Fat and gluten development - Salt Fat Acid Heat

Question

I am reading Salt Fat Acid Heat. I am still in the beginning but it has changed my approach to cooking, it is much more fun now. Nevertheless, there is something I am not getting when it comes to fat and gluten. This is an excerpt from the book:

Cold-handed or not, consider temperature when you seek flakiness to create layers of developed gluten interspersed by pockets of fat. The warmer, and hence softer, your butter, the more readily it will combine with the flour. Because fat inhibits gluten development, the more intimately the two ingredients combine, the more tender—not flaky—a dough will be.

To prevent gluten from developing, keep butter cold. This will protect the delicate bonds of its emulsion while you mix and roll dough. Butter contains about 15 to 20 percent water by weight. If butter softens and melts as it’s worked into the dough, its emulsion will break, releasing that water. Water droplets will bind with the flour, developing into long gluten strands that will cause the dough’s delicate layers to stick together. If they’re stuck together, they can’t steam apart and flake as they bake. The pastry will emerge from the oven chewy and elastic.

these paragraphs are just after the "powers of pie" image, I cannot provide the page numbers because I have a translated version.

What I don't get is: From this section The warmer, and hence softer, your butter, the more readily it will combine with the flour. Because fat inhibits gluten development, the more intimately the two ingredients combine, the more tender I understand that if the butter if warmer, it will combine faster and will inhibit gluten development and because of that, the dough will be tender.

But then she states: If butter softens and melts as it’s worked into the dough, its emulsion will break, releasing that water. Water droplets will bind with the flour, developing into long gluten [...] The pastry will emerge from the oven chewy and elastic, which seems to contradict by saying that melted butter will increase gluten development due to the water it contains and this will make the pastry to be chewy and elastic.

It is confusing to me because in the first excerpt it seems to imply that warmer butter prevents gluten development, while the second seems to imply that warm butter will enable gluten development.

What am I missing?

Answer 1

You haven't missed anything, I agree it could be worded better. Both are true, just not at the same time. As butter warms it combines more readily with your flour, but as long as you keep it from getting too warm the emulsion won't break down. At this point if the butter warms too much your pastry become less flaky. If the butter warms further the emulsion breaks down and water is released, making your pastry tough.

Answer 2

I agree with @GdD's answer but I think it's worth elaborating a little further, because the passage in the book is indeed a little confusing and misses the mark a little IMO.

As we all know and agree, fat makes gluten formation more difficult. Difficult does not mean impossible, though (e.g. brioche), so the book seems to be warning that if the water from the butter escapes into the dough prior to baking, it will induce undesired gluten formation and lead to a chewy crust.

Ultimately, the issue with cold vs. warm butter is in how it distributes in the dough prior to baking. With pastry dough you want little (sometimes not-so-little, e.g. in puff pastry) chunks of intact butter spread throughout to create those non-uniform steam pockets that keep the layers separate and intact (as the book says).

But at the same time, you do want some gluten formation in a pastry crust, which is why you add a little ice water. Assuming the butter stays cold and intact, you wind up with lightly hydrated flour (JUST enough to keep it all together) dotted with solid clumps of butter. The contrast between those as they cook is what defines pastry crust. The lightly hydrated flour forms nice rigid flakes, the steam from the butter causes those flakes to separate and puff while baking, and the fat from the butter helps ensure and maintain the separation (and of course, is delicious). It's a delicate dance.

If the butter is warm and loses its emulsion prior to baking, all that contrast disappears and you tend toward a homogenous mixture of flour, water, and fat, like under-kneaded brioche. Rather than be concerned with excess gluten formation due to the water from the butter, unless you're working the heck out of it which you shouldn't be doing anyway, I'd be more concerned with the fat from the butter inhibiting virtually all gluten formation, i.e., no flakes. Rather than soft and chewy, I'd expect it to be crumbly and greasy. (And having once tried to bake under-kneaded brioche, this is exactly what I got).

Ultimately, the advice is right - keep everything you can as cold as you can when you're making pastry dough. If you can see little chunks of butter dotted throughout your dough before baking, you know you're going to have a beautiful result.