As presented above, scientific evaluation of essential factors relative to the quality of flour can be, and usually is made, by laboratory analyses. As a rule, both commercial and serious home bakers in the US are given minimal technical information regarding the majority of the wheat flours that are available for use. More often than not, they are provided the type flour, i.e. patent, high-gluten, all-purpose, bleached or unbleached, pastry, etc., whether or not the flour is made up of hard or soft wheat, or a blend, and a per cent protein content. Other information, such as the results from laboratory analyses, is not readily obtainable. In fact, many bakers are not aware that the information derived from the various tests and analyses described here are available in the laboratories of the commercial millers. We have not ascertained why these results are not generally available, nor why bakers have not demanded why they are not made available.
By contrast, Italian commercial bakers have a greater variety of flours and more technical information about these flours available to them. For instance, a list of the flours available from Molino SIMA di Argenta includes 20 types of flours and their technical and analytic data. These data include the "W", "P/L" and percent dry gluten [gluten producing albumen(protein)] and are provided with a description of each flour and its suggested use.
American flour companies provide only sparse information about the flours they sell. The following discussion is excepted from a text by Corriher (10) regarding current domestic flour product labeling practice in the US:
"The amount of protein in a particular flour is an indicator of bread-baking quality for plain white flour alone because rye flour, oat flour, and rice flour contain proteins unconnected with gluten, as does whole wheat flour with the proteins in the wheat germ. That means reading the label on these flours relative to their protein content will not reveal much about the bread they will make."
Unfortunately, new US Food and Drug Administration (FDA) regulations have made labels less informative even for white flour. The protein content stated on the label of a bag of flour is subject to a round-off rule, so flour labeled as having 9 grams of protein per serving actually can have from 8.50 to 9.49 grams. Under the old regulations (before May 1994), the serving size was 1 cup, and the protein content on the label effectively showed what the best use of a flour was. Thus, a flour labeled as 9 grams (protein) was indeed a low-protein flour, ideal for pie crusts and quick breads whereas a flour labeled as 14 grams protein (13.50 to 14.49 grams per cup) was a high-protein flour, excellent for yeast breads.
Under the new regulations, however, the serving size is 1/4 cup or about 30 grams. With rounding, any flour containing 2.50 to 3.49 grams of protein per 1/4 cup can be labeled as containing 3 grams of protein. This means both moderately low-protein Southern flour (about 9 grams per cup) and high-protein unbleached flour (about 14 grams per cup) can be labeled as 3 grams per 1/4 cup. In fact, most flour on the market now says 3 grams of protein, telling you almost nothing about the protein content so important to baking and to cooking.
You can call the flour company and ask the exact protein content, but in the experience of The Artisan staff what you are told by a consumer representative is not always reliable.
We have provided the following table (Table XIII) from Corriher as a general guide. This provides approximate values for protein in both grams per cup and percentages. The measure of flour strength that is used professionally is percentage protein, and this same parameter is important to home bakers.