Bakers have known for a long time that freshly milled flour makes a weak gluten, a slack dough, and a dense loaf. As the flour ages for a few weeks in contact with the air, its gluten and baking properties improve. We understand now that oxygen in the air gradually frees the glutenin proteins’ end sulfur groups to react with each other and form ever longer gluten chains that give the dough greater elasticity. Beginning around 1900, millers began to save time, space, and money by supplementing freshly milled flour with oxidizing chlorine gas and then with potassium bromate. However, worries about the potential toxicity of bromate residues in the late 1980s led most millers to replace bromate with ascorbic acid (vitamin C) or azodicarbonamide. (Ascorbic acid itself is an antioxidant, but becomes oxidized to dehydroascorbic acid, which in turn oxidizes the gluten proteins.) In Europe, fava bean flour and soy flour have been used as flour improvers; their active fat-oxidizing enzymes, which generate the typical beany flavor, also indirectly cause the oxidation and elongation of gluten proteins.