WEBVTT - Why Does Microwaved Coffee Taste So Bad? 0:00:02.040 --> 0:00:07.160 Welcome to brain stuff from how stuff works, Hey, brain stuff, 0:00:07.200 --> 0:00:10.600 Lauren vocal bomb here. Hot coffee is supposed to be hot. 0:00:11.000 --> 0:00:13.760 Cold coffee is supposed to be cold, and that's the deal. 0:00:14.080 --> 0:00:17.599 It's pretty simple. The problem, then, with hot coffee is 0:00:17.640 --> 0:00:19.880 that you can't drink the whole cup while it's at 0:00:19.880 --> 0:00:23.000 the optimal temperature unless you're willing to really guzzle it. 0:00:23.840 --> 0:00:26.079 So when it gets cold, you've got a few choices. 0:00:26.560 --> 0:00:29.560 Drink it cold, reheat it, or just pour that cup 0:00:29.600 --> 0:00:31.720 down the drain and start over with a fresh pot. 0:00:32.440 --> 0:00:35.159 All three of these approaches are either perfectly fine or 0:00:35.240 --> 0:00:39.280 completely barbaric, depending on whom you ask to Some hot 0:00:39.320 --> 0:00:42.800 coffee that's gone cold is revolting to others. The reheating 0:00:42.840 --> 0:00:46.919 process renders it completely undrinkable, but that doesn't stop us 0:00:46.960 --> 0:00:50.200 from occasionally popping a cup of nine hour old office 0:00:50.280 --> 0:00:52.880 Joe into the microwave at four pm to power through 0:00:52.960 --> 0:00:58.280 until bedtime out of some combination of desperation and mild masochism. 0:00:58.600 --> 0:01:02.319 Research into why heating this humble drink is pretty much 0:01:02.320 --> 0:01:05.039 non existent, but it most likely has to do with 0:01:05.080 --> 0:01:08.840 our sense of smell. Humans aren't great at separating our 0:01:08.840 --> 0:01:13.800 gustatory that's taste and olfactory that smell responses, and coffee 0:01:13.800 --> 0:01:16.600 has aromas and flavors that hit all five of the 0:01:16.600 --> 0:01:18.840 tastes that can be picked up by your tongue and 0:01:19.000 --> 0:01:23.520 other mouth and nasal passage nerves. Sweet, salty, bitter, sour, 0:01:23.680 --> 0:01:27.480 and savory. So your personal sense of smell has a 0:01:27.480 --> 0:01:30.520 lot to do with how coffee tastes to you, whatever 0:01:30.560 --> 0:01:34.800 it's temperature, and however that temperature was achieved. That's because 0:01:34.840 --> 0:01:38.800 the chemical makeup of coffee is astoundingly complex. Even though 0:01:38.800 --> 0:01:42.240 its reputation relies heavily on the presence of caffeine, coffee 0:01:42.240 --> 0:01:46.520 gets its flavor from around a thousand different chemical compounds. Also, 0:01:46.680 --> 0:01:49.040 the final flavor of the coffee you enjoyed this morning 0:01:49.280 --> 0:01:52.160 was the product of a dizzy ng array of variables, 0:01:52.200 --> 0:01:55.600 including the temperature and weather conditions the beans grew under, 0:01:56.000 --> 0:01:58.880 when the beans were harvested, how they were dried, stored, 0:01:58.920 --> 0:02:02.280 and roasted, and how they were ground and brewed. So 0:02:02.520 --> 0:02:05.720 while the compound three methyl mutinol might make your cup 0:02:05.760 --> 0:02:09.079 of joe taste a little caramel like and ethyl no, 0:02:09.280 --> 0:02:11.840 it may give it some fruity or notes. Each step 0:02:11.880 --> 0:02:15.040 of the process either brings out or suppresses any one 0:02:15.080 --> 0:02:19.240 of these aromatic compounds differently, which brings us to reheating. 0:02:20.200 --> 0:02:23.400 We spoke with Christopher Hendon, a postdoctoral fellow at the 0:02:23.480 --> 0:02:26.560 Chemistry Department at m I T and author of Water 0:02:26.639 --> 0:02:29.800 for Coffee, a book about how coffee interacts with water. 0:02:30.440 --> 0:02:34.359 He said, reheating coffee in principle can be an absolutely 0:02:34.400 --> 0:02:38.080 fine approach to achieving a tasty beverage. In practice, this 0:02:38.240 --> 0:02:41.360 is not usually observed because people reheat in ways that 0:02:41.400 --> 0:02:45.280 promote the loss of delicious volatile compounds, and so the 0:02:45.320 --> 0:02:48.960 process of heating, cooling, and heating again drives smelling and 0:02:49.000 --> 0:02:53.280 tasty compounds out of the cup. According to Hendon, coffee 0:02:53.320 --> 0:02:55.519 experts seem to prefer a drink that has been brewed 0:02:55.560 --> 0:02:59.240 within the previous five to twenty minutes. It turns out 0:02:59.360 --> 0:03:01.880 most people for the coffee as it cools to around 0:03:01.919 --> 0:03:05.920 a hundred and fifty degrees fahrenheit that's sixty five degrees celsius. 0:03:05.919 --> 0:03:08.080 This has to do with the way our taste pathways 0:03:08.120 --> 0:03:11.359 respond to temperature in our food. But when we put 0:03:11.360 --> 0:03:13.519 something in our mouth that's too hot or too cold, 0:03:13.760 --> 0:03:16.160 we can't detect all of the compounds that contribute to 0:03:16.160 --> 0:03:19.560 its flavor. Since coffee has loads of these compounds, the 0:03:19.600 --> 0:03:23.520 temperature of the drink can affect the taste. Brewing the 0:03:23.520 --> 0:03:27.359 coffee brings out certain aromatic compounds, but whether the cooling 0:03:27.360 --> 0:03:31.320 process changes the chemistry seems to be controversial. Pendon says 0:03:31.400 --> 0:03:34.480 it is absolutely benign, while others claim it makes the 0:03:34.520 --> 0:03:37.320 drink more acidic as the coffee is exposed to air 0:03:37.440 --> 0:03:41.560 and oxidizes. Reheating coffee to the same temperature it was 0:03:41.600 --> 0:03:43.960 when it was first brewed might help you reach that 0:03:44.000 --> 0:03:47.320 sweet spot temperature wise, but it also has the potential 0:03:47.360 --> 0:03:50.840 to cause additional chemical reactions that further alter the flavor. 0:03:51.480 --> 0:03:53.960 And if you're reheating coffee that already has milk or 0:03:53.960 --> 0:03:57.880 sugar in it, that's even more in the way of flavors, proteins, chemicals, 0:03:57.920 --> 0:04:02.680 and compounds to contend with. So although many coffee connoisseurs 0:04:02.720 --> 0:04:04.920 will tell you it's a lost cause once your coffee 0:04:04.960 --> 0:04:08.080 goes cold, others say it's just important to reheat your 0:04:08.120 --> 0:04:11.000 coffee as slowly as you can in order to prevent 0:04:11.000 --> 0:04:15.320 additional chemical reactions. But if you're reheating in the microwave, 0:04:15.520 --> 0:04:18.440 don't worry about ghosts of past foods heated in that 0:04:18.520 --> 0:04:21.960 microwave coming back to haunt your coffee. And and said, 0:04:22.279 --> 0:04:26.200 the concentration of the volatile chemical composition of say, splattered 0:04:26.240 --> 0:04:29.120 pasta sauce, is pretty low, so I would be surprised 0:04:29.120 --> 0:04:31.760 if we could attribute the bad taste of microwaved coffee 0:04:31.800 --> 0:04:36.000 to only that. Our advice crank your microwave's power down 0:04:36.000 --> 0:04:39.039 to or lower and sap your cup of coffee in 0:04:39.200 --> 0:04:43.320 thirty second intervals to prevent disaster. But of course we 0:04:43.440 --> 0:04:51.200 encourage you to run your own experiments. Today's episode was 0:04:51.200 --> 0:04:54.200 written by Jesselyn Shields and produced by Tyler Clang. For 0:04:54.279 --> 0:04:56.800 more on this and lots of other tasty topics, visit 0:04:56.800 --> 0:05:10.320 our home planet, how stuff works dot com.