species define their potential: differences between Arabica and Canephora varieties are found in the qualities of their genotype – Coffea Arabica has 44 and Coffea Canephora 22 chromosomes.

CULTIVATION AND SOIL

Coffee tree grows in many countries, on each continent with tropical or semitropical zones between the Tropics of Cancer and Capricorn. Robusta beans are more resistant to heat and are cultivated on flat plantations at up to 500 metres altitude. Arabica is planted at elevation of at least 2000 metres, mostly on mountain slopes where the cultivation and harvest picking are tough and meagre. Higher altitudes have a positive effect on the quality of Arabica fruits (lower temperatures and longer ripening period enhance the development of the aroma and acidic flavour) and that is the reason why special attention is paid to this. Plantations facing south give larger yield but require more fertilizers. Coffee trees often face west or north and usually grow in the shelter of shade trees or cocoa, unless cloudy skies make the shade redundant. The shade reduces the pace of soil moisture loss and maintains higher temperatures at night. Both varieties are very sensitive to frost. Coffee trees have to be protected from strong winds and extreme weather conditions common in many coffee producing countries (drought, tornado).

Coffee tree has a lot of other enemies as well. Arabica plantations have been virtually decimated by orange rust. As its name suggests, Robusta is more resilient to disease, pests and heat.

Coffee thrives on fertile, preferably volcanic soil. Coffee plant requires a thick layer of soil for its roots take up to two metres in depth in search for nutritious ingredients. A considerable quantity of humus is required for the growth of a coffee tree and can be improved by adding natural or artificial fertilizers (nitrogen, potassium, magnesium are the main fertilizers). Coffee plantations are established by using seedlings or rooted cuttings and by grafting. The most common method is planting seedlings but this method doesn’t provide maintaining the individual characteristics of the species, whereas rooted cuttings and grafting overcome this problem. The density of trees varies from 1300 to 7000 per hectare, depending on the variety and the shape. High cultivation density is possible in thick coffee shrub as in Caturra or Catimor varieties. All these aspects influence to a large extent the quality of a cup of coffee. The same botanic species produce different coffee depending on the climate, soil, cultivation manner and processing method after harvesting.

HARVESTING

Coffee harvesting is a very delicate process and the secret of high quality coffee depends on how carefully the beans are picked. Uneven ripening, characteristic for a coffee plant, makes the harvesting complicated and a lot of effort has been made towards simplifying this process. Coffee fruits ripen at different times and this occurs not only in two neighbouring trees but in the same tree as well, in the same bunch even. Although it rarely occurs in nature that the fruits of the same tree mature at different times, coffee tree is an exception – one tree, one branch even, may produce immature (green), mature (red) and over-mature (red and black) fruits at the same time. If there are flowers present along with the fruits, the harvesting is additionally hampered.

The best way to ensure a top quality yield is manual harvesting, selecting only the mature, red fruits and picking them one at a time. Such extremely careful and precise method, called selective harvesting, is mostly applied in Columbia but also in Central America, Kenya, Ethiopia and Jamaica.

In mechanical harvesting of the crop a flexible wide-tooth comb acting as a rake is used to pick fruits from the branches. This method is financially more acceptable but the quality of the fruit is poorer. An increasingly popular method of mechanical harvesting uses shaker machines to shake the trunk, separating the fruit from the branches and making them fall off. The worst is the stripping method – fruits from all stages of development (ripe red fruits, green and yellow immature fruits and over-mature black ones) are stripped off the branch with one stroke. Leaves and all kinds of impurities fall off along with the fruits. This harvesting method may influence creating a bad aroma which becomes evident after roasting.

Coffee tree fruit

Coffee tree’s fruit is called coffee cherry or coffee berry and it gets its clear red colour only when it fully ripens, after six to twelve months, and has up to 15 mm in diameter. The shiny and thick external skin (exocarp) expands around the sweet, fleshy pulp (mesocarp). Two protective layers cover the bean: thicker, whiter layer directly attached to the bean – coffee parchment or endocarp and a thin layer, known as the silver skin or spermoderm. Each coffee fruit contains two seeds or beans. The flat sides of the two beans are adjacent and separated by a central groove. The other side is convex. Coffee bean is about 10 mm long and weighs about 0.15 grams. Arabica beans are flatter, longer and their central groove is wavy. They vary in colour from light to dark green with bluish nuance. Robusta beans are rounder, more curved and their central groove is straight. They are pale green in colour, with brown or grey tones.

COFFEE PROCESSING

There are two coffee processing methods: the dry and the wet process.

Dry process: This is the most conventional method of coffee processing. Coffee cherries are spread out and dried in the sun without shade. The fruits are constantly raked and turned by hand until the pulp dries. Some plantations started using hot air dryers. In the drying process, the fruits turn brown. When they are dried, the fruits are ready for hulling. Dried fruits are placed in the rotating drums where they are exposed to blades that break the hull and release the coffee beans. The beans are subsequently graded and sorted according to size, density, colour and even shape. Complex machines are increasingly used for this essential, yet time-consuming and expensive processing method. Coffee beans with hull, as well as black, acidic, fermented or unripe beans are removed since they cause undesirable or bad coffee flavour.

Wet process: This method produces extra quality of 'washed' or 'mild' coffee. After harvesting, ripe coffee cherries are pressed by machine in water through a screen in order to squeeze out the beans and remove some of the pulp. Undamaged, dense seeds are separated from the light ones in the first washing. Sticky mucilage covering the parchments is processed in large cement fermentation tanks, releasing a particular odour called the coffee pulp. The beans are washed with a great amount of water for the purpose of removing the remaining pulp and other impurities and then dried in the sun or, more often, in heated air dryers. As a result, dried green coffee beans are gained, along with the parchment. The wet-processed coffee will be ready for sale and export after the beans have been hulled. Only the countries with good water supply may allow themselves the luxury to carry out such successive washing. The pulp and the sticky mucilage pollute the water. Therefore, new processing methods are developed to minimize water pollution and yet maintain the high quality of the wet process.