Want to know something crazy? Sugar doesn't melt; it undergoes thermal decomposition. That may sound like a pedantic distinction, considering we've all watched sugar effectively melt into a pool of caramel atop crème brûlée, but the implications are huge—worthy of far more explanation than a mere tl;dr.
Man, who am I kidding; you're here for the tl;dr, aren't you? Okay, fine. Here goes: Caramelization occurs independent of melting. Consider the above photo exhibit A—neither brown sugar nor turbinado, but granulated white sugar that I caramelized without melting. It's dry to the touch, and performs exactly like granulated white sugar.
Except, you know, the part where it tastes like caramel.
That opens up a world of possibility, as it works flawlessly in recipes for buttercream, mousse, or cheesecake, which can accommodate only a small amount of caramel sauce before turning soupy or soft. It's also ideal for desserts that would be ruined by caramel syrup, which is by nature too hot for fragile angel food cake, and too viscous for soft candies like marshmallows or nougat. And, compared to caramel powder (made from liquid caramel, cooled and ground), it won't compact into a solid lump over time.
Some bakers work around these issues by swapping in brown sugar for caramel, but why accept an imitation when you can have the real thing? Unlike quirky brown sugar, this "granulated caramel" won't alter the pH of doughs and batters, which can negatively impact how our favorite cookies and cakes spread, rise, and brown (in turn affecting their texture and crumb). For example, sugar cookies made with granulated caramel stay crisp at the edges, and oatmeal cookies spread like they should.
What's more, granulated caramel is free from the impurities that cause molasses-rich sugars to smoke and burn at high heat. Granulated caramel also won't curdle boiled milk, which can happen when you're making eggless custards and cajeta with brown sugar.
Now, with enough technical know-how, almost any recipe can be reformulated to accommodate brown sugar or caramel sauce/syrup/powder, but granulated caramel requires no such precaution. It's a perfect one-to-one replacement for white sugar; no calculations, no adjustments, no tinkering. Just use it to replace sugar in any recipe you love, from the meringue on Gramma's chocolate cream pie to my own angel food cake.
So what makes this magic possible, and why haven't we been doing it since the dawn of time? Well, the answer goes back to that whole melting-versus-thermal-decomposition thing, so bear with me for a sec as we wade into the nitty-gritty.
Melting is a phase change that has no impact on chemical composition, like the transition from ice to water. It's still good ol' H2O either way, right? Under normal conditions, the melting point of any given substance is fixed—when ice hits 32°F, there's nothing we can do to stop it from melting. Phase changes are also reversible; you can melt and refreeze ice as many times as you like, with no loss of quality on either end.
Thermal decomposition, on the other hand, is a chemical reaction that breaks down molecular bonds to produce new substances. While it's not a perfect analogy, imagine a pile of grass clippings releasing carbon dioxide as it turns to mulch in the sun—an irreversible process with variable results (i.e., no two handfuls of mulch are exactly alike, or composted to the same degree). Instead of occurring at a specific point, thermal decomposition occurs over a range of temperatures determined by the intensity and duration of heat.
Still with me?
Heat up some sugar on the stove, and it sure seems to melt, but if it were just a simple phase change, then melted sugar would be perfectly clear, not brown. Melted sugar would taste simple and sweet, not bitter and complex. Melted sugar would cool into crystals, not glass. None of those things are true because heat doesn't cause sugar to change phases. Heat breaks it down into something new: caramel.
In fact, caramel is so unlike sucrose, C12H22O11, that its nature can't be expressed by a single chemical formula. Instead, it's a mixture of caramelan (C15H18O9), caramelane (C12H9O9), caramelen (C36H48O24), caramelene (C36H25O25), caramelin (C24H26O13), and over a thousand other compounds "whose names," one scholar lamented in 1894, "science seems to have invented in a fit of despair."
Realizing that caramel contained more permutations of carbon, hydrogen, and oxygen than their cutesy naming scheme could accommodate, scientists gave up on trying to define it. They even gave up on nailing down a definitive melting point for sucrose. Unlike ice, or even coconut oil, sugar refused to liquefy at a single, consistent, scientifically reproducible temperature. The point of caramelization proved even trickier to isolate, in some experiments occurring at a mere 340°F and in others holding out past 360°F.
If you think that's confusing, you're not alone. Scientists have a better grasp of quantum mechanics than of caramel, which is still poorly understood. But in 2011, a team of researchers finally established that caramelization is a product of thermal decomposition, not melting (you can read the paper here). Not only that, they determined that it's technologically impossible to document the melting of sucrose independent of caramelization.
The significance of that discovery can't be overstated, yet the food world collectively shrugged. Whether sugar melts or decomposes, the results are the same: liquid caramel. Everyone heard the facts, but no one caught the implication. If sugar is governed by thermal decomposition, then caramelization doesn't happen at a specific temperature; it happens across a spectrum, in which liquid caramel happens to be at the end. With the right technique, we can caramelize sugar without liquefying it at all.
High-Heat Versus Low-Heat Caramelization
Caramelization and liquefaction only go hand in hand with high-heat techniques, which speed thermal decomposition. On the stovetop or under a blowtorch, sugar races through the caramelization process so fast, it liquefies in an instant. But in the gentle heat of a 300°F oven, the process is drawn out, revealing myriad stages of caramelization in a crystalline state.
Check it out.
Despite a modest progression of color, the sugar goes through extreme changes in flavor every step of the way. With only one hour of toasting, it mellows with a complexity totally unlike plain sugar. After another hour, it's evocative of caramel the same way unrefined sugar hints of molasses, surely but subtly.
Within three hours, thermal decomposition liberates enough water that the sugar begins to clump as stronger caramel notes develop, changes that intensify into hour four. At five hours, the clumping effect makes granulated caramel visually identical to light brown sugar, but with a unique flavor of its own. Though undeniably caramel, it lacks the bitter notes synonymous with high-heat techniques, giving it a lighter profile. Beyond that point, thermal decomposition will finally liquefy the sugar.
Because water is a by-product of caramelization, and relatively low "roasting" temperatures prevent it from being driven off as steam, deeply caramelized sugar is super clumpy. Stirring from time to time helps release entrapped moisture, but not enough to stop it from cooling into hard, lava rock–like pieces.
Fortunately, these chunks are highly porous and easily demolished in a food processor, where they can be ground until powdery and fine. This free-flowing granulated caramel behaves like white sugar in terms of shelf life, and never needs to be ground again so long as it's kept in an airtight container.
However alluring the darkest shades of caramel are, I'm most excited by the lightest hues. A single hour of toasting won't develop any discernible caramel flavor, but it tames the intensity of marshmallows, angel food cake, and fudge—recipes that rely on sugar for structure, but have a reputation for tooth-aching sweetness.
Lightly toasted sugar brings these desserts into balance without sacrificing structure or distracting from their classic flavor. It even cuts down on the need for salt—a real boon for those on sodium-restricted diets. Not only does toasted sugar taste less sweet, it has less sucrose, fewer calories, and a lower glycemic index than plain sugar. How much lower would depend on the extent of thermal decomposition, but it's a promising notion.
But alas, I digress. My motivations have nothing to do with dietary considerations, and neither should yours. Whether caramelized a little or a lot, toasted sugar is crazy delicious, and I hope you try it at home. The technique itself is as straightforward as toasting bread crumbs: Stir occasionally, and let color be your guide.
As long as thermal decomposition halts before anything liquefies, granulated caramel behaves like sugar, so there are no caveats on its use. I've been playing around with this technique since 2010, having stumbled into it long before I understood the science, yet I've never encountered any technical difficulties with substitutions. So set aside that blowtorch and step back from the stove. There's a new caramel in town, and it has the power to change every recipe you've ever known.