Yeast: Difference between revisions
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"Fermentation is life without oxygen." | "Fermentation is life without oxygen." –Louis Pasteur, 1876 | ||
The conversion of the fermentable carbohydrates (sugars) into ethanol and carbon dioxide gas is achieved by pitching yeast. However, other by-yeast metabolism products are also excreted into the fermenting wort and can affect the organoleptic properties (i.e., taste, color, odor and feel) of the beer. These by-products include esters, aldehydes, vicinal diketones, higher alcohols and acids, as well as sulfur compounds.<ref name="Ferreira">Ferreira, Inês M., and Guido, Luís F. [https://www.mdpi.com/2311-5637/4/2/23/pdf "Impact of Wort Amino Acids on Beer Flavour: A Review."] ''Fermentation.'' 2018, 4, 23.</ref> | The conversion of the fermentable carbohydrates (sugars) into ethanol and carbon dioxide gas is achieved by pitching yeast. However, other by-yeast metabolism products are also excreted into the fermenting wort and can affect the organoleptic properties (i.e., taste, color, odor and feel) of the beer. These by-products include esters, aldehydes, vicinal diketones, higher alcohols and acids, as well as sulfur compounds.<ref name="Ferreira">Ferreira, Inês M., and Guido, Luís F. [https://www.mdpi.com/2311-5637/4/2/23/pdf "Impact of Wort Amino Acids on Beer Flavour: A Review."] ''Fermentation.'' 2018, 4, 23.</ref> | ||
In beer, glucose, fructose, maltose, and maltotriose are all consumed simultaneously. The glucose, fructose and sucrose are depleted first because they are present in lower amounts. The rate of maltotriose consumption is slowest, and so it is the last sugar to be depleted.<ref name=Vriesekoop>https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2010.tb00425.x</ref> | In beer, glucose, fructose, maltose, and maltotriose are all consumed simultaneously. The glucose, fructose and sucrose are depleted first because they are present in lower amounts. The rate of maltotriose consumption is slowest, and so it is the last sugar to be depleted.<ref name=Vriesekoop>https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2010.tb00425.x</ref> | ||
Boiled wort ferments more quickly than raw wort.<ref name=Vriesekoop/> ''Why? Protein coagulation?'' | |||
*[https://www.sciencedirect.com/science/article/abs/pii/S0308814603006034 "The impact of the physiological condition of the pitching yeast on beer flavour stability: an industrial approach"] | *[https://www.sciencedirect.com/science/article/abs/pii/S0308814603006034 "The impact of the physiological condition of the pitching yeast on beer flavour stability: an industrial approach"] |