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Food science: Taste bud hackers

Nature volume 486, pages S14S15 (21 June 2012) | Download Citation


Scientists and psychologists are trying to trick our mouths and minds into enjoying foods that are better for us.

Tucked away in a biotechnology park in North Brunswick, New Jersey, researchers at Chromocell are trying to make us change the contents of our kitchen cupboards. They are screening hundreds of thousands of molecules to find ones that can enhance certain tastes, such as sweet or salty, with the hope of concocting foods that are kind to our waistlines but still excite our palates.

The business of creating taste enhancers and ingredient substitutes for high-sugar, high-salt and high-fat foods is decades old. Artificial sweeteners such as saccharin have been in widespread use since the mid-1900s, for example. But such products have had only modest success. Diet soda, for example, still makes up only 30% of the overall soda market. And potato crisps fried in olestra, a fat substitute with molecules too large to be absorbed by the gut, have fewer calories but prevent the body from absorbing vitamins and nutrients. Consumers complained that these crisps caused unpleasant side effects.

The combined hot and cold sensations of chilli and peppercorn might make a tasty substitute to salt. Image: CHRIS LOSS

People don't derive as much pleasure from most low-fat, low-sodium or low-calorie foods as they do from more indulgent chocolate mousses and French fries. “Fat has a taste and a smell, it can change an item's taste and smell, it has a texture and it changes texture. It's a really tricky little thing,” says Jeannine Delwiche, who leads research into reducing salt, sugar and fat at multinational PepsiCo based in Purchase, New York,. “So when you start to talk about changing fat in a food, you're going to be changing all of those things.” Which means, she says, it's very difficult to create a product that gets it all right. The food industry is hoping that an updated understanding of taste and its underlying biology will yield flavoursome formulations that are better for us than the products on the shelves today.

Fishing for flavours

One of the major steps forward in taste science in recent decades has been the discovery and exploration of distinct taste receptors on the human tongue. Our taste buds have separate receptors for, at the very least, five basic tastes: sweet, salty, sour, bitter and umami (savoury). Of these, the receptors for sweet, bitter and umami are all members of a family of proteins called G-protein-coupled receptors (GPCRs). And because GPCRs are well understood, they provide numerous opportunities for scientists looking for molecules that might trigger them.

Enter Chromocell and Senomyx, based in San Diego, California. These companies have adapted high-throughput screening systems developed by the pharmaceutical industry to find potential drug candidates against GPCRs, to identify molecules that interact with taste cells. “The whole idea of using molecular biology to trick or tweak your taste buds is kind of novel for the food industry,” says Beverly Tepper, a taste researcher at Rutgers University in New Brunswick, New Jersey.

The screening systems work by running a slew of molecules past a panel of taste receptors to see what sticks. To find new sweeteners, for instance, researchers take the protein that taste cells recognize as sweet and express it in a stable cell line. “Then we use this as a fishing net to run thousands of different compounds against that cell,” says Rudy Fritsch, who leads Chromocell's flavours and nutrition research. When the instruments indicate that one of the molecules has stuck to a receptor — much like a key in a lock — then the molecule is worth further investigation.

Senomyx and Chromocell use slightly different systems and maintain slightly different research goals. Senomyx was the first company to use a high-throughput screening approach to taste research and is concentrating on synthetic chemicals. Two of its sweet enhancers are already found in products being sold in test markets in China, Africa, North America and elsewhere.

Chromocell is taking a different tack. Rather than synthesizing potential taste enhancers in the lab, its researchers are putting more emphasis on using their high-throughput fishing net to catch natural compounds. This is an approach with popular appeal — a growing proportion of the public views artificial sweeteners and fat substitutes with suspicion, so many companies are looking instead for natural products.

Not all researchers believe that taste enhancement needs to come from new molecules isolated in a lab. Scientists in flavour houses (companies that develop chemicals for the food and drink industry), food companies and academic institutions are also seeking fresh combinations of existing tastes and flavours, or are tweaking the properties of existing ingredients, to improve a food's health profile while maintaining its appeal. They're looking for tastes and aromas that can elicit either physical or psychological reactions to help enhance flavour.

Playing around with the shape and size of salt crystals, for instance, can help lower sodium intake but maintain saltiness. Smaller crystals, or those produced in the shape of a pyramid, have more surface area and pack a bigger punch to the palate. But such crystals are only effective for solid foods, not in soup or mixtures where the salt is dissolved.

“Scientists and flavour chemists are going to be searching every blade of grass and every leaf in the Amazon for something that might potentiate taste. And there just aren't many things out there like that that have been found,” says Chris Loss, a chef and culinary scientist at the Culinary Institute of America in Hyde Park, New York. Rather than looking for something that tastes precisely like foods higher in sugar or salt, industry researchers are instead aiming to concoct healthier combinations that are just as tasty.

Because the brain associates salt with savoury, umami flavourings such as monosodium glutamate (MSG) — a salt of a non-essential amino acid that is found in many everyday foods, such as cheese and tomatoes — can enhance a food's taste so effectively that less sodium is needed to achieve the desired effect. And adding flavours that the brain associates with sugary items, such as vanilla, can trick us into thinking a food is sweeter than it really is.

Loss has been toying with different combinations that might trick the tongue into thinking it is tasting salt. “Every taste bud is surrounded by chemosensory receptors that pick up on the capsaicin in peppers or the cooling effect from menthol,” he says. Because these receptors are in such close proximity to the ones that sense taste, he wondered if “you could tickle them a little bit”, stimulating the taste receptors without the actual molecular match.

Along with Szechuan cuisine expert Shirley Cheng, Loss has used a combination of chilli peppers and a uniquely numbing type of Szechuan peppercorn to create an alternating combination of heating (chilli) and cooling (peppercorn) effects. He tried to find a combination of these ingredients that would allow him to reduce a dish's added salt. “We did a sensory test and, while we didn't find any increase in perceived saltiness, we found that people liked it equally well,” Loss says.

The renaissance in taste enhancement is not limited to processed and prepared foods. Some scientists are trying to restore taste and nutrition to foods that have gradually had the flavour bred out of them in favour of other traits, such as high yield and resilience to long-distance travel. “If we can make produce taste better, people will eat more of it,” says Harry Klee, a horticultural scientist at the University of Florida in Gainesville.

Working with other researchers at the same institute — Linda Bartoshuk, who studies taste and olfaction and Charlie Sims, who runs sensory testin — Klee has developed chemical profiles of nearly 200 different varieties of heirloom tomato. Those with the most diverse range of sugars, acids and volatile chemicals were presented to panels of 100 consumers. These taste testers noted down which ones they liked and how strong their preferences were, allowing the researchers to determine which properties of the fruits confer the most (and least) desirable flavours. By analysing the highest- and lowest-ranked tomatoes, the researchers determined which compounds contributed to overall taste1. “We could then use that data to extract the ideal recipe of the perfect tomato, which we've done,” Klee says. “Now, we can rescue the genetics of what's in the good ones and try to reincorporate those into commercial tomatoes.”

Scents and sensibility

During the taster panels, Klee and his colleagues also discovered that the smell tests used to assess a food's appeal had been going about it the wrong way. It was generally assumed that a food's odour, sniffed before it was put in the mouth, was enough to determine its impact on taste — the food industry has been operating on that assumption for decades. Indeed other research has shown that when we eat something, the odours that go up to our olfactory bulb from the back of the mouth are processed in a different part of the brain to the odours taken in when we put our nose near something and sniff.

“In previous years, people used the wrong volatiles,” Bartoshuk says. So she, Klee and Sims used a different method. By sorting the tomatoes according to taste-tester preference, the researchers were able to pinpoint the volatile compounds that actually elicited a response. They used volatiles not just to make a food smell fantastic, but also to taste fantastic — endpoints not as closely linked as had been thought. “Now we know what to look for, we've done it in tomatoes and strawberries, and we're going to do it in blueberries too,” Bartoshuk says.

Fundamentally, the Florida researchers are working towards the same goal as their counterparts in industry. “We've tried to educate people about how to eat healthier diets, but none of us do it,” Bartoshuk says. “I know perfectly well I have no business eating spare ribs but I eat them anyway because I like them. And one way to get people to eat healthier is to make [healthy] foods that they like.”


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  1. Lauren Gravitz is a science writer based in Los Angeles, California.

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