Why does coffee smell so good?
There's really nothing better than waking up and smelling your coffee brewing in the kitchen. It's really the only motivation some of us have to get out of bed — and just the smell of it can help wake us up.
Even people who don't like drinking coffee (yes, they exist) love the smell of coffee. And it's no secret that smell plays a huge role in taste — think about how food tastes different when you have a cold. So what makes coffee's aroma so inviting?
It all comes down to chemistry, and it's not a simple explanation. The compounds produced when we roast coffee beans are similar to any other compound formed during the cooking process — think of freshly baked bread, chocolate chip cookies right out of the oven, or steaks sizzling on a summer grill (hungry yet?).
About 800 different compounds are produced in the coffee-roasting process, and most take place in the thick walls of the coffee bean cells. The profile of coffee roast only includes about 20 major compounds, but there are hundreds of minor compounds that determine the overall smell and taste we experience.
"There are a number of different ways in which coffee’s aroma compounds are created, but they’re all commonly produced as a consequence of the roasting process," an explanation on Compound Interest reads (check out their infographic below). "The Maillard reaction ... is a big contributor here, the reaction between proteins and sugars in the coffee beans producing a range of products. In addition to this, degradation and decomposition of other compounds in the coffee beans can also produce aroma compounds."
Additionally, the brewing part of the coffee-making process isn't about chemical change — it's about extracting compounds from the roasted beans.
The most surprising thing? There are some compounds by themselves that smell absolutely disgusting. That includes methanethiol, which has a smell described as like that of rotten cabbage, and also plays a pretty big role in the smell of farts. There are other sulfur-containing compounds, like 3-mercapto-3-methylbutyl formate, which also is known to have a pretty bad smell when it's by itself.
But when all of these compounds are mixed together, we get the wonderful aroma that is freshly-roasted coffee. The most important sulfur-containing compound is 2-furfurylthiol, which is commonly described as having an aroma of roasted coffee when it's on its own.
So when you're enjoying that delicious, strong cup of morning joe, it's basically a real-time chemistry experiment — where was this lesson in my high school chem class?
Related: What does caffeine look like?
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