Extra virgin olive oil, a common question

Generally, when I talk about extra-virgin olive oil and its amazing properties, I get several questions. The first one is about the adjective "extra virgin", whay is this "extra virgin? What does it mean? I explain that virgin and extra-virgin olive oils are those ones obtained exclusively by mechanical processes of the fresh fruits, the olives and that the difference between extra-virgin and virgin are in some chemical parameters of the oil. Here the chemical aspect! The Reg. CE 2568/91 and the Reg. CE 1989/03 contains the limits of these parameters. The first one is the acidity. Of course, when you are having a dinner with friends, it is not easy to get into chemistry for several time, so the conversation ends after replying to this and last question: what is the acidity of olive oil? I say that by our law the extra-virgin olive oil needs to have an acidity lower than 0.8% in oleic acid. Here the most difficult part, to explain this concept to people never studied it. Olive oil and vegetable oils contains mainly triglycerides that are esters of glycerol and fatty acids. The acidity is the content of the main representative free fatty acid in the oil, so more the free fatty acid, more the acidity, less pure in triglycerides the oil. That's why we call EXTRA-VIRGIN an olive oil with a really low content of free fatty acid, no more that 0.8% by weight. At the end of the conversation probably my friends know something more about chemistry appreciating in any case the beautiful scent of a pure sicilian extra-virgin olive oil in their meals!