Flour is finely milled wheat — the powder that, more than any other single ingredient, underpins the world's bread, pasta, cakes and pastry. Plain white (all-purpose) flour is the starchy endosperm of the wheat grain ground almost on its own; wholemeal (whole-wheat) flour keeps the whole kernel, bran and germ included, for a darker, nuttier, coarser meal. On its own flour is bland and faintly sweet, smelling only of dry cereal, with a soft, powdery, mealy feel. Its magic is chemical rather than aromatic: wet it and work it, and two of its proteins — glutenin and gliadin — knit together into gluten, the elastic, stretchy network that traps fermentation gas and lets a loaf rise. That single property, and how much of those proteins a flour holds, is what divides strong bread flour from soft cake flour and silky Italian 00.