Stages of Coffee Production
 


Figure 1: Coffee in different stages of production. From the left,
coffee in parchment, green coffee as it is received by the roaster,
roasted whole bean coffee, and roasted ground coffee.

 
 

Coffee is the roasted seed of the coffee plant. Coffee is grown in the tropics and goes through many stages and states before it becomes a consumable beverage and each of these stages affects the flavor and quality of the final product.

The two main stages are green and roasted.

Green Coffee

Two different species of plants are commercially grown to produce coffee, though there are over 20 different species in the genus coffea. Coffea Arabica (referred to as “Arabicas”) is predominant; Coffea Rubicae and Coffea Robusta (referred to as “Robustas”) are easier to grow and produce greater amounts of coffee, but do not have the quality of flavor of the Arabicas. Within these species are several varieties.

 


Figure 2: An Arabica Tree


 Figure 3: A Robusta tree. The leaves
are larger and have a rounder shape

 

The flavor of the coffee is also affected by climate, altitude, methods of cultivation, and soil type. Diseases, such as various funguses and insects, can affect the health of the tree and how the coffee tastes.
 


Figure 4: Broca beetle emerging from
a coffee seed in a man's hand.


Figure 5: Broca damaged coffee
in parchment.
 


Figure 6: Severely insect damaged
coffee without parchment.


Figure 7: Leaves that have the "ojo de gallo"
(eye of the rooster) fungus on leaves.

 

Coffee starts out as a blossom (with a jasmine-like aroma) and develops a fruit that gradually ripens from green to red. The resulting seed will be at its sweetest if the coffee is harvested when it is red-ripe.
 


Figure 8: Buds on a coffee tree.


Figure 9: Flowering.

 


Figure 10: Coffee ripens at different rates
and so is usually harvested by hand.


Figure 11: Harvest.

 

Once the coffee is harvested, the cherry must be removed from the seed. There are two methods of doing this and flavor is affected by the method chosen. The wet (or washed) process pulps the coffee and then sits under water for a period to degrade the sticky substance surrounding the seed (called the mucilage or honey). The coffee is then rinsed in sluices and can be separated according to density during this stage.
 


Figure 12: Pulping the ripe cherry.


Figure 13: The tray ensures that only
the ripe beans that have had the fruit
removed go on to the next stage.

 


Figure 14: Coffee with pulp removed
in ferment tank.

 


Figure 15: In the natural process,
cherries are spread out to dry. This
process takes about two weeks longer
than the wet process.

 


Figure 16: Drying coffee on patios.

     
 

The coffee is capable of picking up microbial infections at this stage, resulting in a variety of flavor taints and faults, ranging from winy/grape-like flavors, overly vinegar flavors, or even garbage-like ferment. Processing must begin within 24 hours of the cherry being harvested or off-flavors are more likely to develop.
 


Figure 17: Coffee is also dried mechanically.

 

The coffee is then dried from a moisture content of about 65% percent to a moisture content of about 12% for transport. If the coffee was shipped at its original moisture level, it would likely develop various funguses and/or microbial infection that will result in mildew, dirty, or sour flavors.

If the coffee is dried too quickly and/or at too high of a temperature, it will lose much of its characteristic flavors, especially sweetness, aromatics, and tanginess. On the other hand, if it is dried too slowly, it runs the risk of picking up funguses and microbial contamination.

After drying, the coffee must have its outer layer of parchment removed and will be sorted according to density, bean size, and defective beans (the black, sour, and other problematic beans are removed).
 


Figure 18: Coffee during
parchment removal.


Figure 19: This machine shakes the beans
over screens with different sized holes to
classify the beans according to size.

 


Figure 20: The gravity table uses air from underneath and shaking to separate
coffee according according to density.


Figure 21: One of the most labor intensive aspects of producing green coffee is getting rid
of defective beans. This is often done by hand.

 


Figure 22: Selection is also done using sophisticated electronic devices that read
the color of each bean.


Figure 23: For electronic sorting, a
large number of machines are required.

 

These processes are carried out either by the individual farmers or in large mills, depending upon the level of development within the country and the traditions that exist.

 


Figure 24: This farmer in Columbia dries
his coffee on the roof. The pitched roof
at back can be pulled over in case of rain.


Figure 25: In this machinery, pulping can
be accomplished on a much larger scale.

 

Finally, the coffee is packed into bags for shipping. Traditionally, bags containing about 150 pounds are used, but there are also full shipping container bags.
 


Figure 26: Green coffee ready for shipment.

 

Roasting

The best roasted coffee is the freshest roasted coffee and that is why most coffee is roasted in the country of consumption.

In determining the flavor profile of the coffee, the roaster must consider what flavors the selected green bean is capable of producing when roasted, in the case of blends how these flavors will combine with others, and roasting parameters. Roasting parameters include the degree (darkness) of roast and development of flavor as measured by time and temperature.
 


Figure 27: A typical drum roaster
(courtesy Java City, Sacramento, California).
 

There are several different kinds of roasters, but the most common is the drum roaster. A metal drum holds the green coffee which turns over a gas flame so that the batch roasts evenly. These roasters are manufactured in various sizes, from a capacity of 2.2 kilos up to 250 kilos and larger.

Once the roaster is warmed up, a measured amount of green beans (the “charge”) is loaded into the drum. The roasting technician monitors the progress of the roast by watching the bean temperature and occasionally examining a sample using the tryer. Finally, when the appropriate level of roast has been attained, the coffee is released into the cooling tray.
 


Figure 28: Beans are stirred and a fan pulls air
through the hot beans as they are cooled.

The coffee technician plays an important part in this part of the process. If the coffee comes into contact with too much heat too quickly, charring will result, causing burned and bitter flavors. However, if the heat is introduced too slowly, the coffee will not roast properly and reach a stage called “baked” with little real coffee flavor.

Most coffee is sold in a ground state. Commercial grinders are usually roller mills that minimize the contact between metal and coffee particles, preserving the flavor that can be lost if the coffee overheats during grinding.

The final stage is packaging. If the bag or can is to be sealed, the coffee must be allowed to degas. During roasting, the sugar browning reactions have produced a lot of carbon dioxide that is released from the bean gradually. If the coffee is sealed in a package immediately, this release will cause the package to balloon or burst. The finest coffees are packaged using one-way valves that allow the gas to escape but do not allow oxygen (which causes staling) to enter the package.

Though it is one of the most common beverages known, the production of coffee is a process that requires several stages. The flavor of the final coffee beverage is affected at all stages. Looking into the cup, it is sometimes hard to believe that so much hard work and expertise went into the production of coffee.