Olive oil is like a good wine. "The quality depends on many things - weather, the season, the year, the area, the variety of olive and the crop condition," according to the Department of Agriculture. Also like wine, one year may be good while the next a disaster.

Even though the United States produced over 4 billion pounds of cooking oil in 1977, none of it was olive oil. (California grows olives but does not manufacture oil.) "Virginia" olive oil imported from Italy, Spain, Greece and France, is the oil from the first pressing. The oil extracted after the first pressing is of inferior quality and though edible is not "Virgin" oil. There is also no guarantee that the oil you buy is really from the first pressing unless it states 100 percent virgin olive oil. To appraise its purity test a variety of oils or write the company.

The distinctive flavor of the olive is best retained by extracting the oil by the "cold pressed method." The health food crowd prefers cold pressed oil because some of the vitammins E and K are retained. Adequate research, however, has not been done to confirm the nutrition value of oil. There is also another problem. Cold pressed oils have been extracted at a temperature only slightly lower than hot pressed, so the consumer doesn't really know if the nutrients have been killed off. If the oil has been kept below 212 degrees (the boiling point of water) then it's the real stuff. Hot pressed oils are boiled, filtered and bleached to resist oxidation. Cold pressed olive oil should be refrigerated to retard rancidity.

While many Mediterranean recipes call for cooking the ingredients in olive oil, alternatives should be considered for at least two reasons.

The first is price. Olive oil from the supermarket costs $1 a cup. Its remarkable flavor might be considered essential in a salad dressing, but it has become a very costly cooking agent.

Second, cooking oils have different smoking points. Olive oil has the lowest and will catch on fire or smoke at 400 degrees. Among the cheaper alternative oils, safflower, cottonseed, corn and soybean have higher smoking points than peanut and sesame. (Soybean oil becomes foamy when heated, so it should not be used for deep frying). Walnut, hickory and sesame oils have very distinctive flavors and should be combined with a lighter oil. Nut oils also tend to break down under high heat and therefore are better suited for salad dressings.