White sugar is perhaps the most modest member of the pantry, so unobtrusive that we tend to take it for granted. Certainly it’s true that white sugar lasts forever, unless it gets wet. And regardless of its source (sugar cane or sugar beets), all granulated white sugar tastes the same. It’s 99.9% pure sucrose, refined and processed into small crystals.
The size of the crystals determines the sugar’s use in the kitchen. The most common white sugar—what most of us spoon into coffee and use for baking—is simply called standard granulated sugar (though it’s sometimes labeled “fine granulation”). An all-purpose sugar, it dissolves readily in warm and hot liquids and works in most types of cooking.
Confectioners’ sugar (a.k.a. icing or powdered sugar) is pulverized granulated sugar that’s been milled with a bit of cornstarch (about 3% to 4%). Since confectioners’ sugar is so fine, it dissolves readily in any liquid or fat, hot or cold, so it’s often used to sweeten uncooked foods without making them grainy. Its powdered texture also works beautifully to dust on desserts. The cornstarch, which absorbs moisture from the air and helps prevent clumping, sets this sugar apart from the other white sugars in several ways. Some people notice the raw taste of the starch in uncooked foods. The cornstarch can be a plus, however, helping to stiffen meringues, harden decorative royal icings, and thicken uncooked candies.
Superfine sugar also dissolves well in cold and room-temperature liquids, making it useful for meringues (which weep if there’s any undissolved sugar). But unlike confectioners’ sugar, superfine sugar is granulated. It’s also called ultrafine, instant dissolving, bar, or castor sugar, its British name.
Of all the granulated sugars, superfine has the tiniest and most uniform crystals. The tiny granulation improves the texture of cakes and other butter-and-sugar batters because the crystals’ many sharp edges cut into the butter during creaming, forming many air pockets. If you can’t find superfine sugar, you can make your own by grinding granulated sugar in a food processor for 30 to 40 seconds.
While shopping for sugar, keep in mind that the sugar industry has not standardized its labels, so stay alert to inconsistencies between brands.