How to Test the Purity of Olive Oil

Labels can make many promises, but when it comes to the purity of your olive oil, how do you know what's promised is the truth — or creative marketing?

Here's a simple test: put a small amount of oil in a glass and put it in the fridge for 24 hours. If the oil becomes gel-like, then it is mostly olive oil. If the sample remains liquid, there are other oils in the bottle. It's not pure.