How Is Olive Oil Tasted and Evaluated for Quality?

How Is Olive Oil Tasted and Evaluated for Quality?
Professional tasters pour a small amount of EVOO into a stemless blue tasting glass.  The blue glass obscures the color of the oil so that the taster is not biased by the appearance of the oil.  The glass is cupped in the hands and swirled to warm the oil, then smelled for aroma.  A good oil will have a nice fresh fruit aroma; a bad oil will smell fermented or rancid. The oil is then sipped and mixed by pulling in air around the teeth and lips. This volatilizes the oil, which amplifies its flavor. After the oil coats the inside of the mouth, the taster swallows and breathes out through the nose. This provides what is called the retro-nasal effect, further enhancing the flavor characteristics. A good oil should taste like fresh olive fruit with some bitterness and pungency.  A bad oil may taste slightly flat, fermented, greasy, or even rancid.
– Paul Vossen