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The principles of fats and oils

Manufacture and purification of oil


There is an extremely long tradition of extracting oil. Even in ancient times, plant oils were used as a base product in various areas such as nutrition, cosmetics, medicine and fuels. In earlier times, oil was extracted in an extremely simple form. Over time, however, it was continually improved to achieve the maximum possible oil yield. (1)

Oil is extracted from oil seeds (e.g. sunflower seeds or linseeds) or oil fruits (e.g. olives). A distinction is generally made between two different processes for extracting oil: pressing and extraction. In many cases, both processes are used in tandem in order to get the most out of the base product.




The extraction of oil starts with cleaning and, where necessary, shelling the oil seeds. The oil seeds and fruit are then crushed by breaking and grinding. This ensures the maximum possible yield from the subsequent pressing.

Prior to pressing, the ground raw products are heated to a temperature of approximately 38 °C. Regular stirring during this process will prevent scorching. The benefit of heating is that the oil content becomes more fluid and can consequently be expressed more easily and effectively.

The heated mass is added to a worm extruder and compacted more and more tightly by the rotary motion. The freshly pressed oil is then slowly released as a result of the increasing pressure.

Not all of the oil is extracted from the oil seeds by pressing, so there is a subsequent "extraction" after the pressing. Using a solvent (usually hexane), the walls of the seed cells are opened at low temperatures and the remaining oil is released.

At the same time, all useful liposoluble contents such as vitamin E are also extracted from the cells.After the extraction, the solvent is completely removed from the oil by means of evaporation.

The last step in the production of oil is the "refinement" (purification) of the oil. Undesirable flavourings and escort substances are then removed from the oil in various phases and at temperatures no higher than 200 °C. By removing substances harmful to the environment, fibrils and colourings which have entered the oil and by diluting extremely intense inherent flavourings, the oil is made more durable and the appearance is improved. In some cases, oils are not edible until they have been refined. This is the case with soya bean oil, for example. This would not be fit for consumption without refinement, as it contains a number of bitter compounds.

However, useful ingredients such as unsaturated fatty acids or vitamin E are not impaired by this step and remain in the oil. 

There are, however, exceptions which prohibit the refinement of certain oils. This is the case with cold-pressed olive oil, for example, which cannot be refined according to EU directives. (2)

These oils are described in retail as cold-pressed or cold-crushed; this means that "no external heat was applied during pressing".




This method consists of an extremely gentle pressing, but the oil yield is not particularly big. Cold-pressed oils are then only washed, dried, filtered and steamed slightly. Residues which are transferred from the oil fruit to the oil are not removed from the oil as a result of this process. It is therefore particularly important for cold-pressed oils to select the oil fruits carefully so that all health risks can be excluded. Unrefined oils are described as "virgin oils". (3)

In its product line of premium oils, HollaOils exclusively utilizes high-quality sunflower material. Only cold-pressed oil from controlled-origin sunflower seeds is employed, preventing the presence of hexane in the final product. This focus on quality over quantity results in a remarkable enhancement of the end product's overall quality.


(1)      Structure of fats, p. 18 f; from: Natürlich mit Pflanzenöl, 2nd edition, Margarine-Institut; Hamburg.

(2)      http://www.dgfett.de/material/raffin. php Last updated 08 Apr. 2014

(3)     Gift from the sun: plant oil, p. 18 f, from: Natürlich mit Pflanzenöl, 2nd edition, Margarine-Institut; Hamburg.

 

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