A coffee tree can produce between 5 and 10 kilograms of beans per year, but the first harvest does not take place before 3 to 5 years. The crops then increase from the 5th to the 20th year and reach their maximum productivity between the 6th and the 8th year of the shrub. After 20 years, their yield drops again and the coffee trees are replaced by young shrubs. Coffee trees live in
average between 30 and 50 years, but can reach 100 years.
Harvesting north of the equator is generally from September to December, while it already begins in April or May in the south, and may even extend to August. In countries located directly on the equator, it is even possible to produce coffee all year round. The coffee year designates the harvest period fixed between October 1 and September 30 of the following year.
Cherries must be harvested within 14 days of reaching maturity, at the risk of becoming overripe and thus unsuitable for production. Given the need to harvest fruit over several hundred hectares in this short period, the harvest requires a large workforce, which always represents a logistical challenge for producers.
When they are not ripe, the coffee cherries are green, before gradually becoming yellow, then red. When they reach final maturity, they are dark red. Overripe coffee cherries have a blackish color. However, there are varieties of coffee whose cherries do not turn red. The Yellow Bourbon variety from Brazil, for example, has yellow cherries when ripe. As with wine, there are also late harvests. The cherries are then often very dark red, even black.
Dry cherries on the tree should also be removed, as they are susceptible to disease, germs and pests. To ensure that only ripe and whole cherries are picked and that the quality level is at its maximum, harvesting is often done by hand.
There are generally three harvesting methods :
- “picking” – manual harvesting
- “stripping” – hand scraping
- “Harvester” – mechanical harvesting
The picking method consists of picking the cherries from coffee in hand, because mechanical harvesting is not possible for cost reasons or because a harvester cannot be used in mountainous regions. The cherry is ready to be harvested when it has a hardness that easily takes the bean out of the fruit by pressing it. Picking is the most tedious method of harvesting, because only ripe cherries are picked.
It should not be forgotten that it takes approx. 15 kilograms of fresh coffee cherries to produce only 2 to 2.5 kilograms of green coffee. A coffee picker needs 3 to 7 days on average, with a daily yield of 50 to 120 kg, to fill a bag of green coffee weighing 60 kg.
Another method of harvesting is stripping. It consists of de-stemming all the cherries from a branch and dropping them in a net or a basket, where they are then sorted. De-stemming allows the pickers to have a higher yield, which is however relative since it is then necessary to sort the cherries from foreign bodies. The scraping method is mainly used for robusta coffees, as well as for arabica coffees from Brazil and Ethiopia.
The third method is mechanical harvesting, also called “Harvester”, used on large farms. The machine then shakes the branches of the coffee tree to drop the cherries on stretched nets. Although this method is faster, it is only applicable to lowland plantations.
After harvest, the cherries go through several stages of processing before the roasted beans can be made into drinkable coffee. There are three main processing methods: “wet”, “dry” and “semi-wet”. The first and last stages of treatment are the same for all methods, however.
The dry method
> Sorting and sieving
> Drying the cherry
The unwashed / dry method begins by sorting the coffee cherries using a sieve or machine, that is, removing the leaves and insects and cleaning up the dirt. The cherries are then spread over large drying areas, where they are moved several times a day to ensure sufficient ventilation. They are sufficiently dry when the pulp is completely dry outside and it is hard to the touch. You can then hear the beans when you shake the cherries.
This process can take 3 to 6 weeks. As soon as the drying phase is finished, the grains are stored in the form of whole dried or peeled cherries.
The wet method
> Sorting and cleaning
> Removing the pulp (pulping)
Wet process: The wet method (fully washed) places the sorted and pulped coffee cherries in fermentation tanks. This is where the mucilage, the sweet viscous skin that sticks to the parchment, is eliminated by the enzymes of fermentation. This step allows the roasted coffee to acquire its delicate, sparkling and fruity acidity. After fermentation, the pulp residue is removed by friction (grains) or using mechanical brushes. This is the “washing” phase.
The semi-dry method
> Sorting and cleaning (flotation channel)
> Removing the pulp (pulping)
> Removal of the viscous layer
> Washing = elimination of the viscous layer
Besides the dry (unwashed) and the wet (fully washed), there are various semi-dry (semi-washed) methods. We thus find coffee “honey processed”, “pulped natural” or “semi-washed”. With the semi-washed process, the Pergaminos (pulped coffee cherries) are cleaned of the mucilage residues then dried, while that the “honey processed” treatment consists in drying the Pergaminos with the mucilage.
The advantages of this method are that it is economical in water and it makes it possible to easily sort the fruits during the pulping process.
After processing, the coffee beans are further processed to eventually remove the dried cherry, the parchment and the silver film.
The following steps constitute the transformation:
> Second sorting and cleaning
> Bean removal
> Quality test
> Packaging in bags
The beans thus prepared and cleaned then pass to the phase of hulling (generally in the huller) to be rid of the parchment. After the husking, the beans are subject to a final classification, that is to say they are classified by size, then by density and by color. Sorting by size is essential for homogeneous roasting of the beans. The denser the beans, and
similar in size and color, the higher the quality.
Transport and storage
The last step is the transport and storage of the coffee beans. The green coffee beans are first packed in bags, which must then be transported to a port from where they are shipped by ship.
During transport, it is crucial to constantly monitor the temperature, humidity and water content of the beans in order to prevent mold and fermentation, and thus guarantee quality. The discharge process must also be done quickly to prevent the coffee beans from thermal shock.
too large, which could cause more severe moisture damage. Since coffee is a living natural product, it is important to always work with caution to prevent loss of quality, which can occur at any stage and result in the loss of the delicate acidity of coffee.