white flour has been around for ages--at least since the middle ages. it was, up until very recently, very expensive.
first you had to hull the wheat, and remove the germ. then you ground the endosperm of the wheat, and aged the flour. it would naturally whiten with age.
whole wheat flour, has the hull, and the germ. the wheat germ adds nutrients, but it also is rich in oil. the oil goes rancid fairly quicly, so if you age whole wheat flour, it goes bad. most commercial whole wheat flours suggest you refridgerate or freeze flour that will not be use in a month-- and most have some preseratives to help keep the natural oil from going rancid.
stone ground flours keep a bit longer, since the stone never get as hot at the the steel grinder in modern high speed mills. keeping the wheat germ oil cool, helps preserve it.
bleaching flour can be done with chemicals (fumes) or with time, or.. (i forget.. Light?) in any case "unbleached" flours haven't been aged to whiteness, they use the third method. it doesn't include any thing (chemical, additive), but does get the flour whiter faster than aging. since there is nothing added, the process for legal purposes, is considered "Unbleached".
