Tuscan or sicilian?
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As you can expect, there is no such thing as "best," only what tastes best to you, as the taste profiles -- fruity, bitter, peppery, etc.-- vary greatly and affect your tastebuds differently than other people's. We use the Sicilian Frantoia almost exclusively because we like it and it is reasonably priced. We also like Ranieri from Liguria. Some people swear by the less expensive Spanish Columela, though we haven't tried it.
I've read also capezzana uses 3 varieties of olives and is rich that way. Will try Ligurian
Francois is our fave. Also like jansal valley wasabi infused olive oil for a hot kick ( but mainly as a finishing oil)...
Whichever brand or location you choose, the best quality products will have a date on the label just like wine. Olives preseason the late fall usually do not hit North American shelves until the following spring at best. So, look for a date with a year. A date three years old will not be as fresh as one a year old.
"preseason" should say "pressed". (darn iPad speller)!