Powdered sugar, also known as confectioners’ sugar or icing sugar, is a finely milled form of granulated sugar. This fine texture allows it to dissolve quickly and create smooth icings and glazes. Commercial powdered sugar generally contains between 3% and 5% corn starch by weight. This small addition is standard practice and differentiates it from pure, finely ground sugar.
The Standard Ratio and Quantity
The quantity of corn starch in commercially produced powdered sugar is highly standardized across the industry. Most manufacturers aim for a ratio where the corn starch accounts for approximately 3% of the total weight of the product. This precise measurement ensures consistency for both home bakers and industrial food production. The remaining 95% to 97% of the product is pure sucrose, which is granulated sugar mechanically ground into a powder.
To put this small percentage into a practical context, the ratio is roughly equivalent to adding one teaspoon of corn starch per cup of granulated sugar before processing. This amount achieves the desired functional properties without significantly altering the sweetness or flavor profile.
Why Corn Starch is Added
The primary reason corn starch is incorporated into powdered sugar is to act as an anti-caking agent. Fine sugar particles are highly susceptible to clumping due to static electricity and the absorption of ambient moisture. Sugar crystals are naturally hygroscopic, meaning they readily attract and hold water molecules.
Corn starch is added because it coats the individual sugar crystals, creating a physical barrier. Corn starch is also more hygroscopic than sugar, absorbing atmospheric moisture first. By absorbing this moisture, the corn starch prevents the sugar particles from sticking together and forming hard lumps. This ensures the powdered sugar remains free-flowing and maintains its texture for a longer shelf life.
Making Your Own and Substitutions
If powdered sugar is unavailable, a substitute can be created at home. This is done by grinding granulated sugar in a high-powered blender or food processor until it reaches a fine, powdery consistency. The milling process transforms the coarse crystals into a fine powder.
When making powdered sugar at home, you can omit the starch entirely, but the resulting product will clump faster and may require sifting. Alternatively, substitute starches can be used for those with corn sensitivities. Tapioca starch or potato starch are effective alternatives that can be added in the same ratio to achieve the anti-caking effect. Any homemade version will generally have a shorter shelf life and requires storage in an airtight container.