Ethanol
Ethanol (also known as ethyl alcohol) is the principal form of alcohol present in wine, produced through the metabolic activity of yeasts during primary fermentation. It plays a central role in the composition, sensory profile, and stability of wine, while also being subject to regulation in labelling and trade[1].
Chemistry and formation
Ethanol is generated when yeasts, primarily strains of Saccharomyces cerevisiae, convert grape sugars into alcohol and carbon dioxide during primary fermentation[2]. The final concentration of ethanol in wine depends on factors such as the initial sugar content of the must, fermentation temperature, yeast strain, and nutrient availability[3]. Under anaerobic conditions, yeasts typically achieve alcohol yields of 11–15% by volume, although some specialised fermentations produce higher or lower values.
Role in wine
Ethanol contributes to the perceived balance and body of wine by enhancing mouthfeel and viscosity[4]. It also influences the volatility of aromatic compounds, allowing flavours and aromas to be more readily perceived. Moderate levels of ethanol can provide warmth and roundness, while excessive concentrations risk overshadowing fruit character and accentuating heat. Its interaction with acidity, residual sugar, and tannins is critical in shaping the overall sensory impression of a wine[5].
Measurement and regulation
Alcohol levels in wine are expressed as alcohol by volume (ABV), typically ranging from 8% in lighter styles to over 15% in fortified or warm-climate wines[6]. Several analytical methods are employed to measure ethanol content. Traditional distillation techniques remain in use, while modern laboratories favour gas chromatography or infrared spectroscopy for greater precision[7]. International regulations often set tolerances for declared ABV on labels, typically allowing for small variances of 0.5–1%. In some regions, alcohol level is also tied to taxation or wine classification, as in the European Union’s categories of table wine and fortified wine.
Stability and ageing
Ethanol contributes to microbial stability by inhibiting the growth of many spoilage organisms[8]. At levels above 14%, it suppresses most yeasts and bacteria, aiding preservation. Ethanol also plays a role in the extraction of phenolic compounds during maceration, particularly in red winemaking, where it enhances colour stability and tannin structure.
During bottle ageing, ethanol can slowly react with acids to form esters, contributing to the development of tertiary aromas. In barrel-aged wines, it assists the extraction of compounds such as vanillin and lactones from oak, shaping aromatic complexity[9]. However, very high alcohol levels may diminish perceived freshness, mask varietal character, and shorten the optimum drinking window.
Health and sensory thresholds
In sensory analysis, ethanol is generally recognised by its warming effect and by the perception of heat at concentrations above 13–14%. At lower levels, it enhances fruit expression, but above 15–16% ABV it can dominate the palate. Beyond its sensory role, ethanol is physiologically significant, being both psychoactive and subject to legal restrictions in marketing and consumption of wine[10].
See also
References
- ↑ Jackson, Wine Science: Principles and Applications, 5th ed., Academic Press, 2020, pp. 173–180. ISBN 978-0128161180.
- ↑ Boulton, Singleton, Bisson & Kunkee, Principles and Practices of Winemaking, Springer, 1999, pp. 87–95. ISBN 978-0834217011.
- ↑ Ribéreau-Gayon, Dubourdieu, Donèche & Lonvaud, Handbook of Enology, Vol. 2: The Chemistry of Wine, Wiley, 2006, pp. 39–43. ISBN 978-0470010396.
- ↑ Peynaud, The Taste of Wine, Wiley, 1996, p. 211. ISBN 978-0471113768.
- ↑ Robinson (ed.), The Oxford Companion to Wine, 4th ed., Oxford University Press, 2015 (entry: alcohol). ISBN 978-0198705383.
- ↑ Jackson, Wine Science: Principles and Applications, 5th ed., Academic Press, 2020, pp. 174–176. ISBN 978-0128161180.
- ↑ Boulton, Singleton, Bisson & Kunkee, Principles and Practices of Winemaking, Springer, 1999, pp. 132–134. ISBN 978-0834217011.
- ↑ Ribéreau-Gayon, Dubourdieu, Donèche & Lonvaud, Handbook of Enology, Vol. 2: The Chemistry of Wine, Wiley, 2006, pp. 40–41. ISBN 978-0470010396.
- ↑ Jackson, Wine Science: Principles and Applications, 5th ed., Academic Press, 2020, pp. 178–180. ISBN 978-0128161180.
- ↑ Robinson (ed.), The Oxford Companion to Wine, 4th ed., Oxford University Press, 2015 (entry: alcohol). ISBN 978-0198705383.