We’ve received some questions lately about whether freezing olive oil can verify the purity of the oil. One theory we’ve heard is that only authentic Extra Virgin Olive Oil will turn solid in the refridgerator, and lesser oils will remain liquid. From what I’ve discovered through some research, this is not true. All oils will eventually turn solid if the temperature gets low enough, but some oils have been treated or ‘winterized’ to reduce the temperature at which the solids will form, for cosmetic purposes (because consumers might not buy the oil if it appears chunky or cloudy.) Further, the exact temperature at which an Extra Virgin Olive Oil will freeze (or turn solid) can not be predicted ahead of time, since it depends a great deal on the type of olive and the degree of ripeness at the time of pressing.
Here is a link to an article with much more information.