Thread by @AchemsInfo

Yesterday we talked you through the jellybean illusion. You probably experienced a couple of things, let's see if you agree with the following...

At STEP 3, while chewing with nose pinched, what did you taste? Probably just some sweet, maybe a bit of sourness, right?
And you probably could not identify any specific flavor, correct?

And then after releasing your nose, and exhaling through your nose, didn't the flavor all of a sudden just jump out at you. Only NOW you could "taste" lemon or orange or strawberry or whatever characteristic flavor.

After you breathed out through your nose, you were actually SMELLING an odor that was coming from the back of your mouth. We call that retro-nasal olfaction, as opposed to orthonasal olfaction, which is what happens when you sniff with your nostrils.

So when you usually say that something "tastes" like strawberries, that is really a combination of taste and retro-nasal odor perception. And the characteristic differences between the Jellybean flavors mostly comes from the odors.

When you have a cold and you can't "taste" anything? Actually, you just can't smell anything.

But, interestingly, it seems like all of that is happening in your mouth, and that is why most people speak of "taste". In science we refer to this set of experiences - together with other experiences like creaminess or spicy - as flavour.

So now you also understand how having a working sense of smell is really central to the enjoyment of food, something that people that have a dysfunctional sense of smell (anosmia) sorely miss on a daily basis.

Here is a really cool video where you can see how the tongue pushes up the air after swallowing towards the nasal cavity. From: A Olthoff et al, Gastroenterology research and practice 2014
biomednmr.mpg.de/images/stories…

So, just to recap, smells can be perceived 2 ways: from the nostrils (ortho-nasal) or the oral cavity (retro-nasal). The illusion is that you don't realize so much of the Jellybean flavor is actually perceived by your nose, but also that is feels like it happens in your mouth.

If you want to read more, take a look at these papers:
link.springer.com/article/10.375…
cell.com/abstract/S0896…
academic.oup.com/chemse/article…

And if you want to use this demonstration for science #outreach activities, you can use this coloring plate as a hand-out.
For this and other educational activities in the chemical senses: achems.org/web/resources-…