How is olive oil refined?

Olive oils of low quality (high acidity, large amount of insoluble matters, and bad aroma and flavor) are subjected to refining processes that typically include:

1. Degumming: This process removes insoluble impurities, such as gums (phospholipids), in the oil. Usually, phosphoric acid or citric acid water is used.
2. Neutralization with Alkali: This step removes free fatty acids by the use of an alkali, such as caustic soda (sodium hydroxide).
3. Decolorizing: This step is used to decolorize the oil by filtration or treatment with absorbent clay.
4. Soft Deodorization: This process eliminates undesirable odors by purging nitrogen gas into the oil at a temperature as high as 250 °C.
5. Enrichment with VOO: This enhances the flavor and quality of the oil. 5–15% addition.