On Food and Cooking

Improving and Bleaching 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