“Why is intentional cold coffee delicious, but warm coffee that has gone cold disgusting?” she asks in the video.
Her post got all kinds of attention online, including from Dan McLaughlin, a professional coffee roaster and popular TikToker (@softpourn). McLaughlin’s videos feature all kinds of insights about brewing coffee, but this clip struck a distinct chord on the app.
In it, he explains the chemical processes that affect hot coffee as it cools down.
“It’s a chemical reaction,” McLaughlin says at the start of his clip. “Coffee has chemicals in it called lactones, and as hot coffee cools down, a chemical reaction happens where those lactones turn into carboxylic and chlorogenic acid.”
Thankfully, it doesn’t take a chemistry degree to understand that process. As McLaughlin explains, those acids make the coffee taste, well, more acidic.
But the process only happens if the coffee has time to cool naturally. Iced coffee, meanwhile, is made from an immediate change in temperature, and therefore won’t be as acidic as coffee that started out hot and then got cool.
“And you get even less out of cold brew, because that was never hot,” McLaughlin adds. “So that reaction takes place even less.
However, as McLaughlin adds, there are some advantages to drinking your coffee at room temperature. It all comes down to the difference between acidic flavor and acidity from the lactone-to-acid reaction.
Coffee that’s made intentionally to taste acidic is much different than coffee that sits out and becomes acidic due to a chemical reaction.
“A good, high-quality coffee with a nice bright acidity will actually start to taste sweeter and really good as it cools down,” McLaughlin says. “Whereas a coffee that’s acidic and not very good and lower quality, will taste worse.”
Part of this is because, in some cases, food tends to taste worse when it’s too hot. Numerous studies have shown that as food cools down, our perception of its flavor changes. Often, it’s harder for our taste buds to detect subtle flavors at higher temperatures.
So, if lukewarm coffee tastes “disgusting,” it may be evidence that the coffee isn’t super high quality. That said, McLaughlin also emphasized that while his explanation is based on science, flavor is totally a matter of preference.
“I used some very definite language here but it’s not reflective of people’s subjective tastes. You can definitely enjoy acidic coffee,” he wrote in a follow-up comment.
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