Reader Molly wants to know what goes on — exactly — when sugar caramelizes. She says she hears the word “caramelization” bantered around quite a bit, but never hears it fully explained. Molly, I feel your pain. In the same way chemists love the word catalyst and physicists love resonance, TV chefs love caramelization. That and Maillard reaction. All are nice, neat, precise-sounding words that people use to describe phenomena that ultimately aren’t all that well understood. Caramelization itself is a bewilderingly complicated process, which no one has the time, energy, or corporate funding to sort out completely.
Which is not to say that we don’t know anything about it. For example we know that when sugar (sucrose) molecules are heated beyond a certain point (about 180 degrees Fahrenheit) they decompose into their component molecules: glucose and fructose. As temperatures rise, those molecules themselves break into pieces which recombine into various new molecules. Which is a polite way of saying that when you cook sugar, a truly riotous and chaotic orgy of destruction and mutant molecule recreation takes place — all in a virtual eye-blink. Sugar molecules fly apart into pieces, which then come back together as new molecules, fly apart again in the rising heat, or perhaps react with other just-created whats-its to make ever more new and unusual molecules, which react once again, and so on. What you get in the end is a crazy mishmash of literally thousands of different, chemically distinct compounds.
Exactly what they all are, well, no one really knows that. Some of them don’t have names yet. Others are pretty well understood. For example there’s diacetyl, the compound responsible for the creamy, buttery flavor caramel is so well known for. There’s furans, which is gives caramel its nutty taste. Maltol brings fruity flavors to the party. Then there are lactones and esters that impart various flower- and fruit-like notes. Many of these compounds are volatile, meaning the go airborne, producing aromas of varying intensities.
And then of course there are the pigments. These are very long-chain molecules known as polymers with names like caramelins and caramelans. The colors they produce are of course brown, but they also create orange-y hues that give caramel the sort of soft, evening glow it often has.
All of this rampant breakdown and creation comes at something of a cost to the sugar syrup itself, which gets less sweet as the cooking process proceeds. That’s because, quite obviously, there’s less and less sugar in the pot as the molecules break down into other things. People have differing opinions on where the caramelization process should stop. I tend to let it go on for a while because I like an edgy, slightly acid, slightly bitter caramel that’s full of character. But of course you have to be careful when you live on the cooked sugar edge like that, as caramelization is an exothermic reaction, meaning it generates its own heat. So the hotter it gets the hotter it gets, and before you know it you’ve got a runaway train on your hands.
This is all quite amazing when you consider that the starting point was a simple, uniform, white crystalline powder with a rather one-dimensional sweet taste and barely any aroma at all.
But if you thought that was complicated, we haven’t even begun to talk about the Maillard process, which is quite similar to caramelization, save for that it includes amino acids which are derived from the proteins in, say, meat. So in addition to carbon-, hydrogen-, and oxygen-based molecules, you also have things like sulphur and nitrogen in the mix, which produce an even broader, more bewildering array of chemical tinker toys, with flavors and aromas all their own.
But I think you get the broader point, reader Molly. I think the thing I like most about the caramelization process is that it never proceeds in the same way twice. Every time you do it you get a slightly different flavor profile, which is the bane of commercial caramel producers everywhere, but which also makes every apple tarte tatin as singular as a finger print. And do I ever love that idea.
Thanks for a great question, Molly. I hope this helped!