No, corn flour and plain flour (all-purpose flour) are not interchangeable in most recipes. They have different properties and behave differently when used in cooking and baking.
Corn flour, also known as cornstarch, is a fine, powdery starch extracted from corn kernels. It is primarily used as a thickening agent in sauces, soups, and gravies. Corn flour has a high starch content but lacks the gluten protein found in wheat flour, which gives structure and elasticity to baked goods.
Plain flour, or all-purpose flour, is a versatile flour that contains both gluten-forming proteins (glutenin and gliadin) and starch. It is commonly used in a wide range of recipes, including bread, cakes, cookies, and pastries.
Substituting corn flour for plain flour in a recipe that requires structure and gluten development, such as bread or cakes, is not recommended. Without gluten, the baked goods may turn out dense, flat, or crumbly. However, corn flour can be used as a thickener in some recipes that call for plain flour, particularly in sauces or gravies.
If you find yourself in a situation where you need a substitute for plain flour, options like bread flour, cake flour, or gluten-free flour blends may be more suitable, depending on the recipe. It's best to consult a recipe-specific substitution guide or seek advice from a culinary expert to ensure the best results.