If you’re a foodie interested in new flavors and trends, the expanding world of olive oils offers a new challenge.

Premium olive oils made by artisans have become the new darling of trendy cooking as the health benefits — and pleasures —of the Mediterranean kitchen become popular. In California, producers are planting olive trees as aggressively as they’re expanding vineyards, and we’re just starting to see the fruits of that labor.

It only takes a quick visit to a market to see the expansion in the olive oil market. In addition to giant gallon tins of olive oil, you can see an assortment of bottles with prices as high as $50 for ½ liter.

Two factors drive the interest in the oils. One is research showing olive oil is one of the healthiest oils available to satisfy the innate human craving for fats. It’s a monounsaturated oil containing no cholesterol, unlike oils from animal fats. It doesn’t contribute to artery-clogging and actually may help reduce build-up. Unfortunately, it’s just as fattening. All fats contain the same energy, so olive oil contributes the same 9 calories per gram as high-cholesterol butter or highly saturated palm oil.

Olive oil also tastes good. Though you can buy highly refined and virtually tasteless "pomace" cooking oil that’s great for frying, even standard olive oil contributes some flavor of olives.

Beyond the rare neutral oils, however, there’s a large selection facing the prospective buyer. The imports traditionally popular here have been labeled "olive oil" and "extra-virgin olive oil." extra-virgin olive oil is considered the finest and fruitiest of the olive oils because it’s the result of the first pressing of the olives and is no more than 1 percent acid. It is, therefore, also the most expensive. McEvoy oils of Mann County, Calif., exhibit acidity under 0.2 percent. Long Meadow Ranch, a modern Tuscan style estate in Napa Valley, makes Prato Lungo oil with acidity of 0.05 percent from century-old hillside French varieties.

Virgin olive oil is also a first-press oil, with a slightly higher level of acidity of between 1 percent and 3 percent. Products labeled simply "olive oil" are a combination of refined olive oil and virgin or extra-virgin oil. There’s also light olive oil, which has the same number of calories as any other type of olive oil. The word "light" refers to the fact that this oil is lighter in color and fragrance and has little of the classic olive-oil flavor. This makes it more ideal for use in cooking or baking than other olive oils where an olive taste may not be

Beyond the minimum standards, what distinguishes the various extra-virgin oils? Taste. They taste very different from each other and from the olive oils most of us have known.

Traditional olive oils sold here have a distinct olive flavor, but the overwhelming sensation olive oils is the slippery fattiness. New oils reflect the variety of the character of olives used, the different growing and harvesting practices, and differences in processing.

Most olives grown in California are destined for canning. Venerable Mission, Manzanilla, Sevillano and Ascolano varieties that date back to Spanish ancestors also produce copious quantities of relatively bland oil.

By comparison, most up-and-coming oil producers use Italian varieties only recently becoming known here. They include Frantoio (also the Italian term for an olive oil press), Leccino, Pendolino, Maurino, Coratina and Leccio del Como.

Many of these trees were imported by Nan Tucker McEvoy, the godmother of today’s California olive oil business. It was a slow process, requiring a quarantine to make sure the trees didn’t contain pests that could threaten American agriculture.

Starting with those 4,000 trees, she now has 11,000 trees planted on 70 acres of her 550-acre ranch in Mann County. She also sells trees from her nursery.

When the trees mature, which takes eight years, they produce about 1.5 to 1.75 gallons of oil from 100 pounds of fruit, and since the ranch is planted with 170 trees per acre, it will yield 4 to 6 tons or 120-180 gallons per acre. Eventually, she will have 13,000 trees, but this year, the production is only 1,500 gallons. It’s not a business for those looking for a quick return.

McEvoy blends her oils, which is generally a necessity at present production levels, but she may bottle the varieties separately when volume increases.

There are about 50 to 60 other new artisanal producers in California, though few are as big B.R. Cohn Winery has 10,000 trees, including 125-year-old trees in Sonoma and newly planted trees in Calaveras County, though the latter operation was sold to Kalm.

A number of growers have planted 4,000 trees, but almost none are in full production. Some are organically grown.

Along with the variety, a big factor in flavor is when the olives are picked. Pick them early and you get "green" herbaceous qualities like green peppers. This style is favored in Tuscany. Let the fruit ripen more, the flavors become mellow and fruity and yield increases.

To harvest the underripe fruit, producers lay nets on the ground and knock off the olives with flapping forks operated by air compressors. For mature fruit, it’s possible to shake the shake the whole tree, a practice popular in California’s Central Valley for fruit destined for canning.

The olive mixture of green, khaki, brown and black is first crushed, then the oil is extracted by pressing, using a centrifuge or other method.

McEvoy and a few other producers use huge traditional granite wheels to mash the olives, including the oil-rich pits. Ed Stolman, a partner and manager of The Olive Press, a supplier of artisanal oils in Glen Ellen in Sonoma County, Calif., says he intended to buy a press with stone wheels. But, he says, the Italian company he bought his equipment from convinced him to use a hammer press.

The oil is then extracted from the pulp and separated from the water in the fruit, then lightly filtered and settled. The way the oil is extracted is considered a point of differentiation by producers, but all use gentle procedures very different from the heat and solvents used by large firms.

More significant than the processing system is the actual taste of the oils. Taste them side by side and the difference is remarkable. Visit the Olive Press in Glen Ellen and you can compare many varieties — and see the press and buy oils.

Where to buy

Artisanal oils are available in most gourmet shops and some supermarkets. True extra virgin oils typically cost at least $16 per liter; the artisanal oils are more, $10 and up per ¼ liter (250 milliliters, about a cup). McEvoy is $15, Long Meadow Ranch $50 per half liter.

A number of fine oils are available from the Olive Press, which has a catalog, (707) 939~8900, and website, www.theolivepress.com. Also try McEvoy Ranch, (707) 778-2307 and www.mcevoyranch.com, and Long Meadow Ranch, (877) NAPAOIL, or www.longmeadowranch.com.

Olive oils should be used within a year or so. They don’t need to be kept in the refrigerator but should be stored in a cool, dark place.

Hold an olive oil tasting

Artisanal olive oils are expensive, so a good way to compare them is to have a tasting party where each participant can buy one bottle. The best way to taste is by saturating hearty white bread (not whole wheat or sourdough), though you can slurp it from a spoon. It may take experience to appreciate the more assertive flavors that experts love. To aficionados, the desirable characteristics are grassy, bitter, peppery and a nutty, almondlike flavor. Bad flavors are musty. Some have surprising peppery sensations in the back of the throat, others rich oily sensations.

Food with premium oil

Though you can cook with these oils, their intense flavors can be destroyed by heat; they’re better as condiments than cooking oils. Obvious uses are dipping rustic bread and as salad dressing, but they’re good over cooked and raw vegetables and to richen and flavor soups. Two traditional treats are bruschetta and cannellini beans with oil.

Bruschetta

Slice country white bread about ¾-inch thick and grill or toast until just browning golden. Rub with a cut garlic clove, then place in dish and pour fine olive oil over it liberally, then salt with coarse crystals (preferably sea salt). You also can add ripe tomatoes and other items, though they may obscure the flavor of the oil.

Cannellini beans with extra virgin olive oil

½ lb. dried cannellini beans (similar to white kidney beans)
Small onion, chopped
3 cloves of garlic
Olive oil
½-teaspoon salt
Sprig of thyme
Bay leaf
Salt and pepper to taste

Soak dried cannellim beans overnight and drain.

Sauté onion and garlic cloves in olive oil, then add beans, salt, thyme and bay leaf and cover with 2 or 3 inches of water. Bring to a boil, then reduce heat, maintaining a simmer until the beans are tender by not mushy, about 1½ hour. Make sure water covers the beans.

Drain the beans, then add fresh-ground pepper and additional salt to taste, finishing with a large pour of extra virgin olive oil. Serves four as an accompaniment to lamb or other meat.

Prato Lungo olive oil.

Artisan food oils come in nutty flavors, too

Olives aren’t the only source of premium food oils. In Napa Valley, Yountville’s California Press makes similar premium oils from nuts. The tasty oils have the same healthy monounsaturated fats of olives and boast nutty flavors that add an intriguing touch to dishes.

Nut oils are fairly popular in Europe, particularly in areas that don’t grow olives. Often pressed from broken nut meats that aren’t valuable as food, they’re the staple oil in many regions. Most are extracted with heat and solvents, creating relatively neutral cooking oils.

The California Press takes another approach. Using only

premium quality whole and half nuts, it toasts the nuts to enhance flavors and turn the oils into intense condiments. They also can be used in cooking.

The oils make superb vinaigrettes for salads or can be drizzled over food. They’re a nice alternative to the new American custom of dipping rustic bread in olive oil instead of using butter, and they give a unique taste to

vegetables. They make good mashed potatoes that don’t need gravy or butter and are a nice flavoring for pasta with toasted nuts and cheese.

The company makes oils from walnuts, pecans, ifiberts (hazelnuts), almonds and pistachios. As with the best olive oils, the nuts are cold pressed without heat or solvents. The leftover cake is ground and sifted into "nuggets" and nut flours

for cooking.

Reflecting the ingredients and hand processing, the oils cost $15 to $20 for a 250 mL bottle (about a cup). But because of their intense flavors, these oils go a long way.

California Press products are available by mail by calling (707) 944-0343. The company also offers a sampler gift package. Premium European nut oils also are available at some specialty shops.

PICKING: An employee at McEvoy oils picks olives off the ranch for the company’s extra-virgin oil

THE LAND: The McEvoy olive ranch features trees imported by Nan Tucker McEvoy.