Dough – U.S. Equivalent of French T80 for Sourdough Pain de Campagne

Mark Bittman actually includes a very handy quick-reference flour substitution table in How To Cook Everything (mine is the 10th anniversary edition, not sure if it's in previous editions). This assumes that the bread recipe calls for all-purpose flour and tells you how much you can substitute for the quantity the recipe calls for:

• Whole wheat: use up to 50% in recipes
• Rye:
  • light: up to 40%
  • medium: up to 30%
  • dark/pumpernickle: up to 20%
• Cornmeal: up to 10%
• Buckwheat: up to 20%
• Rice: up to 25-30%
• Nut: up to 25-30%
• Soy: up to 25%
• Spelt: up to 100%; then either decrease water by 25% or increase flour by 25%
• Oat: up to 25-30%

The reason that different types of flours substitute at different ratios is primarily due to gluten content. Breads (both quick and yeast) made with alternative flours, especially non-wheat flours, will be heavier, denser, and less elastic; the substitution ratios above are meant to provide a nice balance between the nutritional and flavor advantages of the alternative flours with the texture qualities of all-purpose flour. For more information about the specific properties of each type of flour listed here, see the section called "The Basics of Flour" in How to Cook Everything (p. 835-838 in the 10th Anniversary ed.)

_{Note: These substitutions are specifically for breads, where you want a sturdy, elastic structure. Low-protein or low-gluten flours may substitute at different ratios in other types of baked goods like desserts where you want a finer, more tender crumb. But I didn't get into that since the question was specifically about bread.}

Yes, and it is very easy. I do it all the time.

You only need a very simple calculation. You don't even have to be precise.

If you do want precision, you will have to find out 1) how much of your flour protein is gluten, 2) how much of your "vital wheat gluten" is gluten, and 3) how much gluten content you need for your recipe. Then use a simple rule-of-three calculation to get the amount needed to add.

I usually don't bother, because 1) and 2) is information which is very hard to find, and due to the large difference in gluten weight and complete weight, imprecision from not using true proportions is minimal. What I do is:

1. Look up the protein content of your flour (usually printed on the package), for example 9.6 grams per 100 grams
2. Look up the gluten content needed for your bread recipe. If it is not specified, 12.5% is usual for bread flour.
3. Add the difference in vital wheat gluten. In the example above, add 2.9 g of vital wheat gluten per 100 g of flour.

This doesn't produce exactly 12.5% gluten content, but I think that it is within the tolerance of most recipes; indeed, not all commercial flours are exactly 12.5%, they vary with brand and season.

I add the powder to the flour and mix it well before making the bread. If I am using a preferment, I add all the gluten to the preferment and make the non-fermenting part with AP flour only, so my gluten can benefit from longer autolysis.

I have no direct comparison with "true" bread flour, as I have never used it. But my breads requiring bread flour turn out good for my standards. There is no problem with bad distribution, the dough turns out very smooth and evenly elastic. There is a pronounced difference to using AP flour only.