Why Powdered Sugar Isn't Always An Ideal Sweetener For Warm Beverages - Tasting Table
Briefly

Granulated sugar does not dissolve effectively in cold drinks, leading to an unsatisfactory sweet layer at the bottom. Powdered sugar often contains cornstarch, which can create a grainy texture and potential chalky flavor in warm beverages. A homemade alternative by blending granulated sugar eliminates these issues, but liquid sweeteners are more effective. Simple syrup, made by mixing equal parts water and sugar, provides a smooth solution for sweetening hot drinks without the texture issues associated with powdered sugar.
Granulated sugar doesn't dissolve well in cold drinks, leaving a sweet puddle at the bottom. Using powdered sugar can add graininess due to cornstarch.
Powdered sugar often contains cornstarch to prevent clumping, which may not blend in well with warm drinks, resulting in a chalky flavor.
Making your own powdered sugar by blitzing granulated sugar in a blender avoids the issues of starch. Liquid sweeteners are preferable for hot beverages.
To sweeten hot drinks effectively, simple syrup made from a 1:1 ratio of water and sugar is recommended, as it dissolves seamlessly in any liquid.
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