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OLIVE OIL PRODUCTION PROCESS
The process of
manufacturing olive oil begins in the fields, where the care taken
during cultivation has to guarantee a sound final product at just
the right point of maturity. The excellence of the oil is strictly
tied to the quality of the oilves, to the care taken during the
production process (picking, manuring, pruning, defence) and
transformation (olive-pressing and all processes leading to the
final product).
Olive-ripening
generally occurs at the end of autumn or at the onset of winter and
its depends on the latitude at which plants are grown, or on the
climatic state and the variety of the olive trees. In any case the
picking takes place when the olives assume a partial or complete
dark shade (the peel colour changes from green to purple). To delay
picking does not mean a better oil yield, on the contrary a
degradation process occurs that negatively effects the quality of
the oil. There are numerous olive picking systems, however, they
can be grouped in 2 main categories: manual and mechanical picking.
Amongst the manual methods, the best results
are achieved with the “brucatura”
(browsing), with this method olives are hand picked individually and
placed in special baskets hanging from the harvester’s belt. This
method is very slow and has a high labour cost.
A faster variation of this method uses a
special net which is laid on the ground under the olive tree and, as
the olives are picked they are allowed to drop onto the net. However,
the softer-pulp olive varieties are often damaged when they fall.
Other manual methods are the “bacchiatura”
(beating down) and the “raccattatura”
(picking up).
Mechanical
harvesting is basically the only option available for very extensive
olive groves: mechanical arms are clasped to the tree trunk or the
main branches of the tree with this method the drupe falls on to a
net. Recently combs have been introduced. These combs are passed
through the branches and the olives fall on a net laid on the ground.
After picking, the olives are taken to the oil mill.
The transport
phase is very important in order to obtain a good quality product.
If the olives are transported in sacks or containers where the
olives are subject to alterations, there is a possibility of
triggering an undesirable fermentation processe, which could then
inevitably effect the quality of the final product. The best way to
transport olives is in crates or well-aired boxes; large companies
use 200-300 kg pallettized boxes.
In order to
obtain a good quality oil, olives should not be dropped in heaps or
stacked for a long time in the oil mill.
It is advisable
that they are pressed with-in 24 hours of the picking.
Before the pressing, it is advisable that the
olives are thoroughly washed in order to eliminate any possible
foreign particles that could negatively effect the quality of the
oil. The process of olive oil extraction can be divided into three
main stages: frangitura
(crushing), gramolatura
(Kneading) and spremitura
(pressing).
Olive milling or frangitura
Frangitura is a
mechanical process that crushes the olives, this is necessary in
order to crush the pulp from which the oil is going to be extracted.
In order to do this one can choose between two technical solutions
in frangitura: the traditional millstone olive press, and the hammer
or disk mechanical press.
The traditional
method, called “a molazze”, that is by mullers, is composed of two
large granite wheels that turn on a granite base, crushing the
olives. The presence of olive stones does not harm the oil in any
way, but rather, makes it easier to separate the oil from the solid
component during the pressing process.
The second
solution is more time efficient than the first, but requires special
care in order to avoid high temperatures.
The gramolatura
Before being
pressed the olive pulp is subject to the process of gramolatura. The
olive pulp and stones are re-mixed in order to reduce the volume and
to separate the vegetable water from the oil, thus breaking up the
oil and water emulsions created during the milling stage.
This operation
takes place at a controlled temperature and allows a delicate
mixing of the olive pulp encouraging the oil to coalesce.
At this stage
particular attention must be paid to both temperature as it should
be low, and to processing times which should not be excessively long
so that oil contact with air and light is as short as possible,
whilst at the same time a good extraction yield is obtained.
Extraction
Two methods can
be used to extract the oil: the traditional vertical pressing method
and the continuous centrifugation method.
In the latter
case manpower saving is guaranteed but particular systems need to be
adopted in order to prevent the oil from being subjected to high
temperatures that could damage its quality. After further decanting
and filtering operations the final product is obtained.
The basic
difference between the traditional and the continuous system is that
the speed of oil production becomes a very important factor
when you want to reduce the olive processing and storing times to a
minimum.
We should,
however, point out that the traditional methods require great
professional experience in managing the plants and taking care of
the state of the “fiscoli” (disk shaped mats on which the olive
paste is spread after being crushed).
These, if not
managed appropiately, are the main cause of oil defects. The
continuous method gives excellent results, even though the crusher
represents the crucial point as it gives more or less satisfactory
results according to the raw material. In conclusion, undamaged
olive pressing at controlled temperatures and sound olives guarantee
the high quality of the oil.
We must mention
that for the previous parametres described the EEC is revising them
in order to achieve a better control on quality. In spite of the
diffusion of oil cultivation, in the world panorama the use of olive
oil is limited to the mediteranean countries.Where as the oils
mainly used in the rest of the world are extracted from peanuts,
soia, sunflower seeds and cotton seeds.
We must,
however, underline that the oil that is most adaptable in a kitchen
used both for raw and cooked food is olive oil.
The
classification of oil, is however, not simple. In various cases the
names used can trick the consumer.
With the
passing of time, oil changes and from the intense characteristic
that it has in the beginning it becomes smooth and more harmonious;
but after a year the oil begins to deteriorate.
Once separated
from the vegetable water, and in order to classify the product the
oil is evaluated from a sensorial, chemical and physical point of
view.
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OIL STORAGE
The oil is
stored in either underground or above ground tanks. Steel tanks are
specifically recommended, preferably placed in areas away from light
and air at a controlled temperature.
In order to
maintain its characteristic composition in time and space, oil
preservation should avoid contact with the worst enemies of fats:
light and oxygen.
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