Caster Vs Granulated Sugar
I often get asked about the difference between granulated sugar and caster sugar and which is best used for when baking… So here’s the low-down:
The main difference between granulated (also known as white table sugar) and caster sugar (also know as super-fine sugar in North America) is the size of the grain.
Granulated is larger and more coarse (I once read that granulated is about 0.5mm in diameter while caster is about 0.35mm in diameter, although I’m not really sure who would measure them!). Because of this caster sugar is generally the most versatile and preferred of the two when baking – its small granules mixes more easily and dissolve more readily when combined with other ingredients giving biscuits, cakes, pastries etc. a more even, less coarse texture. You may have noticed if you have made a cake with granulated sugar that it sometimes can have a ‘speckled’ appearance (on the crust and/or in the crumb) – this is the undissolved sugar in the batter as it is less likely to dissolve than caster sugar. Your cakes and biscuits will have a slightly finer texture when using caster sugar while if you use granulated sugar, your cakes will have a slightly coarser texture and your biscuits will be more crunchy.
Caster sugar is also best to use when making meringues and pavlova because of its ability to dissolve more quickly. Granulated sugar however is great when making toffee (it is less likely to crystalize), and in general cooking and in baking when your want a slightly coarser texture (for example, I often make a traditional Scottish shortbread that has a better, more suitable texture when made with granulated sugar).
My advice is to use whichever sugar is specified in the recipe and if you don’t have caster sugar in your cupboard you can always make it by processing granulated sugar in a food processor or blender using the pulse button until finely ground.
It’s also good to note that icing sugar is just a finer version of caster sugar, with the crystals being ground to a fine powder.