I don't know why About.com warns that "additional protein will increase toughness" when the whole purpose of adding corn starch is to reduce the protein.
All purpose flour should have around 10% protein and 90% starch. Pastry flour has 8% protein and 92% starch. Cornstarch has 0% protein. You only have to mix cornstarch and all-purpose flour in the mathematically correct ratio to get a mixture which behaves like pastry flour in terms of protein toughening.
The numbers above are rounded, but then, different manufacturers will produce flours with different percentage of proteins, and some wheat proteins also get tougher than others depending on the cultivar, and recipes still work with that kind of tolerance. So I use them and mix 80 g AP flour and 20 g cornstarch for every 100 g pastry flour I need, which results in a flour mixture with roughly 8% protein content. I use it primarily for flaky crusts, and it works quite well there.
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:
- Look up the protein content of your flour (usually printed on the package), for example 9.6 grams per 100 grams
- Look up the gluten content needed for your bread recipe. If it is not specified, 12.5% is usual for bread flour.
- 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.
Best Answer
Whole wheat flour is denser, has more protein and tends to dry out products. To compensate, sift more, do not overmix, and up your wet ingredients slightly. From eHow. TLC confirms that whole wheat flour is higher in protein because it is milled from hard wheat which is naturally higher in protein, and then ground whole wheat flour is 25% higher in protein than all-purpose flour.
Some sites (including TLC) recommend only subsituting out up to half of white flour with whole wheat, except if you're using white whole wheat flour (see below).
My secret weapon is white whole wheat flour, which is lighter than standard whole wheat flour and tastes more like white flour but has the same health benefits as the whole wheat flour we're used to. Because so many people are looking for whole wheat recipes, you may want to try a recipe that is specifically designed for whole wheat flour--both for taste and texture. Try King Arthur Flour for recipes (they make my favorite white whole wheat flour, and they have a recipe for whole wheat biscotti!).