For those who didn't grow up on the Mediterranean, olive oil probably wasn't a staple in the pantry. Bland vegetable oils, hydrogenated vegetable fats, butter, margarine and lard have always been the preferred fats in lands where the olive doesn't grow. Only in recent years has olive oil acquired gourmet taste.
For much of Spain, where lack of grazing land meant no animal fats, the use of olive oil has flavoured cooking ever since Roman times. The Spanish word for oil, aceite, comes from the Arabic which means "juice of the olive". Olive oil is the only oil which, extracted by mechanical and physical processes, can be consumed without any further refining. This is know as virgin oil or aceite de oliva virgen, a completely natural product containing all the flavour, aroma, vitamins and other nutritional attributes of the fruit from which it derives.
The oil is classified by degree of acidity, the percentage of oleic acid. The higher the degree of acidity, the stronger the oil's flavour. Extra virgen is allowed an acidity of not more than 1°, fino between 1° and 1.5°. Virgin oils with greater acidity are generally considered too strong-tasting and are treated with refining procedures. What is called aceite de oliva puro, pure olive oil, is actually a mixture of virgin oil and refined olive oil. This may range from an acidity of 0.4° to 1°. It still has the real olive flavour, but without the fruitiness so prized in virgin oil. The higher the acidity, the lower the price.
All other vegetable oils are extracted by means of chemical dissolvents, followed by a distillation process to remove the dissolvents. None is edible at this point and must undergo refining. This consists of neutralization, bleaching, deodorization and winterization. Each step, especially the ones involving heat, changes the composition of the oil and destroys the natural vitamins and antioxidant, which must be replaced as additives. Most other vegetable oils are cheaper than olive oil, which, because of its labour-intensive cultivation and picking, will never be price-competitive.
After olive oil, the most extensively produced oil in Spain is sunflower, aceite de girasol. Safflower oil, aceite de cártamo, is little found in local markets. Buy it in health food shops. Peanut oil, aceite de cacahuete, and soy oil, aceite de soja, are sporadically available. Corn oil, aceite de maíz, has become very prevelant, but is by no means cheap. Rapeseed oil, aceite de colza, is little used as a cooking oil, but has many industrial uses. Aceite de semillas is an authorized mixture of any of these oils except olive and soy.