The Science of Croissants

Like bread, croissants contain yeast which supports their rise and their flavor. Unlike bread, though, they are known for their flaky, pastry texture. What makes croissants so different from other doughy products containing yeast? Well, that all comes down to one ingredient, butter. To most doughs, fats like butter are a bakers worst nightmare. Fat breaks up and weakens strong gluten networks form by flour and water. This helps to create the crumblier texture familiar in things like cakes and pastry dough. The butter also serves a more specialized role in creating this flaky texture. Butter is made up of a majority water. During baking, this water evaporates into steam, which is absorbed in the inner layers of the dough, adding to the flaky texture.

Incorporating the butter takes a special technique. First the butter is rolled into a sheet a little bit smaller than a square section of rolled out dough. Then the dough is folded to encompass the sheet of butter. Next, intermittently storing the dough in the fridge to ensure the butter remains cold, the dough is folded and rolled until it contains the amount of layers desired. My croissants had 27 layers.

The outside texture and color comes from an egg wash. The wash is applied before the final proofing and before baking. The proteins in the egg, when cooked, promote glossiness and browning.