Americans are taught from an early age that there are four basic tastes -- sweet, salty, sour and bitter. But what describes the taste of chicken soup?

To an increasing number of chefs and food-industry insiders, the answer is "umami," dubbed "the fifth taste." First identified by a Japanese scientist a century ago, umami has long been an obscure culinary concept. Hard to describe, it is usually defined as a meaty, savory, satisfying taste.

But now, in the wake of breakthroughs in food science -- and amid a burst of competition between ingredient makers to create new food flavorings -- umami is going mainstream. Chefs including Jean-Georges Vongerichten are offering what they call "umami bombs," dishes that pile on ingredients naturally rich in umami for an explosive taste. Packaged-food companies such as Nestlé, Frito-Lay and Campbell's Soup are trying to ramp up the umami taste in foods like low-sodium soup to make them taste better, while the nation's mushroom farmers are advertising their produce to chefs as an ideal way to get the umami taste.

The food industry is embracing umami as part of an effort to deliver highly flavored foods to consumers while also cutting back on fat, salt, sugar and artificial ingredients. At the same time, more consumers are scrutinizing food labels for chemical-sounding words and unhealthy ingredients.

To understand the taste of umami, imagine a perfectly dressed Caesar salad, redolent of Parmesan cheese, minced anchovies and Worcestershire sauce; or slurping chicken soup; or biting into a slice of pepperoni-and-mushroom pizza. The savory taste of these foods, and the full, tongue-coating sensation they provide, is umami.

While umami is a relatively new concept in this country, it has been well known in parts of Asia for nearly 100 years. It was identified in the early 20th century by Kikunae Ikeda, a Japanese scientist who coined the name umami (pronounced "oo-MA-mee") using the Japanese term for "deliciousness." He found that foods with the umami taste have a high level of glutamate, an amino acid and a building block of protein. Mr. Ikeda developed and patented a method of making monosodium glutamate, or MSG, a processed additive that adds umami taste to food, much as sugar makes things taste sweet.

MSG, which was first manufactured by the company Ajinomoto in 1909, is made through a complex process that involves fermenting corn glucose and other raw materials. Today, an estimated 95,000 metric tons of MSG are sold in North America each year, according to Ajinomoto. It appears in everything from some McDonald's sausage and chicken meals to supermarket items like Campbell's soup, Doritos chips and Kraft macaroni and cheese.
Umami Boosters

See 10 ingredients chefs are turning to to ramp up the umami taste.

Plus, listen to tips on trying umami at home.

What MSG has going for it is that it is a readily available, inexpensive, intensely umami ingredient with no off-flavors -- just as sugar is a classic expression of sweet and salt is perfectly salty. (Other ingredients also add umami, including yeast extracts, but these can add flavors some product developers don't want.) In many parts of Asia, it is as common to add a dash of MSG to dishes as it is for cooks here to toss in a little salt or sugar. But in the U.S., MSG has developed a bad reputation as a suspicious additive that many consumers believe gives them allergies or headaches.

In fact, many studies have found that MSG doesn't cause ill effects. "I don't see normal amounts of MSG as posing a risk to the vast majority of people," says Michael Jacobson, executive director of the Center for Science in the Public Interest, a Washington food-safety advocacy group.

For years, Western chefs and food scientists debated whether umami was a true taste, as fundamental to the sensory system as sweet or sour. That changed in 2000 when scientists at the University of Miami published a study -- partly funded by Ajinomoto -- identifying receptors on the tongue with no purpose other than to recognize the presence of glutamate. Subsequent studies, some funded by the ingredient industry and others without industry funding, identified other umami receptors.

While there is debate about which study is correct, scientists now widely believe that the body was designed to recognize glutamate, says Gary Beauchamp, director of the Monell Chemical Senses Center in Philadelphia, a sensory research institute that also receives some Ajinomoto funding. Just as we crave sweets as a spur to seek out carbohydrates, we are also geared to enjoy glutamate so that we will eat proteins, he says.
[Umami photo]

Jean-Georges Vongerichten's 'umami bomb' of Parmesan custard and white truffles.

A Monell study found that babies will eat more soup if it has small doses of glutamate. (When my 17-month-old son had a recent bout of pneumonia and lost his appetite, a grating of Parmesan, one of the foods highest in glutamate in the Western diet, helped entice him to eat noodles, rice and lentils.)

Umami's acceptance as the fifth taste has spurred everyone from high-end chefs to packaged-food makers to find ways of delivering the taste to foods. Because MSG's negative connotation has persisted in the West, that often means finding MSG substitutes. Mr. Vongerichten creates intense umami-tasting dishes, which he dubs umami "bombs," at his various restaurants. "The ultimate umami dish is expensive," he says, citing a $185 Parmesan custard with white truffles at his New York restaurant Jean Georges. His less pricey umami bombs include a $12 lunch dish of black bread with sea urchin.

Hiro Sone, chef and co-owner of Ame, a new-American restaurant in San Francisco, touts his "umami soy sauce," enhanced with kombu, a type of seaweed, and bonito flakes, which are pieces of dried fish. When added to cuttlefish and sea urchin, the umami sauce is "like an MSG bomb," Mr. Sone says, but without any MSG.

Interest in umami is driving new research and development among companies that create and manufacture flavorings for the processed-food industry. These can range from natural ingredients to artificial flavors that essentially are to MSG what saccharine and aspartame are to sugar. Senomyx, an ingredient-making company in San Diego that went public in 2004, has developed an artificial taste bud, complete with umami receptors, in its lab. The company uses it to test reactions to thousands of ingredients.

So far, Senomyx has identified four new umami ingredients that can often be used in small enough amounts to be listed on a food label simply as "artificial flavors." This is a boon to food companies because it eliminates the need to add an unfamiliar, chemical-sounding word to an ingredient list.

Nestlé is using one of the Senomyx umami ingredients in bouillon cubes in the Caribbean, instant noodle dishes in Brazil and powdered seasoning in parts of Central America, all under the company's Maggi brand.

When Campbell's recently reformulated its soups to lower the sodium content, part of the focus was on "including ingredients that would provide umami-type characteristics," says George Dowdie, Campbell's senior vice president of global research and development and quality. Mr. Dowdie wouldn't reveal which ingredients did the trick but says it was a combination of natural foods -- things like cheese, mushrooms and tomatoes -- and proprietary flavorings from flavor companies. He adds that the company is hoping to learn more about umami through a research deal it has made with Senomyx.

In mid-July, Frito-Lay, a unit of PepsiCo, hired its first executive chef, Stephen Kalil. Mr. Kalil says he is experimenting with umami ingredients from Latin and Asian cultures -- like cheese powder, anchovy powder, fermented soybean products and mushroom powder -- to create new flavors for brands including Lay's and Flat Earth vegetable and fruit crisps. The company has no plans to replace the MSG in certain products, however. "If we were to change the flavor of Doritos, for our 18-to-24-year-old male consumer there would probably be a riot," says Mike Zbuchalski, vice president of culinary innovation for Frito-Lay North America.

Dairy Management Inc., a trade group for the dairy industry, recently funded research into what compounds cause the umami taste in Swiss and cheddar cheese, in the hope of learning how to give cheese umami taste more consistently and quickly.

The Mushroom Council, a trade group for the mushroom industry, has distributed a report to restaurants about how mushrooms contribute to umami. Titled "Umami: If You've Got It, Flaunt It," it offers instructions in "building the U-bomb," by sautéing mushrooms and adding them to grilled steak.

Some of the biggest promoters of the idea that there are umami-rich alternatives to MSG in many foods we eat are MSG makers themselves. A consortium of MSG manufacturers, led by Ajinomoto, sponsors the Tokyo-based Umami Manufacturers Association. The group hosts conferences about umami and publishes a Web site in English featuring MSG-free umami recipes.

"We are hoping that eventually people will become familiar with why this flavor enhancer is in our food -- well, because it's giving my food the taste that I like," says Kitty Broihier, a consultant for Ajinomoto Food Ingredients, a Chicago-based subsidiary of Ajinomoto. By emphasizing that the glutamate in food is the same as the glutamate in MSG, makers hope to make people think of MSG as a more natural ingredient.

For home cooks, umami can open up an entire pantry of ingredients. Just as a few shakes of salt can improve a dish, a correctly applied dash of cheese, wine or even ketchup can pump up the umami, without overwhelming the dish with the flavor of the added ingredient. Cooks skilled in umami can reduce the fat and salt content of foods without sacrificing flavor. There are several ways to boost the umami taste in a meal (see the accompanying graphic for umami tricks used by top chefs). One is to add ingredients rich in glutamate, such as Parmesan (even a rind tossed into the soup pot deepens flavor) or other types of aged cheese; soy sauce; tomato products such as juice, paste or ketchup; and fish-based sauces (like Worcestershire and Thai fish sauce). Another is to use foods high in certain nucleotides, another compound that contributes to the umami taste. These include many kinds of seafood, mushrooms and meat, especially veal and stocks made from bones.

For a more powerful effect, cooks can combine foods from those two categories. For reasons scientists don't entirely understand, when glutamate is combined with certain nucleotides, the umami effect is magnified.

Finally, cooks can build umami flavor through technique. In general, any process that breaks down protein, including drying, aging, curing and slow cooking, increases umami. This is because glutamate, normally bound up in proteins, is released into a form the tongue can perceive as umami when proteins are broken down, says Chris Loss, a senior culinary scientist at the Culinary Institute of America in St. Helena, Calif.
Gary Danko's Tomato Soup

Roasting tomatoes increases their umami taste. In this recipe from Gary Danko, chef at San Francisco's Restaurant Gary Danko, the addition of tomato paste, ketchup, Worcestershire sauce (based partially on umami-rich anchovies), soy sauce and grated Parmesan pumps up the rich, savory taste. When using canned tomatoes, Mr. Danko prefers to use whole tomatoes in purée, imported from Italy. However, canned whole tomatoes in juice will work as well.
[Tomato soup photo]

Yield: Serves 6 (about 8 cups)
Preparation time: 30 minutes
Cooking time: 55 minutes total

2 pounds plum Roma tomatoes or 3 (28-ounce) cans whole tomatoes
6 garlic cloves smashed and peeled
3 small yellow onions (about 1 pound), peeled and cut into ½-inch dice
2 teaspoons salt
¼ teaspoon dried thyme
4 tablespoons extra-virgin olive oil
1 stalk celery or ½ fennel bulb (about 4 ounces), cut into ¼-inch dice
¼ cup tomato paste
3 tablespoons tomato ketchup
2 teaspoons Worcestershire sauce
1 teaspoon soy sauce
¼ teaspoon Tabasco sauce
2-3 cups chicken broth, vegetable stock or water
4-6 large fresh basil leaves, chopped
2 fresh mint leaves, chopped
¼ cup finely grated Parmigiano Reggiano cheese
Pairings
[john and dottie]

Wall Street Journal wine columnists Dorothy J. Gaiter and John Brecher suggest wine pairings for this meal.

With the tomato soup, Chef Danko suggests dry rosé Champagne and we're so pleased to hear someone recommending bubbly with meals. Too often, people think of sparkling wine simply as a celebratory beverage to drink on its own, but bubblies are often great with food. Chef Danko particularly likes Dom Ruinart rosé Champagne (about $68). We'd also suggest rosé Champagne from Louis Roederer, Moët & Chandon, Camille Savès, Gosset, Taittinger, Veuve Clicquot and Henriot. Those will all cost around $40 to $70. Fortunately, the world is awash in good rosé sparklers at thriftier prices. Cristalino, which is a Cava from Spain, makes a delightful rosé sparkler for around $8 and, in Alsace, Lucien Albrecht makes a rosé bubbly for about $19 that's the best non-Champagne pink sparkler we've had in some time. You can contact us at wine@wsj.com.

* Preheat the oven to 375 degrees.
* If using fresh tomatoes, wash, dry and core them. If using canned tomatoes, drain tomatoes, reserving the purée or juice. Halve the tomatoes lengthwise.
* Divide tomatoes between 2 shallow baking pans, arranging them cut-side down in a single layer without crowding. Sprinkle the garlic, onions, salt and thyme over the tomatoes and drizzle with oil.
* Roast until tomatoes are slightly browned and tender, about 45 minutes. Let cool slightly.
* Put the celery or fennel, tomato paste, ketchup, Worcestershire, Tabasco and soy sauce in a blender. Add some of the roasted tomato mixture and stock and blend until smooth. Strain through a medium strainer into a pot, pressing the solids with the bottom of a ladle or a rubber spatula to remove the seeds and small skin particles. Working in small batches, continue to purée and strain the remaining tomato mixture, the reserved purée or juices from the can and the remaining stock into the pot, using 2 cups of liquid total.
* Bring soup to a slow simmer over medium-high heat, stirring to combine, about 10 minutes. Thin with additional stock if necessary. Correct salt as needed.
* Serve in bowls with a sprinkle of basil, mint and cheese.

Jody Adams's Balsamic-Marinated Chicken Stuffed With Green Olives (a.k.a. Roxanne's Roast Chicken)

Chef Jody Adams has served a duck dish using the same marinade and technique at Rialto in Boston for about 20 years, she says. Five years ago, while attending a culinary lecture about umami, she realized why this dish is a customer favorite: The soy sauce, balsamic vinegar, olives and poultry are all rich in umami compounds. A long marinade and slow roasting magnifies those flavors.
[roast chicken]

Yield: Serves 4
Prep time: 10 minutes (plus the time to bring chicken to room temp.)
Cooking time: about 1 ½ hours (mostly inactive aside from turning the chicken)
Resting time: 10 minutes

½ cup balsamic vinegar
¼ cup soy sauce
¼ cup Dijon mustard
1 ½ teaspoons mustard seeds
1 ½ teaspoons dried rosemary
1 ½ teaspoons freshly ground black pepper
½ small white onion, chopped into ¼ inch dice
1 (4-pound) roasting chicken
12 large pitted Sicilian green olives

* Mix the vinegar, soy sauce, mustard, mustard seeds, rosemary, pepper and onion together in a bowl large enough to hold the chicken, and set aside.
* Remove the package from the cavity of the chicken; reserve for another use or discard it. Taking care to work directly over a sink, and not spray chicken juices around the kitchen, rinse the chicken inside and out and then dry thoroughly with paper towels. Roll the chicken all around in the marinade, making sure plenty of marinade flows inside the cavity. Cover and marinate 8 hours to overnight in the fridge. Alternatively, put the chicken into a large resealable plastic bag, pour the marinade over the chicken and into the cavity, seal, and refrigerate.
* Prior to cooking, bring the chicken to room temperature. Preheat the oven to 375 degrees.
* Remove the chicken from the marinade, allowing any that clings to the chicken to remain. Save the marinade in the bowl. Put the olives in the cavity of the chicken. Set the chicken, breast side down, on a non-stick rack, or a rack sprayed with cooking oil, in a roasting pan. Add ½ inch water to the roasting pan to prevent the juices from burning. Roast for 50 minutes. Flip the bird, taking care not to lose the olives; pour the reserved marinade over the bird; tuck the wingtips underneath and continue roasting for 40 minutes or until the chicken is done. If the skin begins to get too brown, tent the breast with a piece of foil and continue roasting until the bird is done. The chicken is done when the leg bones have a little play in the socket when you try to wiggle them. A thermometer inserted into the thicket part of the thigh should read 170 degrees.
* Transfer the chicken to a cutting board or serving platter and let the chicken rest 10 minutes before carving.