Sugar
Sweetener, tenderiser, browning agent, moisture-holder and aeration aid — most of which have nothing to do with taste.
Also called caster sugar (UK) — A finer grind than granulated, used where rapid dissolution matters.; superfine sugar (US) — The US term for what UK usage calls caster sugar.
Sugar’s functional roles in baking substantially outweigh its role as a sweetener, and reducing it in a formulation therefore changes far more than sweetness.
It competes with flour proteins for water, which slows gluten development and tenderises. It provides reducing sugars for Maillard browning and caramelises in its own right. It holds water, delaying the perception of staling. Its crystals cut air pockets into fat during creaming, which is a mechanical aeration function that dissolved sugar cannot perform. And it lowers the temperature at which egg proteins set, which affects when a cake’s structure locks in.
Cutting the sugar in a cake by a third does not produce the same cake, less sweet. It produces a paler, drier, tougher, faster-staling cake.
What changes if it is left out
Sweetness, browning, tenderness, moisture retention and creamed aeration are all reduced together. In a creamed batter the aeration loss alone is often enough to change the product’s character.
RecordedPaula Figoni, John Wiley & Sons
Grain size is a functional property, not a refinement
Caster sugar dissolves faster than granulated, which matters wherever sugar has to be in solution before something else happens — in a meringue, or in the sugar-and-egg film that gives a brownie its papery top.
It also matters in the opposite direction. Larger crystals survive creaming longer and cut more air into the fat, and they dissolve more slowly in a cookie dough, which affects spread. Choosing a sugar by grain size is a genuine technical decision in a way that choosing it by brand is not.
Related
Used in
Sugar governs spread as much as sweetness here: dissolved sugar lowers viscosity and delays the set.
Sugar dissolved in egg forms the meringue-like film that becomes the characteristic papery top.
Sweetness, tenderness, and competition with the yeast for water.
Tenderness, browning and yeast food.
Sweetness, and fast browning.
What it does
Gluten inhibition
Sugar competes with flour proteins for water, slowing hydration and therefore development — a tenderising route quite separate from fat’s.
Browning contribution
Supplies reducing sugars for Maillard browning and caramelises in its own right, which is why cutting sugar leaves a bake pale.
Moisture retention
Holds water and slows its loss, which delays the perception of staling without slowing retrogradation itself.
Aeration
Crystals cut air pockets into fat during creaming — a mechanical function that dissolved sugar cannot perform at all.
The science behind it
Sugar supplies one of the two required reactants, which is why a low-sugar bake stays pale even when fully cooked.
Can be replaced by
Works by weight and changes the chemistry: it adds acid and moisture retention. In a bicarbonate-leavened recipe the direction of that change matters.
Chemically identical, physically finer. Safe by weight; expect a lighter crumb, a more stable meringue and slightly more cookie spread.
Compared in
The refined reference the comparison is against.
One side of the comparison, so the comparison is reachable from the record a reader is more likely to land on first.
Competes for water
Hydration
Sugar is hygroscopic and dissolves into the water rather than sitting beside it, so water held in syrup is not available to hydrate flour. This is why a high-sugar dough behaves stiffer than its liquid content suggests, why sugar delays gluten development, and why reducing sugar in a cake changes texture and not only sweetness.
Covered in
The sugars, and when the difference matters
The reference.
What happens when you reduce the sugar
The ingredient whose six jobs the guide enumerates.
History and culture
The commodity whose price falling made a modern cake batter thinkable.