Influence of Different Closure Systems on Yeast Metabolism During the Secondary Fermentation of Traditional Method Sparkling Wines.

Secondary fermentation is a critical stage in the production of traditional method sparkling wines, during which yeast metabolism drives major changes in wine composition. However, the biochemical processes occurring during this phase and the influence of bottle closure systems remain poorly understood. This study evaluated the evolution of basic oenological parameters, free amino acids and volatile compounds during the first 90 days of secondary fermentation under two bottle closure systems: crown cap and tirage-cork. Fermentation time was the principal factor governing wine composition, with the most pronounced metabolic changes occurring between 30 and 45 days after bottling. Active nitrogen metabolism was evidenced by substantial amino acid redistribution, particularly involving ASN, ORN, AAA, GLU and ASP, while the accumulation of higher alcohols and other fermentation-derived volatiles reflected intense yeast metabolic activity during bottle fermentation. Although both closure systems successfully completed fermentation, tirage-cork-fermented wines showed a tendency towards faster fermentation progression and distinct patterns of amino acid and volatile compound development. Pearson correlation analysis revealed generally weak to moderate associations between amino acids and their corresponding volatile compounds, supporting the view that aroma formation results from the integration of multiple metabolic processes rather than from precursor availability alone. Overall, the results suggest that closure-associated metabolic divergence becomes detectable during the active phase of secondary fermentation and may contribute to differences in nitrogenous and aroma-related compounds. These findings suggest that bottle closure may represent an important technological variable associated with differences in the metabolic and compositional trajectories observed during the active phase of secondary fermentation. Given the limited biological replication of the present study, these observations should be interpreted with caution and warrant confirmation through studies incorporating biological replication and direct measurements of oxygen transfer.