Bitter blockers a new way to alter taste

BY FAYE FLAM

Knight Ridder Newspapers

Story last updated at 6:57 a.m. Monday, May 19, 2003

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If Shawn Marcell and his colleagues succeed, the world will soon be introduced to a new kind of food additive that will change the taste of canned soups, coffee and dozens of other staples of the American diet.

Called bitter blockers, these substances are designed to fool the cells in your taste buds into ignoring bitter elements in food, beverages or medicine.

Bitter blockers represent a new approach to altering taste, based on the scientific understanding of the way the sense of taste works. While cooks have long used salt, sugar, spices and other flavorings to cover up bitterness, the new technology of taste promises to work directly with your sensory system, interfering with the connections between your taste buds and your brain.

"There's a huge interest in this in the pharmaceutical industry," said Marcell, chief executive officer of Linguagen Corp. in Cranbury, N.J. A spoonful of sugar is not enough to get some really bad medicines to go down, apparently. Marcell said pharmaceutical companies spend millions seeking formulations that children can tolerate.

Marcell, who has a business background coupled with an enthusiasm for the science of taste, argues that bitter blockers will most likely improve America's health. The ones they've discovered so far are natural substances already found in foods such as meat, fish and milk.

These substances have virtually no calories and no sodium, Marcell said.

They could tremendously cut down on the large amounts of salt, fat and sugar often used to make canned soups and other processed foods palatable.

Many canned foods taste bitter because they must be cooked at high heat to kill bacteria. The cooking triggers a chemical process called a maillard reaction, which produces bitter by-products.

Bitter blockers also might be added to artificially sweetened sodas to cut the Nutrasweet/saccharin aftertaste. That improvement could steer more people away from high calorie, sugar-laden drinks.

In their laboratory, situated in an office complex off the New Jersey Turnpike, Linguagen scientists have discovered 20 bitter blockers. One of them, AMP (adenosine monophosphate), is less than a month away from securing approval from the federal Food and Drug Administration, Marcell said.

Because AMP has been found to occur naturally in foods, it does not have to go through the usual six to 10 years of testing required by the FDA for a new food additive, he said. Instead, it falls into the category of "Generally Regarded as Safe," and can be approved much faster.

The search for bitter blockers has gone on for years. Bitterness stands out as the one truly unpleasant member of the five types of taste sensations, which also include sweet, sour, salty and a new one discovered in Japan called umami, a taste that's in meat and mushrooms and doesn't translate well into English but might very roughly be described as savory.

Smell is also important in sensing more complex flavors beyond the basic five. How exactly we sense these various tastes was something of a mystery until recently.

Gone is the old theory that different areas of the tongue are responsible for discerning different tastes. Instead, inside the taste buds, which are distributed around your tongue, are a variety of specialized cells called receptors. Each type is geared to taste different substances.

Molecules that transmit flavors will fit, lock-and-key style, into docking ports on these taste receptors. Say you take a swig of stale, black office coffee. The molecules of caffeine and other bitter substances will activate some of the bitter receptors on your tongue. This sets in motion a chain of chemical events, or cascade, that eventually sends a nerve impulse to your the brain, telling you that the coffee tastes terrible.

Flavor chemist Robert Margolskee, who founded Linguagen in 1995, discovered one of the key players in this cascade. It's a protein called gustductin, which swings into action once a flavor receptor is triggered.

After he discovered gustductin in the early 1990s, Margolskee started to look for substances that would interfere with it or with other links in the chain of taste perception.

But tasting bitter substances is a complicated matter. Humans have at least 25 kinds of bitter receptors, each sensitive to a slightly different array of bitter substances.

Such a redundant, complicated system appears to have evolved in humans and other animals in order to help us avoid poisonous substances.

But at the same time, sometimes the most healthful foods, like broccoli, cauliflower and Brussels sprouts, contain both a small amount of a bitter-tasting chemical and some important cancer-fighting nutrients.

Gary Beauchamp, director of the Monell Chemical Senses Center at the University of Pennsylvania, said that Linguagen's potential new products are not the only substances known to block bitterness.

Two years ago, Monell researchers compared the bitter-blocking properties of dozens of different substances, adding them to quinine, acetaminophen and other notoriously bitter medicines. The researchers taste-tested these on a group of volunteers, who reported that they liked the effects of AMP as well as sodium and MSG (monosodium glutamate).

Sodium can come in forms other than ordinary table salt, or sodium chloride, said Beauchamp. In other forms, sodium will taste less salty.

Study subjects reported that MSG and AMP worked equally well, but both imparted a not-always desirable savory taste.

Beauchamp said that Linguagen pioneered a unique method to search for bitter blockers, a method that's also being applied to a search for new sweeteners.

"We're trying to reconstruct your tongue in a test tube," said Steve Gravina, Linguagen's research director.

He said he tests about 1,200 substances a day, all of which are compounds that occur naturally in plants.

The candidate compounds come from companies that specialize in creating vast "libraries" of them, he said. Other researchers use the same libraries and similar methods to investigate whether different substances fight cancer or kill viruses.

Gravina says the test tube assay is just a first step.

Those candidates that look promising are tested on rats whose water has been laced with some colorless, odorless but bitter compound, such as caffeine.

If the rats seem to like an otherwise nasty drink with the blocker added, and even choose it when ordinary water is around, then the researchers know it's working.

Linguagen researchers farm out their official taste-testing trials to Rutgers University's Cook College in New Brunswick, N.J. There, nutrition and food science professor Beverly Tepper allows visitors and reporters to take the test, which involves tasting the experimental bitter blocker in a caffeine solution, coffee and grapefruit juice.

The caffeine solution tasted horribly bitter with a nasty lingering aftertaste.

With AMP added, it still tasted bitter but the sensation went away almost immediately. In lukewarm black coffee, AMP also cut the aftertaste and seemed to bring out more subtle, roasted flavors that were overwhelmed initially by the bitterness.

In the grapefruit juice, the AMP made it ever so slightly sweeter.

Soon, said Marcell, canned goods could start to contain AMP or other bitter blockers to eliminate unpleasant or bitter tastes.

Bitter blockers might end up in packets next to the sugar, saccharin and Nutrasweet.

They might even find their way into kitchen cabinets, where cooks could add them to foods such as tofu and broccoli. Perhaps, with help, Brussels sprouts could gain newfound popularity.