2024, Vol. 5, Issue 2, Part D

Wine quality and sensory expression are strongly influenced by the interactions between grape-associated microbial consortia and the biosynthesis of volatile aroma compounds during fermentation. Vineyard management practices, particularly herbicide use, may inadvertently reshape microbial succession and disrupt aroma balance, but systematic evidence remains limited. This study aimed to investigate the impact of herbicide exposure on microbial dynamics and aroma compound variability in spontaneous red wine fermentations, using Vitis vinifera cv. Cabernet Sauvignon as a model. Grapes were harvested from two vineyard plots—one subjected to routine herbicide application and one herbicide-free control—and subjected to spontaneous fermentations in triplicate. Microbial communities were evaluated using both culture-dependent plating methods and culture-independent Illumina MiSeq sequencing of 16S rRNA and ITS regions. Volatile compounds were quantified via solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS), and data were analyzed using multivariate statistical tools including PCA, PLS-DA, and ANOVA.

The results demonstrated significant differences between herbicide-exposed and control fermentations. Herbicide-exposed musts showed reduced non-Saccharomyces yeast abundance, accelerated Saccharomyces cerevisiae dominance, and lower lactic acid bacterial populations, leading to a reduction in microbial diversity (Shannon index 2.1 vs. 2.9; p < 0.05). These microbial shifts were directly associated with chemical modifications: ester concentrations (notably ethyl acetate and ethyl hexanoate) were significantly reduced, while higher alcohols (isoamyl alcohol, 2-phenylethanol) and volatile phenols (4-ethylphenol) were elevated. PCA and PLS-DA revealed clear clustering between treatments, with esters driving control fermentations and higher alcohols/phenols dominating herbicide-exposed fermentations. Correlation analysis confirmed strong positive relationships between non-Saccharomyces diversity and ester levels (r = 0.73, p < 0.01) and negative correlations between lactic acid bacteria and volatile phenols (r = -0.59, p < 0.05).

In conclusion, herbicide exposure reshapes microbial succession and aroma compound production, compromising wine typicity and sensory balance. These findings highlight the need for sustainable vineyard practices and targeted microbial interventions to safeguard wine quality, authenticity, and terroir expression.