Before
a margarine or spread can be made, the oils and fats must be extracted
from their original source. Some oils, especially virgin olive
oil, do not undergo this process as they are pressed straight from the
seed or fruit without further refining. For most oils though, the
process is more complex. The vegetable seeds or nuts contain oil
trapped inside shells and cells. The seeds therefore must be
washed, crushed and heated, before the oil is removed in a solvent
extraction process. These processes commonly occur in the country
in which the seeds/fruits are sourced.
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Once the oil has been extracted
from its source (the seeds or beans) it must be refined. The 'crude' oil
will undergo this process to remove its unwanted taste, smell and dark
colour, which are generally undesirable in the finished food products.
Refining also removes impurities, which would cause deterioration of the
oil at a later date. The exception to this would be oil such as virgin
olive oil, which receives minimal processing in order to maintain its
distinctive colour and taste.
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Removal
of "free" fatty acids
Crude
oil must be neutralised to remove any 'free' fatty acids (those which
may have broken away from the triglyceride molecule) which, with time,
would otherwise react with oxygen and cause the oil to develop a rancid
taste. The neutralised oil is washed and dried thoroughly, as a high
moisture content would also cause deterioration of the oil.
Removal
of colours and Impurities
Colour and impurities are removed by passing a special absorbent earth
through the oil, which is carefully filtered out to leave the oil clear.
Oil
Modification
The
crude vegetable oils used for the manufacture of spreads are generally
liquid at room temperature. These oils can be made harder to provide a
product that spreads by raising their melting point. The technique
used to modify fat is called rearrangement.
Rearrangement
Rearrangement is a process where two different oils are combined to
produce a fat with different melting characteristics.
Removal
of unwanted smells and tastes in the oil
The removal of unwanted smells and tastes in the oil is achieved by blowing
steam though the heated oil and a vacuum draws off the steam along with the
smell and taste.
Blending
Various oils are mixed or blended to give the desired texture/consistency in
the final spread product. A tub of soft margarine will have a larger
proportion of soft liquid oils, while a packet margarine will contain a higher
solid fat content.
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