“Love chocolate?” asks Laura Moss (@LauraJMoss). “What if you could make it taste sweeter? Believe it or not, you can accomplish that goal without altering the chocolate at all.” [“The science of taste: Why everything from sound to shapes can affect your taste buds,” Mother Nature Network, 19 May 2014] That’s because so much of what we taste has nothing to do with our tongues. Moss explains:

“Studies show it could be as simple as placing the chocolate on a white plate and eating it while listening to a high-frequency sound and looking at a round-shaped object. Up to 80 percent of what we consider taste is actually our sense of smell, but there’s more to taste than olfactory glands and taste buds. Taste can be influenced by a variety of factors — from color and cutlery to emotion and price.”

I’ve discussed how our senses affect how food tastes in previous articles (see, for example, “Food Flavors: Making ‘Senses’ of it All“). In this article, I’d like to focus on how our sense of smell affects the taste of the food we eat. Alan McStravick asserts, “The sense of smell in humans has undergone many permutations as we have traveled through evolutionary time.” [“Decoding The Unique Characteristics Of Aroma,” redOrbit, 27 June 2014] He continues:

“It was once believed that each successive version of our olfactory ability was weaker than the last. Scientists claimed as our sense of sight became ever greater and required more of our energy, our sense of smell suffered. They cited the gradual reduction of our noses paired with the movement of our eyes closer to the middle of our heads as proof of this phenomenon. Of course, as Gordon M. Shepherd published in his study in 2004, humans and other primates have actually been shown to possess better senses of smell than previously believed. ‘If human smell perception is better than we thought,’ he explained, ‘it may have played a more important role in human evolution than is usually acknowledged.'”

In the Shepherd study referred to by McStravick, Shepherd admits that “the low number of functional olfactory receptor genes in humans compared with rodents — and presumably most other mammals — is directly correlated with the evolutionary decline in the human sense of smell.” [“The Human Sense of Smell: Are We Better Than We Think?” PLoS Biology Journal, May 2004] He reports, however, that humans have compensated for this loss of receptors in other ways (e.g., “the structure of the nasal cavity, retronasal smell, olfactory brain areas, and language”). “In these arenas,” he writes, “humans may have advantages which outweigh their lower numbers of receptors.” He continues:

“Here, then, is the mystery: how can one reconcile a relatively high sensitivity to smell with a relatively low number of olfactory receptors in the nose? To answer this question, I think we need to look beyond the olfactory receptor genes and consider olfaction in its full behavioral context. This requires considering several overlooked aspects of the olfactory system: the nasal cavity, the oropharyngeal cavity, the olfactory brain, and the role of language.”

We all know that particular aromas can spark memories of past events or circumstances. We know that smart bakers pipe the aroma of their baking goods out into the air to attract customers. But our sense of smell may work in more subtle ways as well. Catherine Griffin (@cthegriffin) agrees that our sense of smell may be better than we give it credit. “How good is your sense of smell?” she asks. “Apparently, it’s good enough to detect dietary fat in food. Scientists have discovered that humans can sniff out fat in foods before eating it. The findings could lead to innovative methods of using odor to make low-fat foods more palatable to aid public health efforts.” [“Humans Can Sniff Out Dietary Fat: Sense of Smell Impacts What We Eat,” Science World Report, 23 January 2014] She adds, “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.”

Our sense of smell not only tells us what food is good for us it warns us about food that could be potentially harmful. April Flowers reports, “Eating spoiled food can be fatal as it allows bacterial pathogens to enter the digestive system. One of the main tasks of the sense of smell is to detect signs of decay, allowing us and other animals to avoid such food poisoning.” [“When Good Food Goes Bad, Smart Flies Keep Their Distance,” redOrbit, 7 December 2012] Remarking on Flowers’ article, McStravick writes, “While that is an important role for our noses to play, a far more pleasant job for our nose is its ability to discern among the many different aromas of the foods we love and enjoy.” He continues:

“When I suggest the aromas of a freshly baked warm loaf of bread or steamed broccoli or strawberries resting on a dollop of whipped cream, it is likely you can experience a recall of the scents of those items without actually smelling them. But just what is it about those foods that give them their distinctive scent profiles? The answer is likely to surprise you. It is a well-known fact that our sense of taste is aided by our sense of smell. Without a properly working nose, we would be unable to detect the flavors of sweet, bitter, salty, sour and savory. This is because the more than 10,000 identified food compounds contribute to our overall sensory impression of the foods we eat and beverages we drink. Scientists from the Technische Universität München (TUM) and the German Research Center for Food Chemistry (DFA) performed a meta-analysis on the odorant patterns of 227 different food samples to try and understand why and how a certain food smells the way it does. From frying bacon to the pungent but sweetly sour orange rind to a robust and spicy red wine, the amount of almost infinite aromas available to humans are actually derived from just 230 odorants. Each individual food or beverage item typically only seizes on a combination of between 3 and 40 of these odorants – in specific concentrations.”

As a side note, the fact that odors are created by combining a relatively small number of odorants encouraged David Edwards, an engineering professor at Harvard, to invent “a device called an oPhone that sends and receives photos and scents.” [“You’ll Be Able To Text Your Friend A Smell In A Few Days,” by Alexis Kleinman (@alexiskleinman), Huffington Post The Blog, 14 June 2014] The oPhone allows you to “mix-and-match 32 basic scents to create more than 300,000 unique aromas.” There is a video associated with Kleinman’s article and participants in the video express skepticism about the oPhone and doubt that it will catch on. In fact, they seem pretty convinced that mostly foul aromas will be transmitted by people looking for a good laugh. McStravick, however, believes that this kind of technology will catch on. He writes, “Perhaps most interesting of all is that this latest odorant mapping will yield a far more precise natural simulation of odors. Imagine a not-too-distant future where text messages will be accompanied by scent messages. Because that future is coming and it smells great.” I guess we’ll just have to wait and see whether fragrant or foul smells dominate the airwaves. Returning to the subject at hand — how our sense of smell affects our sense of taste — McStravick writes:

“Where this really gets interesting is when the aromatic molecular combination slips past our nostrils, causing our brain to translate them into olfactory stimulus patterns. For this to be achieved, the aroma has to interact with one or more of the 400 olfactory receptors in our nose. ‘A combination of between just a few key odorants creates an authentic perception of odors,’ stated professor Thomas Hoffman, TUM Chair of Food Chemistry and Molecular Sensory Science. He continued, ‘This is all the more surprising given that the olfactory quality of the combinations is not determined by the individual components.’ As the team explains further, a smell is not a smell until the above process has occurred. Were a chemical odor pattern to somehow bypass the olfactory receptors to be processed in the brain, the individual odor components simply wouldn’t add up. The individual olfactory notes are necessary for translating that chemical odor pattern into a new odor identity. … ‘By mapping the odorous substances of the 230 currently known key odors, scientists can test which receptor combinations are “reserved” for food odors,’ explained Hoffman. To date, scientists have identified 42 receptors that respond to food odors – with the majority binding multiple odor molecules. ‘This will help us explain the biological relevance of odors in even greater detail.'”

Shepherd concludes, “Much about the sense of smell seems enigmatic and conflicting. This is partly because of the inherent difficulties in presenting smell stimuli, and partly because there is not yet a recognition of all the relevant mechanisms that are involved. … The sense of smell is more important in humans than is generally realized, which in turn suggests that it may have played a bigger role in the evolution of human diet, habitat, and social behavior than has been appreciated. All of these considerations should stimulate a greater interest in this neglected sense.”