Centrifuges for the edible oil industry | 
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The use of separators and decanters in the edible oil industry
Most oils and fats contain undesirable contaminants, which have to be removed in order to achieve consumer acceptance. As a result, these oils and fats are mostly subjected to refining.
This refining usually consists of the following process stages, in which edible oil separators are used:
Oils with an appreciable content of phosphatides, vegetable mucilage,
colloidal compounds etc. are usually de-gummed. This is done, among other
things, to increase their shelf life.
Here, various methods are used for de-gumming.
These include, for example:
- Water de-gumming for the hydratable gums.
Through hydration, the phosphatides become water-insoluble, are
precipitated out of the oil and can then be removed centrifugally,
using separators.
- Acid de-gumming for the non-hydratable gums.
Non-hydratable gums can be conditioned into a
hydratable form by the use of strong acids. This destroys the phospho-
lipids, so that, after mixing the oil with a suitable acid and following a
short reaction period, hot water can be added.
The gums are then removed centrifugally, using a separator.
In the case of acid de-gumming, a further distinction can be made
between different processes, such as simple acid de-gumming, special
de-gumming etc.
In all the methods of de-gumming above, edible oil separators are
generally used.
Various processes take place in oil which split the fat and lead to the formation
of free fatty acids (FFA).These must be removed as far as possible.
In the standard neutralisation process, the free fatty acids are converted into
soapstock, using caustic soda, and are then removed centrifugally, using a
separator.
In order to achieve a further improvement in the quality of the oil, particularly
with regard to its colour and flavour, a second neutralisation can also be carried out.
However, this is only of significant benefit for certain oils.
In order to remove soaps still contained in the oil, hot water is added to the oil,
followed by mixing. This mixture is then passed to a separator, in which it is
then separated into washed oil and soapstock.
The washing may be carried out as a one- or two-stage process.
If the oil contains waxes, stearin or other substances with a high melting point,
which crystallise at low temperatures, causing the oil to become cloudy, the oil is usually subjected to winterization.
Separators are also used in the winterisation process.
When it runs out of the screw press, the oil still contains a large solids fraction. It is therefore passed through a decanter, in which most of these solids are extracted centrifugally.
In order to optimise the separation of the solids, hot water is often added to the oil before it goes to the decanter. This causes the fine solids present to swell and makes them considerably easier to remove.
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