From top left-clockwise, rye flour, whole wheat flour, bread flour, and all-purpose flour

Flour is an ingredient that we often take for granted. Have you wondered what the difference is between conventional and stone ground flour? Conventional flour has the bran and germ removed as these will become rancid within just a few weeks.  Stone ground crushes the entire grain, so the bran and germ remain in the flour, adding flavor but shortening shelf life of the flour. Store these types of flour in the freezer to keep them fresh.

Have you ever wondered why flour is bleached? Freshly milled flour will make a very dense loaf of bread. After the flour ages, it will produce a much nicer loaf. A chemical reaction occurs at the end of the glutenin (one of the two proteins that combine to make gluten) protein molecule; this change makes the gluten longer and more elastic. Starting early in the 1900s millers began to bleach flour which caused the chemical reactions to happen immediately instead of occurring over the course of a few weeks.

All wheat flour contains gluten; it is the protein in flour that provides structure in baked foods. Some flours contain more protein than others; bread flour can be 12-13% protein while all-purpose flour has only 11-12% protein. Pastry flour can be as low as 7-8% protein.

Whole wheat flour may be high in protein, but much of that protein comes from the germ and aleurone layer of the wheat. These proteins will not combine to form gluten; they do interfere with gluten formation. This causes a much more dense loaf of bread. Bread flour has very strong proteins that make a light, high, and chewy loaf. Pastry flour has weak gluten that makes a crisp and tender pie crust.

Much of the information in this post is taken from “On Food and Cooking, the Science and Lore of the Kitchen”, Harold McGee, 2004 chapter 10.

Liz Meimann

I received both my undergraduate and graduate degrees in Food Science at Iowa State University. I love to quilt, sew, cook, and bake. I spent many years gardening, canning, and preserving food for my family when my children were at home.

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3 thoughts on “Flour

  1. Hi Liz,
    Thank you for this informative post. I’m a retired dietitian! in Australia and never thought to ask myself why flour is bleached and how, until it came up in a discussion group yesterday. It was partly answered there but you have filled in enough gaps for me to be satisfied, at least for now.

  2. I have a Komo stone grain mill and have baked bread for 15 years.
    I have recently been experimenting with 100% whole grain sour dough bread
    My recipe uses an extremely hot oven and pans Why
    The dough doesn’t rise like I’m use to does not hold its form
    Do you have any insight. Im definitely missing something
    Maybe more Practice:-)

  3. Hi Corinne, there are several things that I don’t know from your message. Are you using the same recipe that you used prior and replacing whatever flour you were using with the whole wheat flour? I am going to start my reply with that assumption. Unlike white flour, whole wheat and other unrefined grains–contains germ and bran and less gluten. These two components add minerals and dietary fiber. They also add a nutty flavor to a loaf of bread, as well as a fuller texture. All of this good stuff also make life harder for bakers. For one thing, bran and germ soak up water tends to dry out a loaf and make it crumbly. For this reason, one cannot simply substitute whole grain for white. Germ and bran also add weight to the dough, which can impede its capacity to rise leading to dense. However, a whole wheat loaf can be surprisingly light as well as healthy with some changes in the recipe. Whole grains need more water–a ratio of about 14.5-17 ounces of water to 1 pound of flour which makes for an almost gooey dough. Over kneading can also be a problem. The bran has sharp edges which can cut the the frail gluten strands which in turn contributes to low rise. Whole grain breads also need more rising time but one has to be careful not to let the rising time go too long. When the yeast stops metabilizing the sugars in the flour and fermenting stops, the process reverses and the loaf starts to fall. When using a percentage of 1 percent yeast of the flour weight, the dough can usually rise for about 3.5 hours at 75F to attain maximum volume. If yeast percent is reduced, the rising time can go longer. Using some white flour may also help with rise and tenderness. If I have missed the mark with my assumption, do reply with more info and I’ll be glad to try again.

    Another resource that may help, “Great Whole Grain Breads” by Beatrice Ojakangas is a wonderful book and discusses some of the things I’ve mentioned and more.

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