All in the best possible taste ...

As biotech firms have learned the hard way, anyone with a professional interest in 'meddling' with our food, and God forbid, talking about genetics in the same breath, is not likely to win any brownie points with consumers at the moment.

However, the men and women in white coats might just move up in the popularity stakes if they can help tackle the nation's expanding waistline by tricking our taste receptors into believing that healthy foods taste saltier, fattier and sweeter than they really are.

While experts in the field of genetics and sensory perception have yet to convince our kids to wolf down their sprouts with gusto, they are not far off, says Professor Tim Jacob, at Cardiff University's school of biosciences.

"There is still plenty that we don't know, but we have made enormous strides in the last few years by cloning the taste receptors for umami, sweet or bitter tastes and learning more about thermo-receptors, which bind compounds like menthol to give the sensation of coolness."

Using biological screening techniques, he says, millions of molecules can now be evaluated to find out which substances bind to which specific taste receptors. Anything that binds and activates our sweet receptors, for example, will taste sweet.

"If it binds the sweet receptor it means that we will perceive it as sweet," explains Dr Charles Zuker, professor of biology and neurosciences at the University of California, San Diego. "It doesn't matter if it looks like a sweet molecule or behaves like a sweet molecule; if it binds and activates the sweet receptor, it will be sweet."

Moneyspinner

The commercial potential of this discovery is immense, says Jacob. "The food industry is well aware of the potential. It takes us into a new league. Yes, you can do psychometric tests asking people how much sweeter this product tastes than that one, but that's subjective. Now, you can build robotic testing systems that can screen thousands of new chemical compounds a day. If a compound binds to a [cloned] taste receptor, it will probably activate it."

A major goal of the food industry has been to create a sweetener that tastes like sugar but is low-calorie, says Steven Munger, an assistant professor of anatomy and neurobiology at the University of Maryland. "It would be invaluable to know how the natural substance interacts with taste receptors so that synthetic products can be created to mimic that interaction."

Dr Munger identified the parts of two taste receptors (T1R2 and T1R3) that are critical for the detection of sucralose and natural sugars. "Previous research told us that aspartame only interacted with T1R2, while another, cyclamate, only interacts with T1R3," says Dr Munger. "We found that sugars and sucralose interact with both T1R2 and T1R3, but at different levels of intensity. This suggests that sucralose interacts with the receptors in a similar way to natural sugars, and that sugars and sucralose may need to interact with both receptors to elicit a sweet taste."

Conversely, scientists are also trying to identify compounds that could block or inhibit bitter taste receptors and momentarily block our perception of bitterness when consuming bitter-tasting medicines, diet soft drinks, coffee or even vegetables, he adds.

Other companies foresee additives that precisely mimic the taste and feel of rich foods without the fat, room deodorants that temporarily block the ability to perceive unwanted smells, and crops or fertilisers containing compounds that repel insects because they taste bitter, but are not toxic.

As knowledge of how we perceive and process food sensory cues grows, the design of new flavour compounds will proceed in a "focused, efficient and informed manner", says Carol Christensen at the Monell sensory research facility at Thomas Jefferson University in Philadelphia.

Senomyx was set up in 1999 by Charles Zuker and a clutch of other experts in neurobiology, molecular biology and biochemistry to find industrial applications for their research into sensory perception.

Senomyx now has eight "product discovery and development collaborations" with companies including Cadbury, Nestlé, Kraft, Campbell Soup and Coca-Cola, says the company. "Our novel flavour ingredients will enable companies to improve the nutritional profile of their products and generate cost savings, while maintaining or enhancing taste.

"We license our ingredients to collaborators on an exclusive basis, which will provide them with the ability to differentiate their products. Our focus is on the development of flavour enhancers which will allow for the reduction of MSG (monosodium glutamate), sugar and salt. We also have a bitter modulation programme to improve the taste of food, beverage and pharmaceutical products."

As Klaus Gubernator, a chemist at Senomyx, says: "If you have a receptor and a meaningful readout system, you can go fishing in the universe of organic chemistry and find active molecules everywhere."

Alcoholics anonymous

While the big bucks may come from developing products that will taste sweeter, creamier or saltier than they really are, however, there may also be commercial value in finding out more about the genetic basis for differences between individuals in sensory perception, says Leslie Stein, communications chief at Monell.

"Our research is interdisciplinary; we have sensory psychologists, biophysicists, biochemists, behavioural neuroscientists, environmental scientists and geneticists. Many studies focus on how genetics, age, gender, experience, and the environment influence sensory capabilities."

A key genetically determined taste difference between people is the ability to taste a bitter compound called 6-n-propylthiouracil (PROP), which is associated with a newly discovered taste receptor gene called TAS2R38.

People who cannot taste the bitterness of PROP are called non-tasters, and are able to knock back more pints than their PROP super-tasting drinking buddies, as they do not notice the bitterness or astringency in the alcohol.

However, this does not mean that non-tasters are heading for an early grave, says Valerie Duffy, associate professor in the School of Allied Health at the University of Connecticut. "PROP non-tasters experience less negative oral sensations from vegetables [they don't pick up the bitterness in sprouts], and eat more vegetables than PROP super-tasters, which may decrease their risk of chronic diseases." Super-tasters also feel more burn from chillies and more creaminess from fats and thickeners.

Awareness that responses to foods can vary because of genetic differences between individuals and groups is also likely to change the way the industry tests new products, with companies likely to try and get a genetic cross section of consumers for clinical or sensory trials in future, says Dr Angus Knight, principal scientist at Leatherhead Food International.

However, the relative importance of genetics versus other factors such as age, gender and conditioning in determining differences in sensory perception between individuals is not yet properly understood, stresses Jacob. "We can train ourselves to enjoy less sugar in products, although we don't seem to be able to do this with bitter, which makes sense in evolutionary terms as bitterness warns us that something is toxic. Sensory perception also changes with age, which explains why children don't like sprouts or strong cheese, but can stomach them as adults."

While the health benefits of fooling our taste buds into believing sprouts taste sweet might seem compelling, consumers don't want foods packed with ingredients that sound like they have been created in a laboratory, says Michael Jacobson, executive director at the Centre for Science in the Public Interest in Washington.

"Companies love artificial flavours because they are cheap," he says. "But many people's whole diets are made of 'fake foods'. It seems like this would just open up new avenues to facilitate the production of fake foods."

But 'tricking' our taste buds doesn't necessarily mean pumping food full of artificial rubbish, stresses Knight, who is convinced he can make an ambient ice-cream if he gets some industry interest.

"Once we know what triggers the receptors, we can go and find natural sources for these flavour compounds, or develop them through marker assisted breeding programmes." FM

How we taste

Smelling and tasting begins when molecules detach from foods and float into the nose and mouth, dissolve in watery mucous and bind to and stimulate receptor cells. These cells transmit electrical signals to brain centres where we perceive odours or tastes, and where we remember people, places, or events associated with these olfactory (smell) and gustatory (taste) sensations.

We typically describe only five categories of tastes (sweet, sour, umami, bitter, salty). However, each category probably has more than one type of receptor.