What is Fermentation?
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.
Commercial dough fermentation can happen in various steps: bulk fermentation, intermediate proofing, and final proofing. Bulk fermentation is the period in which the dough is maturing just after the dough has been mixed. The length of bulk fermentation can vary from 0-15 minutes (a no-time dough) to 4-5 hours (traditional baguettes or sourdough).
An optional process of pre-ferment, in which a certain fraction of flour and water are combined and fermented before the final dough is mixed, is sometimes used to shorten the bulk fermentation time. Intermediate proof is the period between dough division and loaf shaping, which is usually 15-30 minutes.
Final proof is the period of fermentation after shaping in which the loaves are able to grow in size as much as possible before they are placed in the oven, which is about 45-90 minutes. However, final proof could be 3-5 hours for some artisan-style bread or sourdough varieties. There is a remaining period of fermentation called oven spring in the first 5-10 minutes of baking before the yeast dies from exposure to the rapidly increasing loaf temperature.