Why does hot coffee that goes cold taste bad, but iced coffee or cold brew taste fine?
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Hot water pulls out more of the bitter stuff like tannins, cold water doesn’t so it’s not as bitter. Iced coffee I guess just has less bite when it’s cold because it should have the same composition as hot coffee
We brew coffee and then put it in the fridge when it cools off a bit. Flavor is amazing and no bitterness. Don’t put ice in it either as it waters it down nor do we add sugar/milk. We started this by accident after having to run to the hospital after making a fresh pot of coffee. Didn’t want to toss it and didn’t want to leave it on the hot plate, so we put it on a hot pad in the fridge. Sometimes I’ll get new/different brands and taste them hot then cold to see how much the flavors change.
Ice Coffee is cooled down immediately after brewing so the oils in it have not evaporated away, and other compounds have not oxidized due to exposure to air. It is still fresh and so still tastes good. Standard hot coffee that is allowed to go cold in your cup over the course of an hour or more has had more of the oils evaporate due to being at a high temp longer, and had more of the compounds oxidize due to sitting for an hour or more. The temperature is a very small factor in it starting to taste bad, it effectively going “stale” or the coffee equivalent of going flat over time is the factor.
In general, when food or drink is hot, the flavor is mellowed out, and when it’s cold, it’s intensified – and that’s especially true with bitter flavors. With hot coffee, since we want it to be served hot, we brew it to an intensity that tastes good at that temperature. When it cools down, it ends up tasting too strong and bitter, because those flavors are intensified past where we wanted them.
When we make iced coffee or cold brew, we brew it to an intensity that tastes right when it’s cold *and* diluted with ice. So we engineered it to have a good flavor at that temperature – if you took an iced coffee and heated it up, it would actually taste *too* mellow and diluted, compared to what you’d expect from a regular hot cup of coffee.
Coffee contains (among other things) *aromatic oils*, that is, oils that vaporize at lower-than-boiling temperatures. These oils are what make coffee smell so good when it’s being brewed traditionally.
Those oils also help balance the flavor of the coffee, specifically offsetting the bitterness of the roasted beans. More oil in the coffee = less bitter flavor… but less delicious inviting aroma.
Making traditional coffee, and letting it cool in the open, means you lose most of those oils and the remaining drink is bitter.
Making coffee via a cold-brewing method means the coffee never gets warm enough to vaporize the aromatic oils, so they remain in the coffee and balance out the bitterness.
Coffee from a gas station that cools down tastes terrible because first its low quality, and second, its over cooked sitting in the machine ready to serve.
I make high quality coffee via pour over method, and when it cools, it tastes different than when it was hot, but not at all bad.
The difference between the two is astonishing. Ive had gas station coffee that tasted fine hot, and like a tire cold. This doesnt exactly answer your question via chemistry, but I suspect if you’re running into this situation, lower quality coffee is part of the equation.
As an old nurse, I can tell you that coffee at any temperature is acceptable. We often pour coffee that we don’t get to for an hour or more.
❤️☕️
long time specialty coffee barista here. “specialty coffee” is used to denote high-quality beans that are sourced directly from farms, not bought on the commodity markets. the roasters we worked with were extremely dedicated, and the product was often very different than what most people are accustomed to. a light-roasted high quality coffee should have a color like tea, a clean body (not thick!!!!!!!!), and a juicy, flavorful, sweet flavor. good coffee is truly more like tea than the coffee you’d get at starbucks or dunkin donuts, to the point that those latter drinks are almost unrecognizable as coffee to me.
here’s my point.
if you’re drinking GOOD coffee, it tests *best* at lower temperatures, somewhere between hot and room temperature when the flavors have had time to develop and it reaches a temperature that won’t scald your taste buds. it will continue to taste good as it turns lukewarm and cool. so if your coffee tastes bad when it’s cooler, it was never good coffee to begin with. as such, i cannot really answer your question, as the premise of the question (“hot coffee that goes cold taste[s] bad”) is itself flawed. but i’ll try to answer somewhat.
iced coffee that you get at many shops is simply yesterday’s brewed coffee poured over ice. if that tastes good to you, then that’s great, i’m jealous! at best, it’s tolerable to me. i make no apologies for being a snob so save your breath if you want to call me out on it. cold brew makes good coffee because for whatever reason the low temperatures never extract some of the harsher notes from even low-quality coffee. i suspect that most places are doing a better job at filtering cold brew, because partly why warm coffee that goes cold tastes bad is due to unfiltered solids continuing to brew, leaving bitter/sour tastes.
I prefer my iced coffee brewed hot, then allowed to cool before putting it in the fridge. I tried cold brewing my coffee, but I didn’t like it. To each their own 🤷🏻♀️
I get so upset when people try to dump out the old coffee. SAVE it for MEEEE. I am gross and have no taste, and prefer any coffee that is not hot. Obviously iced and cold brew are slightly better than day old, but I will drink the hell out of that shit.
The science here made me finally understand (a little) why people are so grossed out that I insist they save me the old coffee.
Pease porridge hot, pease porridge cold,
Pease porridge in the pot, nine days old;
Some like it hot, some like it cold,
Some like it in the pot, nine days old.
This is my theme song when it comes to coffee.
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