Check the label to make sure it has been made from local olives.
Then choose an extra virgin oil, extracted after the first cold
pressing. The quality of an oil depends primarily on its level
of acidity; the lower the better. Best of all is <1%, between
2 and 3% of acidity is still good but of a more ordinary quality.
Olive oil has several different appellations :
Extra virgin olive oil,
Fine virgin olive oil,
Standard virgin olive oil,
Refined olive oil,
Refined olive husk oil.
Choosing an olive oil is similar to choosing a wine; it must be
tasted first. (There are professional olive oil tasters) :
Some oils go better with fish, salads or cheese. Each valley offers
an oil with a different degree of fruitiness, astringency and
lingering finish or aftertaste.
Certain oils can have a "green fruitiness" reminiscent
of the fragrance of fruit, (blackcurrant, tomato, apple). They
are relatively mild and perfect for cooking because they have
good heat stability.
Other oils have a "black fruitiness", (fragrance of underwoood,
mushrooms and truffles). These oils go best with salads and cold
dishes.
Oils from the Alpes de Haute Provence region have the reputation for being strong,
with a a bold green colouring.
Oil from Nice is
very mild with a delicate fruitiness and pale green robe or colour.