Editing Croissant (section)

===Fermentation===
[[File:Croissant, cross section.jpg|thumb|Cross-section, showing texture]]
Croissants contain yeast, ''[[Saccharomyces cerevisiae]]'', which is incorporated during predough formation. When oxygen is abundant, the yeast breaks down sugar into carbon dioxide and water through the process of [[Cellular respiration|respiration]].<ref>{{Cite web|url=http://www.bakeinfo.co.nz/Facts/Bread-making/Science-of-bread-making/Rising-fermentation-|title=Rising (fermentation) |publisher=Baking Industry Research Trust |website=www.bakeinfo.co.nz|access-date=2016-12-14|url-status=live|archive-url=https://web.archive.org/web/20161220163539/http://www.bakeinfo.co.nz/Facts/Bread-making/Science-of-bread-making/Rising-fermentation-|archive-date=20 December 2016}}</ref> This process releases energy that is used by the yeast for growth. After consuming all of the oxygen, the yeast switches to anaerobic [[fermentation]]. At this point, the yeast partially breaks down sugar into [[ethanol]] and carbon dioxide. Once {{CO2}} saturates the dough’s aqueous phase, the gas begins to leaven the dough by diffusing to preexisting gas cells that were incorporated into the predough during mixing.<ref name=":0" /> Yeast action does not produce new gas cells, as the immense pressure required for a single {{CO2}} molecule to create a new gas bubble is not physically attainable<ref>{{Cite book|title=Principles of cereal science and technology|last=Carl|first=Hoseney, R.|date=2010-01-01|publisher=AACC International|oclc=457130408}}</ref>

In order to ensure the flaky texture of the croissant, it is important to balance the yeast activity with [[steam]] production. If the yeast overproduces {{CO2}}, then the well-defined layers may collapse.<ref name=":1" /> During the baking process, this would cause steam to escape too early from the bread, reducing dough lift and flakiness of the final product. Thus, to offset the negative effects of yeast on layer integrity and dough lift, croissants usually contain fewer layers than other puff pastries.