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22.545 Keywords • 49.275 Synonyms • 5.290 Translations • 7.929 Pronunciations • 146.303 Cross-references

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Yeast

English name for yeast; look there.

Single-celled, to the mushrooms counting microorganisms (Thallophyde = plants without roots and leaves), in spherical, oval, oblong to cylindrical or pointed form. The size is between 5 and 14 thousandths of a millimeter (but much larger than bacteria ). Most of them multiply rapidly by cell sprouting, which is why they are also called "yeasts". This process can take up to 35 times. The yeasts need above all else sugar as an energy source, as well as some nutrient and trace elements most of which are in grape available. The yeasts play in the winemaking a crucial role. In the fermentation become the sugars glucose (Glucose) and fructose (Fructose) in ethanol (Alcohol) and carbon dioxide transformed. The French scientist Louis Pasteur (1822-1895) earned particular merit in exploring this complex process.

anaerobic and aerobic process

The process is usually undercut for the most part anaerobic Conditions (that means absence of oxygen). Areobe conditions in the presence of oxygen are important before or at the beginning of fermentation, as the yeasts can only multiply in an oxygen-rich environment. The glucose is processed much faster, that is why in the residual sugar especially fructose present. As early as 1861, Louis Pasteur reported that yeasts consume much less sugar in aerobic environments. At higher glucose levels in grape must from about 100 mg / l but can also under aerobic Conditions alcohol are formed. This is called Crabtree effect (or Pasteur effect). At low glucose levels, yeast in the presence of oxygen causes the sugar to breathe directly, so it is not converted into alcohol.

Yeast genera and species

The most important yeast genus is "Saccharomyces" (sugar mushrooms), of which there are over a hundred different species. The most common in the fermentation of Wine. beer and sourdough involved type is "cerevisiae" (grain), in German aptly "brewer's yeast" or also "baker's yeast". An older name is "Saccharomyces ellipsoideus" due to the mostly elliptical shape of these yeasts. The naming and classification of the different yeasts is extremely complicated. By DNA analysis Many of...

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