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I know some people who refuse to drink in large coffee chains as they say that the coffee they produce tastes "burnt".

Is it actually possible to burn coffee while brewing, or is the flavour they're complaining about coming from something else?

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    Not to get all Skeptics on you, but is there a source you can cite for the claim that large chains burn their coffee while brewing? I've always heard it said that they burn their beans while roasting them, but I've never heard that said about the brewing process.
    – hairboat
    Jan 29, 2015 at 19:46
  • @abbyhairboat You're right in that this probably stems from a misunderstanding on my part. I've done my best to reword the question so that it carries the same meaning without making unsupported claims - but if anyone can suggest improvements I'm open to them!
    – BiscuitBaker
    Jan 30, 2015 at 9:21
  • The "burnt" refers to them over-roasting pretty much all of their bean varieties. Unless you use a pressure cooker, you're not going to get the water above 100 Celsius, so, no, you can't burn it in the brewing process.
    – PoloHoleSet
    Sep 12, 2016 at 13:39
  • @PoloHoleSet Coffee burns at 96 celsius, so boiling water at 100 celsius will burn it.
    – mikemaccana
    Jan 6, 2018 at 23:40
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    @mikemaccana - I stand corrected about not being able to burn it. The "burnt" does refer to over-roasting the beans, because they are definitely guilty of that, but it's good to learn new things. Thanks.
    – PoloHoleSet
    Jan 8, 2018 at 15:26

8 Answers 8

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Burn? I've heard that some large chains "burn" their beans while roasting :-) But not while brewing.

A major coffee chain, seen on almost every other corner in some places, is known for their very dark, "burnt" roast. Many people like this sharp taste and associate it with caffeine and their morning pick-me up.

Other people find this "burnt" roast to be overwhelming and consider this heavy roast to be destructive when using high-quality beans. In any case the burning happens at roast - not when brewing.

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    Now what large coffee chain might that be...
    – Ludwik
    Jan 31, 2015 at 21:27
  • What about instant coffee into a cup? I find some jugs get the water a little hotter than others, and pooring the water in before milk gives it a very strong burnt taste. Wouldn't this count as 'while brewing' burning?
    – user223
    Feb 2, 2015 at 7:25
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    I don't know anything about instant coffee.
    – Mayo
    Feb 2, 2015 at 11:17
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    Call me a lil late on the conversation, but is making instant coffee considered brewing coffee..?
    – NealC
    Jun 15, 2015 at 5:05
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I've had coffee that tasted burnt in a lot of cheaper restaurants and from common coffeemakers in homes. It's uniformly been stuff that's sat on a warmer for a long time (like, an hour or more) after brewing. Keeping coffee on heat after brewing "cooks" it down, just as keeping a soup or sauce on a simmer reduces it. However, it has the opposite effect on coffee than on sauces or soups; instead of making it richer, it destroys the more delicate flavor compounds and makes it taste burnt. Even reheating coffee in the microwave can make it taste more like an ashtray than coffee.

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It depends on the method of brewing. Brewing methods where grounds are exposed to a heat source directly (Turkish, for example) could allow the grounds to be heated to the point that they started to roast/cook/burn (again). Most methods of brewing, however, only have the grounds exposed to boiling or near boiling water which is ~210F and less than would be necessary to start cooking/roasting/burning the coffee beans again.

Many of these other answers actually talk about burning or cooking down stored coffee after it has been brewed.

As to your question about large chains, my person belief is that the burnt taste most people experience is a branding issue. Lightly roasted or medium roasted coffee will taste more like the bean it came from, or its origin. The darker you roast, the more the origin flavors go away and are replaced by the roasting flavors of the bean. As it so happens, the origin flavors of roasted coffee fade very quickly (sometimes in as short as a week). However, the roasting flavors seem to hang around a bit longer. Large chains dark roast their coffee because it makes it easier to consistently produce close to the same taste and the flavor of those dark roasted bean will hang around a bit longer (less shipping and storage concerns).

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Yes, coffee can be burned when brewing. When an empty pot sits on the heating element in a restaurant coffee machine it can get very hot. When the first stream of a new brew cycle hits the bottom of the pot, boils off very quickly, producing a horrible smell and taste that infuses the entire pot.

In addition to the water boiling off, the various organic compounds in the coffee are subjected to temperatures well above the boiling point of water for a brief time, until the volume of new coffee cools the bottom of the pot enough to stop the boiling. Knowledgable staff know to leave a little clear water in the bottom of the pot to prevent the temperature from getting too high before the next pot is brewed.

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In addition to all the great answers (most of the burnt flavor is typical for dark, e.g. italian roast) I want mention something I encountered during my time as a bartender:

When having a portafilter (professional espresso machine, as used for cappuccino etc) it sometimes happens that you prepare (e.g. attach the handle with coffee to the machine) and then something comes up and you don't start the extraction process right away. What happens then is that the hot machine heats up the ground coffee. Which in turn results in a burnt taste of the coffee if left unattended for long enough. My educated guess is that (due to the fact that ground coffee has a very large surface / very small particles) the coffee is burnt/ roasted even further at low temp.

Also note that the water is only 94°C but the metal surroundings do not have to be this "cold". As it should be able to maintain the water temperature even if you brew a lot of coffee.

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It's a bit of a misnomer. This actually happens in both tea and coffee, you don't really "burn" the coffee (or in my experience tea), but excessively high temperatures release chemicals called Tannins that possess a bitter, or "burnt" taste.

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  • Welcome to Coffee SE! Interesting -- esp. because taninns are (at least) sometimes welcome, both in tea and in wine. Can you elaborate your answer a bit? Or give some source for further reading (esp. other than wikiped:))?
    – Ivan Kapitonov
    Jan 23, 2016 at 8:39
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The word bitter is being used to describe two different things. There can be bitterness in a coffee from over extraction which causes tannin to be present in the brew. This can happen with light roast coffees which are over extracted as well as dark roast coffees. Burnt coffee is also described as bitter coffee when it is really a burnt flavour. There is much confusion about this nomenclature.

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    Please try to edit in some references, e.g. on the tannin in overextracted coffee.
    – JJJ ♦
    Nov 15, 2019 at 16:58
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I think I know what you are talking about, the question is if a steam brewer can burn the ground during brewing due to the higher temperature vs. a pump operated brewer here is a link that might help

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  • Consider explaining the information contained in the link.
    – Patrick Sebastien
    Jun 13, 2015 at 15:13

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