What causes pastry to harden when baked?

Pastry hardening during baking is a complex process with several contributing factors:

1. Gluten Development:

* Over-mixing: Mixing dough too long activates gluten, creating a tough and chewy texture.

* Flour Type: High-protein flours (like bread flour) have more gluten, leading to a harder crust.

2. Moisture Loss:

* Evaporation: Water evaporates from the pastry during baking, leaving behind a drier and harder structure.

* Sugar: Sugar draws moisture out of the pastry, contributing to hardening.

3. Starch Gelatinization:

* Heat: Starches in the flour gelatinize when heated, forming a rigid structure.

4. Fat Distribution:

* Melting: Fat in the pastry melts during baking, lubricating the gluten and preventing excessive hardening. However, uneven fat distribution can create dry, hard areas.

5. Baking Time and Temperature:

* Over-baking: Baking for too long or at too high a temperature can dry out the pastry and make it hard.

6. Cooling Method:

* Rapid Cooling: Rapid cooling can cause moisture to condense on the surface, making the pastry soggy and prone to hardening.

7. Ingredients:

* Eggs: Egg yolks contribute to a richer, softer pastry, while egg whites increase gluten development and lead to a harder texture.

* Milk: Milk adds moisture and contributes to a softer crust.

To prevent pastry from hardening:

* Use low-protein flour: Cake flour or pastry flour have less gluten.

* Mix dough gently: Avoid over-mixing.

* Use cold ingredients: Cold butter and water help prevent gluten development.

* Bake at the correct temperature: Follow the recipe's instructions.

* Cool pastry slowly: Let it cool on a wire rack to prevent moisture from condensing.

Note: Some level of hardening is expected in pastry, as it creates a crispy and satisfying texture. The key is to achieve a balance between softness and crispness.