All types of olive oil are made from the mechanical milling of olives. This process removes approximately 90 perfect of the juice of the olive.
While there are chemical and high heat processes that are used in the production of some oils, these processes are not allowed in the production of extra virgin or virgin oils. These types of oils may not be subjected to any further processing or refining after the pressing process occurs.
By the legal definition of olive oil grades as outlined by the USDA, neither extra virgin nor virgin oils are allowed to contain any refined olive oil.
The following is an excerpt from the recent USDA olive oil grades standards revision:
(1) Virgin olive oils
(a)Virgin olive oils fit for consumption without further processing include:
i. Extra virgin olive oil
ii. Virgin olive oil.
(2) Virgin olive oil not fit for consumption without further processing designated lampante virgin olive oil.
(b) Olive oil
(c) Refined olive oil
Types of olive-pomace oil
(a) Olive-pomace oil
(b) Refined olive-pomace oil
(c) Crude olive-pomace oil
According to these standards, olive oil may only come from olives. No other oils may be mixed with olive oil for it to maintain its name for labeling purposes. Virgin olive oils may only be processed through physical means that do not involve altering the oil in any way, and no additives may be added to olive oils that are considered to be virgin.
Olive-pomace oil is a type of oil that is extracted from the pieces of olive that are left over after oil has been extracted. This oil is subjected to thermal treatment and chemical processes that render it unfit for use in cooking. Although some importers may sell this oil as a culinary oil, it is not recommended for consumption.