When Senses Mingle: The Connection Between Taste and Smell
Taste: it’s what makes eating so enjoyable. For all the pleasure taste brings, the mechanisms behind it are underappreciated. Food goes in the mouth, tastes good (or bad), and then it’s swallowed. The apparent simplicity makes taste a process most people take for granted.
Ask any passerby how taste works, and they’ll likely rattle off the basics: taste buds on the tongue pick up sweet, salty, sour, bitter, and umami flavors. And together these five components create, well, the flavor of food.
All of that is perfectly true, but there’s more to food than meets the tongue.
Think of a wine enthusiast sticking their nose into the glass before taking that first sip. Or a picky eater plugging their nose to make unpleasant foods go down easier. As any sommelier or chef can probably tell you, there’s a connection between taste and smell.
But how—and why—are taste and smell related? They’re simple questions with complicated answers. Fortunately for you, what follows digs into those questions and more. So read on to learn all about the taste-smell connection!
Taste vs. Flavor: An Important Distinction
In most situations, people use taste and flavor interchangeably. “This pasta had a nice taste” or “That pizza has great flavor.” For all intents and purposes, the phrases mean roughly the same thing. Parsing out the complex relationship between taste and smell, however, requires more exact language.
So let’s take a look at terminology. Throughout what follows, taste and flavor will refer to two distinct subjects.
- Taste refers to the sense—the chemical process in which taste receptors respond to the molecules in food.
- Flavor, on the other hand, is more abstract. It refers to what might casually be called taste, but is in fact a blend of taste, smell, texture, and more.
In short, taste will be used to describe an individual, isolated sense. Flavor, on the other hand, will describe the overall effect of food on a number of the senses.
What is Taste?
Each sense is a complex subject on its own, never mind putting two together. To avoid biting off more than you can chew, let’s start simple: how does the body translate the food in your mouth into the sensation of taste? Or, to put it a little more simply, how do you taste food?
Taste, also known as gustation, occurs when saliva breaks down and dissolves the food in your mouth enough for the molecules in said food to bind to taste receptors. Your taste receptors are located on the tongue, throat, and roof of the mouth. (Fun fact: Taste receptors are even found in the stomach and intestines, too!)
There are five types of taste receptors, each corresponding to one of the five basic tastes: salty, sweet, bitter, sour, and umami. Contrary to popular belief, specific tastes aren’t restricted to certain parts of the tongue—all five types of taste receptors can be found throughout the mouth.
When a molecule—let’s say a sour one—bonds to the corresponding taste receptor (a sour taste bud), the electrical charge of the receptor cell changes. This electrical impulse is then relayed to a neuron, which sends the information to the brain. And, lo and behold, your mouth puckers up, your eyes squint, and you experience a sour taste.
It seems strange that there are only five distinct tastes. Why five? And, more specifically, why those five? As it turns out, this might be a question for evolutionary biologists.
The Evolving Role of Taste
In the early days of human evolution, taste was a matter of survival. The sense people often take for granted helped early hominids distinguish between nutritious and toxic foods.
And though humans have come a long way since then, many of those evolutionary impulses linger. Have you ever had a craving for a salty bag of kettle-cooked potato chips? What about something sweet? This may be because, on some level, your body still associates those tastes with nutrient-rich foods.
But these days, the five basic tastes are less about survival and more about enjoyment. Most people like to eat—and most people have certain preferences about what they eat. And those preferences, though they might be influenced by evolutionary factors, are based largely on flavor. And this is where smell comes in.
A Brief Overview of Smell
Remember how taste receptors can only register five distinct tastes? Well, the nose knows no such bounds. Scientists haven’t agreed on the exact number of scents humans can distinguish, but the number lies somewhere between 10,000 and 1 trillion. Either way, it’s a whole lot more than five.
But it’s not entirely clear how the body detects so many distinct scents, as there are only a few hundred types of olfactory receptors. (The brain really is miraculous.) These receptors, located in the back of the nose, are actually neurons that go directly to the brain. As molecules float into the nose, they bind to olfactory receptors that send the information to the brain via the olfactory nerve.
That’s enough about the mechanics of smell to provide background for the discussion of the connection between taste and smell. But there is another important distinction to make.
There are actually two types of smell: orthonasal olfaction and retronasal olfaction. Don’t be intimidated by the scientific terms. It’s just a fancy way of distinguishing where the smell entered the nose: orthonasal for the front (through the nostrils), retronasal for the back (through the mouth).
People often forget that the nose and mouth are linked. If you’ve ever laughed while drinking water, one of two things probably happened. You either coughed, sputtered, and spewed water out through your mouth. Or you laughed until the water came out your nose. In retronasal olfaction, molecules take the same route as the water in the aforementioned scenario: into the mouth and then up into the nasal cavity. There, they latch onto olfactory receptors.
This will come into play as you learn more about the connection between taste and smell.
When Taste and Smell Mix: All About Flavor
There’s a good chance you’ve heard that your sense of smell is responsible for a majority of a food’s perceived flavor. People love to throw around statistics, some shockingly high: this person might tell you 75 percent of taste is actually smell; another person claims it’s 90 percent. So which one is correct?
It’s complicated. And, unfortunately, a good way to measure the ratio exactly has yet to be discovered. Here’s what is known.
Smell can impact your perception of flavor in one of two ways: as a constitutive part of that flavor, or as a modulatory force. In the former case, a smell is part of the flavor itself. And in the latter, a smell alters or adjusts your perception of a taste.
One theory suggests that orthonasal olfaction (or smelling through the nostrils) acts as a modulatory force. It primes the pump, so to speak, telling your brain what to expect from your food, thus altering the food’s perceived flavor.
Think again of wine enthusiasts. Why do wine tasters stick their noses deep into each glass before taking the first sip? The practice is, in part, used to identify any imperfections in the wine. But it is also thought to enhance the flavor of wine. As you inhale the aromas of the wine and imagine their sources, you begin to anticipate the flavor. Only then, once the flavor palate of your imagination has been suitably stimulated, do you take a sip.
This process isn’t limited to wine. Pungent cheeses, sautéed onions and garlic, or a steak on the grill can all have the same effect on your nose.
OK—back to wine tasting. Once the wine is in your mouth, your other sense of smell, retronasal olfaction, kicks in. Molecules from the wine float up from your mouth and into the nasal cavity. But, of course, smell isn’t the only sense engaged at that moment. As those molecules are floating up, other compounds stay in the mouth, where they bind to taste receptors.
All of this sensory input is processed by the brain simultaneously. The information from your taste buds and your olfactory receptors blends into one indistinguishable experience. Because these two sensory experiences are so intertwined, retronasal olfaction is considered a key component of flavor.
A Look at the Numbers—Or Lack Thereof—About the Connection Between Taste and Smell
Experiencing a flavor is a difficult sensation to describe. But why? For starters, it’s rooted in experience. To understand the exact flavor you’re tasting, someone would have to eat the same food.
This is partly why it’s so difficult to assign proportions of flavor to smell and taste. Scientists understand both senses from a physiological standpoint. But flavor is, at its heart, a phenomenological (that is, based on direct experience) issue. The blending of both senses creates an experience that is hard to quantify.
If you came looking for numbers, this conclusion might be disappointing. Here’s the good news: you don’t need numbers quantifying the exact connection between taste and smell to enjoy a great meal. If it smells great, tastes great, and has great flavor, who cares what percentage of the work your nose is doing? Just dig in and enjoy some delicious, healthy food with a better understanding of how taste and smell are related.