Today there are many tasty bread options. Some breads are made with wheat flour and contain gluten; others are gluten free. Here’s a hundred-year-old description of the different types of flour that might be used to make bread:
White flour is the most important in bread making. Wheat contains gluten, which is the name given to the protein content. When the grain is ground into a fine flour, the gluten is elastic and has the power of stretching and expanding; making it ideal for bread making since it retains the air and carbon dioxide and hardens on baking, forming the framework of the loaf of bread.
The protein in corn and oats lacks this quality and therefore they are combined with white flour for baking purposes. Rye flour may be used alone or with white flour in bread making.
The Housewife’s Cook Book by Lilla Frich (1917)