A short guide to better understand and if necessary substitute the right flour for every recipe depending on what flour is available in your own country.
In Italy, flours are subdivided according to the extraction (Type) and strength (W). Extraction refers to how much of the gain is left after it has passed through a series of different sieves.
Strength means the ability of the flour to create a stable glutinous structure (and so give shape to solid doughs with a particular percentage of water).
I apologise once more for any technical imprecision, but this description aims to clarify a complex concept and this does not seem to me to be the right place for an in-depth discussion on the subject.
In ascending order of extraction we have the following grades of flour:
type 00 (white) extraction 55%
type 0 extraction 60%
type 1 extraction 65%
type 2 (semi-wholewheat) extraction 80%
Wholewheat extraction 100%
Each “type” of flour can have a different W index, and from the weakest to the strongest we have:
W 60-120 (very weak, for biscuits and cakes)
W 120-180 (weak)
W 180-240 (medium strength)
W 240-280 (for bread, medium strength)
W 280-340 (strong)
W 340-400 (very strong, from Manitoba gain, for strong doughs)
N.B. There are particular flours which are even weaker (for example, buckwheat, some types of spelt) or stronger (industrial flours enriched with dried gluten, etc.)
Wholewheat flour is not usually given a W number because the high bran and wheatgerm content makes it difficult to evaluate properly.
Since we have no W number to work on, if the flour in question is intended for bread making (and so its proteins are suited to developing a good gluten), we can estimate how strong it is based on the percentage of protein indicated on the flour in question:
8-10% weak
11-13% medium
14-15% strong
Written by Matteo Festo (translation by Marie Wilson) in "Natural Leavings", 2017. Digitized, adapted and illustrated to be posted by Leopoldo Costa.