Editing Yeast (section)

=== Baking ===
{{Main|Baker's yeast}}
{{More citations needed section|date=April 2013}}

Yeast, most commonly ''S.&nbsp;cerevisiae'', is used in baking as a [[leavening agent]], converting the [[fermentation (food)|fermentable]] sugars present in dough into [[carbon dioxide]]. This causes the dough to expand or rise as gas forms pockets or bubbles. When the dough is baked, the yeast dies and the air pockets "set", giving the baked product a soft and spongy texture. The use of potatoes, water from potato boiling, [[egg (food)|eggs]], or sugar in a bread dough accelerates the growth of yeast. Most yeasts used in baking are of the same species common in alcoholic fermentation. In addition, ''[[Saccharomyces exiguus]]'' (also known as ''S.&nbsp;minor''), a wild yeast found on plants, fruits, and grains, is occasionally used for baking. In breadmaking, the yeast initially respires aerobically, producing carbon dioxide and water. When the oxygen is depleted, [[fermentation (biochemistry)|fermentation]] begins, producing ethanol as a waste product; however, this evaporates during baking.<ref name="Moore-Landecker-1996"/>

[[File:Compressed fresh yeast - 1.jpg|right|thumb|A block of compressed fresh yeast]]

It is not known when yeast was first used to bake bread. The first records that show this use came from [[Ancient Egypt]].<ref name="Legras-2007"/> Researchers speculate a mixture of flour meal and water was left longer than usual on a warm day and the yeasts that occur in natural contaminants of the [[flour]] caused it to ferment before baking. The resulting bread would have been lighter and tastier than the normal flat, hard cake.

[[File:Dry yeast.jpg|thumb|right|Active dried yeast, a granulated form in which yeast is commercially sold]]

Today, there are several retailers of baker's yeast; one of the earlier developments in North America is [[Fleischmann's Yeast]], in 1868. During World War II, Fleischmann's developed a [[wikt:granulate|granulated]] active dry yeast which did not require refrigeration, had a longer [[shelf life]] than fresh yeast, and rose twice as fast. Baker's yeast is also sold as a fresh yeast compressed into a square "cake". This form perishes quickly, so must be used soon after production. A weak solution of water and sugar can be used to determine whether yeast is expired.<ref>{{Cite web |last=John |date=2023-08-24 |title=Does Yeast Expire? [Active Dry vs Instant Yeast] |url=https://pizzaovenshub.com/does-yeast-expire/ |access-date=2023-09-27 |website=PizzaOvensHub |language=en-US}}</ref> In the solution, active yeast will foam and bubble as it ferments the sugar into ethanol and carbon dioxide. Some recipes refer to this as [[Proofing (baking technique)|proofing]] the yeast, as it "proves" (tests) the viability of the yeast before the other ingredients are added. When a [[sourdough]] starter is used, flour and water are added instead of sugar; this is referred to as proofing the [[Sponge and dough|sponge]].{{Citation needed|reason='Reliable sources needed for the whole paragraph, also maybe some irrelevant information for an WP article'|date=October 2016}}

When yeast is used for making bread, it is mixed with [[flour]], salt, and warm water or milk. The dough is [[Kneading|kneaded]] until it is smooth, and then left to rise, sometimes until it has doubled in size. The dough is then shaped into loaves. Some bread doughs are knocked back after one rising and left to rise again (this is called [[proofing (baking technique)|dough proofing]]) and then baked. A longer rising time gives a better flavor, but the yeast can fail to raise the bread in the final stages if it is left for too long initially.{{citation needed|date=August 2024}}