Whole Wheat Flour is a coarse-textured flour containing the bran, germ and endosperm. The presence of bran reduces the gluten development, therefore, baked products made from whole wheat flour tend to be heavier and denser than those made from white flour. Whole wheat flour, however, is rich in B vitamins, vitamin E and protein, and contains more trace minerals and dietary fiber than white flour. It also contains only five percent fat. In most recipes, whole wheat flour can be mixed half and half with white flour.
All-Purpose (White) Flour is the finely ground endosperm of the wheat kernel separated from the bran and germ during the milling process. After bleaching for further brightness in color, it is enriched with some of the vitamins that were stripped in the first place, however white flour still does not come close to the amount of fiber and nutrients as its whole wheat counterpart. The greatest single cause of iron deficiency – anemia – is connected to the refining of breads, cereals and sugar. Now that our breadstuffs are refined, no foods rich in the B vitamins are ordinarily eaten on a daily basis. Enless the package says “whole wheat” first, it is not truly a whole wheat product, but refined and enriched.
So why do we even have white flour? Because it was engineered to have a longer shelf life. The wheat germ contains fatty, essential oils which oxidize once milled and shorten the shelf life of whole wheat flour. In the olden days, they couldn’t process and use the flour quickly enough to keep it from going rancid, so this was their solution.
White flour is thus better for longer storage use of pre-milled wheat, although it has less nutritional value. That is why the Church encourages us to store wheat kernels instead. They store almost indefinitely (much MUCH longer than white flour) and still retain their nutritional value.