Prized for its contribution to salads and cooked dishes, olive oil is the cornerstone of Italian and other Mediterranean cooking. It is graded according to acidity levels. The highest quality of oil will have the least amount of acid and the best, most intense flavor. Olive oils range in color from golden to greenish; in general, the deeper the color, the more intense the olive flavor.
"Extra-virgin" olive oil, the highest quality and most expensive, comes from the first pressing of the olives. Reserve extra-virgin oil for uncooked dishes such as salads, or to sprinkle onto warm foods just before serving.
"Pure" olive oil (sometimes labeled "virgin") comes from subsequent pressings of the olives. It's less expensive and most suitable for cooking.
Stored in a cool, dark place, olive oil will keep up to six months. In the refrigerator, it can be stored for up to one year; however, it becomes cloudy and thick when chilled. Let refrigerated olive oil warm to room temperature before using it.