What is caster sugar

What is Caster Sugar?

Caster sugar is a refined white sugar with an exceptionally fine crystal structure, making it distinct from standard granulated sugar. The name 'caster' comes from its use in caster (shaker) bottles for sprinkling on desserts and baked goods. In different parts of the world, it goes by various names: superfine sugar in North America, ultra-fine sugar or berry sugar in Canada, and castor sugar in the United Kingdom and Australia.

Crystal Size and Composition

The primary difference between caster sugar and regular granulated sugar is crystal size. Caster sugar crystals measure approximately 0.5 to 1 mm in diameter, roughly half the size of standard granulated sugar crystals (1-2 mm). Both are pure sucrose (C₁₂H₂₂O₁₁) with identical nutritional and caloric content. The finer crystals create a larger surface area relative to volume, which is responsible for caster sugar's superior dissolving properties.

Dissolution Properties

Caster sugar's most important characteristic is its ability to dissolve almost instantaneously in batters and cold liquids without heating. This makes it ideal for whipping into egg whites for meringues, where undissolved crystals would create a grainy, undesirable texture. It also works beautifully in cold drinks, fruit salads, and cold desserts where granulated sugar might leave a gritty residue.

Baking Applications

In baking, caster sugar produces superior results compared to granulated sugar. It creates lighter, more tender cakes with a finer crumb structure because the smaller crystals distribute more evenly throughout the batter. It's particularly valued in sponge cakes, meringues, pavlovas, and whipped cream desserts. The even distribution also allows for more consistent caramelization in some recipes.

Cost and Substitutions

Caster sugar typically costs 20-40% more than granulated sugar due to additional processing. In a pinch, you can create a caster sugar substitute by pulsing granulated sugar in a food processor for 1-2 minutes, though this won't perfectly replicate the uniform crystal size of commercial caster sugar. For most baking applications, this DIY method produces acceptable results.