Managing alcohol in sparkling wine production: adjusting harvest timing and utilizing grape juice in “liqueur de tirage”

Abstract

Context and purpose of the study. Sparkling wine production is majorly impacted by climate change as sugar accumulation and aromatic development in grapes are often decoupled. While advancing the harvest date is a common approach to manage alcohol levels, studies showed that delaying the harvest by one week significantly improved the aroma and sensory characteristics of sparkling wines (Skrab et al., 2024). Using grape juice instead of sucrose in the ‘liqueur de tirage’ for secondary fermentation offers an alternative strategy, thereby reducing the alcohol increase, allowing greater flexibility selecting the harvest date. The “sugar loading” concept, measuring sugar per berry, provides a valuable tool assessing grape maturity but is rarely applied for sparkling wine production. Our study explored various alcohol management strategies for sparkling wine production by experimenting with different harvest dates and using either sucrose or grape juice as the “liqueur de tirage” for secondary fermentation.

Material and Methods. Riesling grapes from Baden-Württemberg (Germany) were harvested in 2021 on four dates based on sugar loading and other indicators (e.g., berry tasting). Starting one week before phloem blockage (17.6°Brix, H1), harvests progressed weekly (19.4°Brix, H2; 19.8°Brix, H3; 20.4°Brix, H4). Must acidity of early harvests was adjusted to match later dates. Base wines were fermented, bottled, and sensory evaluation took place two months later. Experimental batches of sparkling wines were also prepared via méthode traditionnelle using sucrose (24 g/L) or stored grape juice as “liqueur de tirage”. The sparkling wines aged on lees for nine months, were riddled, analyzed and sensory evaluation took place two months later.

Results. For the base wines, the ‘aroma intensity’ descriptors increased significantly between H1/H2 and H3/H4, with the flavor profile evolving from green apple (H1) to citrus (H2), to peach (H3), and pineapple (H4). This trend was reflected in sparkling wines, where early harvests (H1) showed herbaceous notes and lower preference compared to later harvests. Using grape juice for the prise de mousse reduced alcohol and bitterness in sparkling wines while maintaining the quality of mousseux.

Conclusion. Although limited to one season, this study highlights alternative strategies for sparkling wine production focusing on process adaptations to mitigate the drawbacks of using immature grapes for base wine.