Water is a necessary ingredient in the production of doughnuts because it activates the other ingredients, allowing them to perform their functions in building the doughnut's structure. For example, sugar and salt crystals must be dissolved in order for them to act in the dough, whereas larger molecules, such as the starches or proteins, must be hydrated in order for them to absorb moisture. Another important consideration of water is its degree of hardness, which measures the amount of impurities in the water source. Pure water consists of two parts hydrogen and one part oxygen, but water used in baking often is not pure. Baker's salt (NaCl) is usually used as an ingredient due to its high purity, whereas the salts in water are derived from varying minerals. As an ingredient, "salt is added to enhance the flavour of cakes and breads and to ‘toughen up’ the soft mixture of fat and sugar." If relatively soft water is being used, more salt should be added in order to strengthen the gluten network of the dough, but if not enough salt is added during the baking process, the flavor of the bread will not be appealing to consumers.