Fields Of Heather: Bread Flour Protein Percentages

In 2023 I delved into the science behind sourdough baking. Although I've been making sourdough off and on for decades, I've always done it rather.. haphazardly. Like my ancestors, quite honestly. But these days people are SERIOUS about their sourdough, and I was curious.

On the whole, after using scales and obsessing over temps and exact rise amounts.. my best bread was still when I just stopped obsessing and made bread.

But that hasn't stopped my fascination with some of the method discussions - such as, the importance of bread flour. This was an interesting, and frustrating journey. One of the most interesting things to me was to find that regular flour in Canada has more protein than our bread flour in America. And our wheat has more gluten, than the wheat grown in Europe.
There is no standard for protein content in flour in America. It varies by brand. In one brand I found that the protein content was identical in their All Purpose [AP] flour as in their bread flour. In another, the label I found online shows less protein than the label I read in my own store. [See chart at the top of the page].

How important is the protein amount in flour when making bread? Like absolutely everything else in sourdough, it depends. But here's the basic explanation:

"Ultimately, if the proteins in flour form gluten, then the more protein in the flour — i.e., the higher its protein content — the more gluten-forming potential that flour has. Another way to think about it: the higher the protein content, the “stronger” the flour."
I've made great bread with AP flour. I've made bread that didn't rise as well with AP flour. I have made great bread with Bread Flour. I've made bread that didn't rise as well with bread flour. The protein is only one part of the equation.

Use this formula to determine the percentage of protein in flour:
(x) grams of protein per (y) grams of flour
(x) x 100 = (z)
(z) / (y) = % of protein content in the flour

If there is 4 grams of protein per 30 grams of flour, you need to multiply 4 by the number 100 and then divide by 30 This flour has a protein content of 13.33%. The percentages will never be exact, because labels are not that precise. But it will give you a rough percentage.
I also checked the flour at Aldi, thinking that because it's a German company the bread may have a higher protein - but they were on par with gold medal, at 3 grams per a 30g serving - or 10%. My best options locally are King Arthur, Wheat Montana, and Heckers, all having about 13% protein.