Professional olive oil tasting is done from a blue glass (so color doesn't influence judgment). The oil is warmed in the palm to 28°C, covered, and then aromas are inhaled.
Positive attributes are fruitiness (fruttato), bitterness (amaro) and pungency (piccante). These come from polyphenols and are beneficial from a health perspective.
Defects such as musty (muffa), vinegary (aceto) or muddy (morchia) indicate poor quality oil. Quality extra virgin olive oil must not have any defects.