What is Gluten?
Gluten is a protein. It consists of the two proteins glutenin and gliadin, which are both found in wheat, rye, and barley.
Baking
Gluten plays an important role in baking. The gluten is what makes dough elastic, allowing it to trap little pockets of gas and inflate like little balloons. These little balloons cause the dough to rise. That means that high-gluten dough will make fluffy food, and low-gluten dough will make dense food. That’s why we use different types of flour for different types of food.
Bread Flour - High gluten content; obviously used for breads
All-purpose Flour – Medium gluten content; used for cookies, brownies, muffins, and other foods that only need medium rising.
Cake Flour – Low gluten content; obviously used for cakes
Of course, other things can effect how fluffy or dense a food becomes. Other ingredients, such as yeast, and baking time all play a part.