In milling and baking, flour strength describes the ability of the flour’s proteins — chiefly glutenin and gliadin, which combine to form gluten — to develop an elastic network that traps the carbon dioxide produced by yeast fermentation. Strong flour, milled from hard wheat with a high protein content, forms a tough, extensible dough that holds gas well and gives bread good volume, an open crumb, and a chewy texture. Weak flour, from soft wheat with less protein, produces slack doughs suited to cakes, biscuits, and pastry, where tenderness matters more than lift. Millers measure strength with instruments such as the farinograph, extensograph, and alveograph, and bakers select flour of the right strength for each product.