Coffee production
Coffee production is the industrial process of converting the raw fruit of the coffee plant into finished coffee beans. About eight months after coffee cherries appear on a coffee plant, the cherries are harvested either by hand or by machine. Then they are, depending on the method, pulped and then dried or simply set out to dry. After this, the beans are stripped of their remaining dry skin and fruit residue. Once they are cleaned, sorted, and graded, they are suitable for distribution. While all green coffee, produced from immature coffee beans, is processed, the method that is used to process coffee varies, and significantly affects the flavor of coffee once it is roasted and brewed. Coffee production is a major source of income for 12.5 million households, most in developing countries.
Picking
A coffee plant usually starts to produce flowers three to four years after it is planted, and it is from these flowers that the fruits of the plant appear, with the first useful harvest possible around five years after planting. The cherries ripen around eight months after the emergence of the flower, by changing color from green to red, and it is at this time that they should be harvested. In most coffee-growing countries, there is one major harvest a year; though in countries like Colombia, where there are two flowerings a year, there is a main and secondary crop, the main one April to June and a smaller one in November to December.In most countries, the coffee crop is picked by hand, a labor-intensive and difficult process, though in places like Brazil, where the landscape is relatively flat and the coffee fields are immense, the process has been mechanized. Whether picked by hand or by machine, all coffee is harvested in one of two ways:
;Strip picked
All coffee fruit is removed from the tree, regardless of maturation state. This can either be done by machine or by hand. In the first method, pickers generally place a canvas on the ground. They then grab the branch next to the trunk with their hands and pull outward, knocking all of the fruit onto the ground. After doing this with all branches and trees for the length of the canvas, the pickers then collect the coffee in bags. This process can be facilitated through the use of mechanical strippers.
;Selectively picked
Only the ripe cherries are harvested and they are picked individually by hand. Pickers rotate among the trees every eight to ten days, choosing only the cherries which are at the peak of ripeness. It usually takes two to four years after planting for a coffee plant to produce coffee beans that are ripe enough to harvest. The plant eventually grows small white blossoms that drop and are replaced by green berries. These green berries will become a deep red color as they ripen. It takes about 9 months for the green cherries to reach their deepest red color. Because this kind of harvest is labor-intensive, and thus more costly, it is used primarily to harvest the finer arabica beans.
The laborers who pick coffee by hand receive payment by the basketful., payment per basket is between US $1.00 to $10 with the overwhelming majority of the laborers receiving payment at the lower end. An experienced coffee picker can collect up to six or seven baskets a day. Depending on the grower, coffee pickers are sometimes specifically instructed to not pick green coffee berries since the seeds in the berries are not fully formed or mature. This discernment typically only occurs with growers who harvest for higher end/specialty coffee where the pickers are paid better for their labor.
Lots including unripe coffee fruit are often used to produce cheaper mass consumer coffee beans, which are characterized by a displeasingly bitter/astringent flavor and a sharp odor. Red berries, with their higher aromatic oil and lower organic acid content, are more fragrant, smooth, and mellow. As such, coffee picking is one of the most important stages in coffee production.
Wet process
In the "wet process", the fruit covering the coffee beans is removed before they are dried. Coffee processed by the wet method is called wet processed or washed coffee. The wet method requires the use of specific equipment and substantial quantities of water.The coffee cherries are sorted by immersion in water. Bad or unripe fruit will float and the good ripe fruit will sink. The skin of the cherry and some of the pulp is removed by pressing the fruit by machine in water through a screen. The bean will still have a significant amount of the pulp clinging to it that needs to be removed. This is done either by the classic ferment-and-wash method or a newer procedure known either as: machine-assisted wet processing, aquapulping or mechanical demucilaging.
In the ferment-and-wash method of wet processing, the remainder of the pulp is removed by breaking down the cellulose by fermenting the beans with microbes and then washing them with large amounts of water. Fermentation can be done with extra water or, in "dry fermentation", in the fruit's own juices only.
The fermentation process has to be carefully monitored to ensure that the coffee does not acquire undesirable, sour flavors. For most coffees, mucilage removal through fermentation takes between 8 and 36 hours, depending on the temperature, thickness of the mucilage layer, and concentration of the enzymes. The end of the fermentation is assessed by feel, as the parchment surrounding the beans loses its slimy texture and acquires a rougher "pebbly" feel. When the fermentation is complete, the coffee is thoroughly washed with clean water in tanks or in special washing machines.
The fermentation process produces wastewater that contains a high organic load, which should be prevented from entering fresh water supplies. In machine-assisted wet processing, fermentation is not used to separate the bean from the remainder of the pulp; rather, this is done through mechanical scrubbing. This process reduce both water use and the generation of wastewater. In addition, removing mucilage by machine is easier and more predictable than removing it by fermenting and washing. However, by eliminating the fermentation step and prematurely separating fruit and bean, mechanical demucilaging can remove an important tool that mill operators have of influencing coffee flavor. Furthermore, the ecological criticism of the ferment-and-wash method increasingly has become moot, since a combination of low-water equipment plus settling tanks allows mill operators to carry out fermentation with limited pollution. The downside in using a machine assisted process or "semi-wash" is a high chance of the beans being chipped or damaged. The damaged beans are more prominent on lower altitude-grown beans and certain varietals with porous features.
Any wet processing of coffee produces coffee wastewater, which can be a pollutant. Ecologically sensitive farms reprocess the wastewater along with the shell and mucilage as compost to be used in soil fertilization programs. The amount of water used in processing can vary, but most often is used in a 1 to 1 ratio.
After the pulp has been removed, what is left is the bean surrounded by two additional layers: the silver skin and the parchment. The beans must be dried to a water content of about 10% before they are stable. Coffee beans can be dried in the sun or by machine but in most cases it is dried in the sun to 12–13% moisture and brought down to 10% by machine. Drying entirely by machine is normally only done where space is at a premium or the humidity is too high for the beans to dry before mildewing.
When dried in the sun, coffee is most often spread out in rows on large patios where it needs to be raked every six hours to promote even drying and prevent the growth of mildew. Some coffee is dried on large raised tables where the coffee is turned by hand. Drying coffee this way has the advantage of allowing air to circulate better around the beans promoting more even drying but increases cost and labor significantly.
After the drying process, the parchment skin or pergamino is thoroughly dry and crumbly, and easily removed in the hulling process. Coffee occasionally is sold and shipped in parchment or en pergamino, but most often a machine called a huller is used to crunch off the parchment skin before the beans are shipped.
Dry process
Dry process, also known as unwashed or natural coffee, is the oldest method of processing coffee. The entire cherry after harvest is first cleaned and then placed in the sun to dry on tables or in thin layers on patios:The harvested cherries are usually sorted and cleaned, to separate the unripe, overripe and damaged cherries and to remove dirt, soil, twigs and leaves. This can be done by winnowing, which is commonly done by hand, using a large sieve. Any unwanted cherries or other material not winnowed away can be picked out from the top of the sieve. The ripe cherries can also be separated by flotation in washing channels close to the drying areas.
The coffee cherries are spread out in the sun, either on large concrete or brick patios or on matting raised to waist height on trestles. As the cherries dry, they are raked or turned by hand to ensure even drying and prevent mildew. It may take up to four weeks before the cherries are dried to the optimum moisture content, depending on the weather conditions. On larger plantations, machine-drying is sometimes used to speed up the process. Various types of mechanical driers exist and can be fueled by gas, wood, or sometimes discarded parchment. The technique used to dry coffees mechanically can be viewed similarly to the roasting process; a drying regime can be employed in a way to preserve the quality of the beans.
The drying operation is the most important stage of the process, since it affects the final quality of the green coffee. A coffee that has been overdried will become brittle and produce too many broken beans during hulling. Coffee that has not been dried sufficiently will be too moist and prone to rapid deterioration caused by the attack of fungi and bacteria.
The dried cherries are stored in bulk in special silos until they are sent to the mill where hulling, sorting, grading and bagging take place. All the outer layers of the dried cherry are removed in one step by the hulling machine.
The dry method is used for about 90% of the Arabica coffee produced in Brazil, most of the coffees produced in Ethiopia, Haiti and Paraguay, as well as for some Arabicas produced in India and Ecuador. Almost all Robustas are processed by this method. It is not practical in very rainy regions, where the humidity of the atmosphere is too high or where it rains frequently during harvesting.