Stone ground means the grain was milled between two rough granite stones, one stationary and one rotating. This is an old process that is effective at grinding the entire kernel of grain, the bran (outer fibrous seed covering), germ (the tiny little plant ready to grow into a shoot) and the endosperm (the starch or energy that the germ needs to grow until it gets large enough to make its own energy from the sun via photosynthesis). The bran is the part that is least likely to get broken into small pieces, followed by the germ, and the endosperm is the easiest to grind into a fine flour. In other words, the largest pieces found in whole flour are the bran and the smallest are starch.
This whole flour is rich in vitamins, minerals and bran, which makes it nutritious (and tasty). Unfortunately, this nutrition makes it more susceptible to mold and bacteria, meaning it has a shorter shelf life (9 months at room temperature) and we suggest you store it at cooler temperatures when possible.
To create a wheat flour that is a little more like what you find in stores today, we also offer our flour in a coarsely sifted version labeled as high extraction flour in which the largest pieces of the whole flour have been removed. Our high extraction flour has a 75-85% extraction rate (meaning you get 75-85% of the whole wheat kernel, the largest pieces (mostly bran) have been removed).
This is different from the enriched white wheat flour that has become popular over the past century in the U.S. It has been ground in numerous steps between steel rollers with the grain being separated into three components. The white endosperm (starch) is the part sold for flour. The bran and germ (which also contains most of the vitamins, minerals and taste) are typically sold for animal feed. This results in a white flour that has a longer shelf life (it doesn’t have enough nutrition in it to support mold or bacteria growth) and can be mass produced, stored and shipped everywhere.
Because this flour is missing so much nutrition, during WWII the U.S. government began requiring the white flour sold to the troops be enriched with synthetic versions of the major vitamins and minerals that were missing. This practice then spilled over into most flour sold today and is labeled as enriched.
Because this white flour is milled from wheat typically grown in high fertility soils using chemicals for protection against weeds, insects and diseases, the flour usually has residues of glyphosate (Round-Up™), organophosphates (to control grainery insects) and many other such chemicals. In an attempt to avoid these chemical residues, some have switched to organic white flour which can be used as a direct replacement in most recipes. While the absence of these chemicals makes it healthier, it still is missing the nutrition removed with the bran and germ, and organic rules forbid the re-enrichment of the flour with synthetic vitamins and minerals.
Note: Our rolled oats are processed differently from the roller milled wheat described above. The live raw oats are simply pressed between two cold rolls to enable faster water uptake and therefore reduce cooking time. Our rolled oats still contain all the nutrition of the original oat seed, and therefore also have a relatively short (9 months) shelf life.