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← Older revision		Revision as of 13:00, 17 January 2026
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	'''Yeast metabolism''' refers to the biochemical processes by which [[yeast]] converts substrates in [[grape must]] into [[ethanol]], [[carbon dioxide]] and a wide range of secondary metabolites during [[alcoholic fermentation]]. In winemaking, yeast metabolism is central to fermentation kinetics, alcohol production, aroma formation and overall wine balance.<ref>Jackson, ''Wine Science: Principles and Applications''~~, 5th ed.~~, Academic Press, 2020, ISBN 9780128161180.</ref>		'''Yeast metabolism''' refers to the biochemical processes by which [[yeast]] converts substrates in [[grape must]] into [[ethanol]], [[carbon dioxide]] and a wide range of secondary metabolites during [[alcoholic fermentation]]. In winemaking, yeast metabolism is central to fermentation kinetics, alcohol production, aroma formation and overall wine balance.<ref>PhD Jackson, Ronald S., ''Wine Science: Principles and Applications'', Academic Press Inc, 14 April 2020. ISBN 9780128161180.</ref>

	== Role in winemaking ==		== Role in winemaking ==
	During fermentation, yeasts—most commonly strains of ''[[Saccharomyces cerevisiae]]''—metabolise [[sugar]] primarily in the form of [[glucose]] and [[fructose]]. Through glycolysis and subsequent metabolic pathways, sugars are converted into ethanol and carbon dioxide, while energy is generated to sustain yeast growth and reproduction.<ref>Boulton ~~et al~~., ''Principles and Practices of Winemaking'', Springer, ~~1999,~~ ISBN ~~9780834217011~~.</ref>		During fermentation, yeasts—most commonly strains of ''[[Saccharomyces cerevisiae]]''—metabolise [[sugar]] primarily in the form of [[glucose]] and [[fructose]]. Through glycolysis and subsequent metabolic pathways, sugars are converted into ethanol and carbon dioxide, while energy is generated to sustain yeast growth and reproduction.<ref>Roger B. Boulton, Vernon L. Singleton, Linda F. Bisson, Ralph E. Kunkee, & 1 more, ''Principles and Practices of Winemaking'', Springer, 31 Oct. 1998. ISBN 9780834212701.</ref>

	Beyond alcohol production, yeast metabolism is responsible for the formation of numerous compounds that shape wine aroma, flavour and texture, making yeast selection and fermentation management critical oenological decisions.		Beyond alcohol production, yeast metabolism is responsible for the formation of numerous compounds that shape wine aroma, flavour and texture, making yeast selection and fermentation management critical oenological decisions.
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	* Reduction of pyruvate to ethanol		* Reduction of pyruvate to ethanol

	These processes are influenced by temperature, oxygen availability and nutrient status of the must, particularly [[nitrogen]] content.<ref>Ribéreau-Gayon ~~et al.~~, ''Handbook of Enology, Volume 1'', Wiley, 2006, ISBN 9780470010372.</ref>		These processes are influenced by temperature, oxygen availability and nutrient status of the must, particularly [[nitrogen]] content.<ref>Pascal Ribéreau-Gayon, Yves Glories, Alain Maujean, Denis Dubourdieu, & 1 more, ''Handbook of Enology, Volume 2: The Chemistry of Wine - Stabilization and Treatments'', Wiley, 31 Mar. 2006. ISBN 9780470010372.</ref>

	== Secondary metabolites ==		== Secondary metabolites ==
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	== Nitrogen and yeast health ==		== Nitrogen and yeast health ==
	Assimilable nitrogen is a key factor regulating yeast metabolism. Insufficient nitrogen can lead to sluggish or [[stuck fermentation]], while excess nitrogen may increase the formation of undesirable by-products. Winemakers often manage nitrogen levels through vineyard practices or controlled additions in the cellar.<ref>Waterhouse~~, Sacks & Jeffery~~, ''Understanding Wine Chemistry'', Wiley, 2016, ISBN 9781118627808.</ref>		Assimilable nitrogen is a key factor regulating yeast metabolism. Insufficient nitrogen can lead to sluggish or [[stuck fermentation]], while excess nitrogen may increase the formation of undesirable by-products. Winemakers often manage nitrogen levels through vineyard practices or controlled additions in the cellar.<ref>Andrew L. Waterhouse, ''Understanding Wine Chemistry'', Wiley, 19 Aug. 2016. ISBN 9781118627808.</ref>

	== Oxygen and metabolism ==		== Oxygen and metabolism ==

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Created page with "'''Yeast metabolism''' refers to the biochemical processes by which yeast converts substrates in grape must into ethanol, carbon dioxide and a wide range of secondary metabolites during alcoholic fermentation. In winemaking, yeast metabolism is central to fermentation kinetics, alcohol production, aroma formation and overall wine balance.<ref>Jackson, ''Wine Science: Principles and Applications'', 5th ed., Academic Press, 2020, ISBN 9780128161180.</re..."

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'''Yeast metabolism''' refers to the biochemical processes by which [[yeast]] converts substrates in [[grape must]] into [[ethanol]], [[carbon dioxide]] and a wide range of secondary metabolites during [[alcoholic fermentation]]. In winemaking, yeast metabolism is central to fermentation kinetics, alcohol production, aroma formation and overall wine balance.<ref>Jackson, ''Wine Science: Principles and Applications'', 5th ed., Academic Press, 2020, ISBN 9780128161180.</ref>

== Role in winemaking ==
During fermentation, yeasts—most commonly strains of ''[[Saccharomyces cerevisiae]]''—metabolise [[sugar]] primarily in the form of [[glucose]] and [[fructose]]. Through glycolysis and subsequent metabolic pathways, sugars are converted into ethanol and carbon dioxide, while energy is generated to sustain yeast growth and reproduction.<ref>Boulton et al., ''Principles and Practices of Winemaking'', Springer, 1999, ISBN 9780834217011.</ref>

Beyond alcohol production, yeast metabolism is responsible for the formation of numerous compounds that shape wine aroma, flavour and texture, making yeast selection and fermentation management critical oenological decisions.

== Primary metabolic pathways ==
The core of yeast metabolism in wine fermentation is the [[glycolysis|glycolytic pathway]], followed by alcoholic fermentation under anaerobic conditions. Key stages include:
* Uptake and phosphorylation of sugars
* Conversion of hexoses to pyruvate
* Reduction of pyruvate to ethanol

These processes are influenced by temperature, oxygen availability and nutrient status of the must, particularly [[nitrogen]] content.<ref>Ribéreau-Gayon et al., ''Handbook of Enology, Volume 1'', Wiley, 2006, ISBN 9780470010372.</ref>

== Secondary metabolites ==
In addition to ethanol, yeast metabolism produces a range of secondary metabolites that contribute to wine character. These include:
* [[Higher alcohols]]
* [[Esters]]
* [[Volatile acidity]]
* [[Sulfur compounds]]

Many of these compounds arise from amino acid metabolism and lipid synthesis pathways. Their concentrations and sensory impact depend on yeast strain, fermentation temperature and nutrient availability.<ref>Ribéreau-Gayon et al., ''Handbook of Enology, Volume 2'', Wiley, 2006, ISBN 9780470010396.</ref>

Esters formed during yeast metabolism are particularly important contributors to fruity aromas in young wines.

== Nitrogen and yeast health ==
Assimilable nitrogen is a key factor regulating yeast metabolism. Insufficient nitrogen can lead to sluggish or [[stuck fermentation]], while excess nitrogen may increase the formation of undesirable by-products. Winemakers often manage nitrogen levels through vineyard practices or controlled additions in the cellar.<ref>Waterhouse, Sacks & Jeffery, ''Understanding Wine Chemistry'', Wiley, 2016, ISBN 9781118627808.</ref>

== Oxygen and metabolism ==
Although alcoholic fermentation is largely anaerobic, limited [[oxygen exposure]] early in fermentation supports yeast sterol and fatty acid synthesis, improving cell membrane integrity and fermentation reliability. Excess oxygen later in fermentation, however, can alter metabolic pathways and affect wine stability.<ref>Peynaud, ''Knowing and Making Wine'', Wiley, 1984, ISBN 9780471881491.</ref>

== Yeast selection and control ==
Modern winemaking increasingly relies on selected yeast strains with defined metabolic profiles. These strains may be chosen to enhance specific aroma compounds, improve fermentation robustness or reduce the risk of off-flavours. Advances in yeast research and biotechnology have expanded the range of metabolic behaviours available to winemakers.<ref>Pretorius, “Tailoring wine yeast”, ''Yeast'', ISSN 0749-503X.</ref>

== See also ==
* [[Alcoholic fermentation]]
* [[Esters]]
* [[Stuck fermentation]]

== References ==
{{reflist}}

[[Category:Winemaking]]
[[Category:Fermentation]]
[[Category:Wine chemistry]]

Yeast metabolism - Revision history

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