What Sugar Does Besides Sweeten

Sugar has four jobs

Halve the sugar in a recipe and you expect it to be less sweet, but the colour and texture change too. Sugar is doing four things at once.

• Sweetness
• Colour and aroma — caramelisation, and fuel for the Maillard reaction
• Moisture retention, since sugar holds on to water
• Structure: in baking it interferes with gluten and protein setting, which is what makes things tender

Reduce the sugar in a cake and it comes out firmer and stales faster — not because it is less sweet, but because the last two jobs went away.

When sugar is the main ingredient it is all about water

Those four are what sugar does when it is one ingredient among several. Once it is more than half the weight, other jobs come forward — and those jobs, which look unrelated, all come out of one fact: sugar binds water so that nothing else can use it.

• Preservation. Yōkan is concentrated enough that almost no free water is left for a microbe to live on. Keeping a year at room temperature is the consequence, so cutting the sugar does not just cut sweetness — it removes the keeping. Churchkhela lasts months for the same reason.
• A freezing point. Take sugar out of Gelato and it does not come out less sweet, it comes out harder. The sugar was lowering the freezing point of the water.
• Osmotic support. Twenty minutes in plain water reduces a pear to mush; in a syrup sweeter than the fruit, its cell water has no reason to leave and the shape survives (Poire Belle Hélène). Halve the sugar there and what you lose is not half the sweetness but the scaffolding.
• Taking water off something else. Crème Caramel uses this as its design. Poured in hot, the caramel sets like glass; overnight it pulls water out of the custard and loosens back into a sauce. Making it the day before is the recipe, not a convenience.

The same property is a nuisance from the other side. Dasik and Nougat draw moisture out of the air and go soft, which is why nougat is wrapped in wafer paper and Lokum is dusted in starch.

Caramelisation and Maillard are different reactions

• Caramelisation needs only sugar. Around 160C it breaks down into colour and bitter aromatics.
• The Maillard reaction needs sugar and protein (browning and maillard). It starts at far lower temperatures and produces a much wider set of aromas.

A little sugar rubbed on meat browns faster because it supplies Maillard with more to work with. The glossy brown of teriyaki chicken or hong shao rou is both reactions running together.

The flip side: sugar burns easily. A sweetened glaze cannot sit over high heat for long.

There are really two routes to a browned crust. One is to supply more sugar, as here — the malt-syrup wash on Shaobing, the maltose on Peking Duck. The other is to raise the pH: the soda in a Bagel's boiling water is there because the Maillard reaction runs much faster in alkali, and a pretzel is the same principle pushed harder.

Where sugar cannot be added, pH is not the only alternative. A third route is to cut up the protein in advance: a miso glaze scorches in thirty seconds under a grill that would leave a raw surface pale, because a year of fermentation has already turned its protein into free amino acids (browning and maillard). Supply the sugar, raise the pH, or prepare the partner — all three drive the same reaction faster.

Judge caramel by temperature, not colour

By the time you see the colour you want, you are late. Roughly:

• 110-115C: syrup, still colourless.
• 150C: pale gold; aroma starts here.
• 170-180C: amber, where most caramel sauces live.
• Above 190C: bitter, and unrecoverable.

The pan carries it another 20-30C after the heat is off, so pull it one stage early rather than at the colour you are aiming for.

Dishes that stop at each rung

The ladder is not abstract; there is a dish parked at every step of it.

• 110-115C — the syrup in Stroopwafel. Stopping before any colour is the whole point; further on it sets solid between the two wafers.
• 118C — Lokum stops here and carries the water with it into the starch.
• 135C / 145-150C — in Nougat the number is the recipe. 135C gives a chewy nougat and 145-150C a hard one, and nothing else about it changes.
• 155C — Tanghulu drives nearly all the water out so it shatters like glass.
• Hard crack, cast as a sheet — Dobos Torte pours sugar at that stage onto a plate and scores it while it is still plastic. The window is about thirty seconds.

There is a direction the other way too. Bündner Nusstorte adds cream so the caramel will not set at all, because the water and fat in it get between the sugar molecules.

The same ladder runs through savoury cooking, in the glaze

Every rung above is a confection, and the savoury section further down is about taste — sugar damping salt and acid. A glaze belongs to neither and to both. The dish is savoury and holds a spoonful of sugar, but the glaze itself is a small pan of sugar, soy and water, so inside that pan the rules for a syrup apply while the dish around it is not a sweet at all.

• The rung is chosen, and the dishes say so. Dango: "the glaze thickens as it cools. Reduce it to the consistency you want in the pan and it will be jelly on the plate", and its step says to stop while it is still slightly loose, just coating the back of a spoon. The far end is named from the other side by Tteokgalbi — a glaze with sugar and syrup in it "browns fast above 100°C and then burns" — and Teriyaki chicken explains why a pan is more forgiving than a grill about it: the sauce's own water holds it near 100°C until the water has gone.
• Nothing here is measured, and what stands in for the thermometer is a proxy for the same number. Nougat states how a confection does it — doneness "gets measured on the sugar ladder. You judge it by dropping a sample into cold water, not by a clock." A savoury glaze cannot be read that way, so Dak-gangjeong watches for a spatula drawn across the base leaving a trail, dango watches the back of a spoon, and Myeolchi-bokkeum takes the bluntest reading of the three: the syrup goes in with the heat already off, choosing a rung by refusing to climb any further.
• Which rung you want is set by the temperature it will be eaten at. That is why these dishes disagree with each other. Dango "harden as they cool, so this is food you eat where it was made" — the setting is a deadline. Myeolchi-bokkeum and Eomuk-bokkeum are banchan meant to be eaten cold, so the same setting is the thing being designed against, which is what the off-the-heat syrup buys. Dak-gangjeong wants to be crisp cold as well and pays for it differently — it keeps the glaze sparing rather than thinner, because a starch crust drinks a loose one.

So the burning end of this belongs to grilling, which puts a sugary glaze in the last two or three minutes, and the slow drift afterwards belongs to serving temperature, where a stroopwafel's syrup gives its water up to the biscuit over hours. What is decided in the pan is neither of those: it is a texture, chosen for a moment that has not arrived yet.

Sugars do not substitute for one another

• White sugar is pure sucrose. Having no other flavour, it stays out of the way.
• Brown sugar, jaggery and palm sugar retain molasses, which is mildly acidic and carries minerals — so it changes reactions, not only taste. Jaggery in vindaloo is there for its bitter finish as much as its sweetness.
• Swapping white for brown in baking removes that acidity, leaving bicarbonate of soda with nothing to react against. The rise changes.
• Grain syrups — malt syrup, glucose syrup — are mostly maltose rather than sucrose. Maltose is about a third as sweet as sugar, browns readily, and resists crystallising. Yeot is the dish that manufactures it, cutting rice starch with barley-malt enzymes, and the colour and gloss on the skin of Peking Duck is maltose doing the work.

Making crystals, or preventing them

At high concentrations sugar grows crystals as it cools, and how you handle that decides what a confection is — which is a job the four-item list above has no entry for.

• Prevent them. Lokum and Nougat use lemon juice, honey or glucose to make invert sugar. A mixture of differently shaped molecules cannot pack into a lattice.
• Make them, but small. Barfi wants crystals. Stirring hard off the heat seeds a great many at once, so no single one gets room to grow and the block sets smooth.
• The rule therefore reverses inside one pan: do not stir the boiling syrup (a spoon drags crystals off the wall and seeds it early), then stir constantly once it is off the heat.

In savoury cooking, sugar is not there to sweeten

A teaspoon of sugar is routine across Korean, Chinese and Southeast Asian cooking because it damps down salt and acid. It is how you lower perceived saltiness without removing salt, and how you round off the edge of vinegar (balancing flavour).

The 150ml of vinegar in vindaloo, the shrimp paste in laksa, the vinegar and soy in yuxiang eggplant — leave the sugar out of any of them and each strong element steps forward on its own. Taste with and without and you will not notice sweetness; you notice that nothing else is sharp any more.

And there is an order to it

Japanese cooking puts sugar in before salt and soy, and that is not a preference. Sucrose is a much larger molecule than the ions salt breaks into, so it travels into food far more slowly — and salt going in first firms the surface protein, which narrows the road further.

So Nikujaga adds sugar and mirin first, gives them time to get into the potato, and only then adds the soy. Reverse it and you get something salty on the outside and blank in the middle. How salt itself moves is in salt and seasoning.

And that order assumes the sugar has to get in

Everything above is a rule about distance — how far a large molecule has to travel into a solid — so it binds only where something has to travel.

• A glaze has no inside to reach. Gamja Jorim simmers its potatoes in the soy base and reduces the liquid almost entirely away, so what is left sits on the outside, and the corn syrup goes in at the end. Its page states the inversion in as many words: sugar leads "when it has to get inside", and here "the slowness that earns sugar its place at the front is only a cost." Nikujaga draws the line itself — that dish keeps its broth.
• And where the pot holds starch, putting sugar in first is paid for in cooking time. A concentrated syrup holds water back from the starch and pushes up the temperature at which it can swell (thickening a sauce), so the same spoonful that is travelling inward is also slowing the potato down. Gamja jorim puts it plainly — added early it "does not merely fail to glaze; it holds the potato back" — and Pozole states the same thing on the salt side. The front of the order is not free even in the dishes that need it.
• The back of the order is a different clock altogether. Sugar is at the front for distance; the soy is at the back for aroma. Nikujaga separates them — "splitting the soy is aroma, not penetration" — which is why a last measure goes in at the end of a long simmer. Galbijjim keeps both and says why: a short rib genuinely has an inside, so the sugar leads and the soy is split.

So the question to ask before following it is where the seasoning has to end up. Where nothing has to travel, the first half of the order has nothing to sort and only the aroma half survives. That makes it a different kind of instruction from the one in balancing flavour, which orders salt, acid, sweetness and fat by what is hardest to undo in something you can taste at every step.

If you want to cut it

In desserts, about 20% is the safe margin. Beyond that brownies turn dry and tiramisu loosens, because you are removing the structural share along with the sweetness.

Savoury cooking is far more forgiving. If the sugar is there for balance, halve it and pull back slightly on the acid to match.