Bromated flour is largely discontinued in the United States. Ascorbic acid is now being added to strengthen the flour for bread doughs. Bleached refers to flour that has been bleached chemically to whiten or improve the baking qualities. No change occurs in the nutritional value of the flour and no harmful chemical residues remain. It is only a process that speeds up the natural lightening and maturing of flour.
Unbleached flour is aged and bleached naturally by oxygen in the air.
It is more golden in color, generally more expensive and does not have the consistency in baking qualities that bleached flour does. Unbleached is preferred for yeast breads because bleaching affects gluten strength. Patent flour, bleached or unbleached, is the highest grade of flour. It is lower in ash and protein with good color. Market-wise, it is considered highest in value.