The bromide is put in during the mill processing. You can see it clearly labelled in the 25 lbs bags. The gas stings your eyes during the earlier part of the baking process when the oven door is opened.
Info from another forum.Found this in the Encyclopizza:
Flour Treatment and Additives
Flour can be enhanced a number of ways, as discussed here.
CHEMICAL OXIDANTS OR FLOUR IMPROVERS. To perform properly in baking, flour must first undergo oxidation—a process that changes its protein structure for better baking results. Without proper oxidation the bread or pizza crust turns out under-risen and with a coarse texture and overly large cell structure.
Originally oxidation was accomplished by storing flour under controlled conditions for 8 to 10 weeks, and turning it several times to expose the entire stock to air—a process known as aging. It was cumbersome and costly, and also increased the chance of insect infestation. So millers developed ways to circumvent the aging process through chemical treatment, sometimes called chemical aging. Although the methods are different, natural and chemical aging produce the same result: Oxidation of the flour’s protein.
The group of chemical additives
used for oxidizing flour is known as flour improvers, and sometimes also called maturing agents. Traditionally the main flour improver has been potassium bromate. Flour that contains it is referred to as “bromated flour.” However some states have begun viewing potassium bromate as a potentially harmful chemical and, so, have required that it be labeled as such on food products. As a result, millers and bakers have started replacing potassium bromate with alternate flour improvers, most notably ascorbic acid—commonly known as vitamin C. Functionally speaking the main difference between potassium bromate and ascorbic acid is that potassium bromate is a slow-acting oxidzer whereas ascorbic acid is very fast acting. In the end they produce similar results on the dough.
Other flour improvers include potassium iodate, calcium bromate, calcium iodate, calcium peroxide, and azodicarbonamide (ADA, for short). Although they all oxidize flour protein, they vary in the speed at which they do it and also in the dough stage at which it occurs. For example, with potassium bromate and calcium bromate the oxidation occurs during the initial phase of baking, or in the oven. But with the others, including ascorbic acid, it occurs earlier during the mixing and fermentation stages. Oftentimes two or more improvers are blended together and added to flour in combination.
Flour that’s unoxidized, or unaged, is referred to as “green” flour.