At exactly what temperature does caramelization happen?

That’s what reader OB wants to know. Most authorities will tell you, OB, that sucrose caramelizes at 340 degrees Fahrenheit (170 degrees Celsius). That’s true, but then there are some mitigating factors that make the precise caramelization point of table sugar a rather hard thing to pin down. That’s why I generally write “above 300 degrees Fahrenheit” because it’s a safe thing to say. 320 degrees Fahrenheit (160 C) is about the point you usually start to see the first bit of yellowing in the pan. That’s caramelization. But what is going on then if sucrose doesn’t caramelize until 340?

The answer is that when the temperature reaches 320, sucrose isn’t the only sugar you have in the pan anymore. I know what you’re thinking: how the heck did other sugars get in there? The answer is that some of the double-sugar sucrose molecules have now split into their component parts: single-sugar glucose and fructose molecules — and they both have lower caramelization points (300 degrees Fahrenheit (150 C) and 220 degrees Fahrenheit (105 C) respectively).

These are the sugars that are starting to take on color early. By the time you reach 340 any remaining sucrose is starting to caramelize and darkening really starts to accelerate, so much so that by 350 you’d better be planning on stopping the cooking with cream or butter or the whole thing will turn to a sticky ash-tasting mass.

So I hope you sort of see what I mean here, OB. The caramelization point of table sugar is rather fuzzy. I hope that’s not too frustrating an answer!

8 thoughts on “At exactly what temperature does caramelization happen?”

  1. Thanks for the reply. I did some research online and came upon this article which I have not read in ages, and which I have altogether forgotten. The paragraph (the 10th by my count) that starts with “After careful analysis, Professor Schmidt found that…” echoes what you have mentioned above about various molecules breaking down at different times. It seems that the speed at which the temperature rises also has an effect on the temperature at which caramelization starts to take place. Hmmm…

    As for burnt caramel, I came upon a recipe in Michael Recchiuti’s “Chocolate Obsession” for burnt caramel ice-cream that requires you to create a caramel base by cooking the syrup until it is jet black and bubbling (i.e. way past the point at which it turns bitter), so all is not lost if your caramel goes over the edge. I have not braved this recipe yet. My quest for the ultimate caramel fix continues…

    1. Fascinating, OB! Thanks for the great question and the research!

      The recipe idea is way cool, too.

      – Joe

  2. And this is why you are my reference for weight and measurement and temperature, you are precise, or you else you explain why something is not exact.

  3. I found myself wondering what happens on molecular level during cooling. Does hardened caramel retain its glucose-fructose composition? How does (if it does ) the speed of cooling affect things like brittleness? After all caramel is not possible without heat but it is not itself until it cools, literally. And if it isn’t beyond Joe Pastry’s expertise, how much sugar, in any of it’s components, as recognized by the body rather than the palate, remains in bitter caramel?

    1. Hey Dani!

      Those are a lot of tough questions! All I can say is that it depends on how much you cook the caramel. The longer the cooking and the higher the temperature, the more the sucrose breaks down, and the more…”whatsits” are created. The caramel tastes less sweet as a result since there’s less sugar in it, also it gets darker (since some of the whatsits are pigments) and also softer. Why softer? Because many of the molecules produced in the caramelization process are non-uniform. They don’t crystallize and more than that undermine the the ability of the remaining sucrose to crystallize as it cools. Caramel is usually burnt by the time the softness becomes noticeable though.

      As for what the mix is in there, I really can’t say. There can’t be too much fructose and glucose in caramel because both are liquids at room temperature, and as you know, cooled caramel…if it doesn’t have cream or butter in it…is quite brittle stuff. Oh and to answer your question, once sucrose splits into glucose and fructose, it doesn’t re-combine into sucrose.

      The whole process is quite mysterious…which is why it’s so poorly understood even now. Very interesting questions though, Dani! Thanks for a very thought-provoking email!

      – Joe

  4. I was at the Harvard food science lectures this fall; in the first, Harold McGee talked about how given enough time sugar will caramelize at temperatures well below its melting point. To demonstrate he showed us progressive pictures of large sugar crystals (~1cm on a side) he left in his oven for a day or two. They didn’t melt, but after many hours they had taken on color. Even stranger: they caramelized from the inside out. That is, the inside was the darkest.

    1. Fascinating. Sounds sounds something like Maillard reactions, which also happen at low temperatures given enough time. And I mean VERY low temperatures. Maillard reactions make dirt brown!

      Ain’t science wonderful? Thanks so much, Evan! I greatly appreciate you joining the discussion!

      – Joe

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