Fermentation occurs when yeast converts the sugar, present in the flour and dough, into carbon dioxide and alcohol. Yeast provides the enzyme zymase which catalyzes the fermentation of sugar into alcohol and carbon dioxide. The fermentation process largely begins after the dough is mixed. In addition to the leavening effect, or in other words the gas bubbles created by carbon dioxide causing dough to rise, fermentation allows protein and water molecules to move about and further connect to form more gluten networks. Consequently, a longer fermentation time results in better developed and more extensible dough. Alcohol produced during fermentation provides the main flavor in baked bread. Therefore, bread with a longer fermentation time will result in a loaf with greater aroma. Fermentation is an important step in commercial bread production. Proper fermentation provides a resilient crumb, which is soft and smooth to the touch.