What is Caster Sugar?
Caster sugar, often spelled castor sugar, is a term that is used in Britain, but most of us here in the states have never heard of it. It is actually just superfine granulated sugar and you may find it labeled as simply superfine. It’s also called bar sugar since bartenders use a superfine sugar for some cocktail recipes, instead of a simple syrup. In French cooking, it’s called sucre semoule.
Caster Sugar in Canada
Reader Leah Jordana has also let me know that in Canada, caster sugar is known as ‘berry sugar.’ If you are in Canada, you may be able to find Roger’s Berry Sugar in your grocery store.
Certain recipes, such as meringues, ice creams, and sponge cakes might specify a superfine sugar. The difference is that they are not so fine that they are turned into a powder, such as in confectioner’s sugar or icing sugar, which, in the United States, has some anti-caking ingredients (like cornstarch, 3 to 5%) added to keep the sugar from clumping together.
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If you can’t find superfine sugar of any kind at your regular grocery store, or if you are just in a pinch because you have a recipe that calls for caster sugar or super fine sugar (not confectioner’s, icing, or powdered sugar), don’t fret, you can make your own. The first thing to know is that it is probably not a good idea to substitute regular granulated sugar, as they behave differently and if someone bothers to specify caster or superfine in a recipe, there is probably a reason.
While you shouldn’t replace caster sugar with granulated sugar, caster sugar can often be used in place of granulated and may perform better.
Superfine sugars will incorporate more quickly in whips and dissolve more quickly in creamed mixtures. Caster sugar is often chosen as a compromise between regular granulated and powdered sugar in pastry doughs, as well, as it gives some of the functional advantages of powdered sugar (workability) with a little more sweetness to the tongue as with regular sugar. You will often read that caster sugar is used “for cakes and biscuits” and in American that means “cakes and cookies.”
If you do a lot of cakes where you have to cream butter and sugar together, you’ll like it much better than granulated sugar. It works well for sweetening meringues, as well, where it incorporates more widely and quickly than granulated, without the corn starch that is present in powdered sugar. Although you should probably avoid substituting regular sugar for superfine, you can usually substitute superfine for regular in most dessert recipes. For making glazes or icings, however, stick to confectioner’s or icing sugar (they’re the same thing).
Caster Sugar Substitute: Make It Yourself
You can make caster sugar yourself. Making caster or superfine sugar can be easily done with a regular electric coffee grinder like this Hamilton Beach Coffee Grinder. A food processor can also work, and it would stand to reason that this would be superior for larger jobs, but a coffee grinder produces a fine sugar very quickly and evenly. Plus, the problem with a food processor is that unless you have a mini processor, you have to do a large enough amount to cover the blades well. A blender will work pretty well, too. What you are going for is a finely granulated sugar that is still free-flowing and dry, somewhere between regular granulated sugar and powdered sugar. This can take 1 to 2 minutes for large amounts in a food processor, but in a coffee grinder it should will probably take less than a minute and may be done as quickly as 30 seconds.
Most sources will, however, recommend a food processor. The reason I do not like to use a food processor is that the sharp blades of a food processor are not efficient for grinding, but for cutting. If you have a grinding attachment, this may work better. But the grind is uneven and by the time you are able to produce a superfine sugar, some of it will have turned to powder. This is also just a part of trying to produce large amounts in one go. So I recommend the smaller cup of a coffee grinder, and to grind your sugar in batches, so you can get a more even texture. By all means, though, experiment and use the method that works best for you. A coffee grinder, you will find, is useful for a lot more than just grinding coffee. It’s great for grinding spices as well, for example.
Now, grinding up regular granulated sugar is not how superfine or caster sugar is made in the sugar industry, and for that very reason, plus the lower demand, you’ll pay a premium for it, if you can find it at all. In grocery stores, it will tend to be more expensive than both brown sugar and confectioner’s sugar. It can cost up to twice as much, per pound, than regular granulated sugar.
To make superfine sugar, they use a different process that results in finer crystals. But for cooking purposes, you can make do quite well with your own ground up version. Your homemade version will tend to look a bit duller than a store-bought version, as you’ve roughed up the crystals.
What About Homemade Powdered (Confectioner’s Sugar)?
You can also turn granulated sugar into powdered sugar the same way. However, typical grocery store confectioner’s sugar is 10x (10 times finer) and this is hard to achieve at home. You’ll have a mixed blend of fineness. However, if you produce a powder, it will work fairly well in a pinch. Add 1 teaspoon of cornstarch to one cup of regular granulated sugar for this, and make sure to add the cornstarch to the sugar before you grind it.
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