Ingredient

Sugar

In baking, sugar is a structural ingredient that happens to taste sweet. It holds water, tenderises, aerates, browns and preserves — which is why cutting the sugar in a recipe by half rarely gives you the same cake, only less sweet.

What sugar does besides sweeten

• Holds water. Sugar is hygroscopic, so it keeps cakes moist and stops them staling as fast. This is why a low-sugar cake goes dry in a day.
• Tenderises. It competes with flour for water, so less gluten forms. Reducing sugar makes a cake tougher as well as less sweet.
• Aerates. Creamed with butter, sugar crystals cut air pockets into the fat. That is where much of a sponge's lift comes from, and icing sugar cannot do it.
• Browns. Sugar caramelises on its own and takes part in browning reactions with protein, giving colour and flavour to crusts, biscuits and roast vegetables.
• Preserves. In sufficient concentration it makes water unavailable to microbes, which is the basis of jam.
• Lowers freezing point, which is why ice cream is scoopable rather than a solid block.

The sugars

Granulated

Standard white, medium crystal. General purpose, and fine in anything that dissolves in liquid.

Caster

Finer white crystals. Dissolves fast, so it is the one for creaming, meringues and delicate sponges. Blitz granulated briefly to make it.

Icing / powdered

Ground to a powder with a little starch. For icings and dusting. It will not cream air into butter.

Light brown / soft light

White sugar with some molasses returned. Moister, slightly acidic, adds caramel notes and a softer crumb.

Dark brown / muscovado

More molasses. Strongly flavoured, noticeably acidic, keeps things very moist. Gingerbread, Christmas cake, barbecue sauces.

Demerara / turbinado

Large, dry, crunchy crystals. A topping sugar. It does not dissolve or cream well.

Golden syrup, honey, treacle

Liquid sugars. They hold more water, brown faster and are not straight substitutes by weight.

Brown sugar is not just brown

The molasses in brown sugar brings moisture and acidity as well as colour and flavour. The acidity is the part people miss: it reacts with bicarbonate of soda, so a recipe using brown sugar and bicarbonate is relying on that reaction for lift. Swapping in white sugar removes the acid and the thing does not rise properly.

It also holds more water, so brown-sugar biscuits stay chewy where white-sugar biscuits go crisp. If a cookie recipe gives a ratio of the two, that ratio is the chewy-to-crisp dial and is worth adjusting deliberately rather than ignoring.

Hard brown sugar has simply dried out. A slice of bread or a damp cloth in the container overnight, or a few seconds in a microwave, brings it back.

Reducing it

A reasonable thing to want, and it has consequences worth knowing before you start.

• Cutting up to about a quarter of the sugar in a cake usually works with only a small loss of moisture and browning.
• Cutting more than about a third gives a drier, tougher, paler result that stales faster.
• In meringue, jam, caramel and ice cream, sugar is structural in a way it cannot be reduced out of. Those recipes are not adjustable.
• In biscuits, sugar controls spread. Less sugar means less spread and a cakier result.
• Sugar substitutes do not do any of the non-sweet jobs. Recipes formulated for them are different recipes.

Common questions