Olive oil contains small amounts of free fatty acids (meaning not attached to other fatty acids in the form of a triglyceride). Free acidity is an important parameter that defines the quality of olive oil. It is usually expressed as a percentage of oleic acid (the main fatty acid present in olive oil) in the oil. As defined by the European Commission regulation No. 2568/91 and subsequent amendments,[1] the highest quality olive oil (extra-virgin olive oil) must feature a free acidity lower than 0.8%. Virgin olive oil is characterized by acidity between 0.8% and 2%, while lampante olive oil (a low quality oil that is not edible) features a free acidity higher than 2%.[2] The increase of free acidity in olive oil is due to free fatty acids that are released from triglycerides.