Wheat flour becomes sticky when water is added to it due to the formation of gluten. Gluten is a protein complex found in wheat and other cereal grains like barley and rye. When you mix water with wheat flour, the gluten proteins in the flour interact with the water, causing them to hydrate and undergo a process called gluten formation.
Gluten formation occurs when two proteins in wheat flour, glutenin, and gliadin, combine and form a network of elastic strands. These strands provide structure and elasticity to the dough. The more you mix the flour with water, the more extensive the gluten network becomes, leading to a stickier and more elastic dough.
The stickiness is a result of the gluten's ability to trap water and hold it within the dough. This property is crucial in baking as it gives the dough its ability to rise and hold its shape during the baking process. The sticky nature of dough can be both beneficial and challenging, depending on the type of baked goods you want to produce. For bread-making, the stickiness helps the dough rise and gives it a chewy texture, while for pastries and delicate cakes, bakers aim to minimize gluten formation to achieve a tender and crumbly texture.