But there's more to it than that. Protein also affects the amount of water the flour can absorb. It's thirsty. Dough made with flour that has a higher gluten content will seem less wet than a dough made from flour with a lower gluten content.
Two people can make the same dough recipe and one will say that the dough was too wet while another one might say it was too dry. Measuring errors are one common problem. But even if the measuring is precise, the doughs can feel different depending on the type of flour used.
Even if you're using the same brand of flour as the recipe-writer, you're not assured that the protein level is the same. Although brands state the percent of protein on the bag, you're probably not getting exactly that number - the true percentage can vary a bit, depending on the manufacturer's tolerances.
But how much difference does it make?
This test was easy. I started with four different types of flour in four bowls - 100 grams each of bread flour, all purpose flour, unbleached cake flour and cake flour - and I added 90 grams of water to each bowl.
In the photo above, clockwise from the top left are bread flour, all-purpose flour, unbleached cake flour, and bleached cake flour. The bleached cake flour looks thicker in the photo, but looks are deceiving. It wasn't thicker, it's just that the others were smoother.
Bread flour, with the highest protein content, was the thickest dough. It was stirrable, but it started developing gluten right away. After a short rest, I could lift the whole clump of dough with the spoon.
All purpose flour was a little wetter, or less thick, if you prefer to think of it that way. It was much more stirrable, but started to develop gluten fairly quickly. After a short rest, I could pick up most of the doughball on the spoon, but since it was looser, it flowed off the spoon. It was a smooth dough.
|All purpose flour|
Unbleached cake flour is new on the market - until recently, all cake flour was bleached. The unbleached cake flour is formulated to have the same protein content as the bleached cake flour, but without undergoing the chemical bleaching process.
The unbleached cake flour was even looser than the all purpose flour. There was less gluten development, so it fell off the spoon in ragged clumps. It's not as bright white, and there was some gluten development. Not nearly as much as the bread or all purpose flours, but more than the bleached cake flour.
|Unbleached cake flour|
The bleached cake flour, besides being the loosest, also resisted forming gluten, even after quite a long rest. I could pick up a spoon full of it, but it didn't hold together at all. It was a bright white.
|Bleached cake flour|