Carbon dioxide
Carbon dioxide (chemical formula CO₂) is a colourless gas produced naturally during fermentation and widely present in wine. It plays both a technical role in protecting wine from oxidation and a sensory role in providing freshness or effervescence, especially in sparkling wine.[1]
Background
In winemaking, carbon dioxide is formed as a by-product of yeast metabolism when sugars are converted into alcohol. The phenomenon has been observed since antiquity, with the frothing of fermenting vats historically associated with the “life” of wine.[2] Beyond fermentation, CO₂ also serves as a natural protective gas, limiting the impact of oxygen on grape must and wine.
Characteristics
Carbon dioxide is highly soluble in must and wine under pressure but readily escapes as bubbles when pressure is released. Its dissolution affects acidity perception by lowering pH and increasing the sensation of freshness on the palate.[3]
At low concentrations in still wines, CO₂ can accentuate crispness and enhance aromatic intensity, whereas excessive levels may cause prickle or spritz on the tongue. In sparkling wines, retained CO₂ creates persistent effervescence and contributes significantly to texture. From a practical standpoint, CO₂ accumulation in closed spaces such as fermentation cellars presents health and safety risks.[4]
Use in winemaking
Fermentation
During primary fermentation, carbon dioxide naturally blankets the liquid surface, reducing exposure to oxygen and limiting microbial spoilage. In carbonic maceration, whole grapes ferment in a CO₂-rich environment, producing distinctive fruity red wines.[5]
Sparkling wine
In bottle-fermented sparkling wines such as Champagne, Cava, or Crémant, CO₂ is trapped following secondary fermentation, creating characteristic mousse and effervescence. In other cases, CO₂ can be introduced artificially under pressure, though this is generally considered less prestigious.[6]
Still wine
Even in non-sparkling wines, small amounts of dissolved CO₂ are often desirable. Young white and rosé wines may retain a slight spritz to emphasise freshness. Conversely, winemakers may deliberately remove excess CO₂ through racking, stirring, or gentle aeration before bottling, particularly in reds.[7]
See also
References
- ↑ Jackson, Wine Science: Principles and Applications, 5th ed., Academic Press, 2020.
- ↑ Robinson (ed.), The Oxford Companion to Wine, Oxford University Press, 2015.
- ↑ Boulton, Singleton, Bisson & Kunkee, Principles and Practices of Winemaking, Springer, 1999.
- ↑ AWRI, “Carbon dioxide in winemaking”, www.awri.com.au.
- ↑ Jackson, Wine Science: Principles and Applications, 5th ed., 2020.
- ↑ Robinson (ed.), The Oxford Companion to Wine, 2015.
- ↑ Jackson, Wine Science: Principles and Applications, 5th ed., 2020.