I have not yet being invited to an Olive Oil tasting so my curiosity was piqued when I saw Liz Tagami mention Nancy Ash's Oil Tasting Advice (on Olive Oil Source) recently.
As opposed to wine tastings, there is no need for spit buckets and no risk of intoxication.
Getting to your tasting place with a clean palate is still recommended.
Nancy notes this first:
the type of olive (varietal), ripeness at harvest, growing conditions
(climate, soil type), crop maintenance (irrigation, pest control),
handling of fruit from tree to mill, and the milling process itself. For
example, oil made from predominantly unripe (green) olives contain
flavors described as grassy, artichoke, or tomato leaf, whereas riper
olives tend to yield softer flavors often described as buttery, floral,
or tropical."
In between samples she suggests:
green apple (preferably Granny Smith) and then rinsing your mouth with
water."
I will let you discover the rest of her thoughts.
Some California producers now offer on-site olive oil tastings.
An example is Round Pound Estate in Rutherford who besides its Italian and Spanish style oils also has Meyer Lemon and Blood Orange scented options (pictured above).
I read that there are as many as 1000 types of olives grown around the world which opens up an ocean of flavors.