Why Parmesan Smells Like... THAT 🤢🧀

The idea of confusing the smell of parmesan – one of the most popular cheeses in the world – with vomit might sound ridiculous, but once you start digging, you’ll find tons of anecdotal evidence of this exact phenomenon. And not that long ago, I actually had an experience where – in the middle of the night – I mistook the smell of vomit for the smell of pasta. I was horrified – both at the vomit itself, AND at the fact that I could legitimately confuse such a disgusting thing with such a delicious one. Chemically, though, parm and puke have some important stuff in common: short chain fatty acids. These molecules are produced when anaerobic bacteria break down their food – which you probably know as “ fermentation” – a process which happens both in cheese, and in the contents of your stomach. Anything that’s bacterially-fermented will contain short-chain fatty acids, all of which are volatile and have strong, distinctive smells; parmesan cheese just happens to contain two of the very same short chain fatty acids as your stomach contents – butyric acid and isovaleric acid – in about the right quantities to create a scent that’s at least somewhat similar. It seems wild – not to mention totally maladaptive – for humans to even sometimes confuse the smell of something so gross – and potentially disease-laden! – with something we want to eat. But it turns out that, while our noses are really good at picking up even very small amounts of lots of different odors, we aren’t all that good at recognizing what those odors actually are. Research has repeatedly found that, if you ask people to identify everyday smells – stuff like strawberries, molasses, glue – they’ll only be able to accurately name around half in any given session. That’s obviously way worse performance than if you asked people to identify these things by sight. In most cases, smelling seems to be a secondary sense for humans; smells are usually accompanied by other information that helps clue us into what we’re smelling. Like, if an acrid, cheesy smell is accompanied by the sound of puking – or puke itself – it’s probably puke. If it’s at an Italian restaurant, it’s probably cheese…hopefully it’s cheese. So your surroundings create some expectation of what a smell might be. But if those cues or expectations are absent, like in my waking-in-the-middle-of-the-night experience, or when they’re artificial, like in that experiment, or even when the signal is subtle - like when some time had passed after my sniffing session - our not-that-great smell recognition means it’s possible – maybe even easy – to mistake two smells that are even somewhat similar.