Gluten development is crucial to produce a slice of bread perfect for sandwiches
There are two proteins found in wheat flour called glutenin and gliadin. When you mix them together these proteins uncoil and attach to each other forming long chains that gradually stretch and become intertwined. This is gluten. Gluten proteins give structure to baked goods. You want to control the amount of gluten that forms depending on the type of baked good you are making. For example, if you want a firm and chewy French bread you will want a lot of gluten development, so you will want to kneed your dough for a decent amount of time. If you want to make a tender cake you want very little gluten development and will want to mix the flour as little as possible.
How do you know when you have formed enough gluten?
THE WINDOWPANE TEST
To know when your dough has been kneaded enough, you can use a simple and effective test called the windowpane test:
Take a piece of your dough and flatten it a bit in your hands. Then grab the dough using both of your thumbs and index fingers and gently work the dough to spread it out as thin as you can. If the dough has been kneaded enough you will be able to stretch it quite thin, and can almost see through it. If it tears easily, just keep kneading and try the test again after a few minutes.