A field guide to supermarket olive oil

Supermarket shelves can hold twenty kinds of olive oil, with labels promising everything from cold pressing to first harvest. Some of those words are meaningful. Others are just marketing.

Words that matter

• Extra virgin: the highest grade, made without heat or chemicals. Worth paying for when you taste the oil.

• Harvest date: better than a best-before date. Look for oil from the most recent harvest.

• Dark glass or tin: protects the oil from light, which spoils it.

• Single country of origin: not a guarantee of quality, but easier to trace.

Words that matter less

“Cold pressed” and “first pressed” are mostly leftovers from older methods; nearly all extra virgin oil is made this way now. “Light” refers to flavour, not calories.

Buy the smallest good bottle you can find, and finish it within two months.

A simple approach

Keep two oils. A cheaper, mild olive oil for cooking at high heat, and a small bottle of fresh extra virgin for dressing salads and finishing dishes. Store both away from the stove, and taste the good one on bread when you open it. It should smell grassy and taste slightly peppery.

How to taste it

Pour a little into a small glass, cup it in your hands to warm it slightly, then smell it. Good fresh oil smells green: cut grass, tomato leaves, green apple. Sip a small amount and breathe in through your mouth. A peppery tickle at the back of the throat is a good sign, not a fault.

Stale oil smells of crayons or old nuts and tastes flat. It will not harm you, but it will not add anything to your food either. Use it for frying and buy a fresher bottle for the table.

Price is a rough guide at best. In our own blind tasting, two of the three favourite oils were mid-priced supermarket bottles with a clear harvest date. The most expensive oil came fourth.