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Mark Dewis is a king among flavor scientists. But right now, the director of flavor research and development at International Flavors & Fragrances (IFF), one of the world’s biggest flavor companies, resembles nothing so much as a kid who can’t wait for show-and-tell. He grins widely as he describes his new million-dollar machine. “There are only five of these in the world,” he boasts, throwing open the lab door.
Filling the center of the room from floor to ceiling is what looks like a small building with a lot of stainless-steel tubing attached. It’s a high-performance liquid chromatograph, an instrument that separates compounds according to their chemical affinity with certain solvents and resins. Dewis calls it a “Sepbox,” which is his particular instrument’s trade name, and it’s one of the largest on the planet. It is, in effect, a giant mouth, and in cabinets along the wall are jars full of the food he feeds it. The labels look familiar-“oregano,” “olives,” “coffee”-but there are three jars of each, broken down into flakes or waxy pellets by different solvents.
Dewis digs up all kinds of things to be tasted by his stainless-steel pet. When food scientists suspect that there might be, for example, a molecule in orange peel that makes citrus taste particularly fresh, Dewis feeds extracts of peel to the Sepbox, and out the other end come hundreds of chemical compounds, separated into groups, for further analysis. Then, a few years later, a new flavor of energy drink hits the market.
Once upon a time, flavor research was a matter of asking housewives to munch a few potato chips in the hopes that the company had stumbled on the perfect formula for reconstituting potatoes. But as the science became more sophisticated, and market pressures demanded more novelty and authenticity, flavor scientists had to create new varieties like “Mesquite BBQ” chips to sit alongside regular barbecue flavor. To fill that hungry maw, Dewis and his colleagues work to analyze hundreds of thousands of substances and develop compounds that will please the buying public in four ways-through smell, taste, sensation and emotion. To do so, flavor scientists are homing in on molecules, receptors, brain structures and genetic code that will enable them to create flavors tailored to consumers’ palates, health condition, demographics, even genotype. The industry doesn’t just talk about things tasting good anymore. Now it’s about providing an exceptional flavor “experience.” And as scientists learn to exploit the ways we perceive flavor, food manufacturers will be able to refine their products to appeal to us as individuals. Welcome to the world of personally tailored mass-produced food.
Flavor Basics, Basic Flavors
When you deal with flavor scientists, you have to watch your language. In flavor science, “taste” is only what happens on the tongue-the perception of sweet, sour, salty, bitter and the curious savoriness named umami by the Japanese. But the “flavor” you experience when eating a strawberry, for instance, involves far more than your tongue alone.
Smell is arguably the most vital tool in detecting flavor. The complete list of molecules in a strawberry numbers around 250 compounds, including esters, terpenes and lactones. It takes just four compounds to get your nose to recognize the basic flavor-something like a cheap strawberry candy-but taken alone, they smell nothing of strawberries. One, furaneol, smells like cotton candy. Another, gamma-decalactone, is a creamy peach fragrance. Methyl cinnamate smells like guava, and ethyl butyrate evokes pineapple. A fifth note, _cis-_3-hexenol, which by itself smells exactly like cut grass, gives strawberry the bright green fragrance of something fresh and alive. There are still 245 other compounds at work in that single berry. (The only two components that your tongue encounters are the sweetness of sugar and the tartness of fruit acids.)
Until the early 1990s, it was generally accepted that there were anywhere from a handful to a few dozens types of odor receptors inside the human nose, each a paired match with a class of molecules. But as the technology of DNA sequencing became widely available, it became possible to discern the underpinnings of scent receptors, gene by gene.
Using DNA analysis on rats and mice, Linda Buck of the Fred Hutchinson Cancer Research Center in Seattle and Richard Axel of Columbia University identified about 1,000 genes-an entire gene family-that code for individual odor receptors in mammals. Of those genes, only 250 to 400 are active in humans, and the overall and active number vary from person to person, giving everyone a slightly different tool with which to experience the world of odor.
To elicit a particular smell-say, that of the aforementioned strawberry-each odor compound activates several receptors (found on the olfactory neurons) in the nose. Further, each olfactory neuron features only one type of receptor, sensitive to only a certain class of molecules. Since all flavors are combinations of aroma molecules, each flavor will create a particular pattern of activated odor neurons in your nose. Your brain recognizes the pattern of activated neurons and tells you that you’re smelling a strawberry, and not some other kind of fruit. But because each person’s nose has a slightly different constellation of odor receptors, people may perceive a certain scent slightly differently. In 2004 Buck and Axel won the Nobel Prize for Physiology and Medicine for their efforts.
Compared with the puzzle of smell, taste is much more straightforward. “Taste evolved as a sense to make very important decisions about nutrients,” explains Gary Beauchamp, director of the Monell Chemical Senses Center, a nonprofit research center in Philadelphia specializing in taste, smell and chemical irritation. Sweetness signals the presence of calories, vitamins and minerals. Saltiness indicates the presence of sodium (important to keep your heart and neurons going). Bitterness screams “this could be poison!” at your brain.
You detect tastes, of course, with clusters of cells on your tongue-taste buds. And on those cells reside the receptors; most data indicate that there is one type of receptor per cell. Sweet, bitter and umami tastes are basically lock and key. A taste molecule of a certain shape (the key) will bind with a receptor that’s the complementary shape (the lock). And even though research reveals multiple subtypes of the bitter receptor-12, or 20, or up to 50, depending on who you ask-as far as we can tell, when they are activated, it is perceived without nuance. Of all the receptors on the tongue, we know least about how salt and sour interact with their respective target taste molecules.
A third component of flavor is chemesthesis-the feeling of heat, coldness, pain or tingling. Sensate research, as it’s known, began in the 1950s but really didn’t take off commercially until the 1990s, and a slew of sensate products have hit the shelves since. “Cool Burst” and “Ice” show up on the label of products containing a non-minty cooling molecule, which acts directly on cold receptors in the skin of the tongue. Warming sensates, like the molecule camphor, trigger warm receptors, also found in the skin. A compound isolated from the Szechuan pepper will make your tongue tingle. And then there’s capsaicin, a compound found in hot chilies, which acts on both warm receptors and pain receptors in the mouth. Sensates have an advantage over other flavorants: A person can acclimate rapidly to certain smells and tastes because those neurons tire out quickly, but the sensate-receptor neurons’ pathways continue to fire for a longer period of time. For example, the tingling sensation from the Szechuan pepper can last for 20 minutes.
Recent research has centered on the search for sodium, sugar and MSG enhancers that make food taste good with minimal added sweeteners or salt. “It’s a numbers game,” says Mark Zoller, executive vice president of discovery and development at Senomyx, a company in San Diego that finds receptor-linked taste compounds by screening several hundred thousand molecules out of its library of 500,000 synthetic and natural compounds every year “to find that needle in the haystack.” The company’s umami enhancer, capable of replacing or reducing MSG, is already in products by Nestl. And in August, Senomyx announced that it is developing an enhancer to increase the perceived sweetness of sucralose that may allow food manufacturers to use up to 75 percent less of the sweetener in processed foods without any loss of the desired sugary hit.
But understanding the physical processes on the front end of flavor perception is like understanding only the plumbing. Signals from the tongue and nose must still be interpreted by the brain, in areas like the orbitofrontal cortex (which is associated with reward, decision-making and flavor recognition), the hypothalamus and amygdala (involved in the emotional component of smell), and the hippocampus (associated with memories, including food cravings). That’s the stage where things like memories and unconscious judgment come in.
The Pleasure Principle
Ultimately, the flavor industry is in the business of decoding human enjoyment. In animal and human studies, flavor preference appears to be determined primarily by experience. At its simplest, it’s a matter of conditioning. By pairing a positive stimulus with a flavor, the flavor becomes better-liked. “All other things being equal, familiar flavors are liked better than unfamiliar flavors,” explains Marcia Pelchat, a researcher at Monell. “If you could ask a total stranger one question that would tell you more than anything else about what they like to eat, you would ask them where they grew up.”
Flavor science is hoping to create a connection between consumers and their food as strong as that between a child and his mom’s cooking. Deciphering the emotional connection to food involves not just chemistry but neurobiology, personal history and genetics. “Aromas can bring a sensation of love or fear or memory that no other sense can. That’s an area that is just ripe for exploration,” says Marianne Gillette, vice president of technical competencies and platforms at spice and flavor manufacturer McCormick.
In the long term, the flavor business hopes to be able to better target particular tastes according to locale but also to reach consumers according to their demographic group-children versus preteens; men versus women. “In 1988 we might have had a request for a flavor of a Chandler strawberry with fresh ripe notes,” says Marie Wright, a flavor-creation manager at IFF. “Today the request will be for a Chandler strawberry with fresh ripe notes targeted at baby boomers that also gives a feeling of refreshment and invigoration.” Food companies want to be able to provide each of those individuals with a perfectly tailored, emotionally resonant strawberry flavor.
Back in the lab at IFF, Dewis continues to feed the Sepbox to identify the flavors in some of our favorite foods: raspberry jam, chocolate cookies, steak. But despite all the work the company has done to translate the unconscious connection with food into scientific formulas, Wright acknowledges that there’s a mystical quality to taste, one that science hasn’t yet touched. After devoting years to flavor research, she still believes that the palate knows best. “The worst thing you can do,” she says, “is get hung up on analytical data.”
For all the precision that the Sepbox provides in identifying the molecules, and for all that flavor scientists have achieved in creating delicious flavors, until every smell receptor is characterized and the electronic nose is perfected, the most sensitive flavor detector is still the one attached to your head, and only it knows what foods you like best.
Tamara Holt is a cookbook author. She lives in New York City, where she writes about food, health and nutrition.
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