A coffee plant usually starts to produce flowers 3-4 years after it is planted,
and it is from these flowers that the fruits of the plant (commonly known as coffee
cherries) appear, with the first useful harvest possible around 5 years after
planting. The cherries ripen around eight months after the emergence of the flower,
by changing colour from green to red, and it is at this time that they should
Coffee berries are most commonly picked by hand by labourers who receive payment
by the basketful or by weight. As of 2003, payment per basket is between US$1.00
to $10 with the overwhelming majority of the labourers receiving payment at
the lower end. An experienced coffee picker can collect up to 6-7 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
labour. Mixes of green and red berries, or just green berries, are used to produce
cheaper mass consumer coffee beans, which are characterized by a displeasingly
bitter/astringent flavour and a sharp odour. 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, and is the chief determinant for the quality of the end product.
Most of the world's green coffee has gone through some sort of wet
processing including most of the premium coffee.
After the Green coffee is picked the coffee is 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.
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
for several days 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.
In machine-assisted wet processing fermentation is not used to separate the
bean from the remainder of the pulp rather it is scrubbed off by a machine.
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. The parchment is
removed from the bean and what remains is green coffee.
Dry process, also known as unwashed or natural coffee, is the oldest method
of processing coffee. The entire cherry after harvest is placed in the sun to
dry on tables or in thin layers on patios. It will take between ten days and
two weeks for the cherries to completely dry. The cherries need to be raked
regularly to prevent mildew while they dry. Once the skin is dry, the pulp and
parchment are removed from the bean. While coffee was once all dry processed
it is now limited to regions where water or infrastructure for machinery is
scarce. The supply of dry processed coffee is very limited, with coffee from
the Harrar region of Ethiopia and some areas of Yemen and Brazil being the primary
Semi dry process:
Semi dry is a hybrid process in very limited use in Brazil and Sumatara/Sulawesi.
The cherry is passed through a screen to remove the skin and some of the pulp
like in the wet process but result is dried in the sun and not fermented or
Once the coffee is dried to green coffee it is sorted by hand or machine to
remove debris and bad or misshapen beans. The coffee is also often sorted by
size and placed into one of several grades.
Some coffee beans are polished to remove the silver skin. This is done to improve
the green coffee beans appearance and eliminate a byproduct of roasting called
chaff. It is decried by some to be detrimental to the taste by raising the temperature
of the bean through friction which changes the chemical makeup of the bean.
Green coffee is fairly stable if it is stored correctly. It must be placed in
containers that can breathe — often, some type of fiber sack — and
kept dry and clean.
All coffee, when it was introduced in Europe, came from
the port of Mocha in what is now modern day Yemen. To import the beans to Europe
the coffee was on boats for a long sea voyage around the Horn of Africa. This
long journey and the exposure to the sea air changed the coffee's flavor. Later,
coffee spread to India and Indonesia but still required a long sea voyage. Once
the Suez Canal was opened the travel time to Europe was greatly reduced and
coffee whose flavor had not changed due to a long sea voyage began arriving.
To some degree, this fresher coffee was rejected because Europeans had developed
a taste for the changes that were brought on by the long sea voyage.[citation
needed] To meet this desire, some coffee was aged in large open-sided warehouses
at port for six or more months in an attempt to simulate the effects of a long
sea voyage before it was shipped to Europe.
Although it is still widely debated, certain types of green coffee are believed
to improve with age; especially those that are valued for their low acidity,
such as coffees from Indonesia or India. Several of these coffee producers sell
coffee beans that have been aged for as long as 3 years, with some as long as
8 years. However, most coffee experts agree that a green coffee peaks in flavor
and freshness within one year of harvest, because over-aged coffee beans will
lose much of their essential oil content.
Decaffeination is the process of extracting caffeine from green coffee beans
prior to roasting. The most common decaffeination process used in the United
States is supercritical carbon dioxide (CO2) extraction. In this process, moistened
green coffee beans are contacted with large quantities of supercritical CO2
(CO2 maintained at a pressure of about 4,000 pounds force per square inch (28
MPa) and temperatures between 90 and 100 °C [194 and 212 °F]), which
removes about 97 % of the caffeine from the beans. The caffeine is then recovered
from the CO2, typically using an activated carbon adsorption system.
Another commonly used method is solvent extraction, typically using oil (extracted
from roasted coffee) or ethyl acetate as a solvent. In this process, solvent
is added to moistened green coffee beans to extract most of the caffeine from
the beans. After the beans are removed from the solvent, they are steam-stripped
to remove any residual solvent. The caffeine is then recovered from the solvent,
and the solvent is re-used. Water extraction is also used for decaffeination.
Decaffeinated coffeebeans have a residual caffeine content of about 0.1 % on
a dry basis. Not all facilities have decaffeination operations, and decaffeinated
green coffee beans are purchased by many facilities that produce decaffeinated