Powdered sugar is an extremely finely grained sugar meant for use in frostings and candies, and as a garnish for fruits and pastries. It is also called icing sugar and confectioner’s sugar. When choosing powdered sugar, you’ll have to go by the look and feel of the sugar and its packaging, since you won’t be able to open a package or take some from a bulk bin in the market in order to get a taste until you buy the sugar.
Packaged powdered sugar should be fairly loose within the package, rather than lumpy or congealed into one mass. Most brands include cornstarch or another edible anti-caking material. If the ingredients list has something like cornstarch listed but the sugar is still lumpy, do not buy the bag. In some cases the sugar almost completely fills the bag, making it a bit difficult for it to move freely when you inspect it, but you should still be able to tell if the sugar is loose or stuck together.
Turn over the packages to check for cuts and holes. Store employees opening boxes of sugar can inadvertently slash the packaging with a box cutter. The sugar doesn’t necessarily spill out until you hold the bag a certain way, so it is possible to grab a bag off a shelf and not realize until you get home that there is a large tear on one side. Pests can get into the sugar if the package is open, plus you’ll basically lose money on the sugar that does spill out if you still buy the torn package.
Avoid dusty bags of powdered sugar. This can be a sign that customers are not buying that brand for some reason. That doesn’t necessarily mean the sugar is bad, though it is one possibility to consider.
Bulk bins of powdered sugar don’t have packaging you can inspect, but you can check out how quickly the supply of sugar dwindles. This again can be a sign of whether or not people like the sugar. For both bulk and packaged powdered sugar, the color should be white, with no specks or debris inside, and the texture should be powdery, not granulated like table sugar.
Check the plant origin of the powdered sugar if you are allergic to or sensitive to sulfites. Powdered sugar that is made of beet sugar may contain sulfites or sulfite residues, which could set off a reaction. The package or bulk bin label will likely tell you if it is cane- or beet-based.