the nose knows

This was an easy experiment to get volunteers for here at America’s Test Kitchen Kids. (Who doesn’t love jelly beans?!)

We did this experiment with more than 25 people in our lab. Every single person had trouble identifying the jelly bean flavors when they held their noses. “It just tastes sweet, like sugar,” said one taster. Another reported, “I have no idea what flavor this is, but I really hope it’s not buttered popcorn. Ugh, that’s the worst.”

But as soon as they let go of their noses, all the tasters could immediately tell what flavor jelly bean they were eating. (And it was raspberry, not buttered popcorn. Crisis averted.)

Is this what you observed, too?

So what’s going on? Why do jelly beans have ZERO flavor when you hold your nose and then a ton of flavor when you can breathe in and out? First, we need to break down the difference between taste and flavor. They’re actually not the same thing. (Surprise!)

We get the taste of a food from the tastebuds in our mouth and on our tongue. They tell you if something is sweet, sour, salty, bitter, or umami (savory).

When you chewed the jelly bean with your nose closed, your tastebuds detected that it was sweet, since jelly beans contain a lot of sugar.

But there’s more going on here. When you’re chewing, you’re also breathing in and out through your nose. When you breathe out, the odor—or smell—of whatever you’re chewing flows from your mouth up into your nose. The smell gets to your nose through a passage at the back of your mouth. When you had your nose pinched close, the smell of the jelly bean couldn't travel up through your mouth into your nose.

This way of smelling is known as retronasal olfaction (“ret-ro-NAY-zal ol-FACK-shun”). Say that five times fast. (You also can detect smells when you breathe in through your nose—this is just called olfaction. Not quite as fun to say.)

Let’s break that down. Retro can mean “back” or “behind.” Nasal means “related to the nose.” And olfaction means “the act of smelling.” So retronasal olfaction means “smelling through the back of the nose.”

So when you let go of your nose and chewed the jelly bean, you were able to breathe in and out through your nose again. That allowed the jelly beans' smell to travel up into your nose. Suddenly, your brain could put together what your nose knew and what your tastebuds tasted, and ta-da! You figured out the flavor of the jelly bean.

(Fun Fact: Did you ever notice that when you have a stuffy nose, a lot of foods just taste kind of, well, blah? That’s because your stuffy nose prevents some air from moving through your nose. It limits your retronasal olfaction.)