Welcome to brain stuff from how stuff works, Hey, brain stuff, Lauren vocal bomb here. Hot coffee is supposed to be hot. Cold coffee is supposed to be cold, and that's the deal. It's pretty simple. The problem, then, with hot coffee is that you can't drink the whole cup while it's at the optimal temperature unless you're willing to really guzzle it. So when it gets cold, you've got a few choices. Drink it cold, reheat it, or just pour that cup down the drain and start over with a fresh pot.
All three of these approaches are either perfectly fine or completely barbaric, depending on whom you ask to Some hot coffee that's gone cold is revolting to others. The reheating process renders it completely undrinkable, but that doesn't stop us from occasionally popping a cup of nine hour old office Joe into the microwave at four pm to power through until bedtime out of some combination of desperation and mild masochism.
Research into why heating this humble drink is pretty much non existent, but it most likely has to do with our sense of smell. Humans aren't great at separating our gustatory that's taste and olfactory that smell responses, and coffee has aromas and flavors that hit all five of the tastes that can be picked up by your tongue and other mouth and nasal passage nerves. Sweet, salty, bitter, sour, and savory. So your personal sense of smell has a lot to do with how coffee tastes to you, whatever
it's temperature, and however that temperature was achieved. That's because the chemical makeup of coffee is astoundingly complex. Even though its reputation relies heavily on the presence of caffeine, coffee
gets its flavor from around a thousand different chemical compounds. Also, the final flavor of the coffee you enjoyed this morning was the product of a dizzy ng array of variables, including the temperature and weather conditions the beans grew under, when the beans were harvested, how they were dried, stored, and roasted, and how they were ground and brewed. So while the compound three methyl mutinol might make your cup of joe taste a little caramel like and ethyl no,
it may give it some fruity or notes. Each step of the process either brings out or suppresses any one of these aromatic compounds differently, which brings us to reheating. We spoke with Christopher Hendon, a postdoctoral fellow at the Chemistry Department at m I T and author of Water for Coffee, a book about how coffee interacts with water. He said, reheating coffee in principle can be an absolutely
fine approach to achieving a tasty beverage. In practice, this is not usually observed because people reheat in ways that promote the loss of delicious volatile compounds, and so the process of heating, cooling, and heating again drives smelling and tasty compounds out of the cup. According to Hendon, coffee experts seem to prefer a drink that has been brewed
within the previous five to twenty minutes. It turns out most people for the coffee as it cools to around a hundred and fifty degrees fahrenheit that's sixty five degrees celsius. This has to do with the way our taste pathways respond to temperature in our food. But when we put something in our mouth that's too hot or too cold, we can't detect all of the compounds that contribute to its flavor. Since coffee has loads of these compounds, the
temperature of the drink can affect the taste. Brewing the coffee brings out certain aromatic compounds, but whether the cooling process changes the chemistry seems to be controversial. Pendon says it is absolutely benign, while others claim it makes the drink more acidic as the coffee is exposed to air
and oxidizes. Reheating coffee to the same temperature it was when it was first brewed might help you reach that sweet spot temperature wise, but it also has the potential to cause additional chemical reactions that further alter the flavor. And if you're reheating coffee that already has milk or sugar in it, that's even more in the way of flavors, proteins, chemicals,
and compounds to contend with. So although many coffee connoisseurs will tell you it's a lost cause once your coffee goes cold, others say it's just important to reheat your coffee as slowly as you can in order to prevent additional chemical reactions. But if you're reheating in the microwave, don't worry about ghosts of past foods heated in that
microwave coming back to haunt your coffee. And and said, the concentration of the volatile chemical composition of say, splattered pasta sauce, is pretty low, so I would be surprised if we could attribute the bad taste of microwaved coffee to only that. Our advice crank your microwave's power down to or lower and sap your cup of coffee in thirty second intervals to prevent disaster. But of course we encourage you to run your own experiments. Today's episode was
written by Jesselyn Shields and produced by Tyler Clang. For more on this and lots of other tasty topics, visit our home planet, how stuff works dot com.