We all know that extra virgin olive oil has the best taste and is the best for you, but what makes it extra virgin?
The answer lies in the process that the olives go through to become olive oil.
Once the olives have been picked from the tree and washed they're turned in to a paste and placed into a centrifuge. This machine spins the olive paste - a lot like the spin cycle in your washing machine - to extract the oil from the olives.
The centrifuge part of the process is most important in determining the quality of the olive oil, specifically the heat that the olive paste is subjected to whilst it's spun: the higher the temperature, the more oil will be extracted. However, the quality of the oil drops as the temperature rises because the heat modifies the compounds in the oil. The general rule is that if the olive paste stays below 30 degrees centigrade, the oil extracted will have the extra virgin characteristics that are so sought after.
Once the process is completed the oil is tested to make sure that it can claim the extra virgin title. This is based on the acidity, which can be no more than 0.8%.
So, now you know that it's the heat which makes the difference, best keep your extra virgin olive oil away from the stove top!