Water

Because gluten proteins must absorb water before they can be developed, the amount of water in a formula can affect toughness or tenderness.

In general, glutens absorb about twice their weight in water. Much of the water added to flour is absorbed by starch, so it is not all available to the proteins. Starving proteins of water keeps products tender by preventing gluten development. Piecrusts and crisp cookies, for instance, are made with very little liquid in order to keep them tender. Adding even a little extra water to these formulas activates more gluten and toughens the product.