You guys know an impressive amount about this
Unfortunately the truth about American-made flours is discouraging. Between the world wars, mills around the country started developing ways to speed up production of flour because of shortages. One of the things they did was to add potassium bromide to the wheat to speed up the curing process and to improve "panification" specs for poorer-quality wheat berries. The idea was to make more bread from more wheat. Swans Down and Softasilk were specialty cake flour brands that used to be made from a variety of "Soft" wheat grown in the Pacific Northwest off of volcanic soils.
Of course, as usual, once the wars were over and the big milling companies had these new technology-enhanced methods for extracting more product from the resource, they kept going. Nobody complained about the quality of the flours mostly because, during the late forties and fifties, people didn't bake at home as much as they did before the wars. Think Wonder Bread and Cake Mixes.
Bleaching is simply pumping flour into a silo with chlorine gas; what they don't want the consumer to know is that this process strips the wheat of practically all(except starch and gluten) of nutrients that Mother Nature put inside it and all of the carotene (the flavor). What we end up with is a powder that has less flavor than saw dust and chemical nutrients injected back into the dust to satisfy the FDA (as in "helps build strong bodies 12 ways"). Most people don't care because to most people wheat doesn't have a big flavor profile unless you're making French and Italian breads that only have 4 ingredients and guess which is the biggest one. Bleaching also improves the tenderness of the final product and that's why it's great for things like Angel Food Cake.
So-called Artisan Bakeries care about this and go to the expense of buying Organic and Natural Flours, such as King Arthur, because they are neither bleached nor bromated. I think this makes a big difference but even I, with all my high-faluttin' artisanl baker Larnin', prefer to use "Cake" flour for things like Angel Food and Chinese Dim Sum. In Europe, flours have a completely different profile from American flours even though most of the wheat used in milling those French, German, Italian and, I don't know about Spain (Franco screwed up their bread production for decades) comes from this continent. It you're interested in this, go to the King Arthur web site and see all the varieties of flour that are available. They used to have a wonderful cake flour labeled "Guinevere", which was bleached but not bromated, but when the original family sold the company it was discontinued. Now their "Cake" flour product is their wonderful "Family" flour cut with some cornstarch (which is, BTW, the way French bakers make their own "Cake" flour. It works, but it's not the same as Swansdown or SaS.
