Pressing tree-ripened olives extracts a flavorful, monounsaturated oil that is prized throughout the world both for cooking (particularly in Mediterranean countries) and for salads. Today's marketplace provides a wide selection of domestic olive oil (most of which comes from California) and imported oils from France, Greece, Italy and Spain. The flavor, color and fragrance of olive oils can vary dramatically depending on distinctions such as growing region and the crop's condition. All olive oils are graded in accordance with the degree of acidity they contain. The best are cold-pressed, a chemical-free process that involves only pressure, which produces a natural level of low acidity.
Extra virgin olive oil, the cold-pressed result of the first pressing of the olives, is only 1 percent acid. It's considered the finest and fruitiest of the olive oils.