GC-MS Tracks Climate's Effect on Wine Aroma

As climate change occurs and temperatures rise, wine is ending up containing more alcohol, and the usual balance between a wine's pH and its acidity is starting to shift in unusual ways. These changes also seem to be encouraging the buildup of two specific flavor-related compounds in wine: γ-nonalactone (γ-C9) and massoia lactone (MLac). Researchers at the Department of Agricultural Sciences, Division of Vine and Wine Sciences of the University of Napoli (Italy) looked at how alcohol content and acidity levels affect how noticeable these two compounds are, both chemically and in terms of taste. To test this, researchers took a red wine with its natural aroma removed and recreated it in nine different versions, varying both the alcohol content (12%, 14%, and 16%) and the balance between pH and acidity, then added the two flavor compounds back in to see how they behaved under each condition. Headspace release was quantified by solid-phase micro-extraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and trained assessors performed triangle tests and rate-all-that-apply (RATA) profiling (orthonasal, retronasal, and taste/mouthfeel). A paper based on their work was published in the Journal of the Science of Food and Agriculture.¹

Why Does Climate Change Matter for How Wine Tastes and Ages?

Wine is a complicated drink made up of two main parts. One part is made up of substances that evaporate easily, including alcohol and the various aroma compounds that give wine its smell. The other part is made up of substances that don't evaporate, mainly polyphenols, which affect the wine's color and mouthfeel, and acids, which give wine its sourness and determine its pH.² Within this mix of different chemical components that make up wine, three factors stand out as especially important: alcohol content, pH, and acidity. This is largely because these three factors are particularly sensitive to the rising temperatures brought on by climate change, and changes in any of them can significantly affect how a wine is made, how it performs during production, how it tastes, and how well it ages. As temperatures rise, grapes are producing more sugar, which in turn leads to wines with higher alcohol content.³ When it comes to the aroma-related compounds in wine, research has shown that high temperatures can cause certain specific compounds to build up, namely γ-C9 and MLac. When these compounds accumulate, they create smells reminiscent of prunes and dried figs, which winemakers typically consider undesirable, since these aromas are usually linked to a wine aging prematurely.^4,5

How Do Alcohol and Acidity Levels Affect Whether People Can Smell and Taste γ-C9 and MLac in Wine, and What Does That Mean for Winemaking?

When it came to smelling the wine directly (without tasting it), the team of evaluators made up of 24 participants (11 males and 13 females, aged 22–50 years) were able to detect γ-C9 in every version with lower acidity, and they could also pick up on MLac in versions that had both high alcohol and lower acidity. This lined up with the fact that both compounds evaporated more easily into the air above the wine when alcohol was higher and acidity was lower, but not all of the differences noticed could be explained by this alone, suggesting that other factors in the wine itself were also influencing how these aromas came across.¹

When the evaluators described the wine's flavor, higher alcohol and lower acidity shifted the wine's character away from citrus and tropical notes toward sweeter, more perfume-like qualities, along with a fuller mouthfeel. In terms of taste, wines with both high alcohol and low acidity tasted less sour and more bitter.¹

“Overall,” write the authors of the study,¹ “these results suggest that ethanol and acidity act as interactive modulators, influencing volatile organic compounds (VOCs) release, their perceptual integration, and taste balance. In this context, enological practices such as wine acidification, essential to counteract climate-induced imbalances, should be carefully evaluated for their potential ability to enhance the sensory impact of γ-C9 and MLac and overall sensory quality in red wines.”

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References

1. Di Fede, R. S.; Pittari, E.; Moio, L. et al. Impact of Climate-Induced Compositional Shifts of Ethanol and Acidity on Aroma Release and Perception in Red Wine: A Case Study on γ-Nonalactone and Massoia Lactone. J Sci Food Agric. 2026.DOI: 10.1002/jsfa.70876
2. Villamor, R. R.; Ross, C. F. Wine Matrix Compounds Affect Perception of Wine Aromas. Annu Rev Food Sci Technol. 2013, 4, 1-20. DOI: 10.1146/annurev-food-030212-182707
3. van Leeuwen, C.; Darriet, P. The Impact of Climate Change on Viticulture and Wine Quality. J Wine Econ 2016, 11, 150–167. DOI: 10.1017/jwe.2015.21
4. Pons, A.; Lavigne, V.; Eric, F. et al. Identification of Volatile Compounds Responsible for Prune Aroma in Prematurely Aged Red Wines. J Agric Food Chem. 2008, 56 (13), 5285-5290. DOI: 10.1021/jf073513z
5. Pons, A.; Allamy, L.; Lavigne, V. et al. Study of the Contribution of Massoia Lactone to the Aroma of Merlot and Cabernet Sauvignon Musts and Wines. Food Chem. 2017, 232, 229-236. DOI: 10.1016/j.foodchem.2017.03.151