These photos show hard red wheat being ground into flour in my grain mill for making my sourdough breads.
Wheat flour has a number of characteristics that affect the quality of bread. These characteristics produce breads with different textures, flavors and degree of rise. Gluten quality is one of these characteristics.
Hard high-protein flour is bread flour, while soft low-protein flour is pastry flour. Bread flour contains up to 14–18% protein. Spelt is also relatively hard. Softer wheats range from 6.5–11 percent protein and are used for pastries and quick breads. All-purpose flour is a blend of hard and soft wheat.
The protein content and quality of wheat is directly related to the development of gluten—the long, flexible, rubbery strands of protein that form the structure of bread dough, creating millions of tiny air pockets that fill with the carbon dioxide gas produced by yeast. While gluten is a type of protein, not all of the proteins found in wheat link together to form gluten. Protein molecules are composed of linked chains of amino acids. Gluten is composed of two amino acids, glutenin and gliadin. When water is mixed into wheat flour, the water molecules link together with the glutenin and gliadin to create gluten.
The ratio of glutenin to gliadin varies among different wheat species and varieties. Glutenin gives gluten its elastic strength. Gluten with a high proportion of glutenin is very difficult to stretch, like a tight new bungee cord. On the other hand, gliadin adds extensibility — it stretches easily. Gluten containing a higher percentage of gliadin can stretch farther without breaking, which allows it to capture bigger air bubbles, creating a lighter, fluffier texture in the finished bread. However, a very high ratio of gliadin to glutenin creates slack dough that cannot hold its shape without a pan.
Gluten high in glutenin is “strong.” Gluten high in gliadin is “weak.”
- Hard common wheat and spelt have strong gluten. To make free form loaves of whole wheat artisan bread, you must use at least 75 percent hard wheat or spelt flour. However, many artisan bakers use softer or all-purpose flour if they use refined flour to make artisan breads, as too much gluten in white flour creates a dense crumb structure while softer wheats create the more open holes characteristic of artisan breads.
- Durum (called semolina in it’s coarser form) is very high in glutenin and low in gliadin. This makes durum dough very “tight” and time-consuming to knead.
- The ancient wheats (einkorn, emmer, kamut) tend to be high in gliadin, which makes them slack and less able to hold their shape without a loaf pan.