How One Chef Is Tapping into Our Craving Centers to Build a Burger Empire

— -- Umami, a mysterious rich, savory taste – the fifth taste, in fact – is found in many foods we crave, from parmesan cheese and soy sauce to pizza and fried chicken.

Adam Fleischman, a former finance guy turned amateur chef, has built a burger empire on tapping into that umami taste.

“We’re selling a $1 million a week of burgers,” he said.

With around 25 restaurants open – Fleischman said he has lost track -- in Los Angeles, Las Vegas, Chicago and New York, he has muscled his way into an already crowded burger market, competing with the likes of Shake Shack, Five Guys and Five Napkin Burger.

Just one of Fleischman’s bizarre creations include a pumpkin spice latte burger. He also uses parmesan cheese, truffles, caramelized onions and a special house ketchup blend as toppings. While it all might seem a little out there, the concept is all based around turning the burger into a perfect vehicle for a taste explosion of umami.

“I basically just looked at a chart of how much glutamates were in certain foods, and then picked all the top 10 that have the most glutamates and then used those to make the burgers,” he said. “My first idea was pizza, but pizza required special ovens and training … So I started working with burgers.”

Glutamates are natural amino acids that are the main component in many proteins, making certain savory foods delicious. We taste “umami” through the amount of glutamates in foods, starting at birth.

“We are absolutely designed, genetically programmed to be umami cravers because that triggers our brains that this is a food that's going to deliver the necessary protein that we need to sustain our function of our bodies,” said Ihab Bishay, a food scientist with Ajinomoto, an industry leader in umami flavoring.

Western science first recognized umami as the fifth taste in 2009, after salty, sweet, bitter and sour – all based on receptors on the human tongue. But umami was first discovered in 1908 by a Japanese chemist, who figured out a way to mass produce it in a laboratory setting and called his creation “MSG,” often associated with Chinese food.

While MSG has long been accused of causing “Chinese restaurant syndrome,” with headaches, dizziness and fatigue, Bishay says the syndrome “has been debunked, pretty clearly among all the regulatory and scientific community.”

"Nightline" checked the claims and found that a majority of studies, many sponsored by producers who use it, show that MSG is safe to consume, and only a tiny percentage of the population actually has a sensitivity to large servings on an empty stomach. Bottom line is MSG is FDA approved, and it’s used in hundreds of food products from Doritos, to Stove Top stuffing to Campbell’s soup.

But Fleischman said he has never used MSG in his restaurants. “I don't have anything against it,” he said. “But I don't use it because to me it's not creative.”

ABC's Nick Watt contributed to this report.