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Coffee
Processing |
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Processing
of coffee is the method converting the raw fruit
of the coffee plant (cherry) into the commodity
green coffee. The cherry has the fruit or pulp
removed leaving the seed or bean which is then
dried. While all green coffee is processed, the
method that is used varies and can have a significant
effect on the flavor of roasted and brewed coffee. |
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| Picking |
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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 be harvested |
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| Coffee
berries are most commonly picked by hand by labourers
who receive payment by the basketful. As of 2003,
payment per basket is between US$2.00 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.
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| Processes |
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| Wet process |
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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.
Any wet processing of coffee produces coffee wastewater
which can be a pollutant. About 130 liters of
fresh waters are used in order to process one
kilogramm of quality coffee.
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| Dry process |
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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 sources. |
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| Semi dry process |
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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 scrubbed. |
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