Olive oil is a fragrant, edible oil made from olives. It is used primarily as a salad dressing and as a cooking oil. It ranges in taste from sweet to bland and consists almost entirely of unsaturated fat (see Fat). Most olive oil has a light greenish-yellow color.
Olive oil is widely used in countries along the Mediterranean Sea. Spain is the world’s leading producer of olive oil. Greece and Italy also make large quantities of olive oil. In the United States, California accounts for almost all of the olive oil production.
Olive oil is made by crushing and pressing ripe olives. Whole olive fruit consists of 10 to 40 percent oil, and the fruit pulp is 60 to 80 percent oil. Producers use hydraulic presses to squeeze the oil out of the fruit under low pressure. This technique, called cold-pressing, generates little heat, and so the oil retains its flavor, color, and nutritional value. Thus, olive oil, unlike most other vegetable oils, needs no further processing before being packaged. In addition, olive oil can be stored for months without refrigeration or danger of spoilage.
Pressing commonly is carried out in several stages, with only some of the oil being extracted at each stage. The process remains basically the same throughout, but the quality of the oil declines with each pressing. In most cases, olives are pressed at temperatures no higher than 80 °F (27 °C). Pressing the fruit produces a mixture of oil and water. The oil is separated from the water in a spinning machine called a centrifuge, or it is skimmed off the water’s surface in a process called decanting.
The first pressing gives the highest quality oil, which is usually called virgin or extra-virgin olive oil. Virgin olive oil is more expensive than other vegetable oils. The lower-quality oils from later pressings are often blended in small amounts with such refined oils as soybean or cottonseed oil. Olive oil that comes from the final pressing is inedible. This oil, called olive residue or olive foots, is used in cosmetics, detergents, soap, medicines, and textiles.
