Self-raising flour is a type of flour that already contains a leavening agent, usually baking powder, mixed into it. The leavening agent helps the baked goods rise during the baking process, making it ideal for recipes like cakes, muffins, and quick breads.
Heating or heat treating self-raising flour is not recommended because it can negatively affect the leavening properties. When self-raising flour is exposed to heat, the baking powder can start to activate prematurely, causing the flour to lose its rising ability before you even use it in a recipe.
If you need to use heated or cooked flour in a recipe, it's best to start with all-purpose flour (plain flour) and add your leavening agent separately (baking powder, baking soda, etc.) according to the recipe's requirements.
In general, it's essential to handle self-raising flour and other leavened products with care to preserve their rising properties and achieve the desired results in baking. Always store self-raising flour in a cool, dry place and follow the recipe instructions precisely to ensure successful baking.