How Smell Impacts Flavor

This is part of a series of activities you can explore on #TasteandSmell Day, September 14, and any day.

If you’ve ever had a stuffy nose from a cold or allergies, or experienced smell loss from Covid, you’ve likely noticed that food doesn’t taste as good, if you can taste anything at all. That’s because our ability to smell has a huge impact on flavor.

The Science: Retronasal Smell

When we think of smell we often think of what happens when we breathe in molecules that have a scent. That’s called orthonasal olfaction.  

There’s another kind of smell, called retronasal olfaction, which happens in the back of your mouth. When you eat or drink, odor molecules are to your olfactory receptors through the passage between your nose and mouth (nasal pharynx) and into your nasal cavity where olfactory receptors detect those aromas. Those signals are sent to your brain. Colds and viruses cause inflammation which blocks air flow and prevents the odor molecules from reaching your olfactory receptors, so no odor information is sent to your brain and your food is not flavorful.

How Much Does Smell Impact Flavor?

You might have seen claims of anywhere from 70% to 90% of flavor is attributable to smell. In fact, there is no empirical evidence for an exact percentage, and like so much involving taste and smell, likely varies between individuals. Scientists do all agree that our sense of smell plays a dominant role in our perception of the flavors we eat and drink.

Try this for yourself: The JellyBean Test

Here’s a simple way to see just how much smell informs flavor. Get a bag of mixed flavor jelly beans. Set a few jellybeans of different flavors before you. Now close your eyes and hold your nose and pop a jellybean in your mouth. See if you can tell what flavor it is. Try a few more. Now, let go of your nose as you chew and see how much of the flavor becomes apparent.

You probably tasted the sweetness of the jellybean, and for some the sourness. Those basic tastes come from your tongue. But you probably had a hard time identifying the specific flavors of the jellybeans you tasted. Even if you were holding your nose tightly closed, as you chewed some scent molecules may have made their way to the olfactory receptors and given you some clues. 

The Difference between Taste and Flavor

We often use the words taste and flavor interchangeably, but there is a difference. 

Taste is what happens on the tongue – it is our taste buds’ response to sweet, bitter, salty, sour and savory (umami). That’s why you were able to detect the sweetness or sourness of the jellybean

Flavor is more complex – it’s a combination of taste, smell, spiciness, texture, temperature, and appearance, with smell the major contributor.