Seed oil

Methods of extraction

Cold pressed

Oil can be extracted using the methods of cold-pressing to crush the seeds at low temperatures to release the oils. Cold pressed oils have a neutral taste when compared to other methods. The disadvantage of the cold pressing process is the low productivity and inconsistency in quality.[1]

Expeller pressed

Expeller pressed oils are mechanically squeezed to produce the oils. Although no heat is directly applied, the temperature increase caused by the friction is not controlled as much as it is with cold-pressed oils. Expeller pressed oil tends to generate oil in higher quantities. The higher temperatures can impart a toasted or nutty flavour to the oil. Expeller pressed oils have been able to achieve 70% oil yields.

Solvent expelled

The seeds are first ground to a paste before being washed with a solvent to release the fat in the seed. Next, the solvent (Hexane is the standard) is removed using heat in a sealed chamber and distilled, leaving virtually no detectable levels of the solvent used. Solvent extraction has been able to achieve 95% oil yields. The high productivity is the main advantage of this process, it also requires less maintenance than other methods of extraction.

Pre-pressing

Extracting the oils first by expeller or cold pressing methods, then solvent expelling the rest of the oils from the leftover matter. This is a method used by larger capacity oil mills. As the energy consumption of the mechanical press increases as more oil is released, it is more efficient to extract the rest of the oil (past around 60%) by solvent extraction.[2]

References
  1. Siger, Aleksander; Nogala‐Kalucka, Malgorzata; Lampart‐Szczapa, Eleonora (2008). "The Content and Antioxidant Activity of Phenolic Compounds in Cold-Pressed Plant Oils". Journal of Food Lipids. 15 (2): 137–149. doi:10.1111/j.1745-4522.2007.00107.x. ISSN 1745-4522.
  2. "Expeller Pressed Method for Vegetable Oil Extraction". www.kmecomp.com. Retrieved 2020-05-28.


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