A gluten matrix is formed when the proteins glutenin and gliadin, found in wheat flour, are mixed in the presence of water. When the batter is agitated, these two proteins form cross-links, disulfide bonds, ionic bonds, and hydrogen bonds. The matrix that forms is strong and very flexible. Although no water is added to the batter, the gluten reacts with the water found in egg whites. Since air has already been entrapped in the foam, the flour proteins can only coat the already entrapped air. This helps to strengthen the cell walls and batter during baking or any other handling. This is beneficial because the meringue on its own is weak, cannot expand in heat, and does not have any elasticity normally expected in cakes.