Food Flavors: Making "Senses" of it All

Stephen DeAngelis

May 9, 2014

When people think about food, they generally imagine how it will taste on the tongue. Most of us know, however, that the enjoyment of food involves most (if not all) of our senses: taste, touch, smell, sight, and (occasionally) hearing (like the sound of popping corn or sizzling bacon). Susan Duncan, a professor of food science and technology in the Virginia Tech College of Agriculture and Life Sciences, thinks that another organ also plays a major role in our preference for certain foods: the mind. “Anyone who has ever been lured by the call of a dozen fat- and sugar-laden donuts in the office break room while a healthy container of yogurt looks on helplessly can relate to Susan Duncan’s research regarding emotions, physiological responses, and eating,” writes Amy Loeffler. [“Scientist pushes boundaries of food sensory research,” Phys.org, 20 March 2014] Duncan told Loeffler, “People don’t realize the subconscious food consumption decisions happening before they get to the point of eating. Our research is striving to understand how people emotionally interact with foods and the relationship to obesity and the science associated with decision-making and choice.” People may not recognize the subconscious decisions they are making, but they are certainly aware that there is an emotional relationship with food. It’s the reason that terms like “comfort food” have become part of our cultural landscape. Duncan is trying to codify our emotional relationship with food by “categorizing language and facial motions for clues to emotional responses to food and conducting taste tests where consumers rate appearance and flavor profile of food products.” Apparently, not all facial clues are as obvious as the well-known sour face or the licking of our lips. “Food is such a positive experience in so many ways,” Duncan told Loeffler. “Our research can help consumers make decisions that are healthy as well as emotionally fulfilling.”

In recent years, eating healthy often means reducing fat — which often means reducing taste. “Scientists have discovered that humans can sniff out fat in foods before eating it.” [“Humans Can Sniff Out Dietary Fat: Sense of Smell Impacts What We Eat,” by Catherine Griffin, Science World Report, 23 January 2014] Griffin reports, “The findings could lead to innovative methods of using odor to make low-fat foods more palatable to aid public health efforts.” In other words, scientists may discover a way to trick our sense of smell into making us think those fat-free foods taste as good as old-fashioned southern cooking. Griffin continues:

“It’s not surprising that humans can smell dietary fat. After all, fat is the most calorically dense nutrient available and thus highly desirable when looking back over the course of human evolution. Being able to detect sources of fat in foods would be evolutionarily advantageous to people. Yet while researchers knew that humans use sensory cues to detect fat, they weren’t sure exactly what sensory systems contributed to this ability.”

Griffin explains that during the experiment researchers had participants smell samples of milk containing different fat content to see if they could distinguish between them. “In the end,” Griffin writes, “the scientists found that participants could use their sense to smell to discriminate different levels of fat in milk. The researchers also noted that there was no relation between weight status and the ability to discriminate fat.” The research was conducted at The Monell Chemical Senses Center, an independent nonprofit basic research institute based in Philadelphia, Pennsylvania. Scientists there aren’t the only ones trying to figure out how to trick our sense of taste. Roxanne Palmer reports, “Taste modification is still a pretty open field, but one that’s heating up quickly. … Some of the biggest food companies in the world are having a go at it – with the aim of shaping the future of nutrition and maybe making a pile of money in the process.” [“Tricking The Tongue: How Biotechnology Might Let Us Cut Sugar And Salt, But Keep The Taste,” International Business Times, 14 December 2013] Palmer’s article focuses on efforts to find healthier ways to sweeten food. “Americans aren’t eating right on their own, so perhaps tricking them into eating a less junky kind of junk food might be the easiest solution,” Palmer writes. She notes that nature itself has provided an example of taste modification in a substance called “miraculin.” She explains:

“One already widely known example of a taste-modifying substance is miraculin, found in the berries of Synsepalum dulcificum, also known as ‘miracle fruit.’ Miraculin is not sweet by itself, but has a curious effect on the palate: for up to an hour after you take it, it will change sour tastes to sweet. Miraculin … has found … life as a party novelty. … You get your friends together and pop a miraculin pill or an actual miracle fruit berry; then you all go to town on a smorgasbord of sour foods, savoring the tasty transformation. Lemons become like candy; tabasco sauce tastes like hot doughnut glaze. Wash it down with a delectable swig of vinegar. … In 2011, a group of researchers found that miraculin’s molecular structure changes in the presence of sour-tasting acids, resulting in a shape that binds strongly to the sweet receptor – not just unlocking the door to taste, but propping it open.”

Palmer calls this effect “hacking the brain” to change tastes. “Scientists have a pretty good understanding of how our taste receptors work,” she writes, “particularly a certain class of taste receptors responsible for detecting sweet, bitter, and savory flavors. When the right food ingredient binds to these little molecular receivers, it kicks off a signaling pathway through the nerves and up to our brains. Knowing the details of the molecular machinery that translates the sugar molecule into a sweet sensation in the tongue and brain is the first step in hacking it.” She goes to note, however, that hacking the brain may not always work. She explains:

“Research conducted with artificial sweeteners has found that replicating a pleasant taste may not be enough to throw the reward switch in our brains that keeps us chasing the sugar-spangled dragon. In one study published in the journal NeuroImage in 2008, a team of researchers led by Guido Frank of the University of Colorado recruited 12 women to try drinks sweetened either with sugar (sucrose) or artificial sweetener (sucralose). The researchers asked the women to rate the drinks, and also scanned their brains with MRI machines. While the subjects could taste sweetness from both drinks, only sugar caused areas of the midbrain connected to reward pathways to light up on the scanner. ‘Thus, brain response distinguishes the caloric from the non-caloric sweetener, although the conscious mind could not,’ Frank and colleagues wrote. ‘This could have important implications on how effective artificial sweeteners are in their ability to substitute sugar intake.’ But then again, maybe our brains will simply adjust to the new sensations. San Diego State University researchers Erin Green and Claire Murphy scanned the brains of both habitual diet soda drinkers and people without a diet soda habit. They reported in the journal Physiology and Behavior that the reward processing regions in the brains of the diet soda addicts reacted almost identically to water spiked with sugar and water laced with the artificial sweetener saccharin.”

Perhaps the most intriguing research reported by Palmer doesn’t involve food at all. “Scientists in Singapore recently unveiled a device to create virtual ‘tastes’ using a little electrode placed on the tip of your tongue. Electrical and thermal stimulation fools your taste buds into registering salty, sweet, sour or bitter flavors. The researchers see their invention as a way for diabetics to enjoy sweetness without affecting their blood-sugar levels, or to enhance the quality of life for cancer patients and other people with dysfunctional tastes. Commercial applications abound as well, especially in the gaming industry; imagine getting a hit of virtual lemon candy or chocolate after completing a level on Candy Crush.” All of this research into how we can trick our sense of taste may seem frivolous, but could result in a genuine benefit to mankind in the years ahead if it gets people to eat more and waste less of the food that is grown.