Bleaching will not affect nutrient value. Different brands will vary in performance. Protein varies from 8 to 11 percent. Unbleached and in some cases conditioned with ascorbic acid, bread flour is milled primarily for commercial bakers, but is available at most grocery stores. Protein varies from 12 to 14 percent.
Cake flour is fine-textured, silky flour milled from soft wheats with low protein content.
It is used to make cakes, cookies, crackers, quick breads and some types of pastry. Cake flour has a greater percentage of starch and less protein, which keeps cakes and pastries tender and delicate. Protein varies from 7 to 9 percent. It is commonly used in biscuits and quick breads, but is not recommended for yeast breads. Pastry flour has properties intermediate between those of all-purpose and cake flours.