To keep powdered sugar dry, you typically use cornstarch to prevent clumping and caking.
Why Does Powdered Sugar Cake?
Powdered sugar, also known as confectioners' sugar, is very finely ground. This fine texture makes it susceptible to absorbing moisture from the air, which leads to clumping and hardening.
The Role of Cornstarch
Most commercially available powdered sugar already contains a small percentage of cornstarch (usually around 3-5%). The cornstarch acts as a drying agent and anti-caking agent. It works by:
- Absorbing Excess Moisture: Cornstarch soaks up some of the ambient humidity, preventing the sugar crystals from sticking together.
- Creating a Barrier: The cornstarch particles coat the sugar crystals, creating a physical barrier that reduces the surface area available for moisture absorption and clumping.
Practical Tips for Keeping Powdered Sugar Dry
- Store it Properly: The most important factor is proper storage. Keep powdered sugar in an airtight container in a cool, dry place.
- Consider Adding More Cornstarch: If you live in a humid climate or find your powdered sugar consistently cakes, you can add a little extra cornstarch (about 1-2 tablespoons per pound of powdered sugar) and mix it in thoroughly.
- Avoid Temperature Fluctuations: Temperature changes can cause condensation inside the container, leading to clumping.
- Reseal Immediately: After using powdered sugar, always reseal the container tightly.
- Use a Desiccant Packet: For long-term storage, consider adding a food-safe desiccant packet to the container to absorb any stray moisture.
- Don't Double Dip: Avoid using a damp or dirty scoop when measuring powdered sugar. This introduces moisture and contaminants.
When to Skip the Cornstarch
As the reference suggests, if you're using the powdered sugar immediately in frosting or dusting over a cake, the cornstarch is less critical. The immediate use minimizes the time it has to absorb moisture.
