Here we have it again – the comparison of coffee and wine, this time when it comes to harvesting. You have a similar development cycle and it is important to pick the cherry in the right moment. Cultivation and further processing require a lot of experience, precise timing, and care. It takes four to seven years until a coffee tree reaches maturity. During this cycle cherries turn from green to yellow to red (except some varieties like for example the yellow Bourbon – those stay yellow when they are ripe). Only cherries with the perfect red color get picked, neither the unripe green ones, nor the overripe black ones. Green cherries contain underdeveloped acids and not a complete flavor profile while black cherries taste fermented. The timing of the harvest strongly depends on the geographical and climate conditions and thus will vary by region and altitude. Typically, there is only one harvest per year, which will last for 2 to 3 months but there are regions with several harvest seasons per year. In countries North of the equator harvest usually occur from September to March, south of the equator harvest is from April to August. Traditionally coffee is harvested by hand by one of two ways: selective harvesting or strip harvesting.
Selective harvesting is the picking of only the ripe coffee cherries by hand. Only the ripe cherries are picked, while the unripe cherries are left of the tree, to be reassessed a few weeks later. This process is repeated until all the viable coffee has been picked.
As only ripe fruit are picked, a lower percentage of green or overripe cherries are harvested which leads to higher prices for producers. When coffee is picked by hand, trees can be planted in steep slopes, easily navigated by humans but not so much by machines, leading to more efficient use of other land for farming.
On the other side hand picking is labor intensive and the farms require a large labor force. This method is suffering due to the cost pressure on wages and the decline of rural workforce due to urbanization trends.
Strip harvesting is where all the coffee cherries are mechanically stripped from the trees at once. This results in harvests of varying maturation levels but is much less intensive and expensive. There are three ways of strip harvesting.
Manual stripping involves pickers placing canvas on the ground, grabbing the branch of the tree, and pulling outwards, knocking off all the fruit onto the canvas. The coffee is then collected in bags and taken to be weighed, where pickers are paid by weight or volume.
The next way is mechanical stripping. It works like manual stripping, but the pickers receive some mechanical assistance. Their tool has “metal fingers” which knock the coffee onto the waiting canvas.
The third way of strip harvesting coffee is using a harvester machine. They use rotating and vibrating mallets to knock the fruit into collection units. They can minimize the yield of unripe cherries by adjusting the rotation and vibration rates and the speed of the whole machine.
The advantages you can see here are fewer labor costs and faster harvests. On the other side as the harvesting is less specialized it leads to varying levels of maturation and if not separated un-uniform drying results in a lower quality product. Furthermore, the needed investment for the machine is not possible for many coffee farmer.
To safeguard high quality later in the process more technology is required which is more capital intense. Finally, this way bears the risks of harvesting higher amounts of unripe cherries which reduces the quantities of the final product, thus leading to less profits for producers.
Each harvesting method has its benefits and drawbacks, and as just one part of the process growers must decide based on budget, desired overall coffee quality, geography and topography of the land, and availability of labor.