Malic acid
Malic acid is one of the principal organic acids found in grapes and wine. It contributes significantly to acidity, freshness and structural balance, particularly in wines produced from cooler climates or harvested at lower ripeness. [[Malic acid]] is biologically unstable in wine and plays a central role in the process of malolactic fermentation.[1]
Occurrence in grapes
Malic acid is synthesised in grape berries early in the growing season and accumulates alongside tartaric acid as a major contributor to total acidity. Its concentration is strongly influenced by temperature, with warm conditions accelerating respiration and degradation of malic acid during ripening. As a result, grapes grown in cool climates or at higher altitudes generally retain higher malic acid levels at harvest.[2]
Unlike tartaric acid, which remains relatively stable throughout ripening, malic acid declines significantly as grapes mature, particularly during warm nights. Vineyard practices and harvest timing therefore have a direct impact on the malic acid content of must and finished wine.[3]
Role in wine structure
In finished wines, malic acid contributes a sharp, green-apple-like acidity that enhances perceived freshness. High levels can produce a hard or angular palate impression, while low levels may result in wines that seem soft or flat, especially in warm-climate styles. The balance between malic acid, tartaric acid and pH is therefore a key determinant of wine style and ageing potential.[4]
Malic acid is particularly important in white wines and sparkling wines, where crisp acidity is often a defining stylistic feature.
Malolactic fermentation
Malic acid is the primary substrate for malolactic fermentation, a secondary biological process in which lactic acid bacteria convert malic acid into softer lactic acid and carbon dioxide. This transformation reduces total acidity, increases pH slightly and modifies mouthfeel and aroma. Winemakers may encourage or suppress malolactic fermentation depending on the desired wine style.[5]
In red wines, malolactic fermentation is almost universal, contributing to microbial stability and textural roundness. In white wines, its use is more selective, commonly avoided in styles where bright acidity and primary fruit expression are prioritised.
Analytical and regulatory aspects
Malic acid concentration is routinely measured during grape ripening and winemaking as an indicator of maturity and fermentation progress. Analytical methods are well established and form part of standard must and wine assessment protocols.[6]
The OIV recognises malic acid as a naturally occurring component of grapes and wine and provides guidelines relating to acid management and authorised oenological practices that may affect overall acidity.[7]
See also
References
- ↑ Jancis Robinson, Oxford Companion to Wine, Oxford University Press, 17 Sept. 2015. ISBN 9780198705383.
- ↑ PhD Jackson, Ronald S., Wine Science: Principles and Applications, Academic Press Inc, 14 April 2020. ISBN 9780128161180.
- ↑ Ribéreau-Gayon et al., Handbook of Enology, Vol. 2, Wiley, 2006, ISBN 978-0470010396.
- ↑ 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.
- ↑ Peynaud, Knowing and Making Wine, Wiley, 1984, ISBN 978-0471881491.
- ↑ Amerine & Ough, Methods for Analysis of Musts and Wines, Wiley, 1980, ISBN 978-0471036732.
- ↑ OIV, “Organic acids in wine”.