The refining methods of vegetable oil are divided into physical methods, chemical methods, and mechanical methods.

Physical methods include decolorization and deodorization.

  • Decolorization uses adsorbents to remove pigments in oil.
  • Deodorization uses water vapor to remove odors from oil under vacuum conditions.

Chemical methods include hydration degumming, acidification degumming, and alkali refining for deacidification and decolorization.

  • Hydration degumming is to add water to cause colloidal substances to swell and precipitate.
  • Acidification degumming is to addition of acid to cause phospholipids and other impurities to form colloidal substances to precipitate.
  • Alkali refining to deacidify, Decolorization involves adding alkali to neutralize free fatty acids and destroy pigments.

Mechanical methods include centrifugation, filtration, and sedimentation.

  • Centrifugal separation uses a centrifuge to separate impurity precipitates.
  • The filtration method uses a filter to separate impurity precipitates.
  • The sedimentation method uses standing water to separate insoluble impurities.

Vegetable oil processing is divided into organic solvent extraction method, pressing method, and pressing-extraction method. Unrefined oil is called "crude oil". The refining of crude oil involves selecting different refining methods according to its impurity components.

For example, in addition to a certain amount of impurities, the oil obtained by extraction also contains organic Solvent, so it is necessary to use all the refining methods mentioned above, including degreasing, degumming, alkali refining, dewaxing, decolorization, deodorization and other treatments during the refining process.

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