When Craig Purdy, a New York entrepreneur, asked chef Jonathan Pratt for an innovative restaurant concept, Pratt jumped at the chance to tell him about umami.

Pizza and portabellas are known for their high umami taste. (Ann Heisenfelt/Dean Fosdick/Associated Press)

He had come to think of it as a clandestine fifth taste, added to the list of what humans already savour — salty, sweet, bitter, sour.

Pratt believed it was also the secret to getting customers to return time and again.

"A popular Hawaiian chef told me it was a craving triggered by foods with high levels of natural glutamic acid," explained Pratt. "And I thought, oh wow, I could open a restaurant where the food is actually addictive."

Now, six years later, Purdy and Pratt run Umami Café in the small village of Croton-on-Hudson, New York.

Every dish at the New York Times-acclaimed café combines at least three umami foods. Their Truffles Mac and Cheese maxes out at five or more, including wine, cream, black truffles and two cheeses — parmigiano reggiano and fontina.

When umami is an unfamiliar concept to some new customers, Pratt tells them to think about the taste of potato chips. You can't eat just one, but it's not because of the salt. If that were the case, pretzels and corn chips would be scarfed down in the same number.

It's actually the umami in the potato that turns the trick, he said. And when potato slices are fried up, they lose water content, which concentrates the glutamic acid in each mouthful.

Umami upsurge

Umami was first identified in Japan, in 1908, when Dr. Kikunae Ikeda concluded that kombu, a type of edible seaweed, had a different taste than most foods.

He conducted experiments that found that the high concentration of glutamate in kombu was what made it so tasty. From there, he crystallized monosodium glutamate (MSG), the seasoning that would become popular the world over.

Decades later, umami became scientifically defined as one of the five individual tastes sensed by receptors on the tongue.

Then in 1996, a team of University of Miami researchers studying taste perception made another breakthrough. They discovered separate taste receptor cells in the tongue for detecting umami. Before then, the concept was uncharted.

"Up until our research, the predominate wisdom in the scientific community was that umami was not a separate sense. It was just a combination of the other four qualities [salty, sweet, bitter, sour]," explained Dr. Stephen Roper, the University of Miami physiology and biophysics professor who helped zero in on the taste along with Nirupa Chaudhari, the team's lead researcher.

After the team published a paper about umami in 2000, there was an upsurge in umami talk. Suddenly, scientific journals and the mass media reported on it. Google tracked thousands of pages of discussion where before there were next to none.

A taste from "your mommy"

The team's discovery was important because umami could now be seen as an ancient sense that was part of human evolution. Moreover, they found that animals were able to savour it as well, which meant it had likely developed early on in the evolutionary process.

"Umami is not something that humans have just evolved. Glutamate taste is as fundamental as sweet, bitter, salty and sour," Roper said.

For North Americans, the flavour tends to be more difficult to identify. In Japan, it's quite easily recognized because the idea of umami is a part of the culture.

But the sense is not based on race or culture. Nearly everyone is able to sense it, although an estimated five per cent of the population has relatively low sensitivity to umami taste.

Scientists think it might be a measure for determining the protein content of food, which is essential for survival: "If umami is a signal for protein, it's a food stuff that we want and need to consume — and indeed it is a universally-preferred taste about our basic nutritional requirements," explained Roper.

How do you know you're tasting it?

Foods high in protein are the ones best for sensing umami. Parmesan cheese, the quintessential umami reference, is high in protein, and aged, which means moisture escapes and glutamate concentrates.

Similarly, cured prosciuto has high levels of it as well.

The flavour also comes in vegetarian form. It's the "meaty" taste especially present in juicy beefsteak tomatoes (the riper the better), sugar snap peas, grapefruit, tofu and shiitake mushrooms.

Piles of umami toppings on pizza — tomatoes, pepperoni, mozzarella and mushrooms — could very well be responsible for why people, and especially kids, love it.

MSG connection

The taste of MSG is a good signifier of how umami is set off by other substances. The seasoning isn't palatable on its own (it's like brownies without the called-for pinch of salt).

In the 1960s, Chinese food laced with MSG (crystallized umami) developed a bad rep for causing health problems in some people. Since then, studies have shown it needn't be unhealthy when used in moderation.

Many Asian foods are packed with natural umami, especially Thai cuisine, which uses fish sauce, a.k.a. umami in a bottle.

Snack food manufacturers also jumped on the umami bandwagon. Hydrolyzed protein, a form of glutamate added to snacks, is what brings shoppers back to the junk food aisle. It's the same technique Pratt uses to keep customers returning to the Umami Café.

Sometimes people even beg for it, he said. They ask for his dishes "like it's the best thing they've ever tasted."

Does the umami addiction work then? "Well, from the moment we opened the café, Pratt said. "It's been busy ever since."

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