The way an olive oil smells the moment you open it tells you almost everything. A genuine extra virgin should smell of fresh grass, tomato, slightly peppery olive leaves. It should never smell ‘greasy’ or rancid — a sign it has gone off.
The second test is taste. Take a spoonful, hold it at the back of the mouth for a few seconds and draw in air. You’ll feel a gentle pepper at the back of the throat — that’s the polyphenols, the mark of a living, well-kept oil.