Acidity and wine freshness

Acidity plays a crucial role in the sensation of freshness in wine, but increasing heatwaves are reducing acidity levels, disrupting the balance of the vine and complicating the choice of harvest dates. Winemakers are grappling with the challenge of preserving freshness when the ripening stages of grapes no longer progress at the same pace.

Ripeness and harvest timing

Harvesting early risks insufficient ripeness, while harvesting later may result in wines with cooked fruit characteristics. The 2022 vintage, despite producing fresh wines, demonstrated this paradox with skill. The 2026 vintage appears to be following a similar path, with professionals adapting their practices from the vineyard to the cellar.

Heat effects on grapes

High temperatures cause malic acid degradation, water loss in berries, and sugar concentration. However, these changes do not necessarily align with the progression of aromatic and phenolic ripeness. The 2022 vintage had already challenged many assumptions, producing balanced wines despite high sugar levels and low acidity. The 2026 vintage seems to push these challenges further.

Heatwave frequency in wine regions

In Bordeaux, the normal climate (1991-2020) had 3.9 days per year reaching or exceeding 35°C. In 2022, this number was 20, and in 2026, it reached 32. In Burgundy, the increase in very hot days is also notable.

Grape conditions in 2026

Julien Viaud, an enologist at Rolland & Associates, observed by mid-August grapes with "high degrees but still insipid and neutral." This presents a dilemma: waiting risks high alcohol levels and low acidity, while harvesting early risks insufficient aromas. Finding a balance point is essential.

Adaptations in vineyard practices

Traditionally, in Bordeaux and Burgundy, leaf removal was used to expose grape clusters to the sun. However, with hotter vintages, some practices have changed. Antoine Médeville from the Œnoconseil laboratory in Pauillac notes that leaf removal is now limited to protect clusters from sunburn and malic acid degradation.

Soil and vine adjustments

At Château Giscours in Margaux, Jérôme Poisson explains that the vineyard is adapting at the soil level, using vegetative cover to absorb rainfall and reduce heat. The vine canopy has also changed, with less pruning and a more "bushy" appearance.

New techniques for acidity preservation

Marie-Laurence Porte, an enologist at Oenosens, is exploring alternative methods such as foliar applications and biostimulants. These methods showed promise in 2022, allowing earlier harvests with better acidity and phenolic maturity. New machines that allow alcohol removal are also being tested.

Vine resilience and harvest decisions

Julien Viaud is surprised by the vine's ability to withstand extreme conditions, though this is not a genetic adaptation but rather the vine's existing mechanisms. Traditional potential degrees no longer suffice for harvest decisions, and a comprehensive approach is now needed, considering sugars, acidity, pH, skins, seeds, tannins, and aromatics.

2026 harvest at Château Giscours

At Giscours, the 2026 harvest began on August 25 and continued until September 21, with multiple passes in the same parcel depending on vine age. Jérôme Poisson notes no major phenolic blockage in 2026. Axel Marchal, a professor at ISVV, highlights improved practices since 2003, including better grape protection and more precise harvest dates.

Fermentation adjustments

Antoine Médeville advises starting fermentation at lower temperatures to avoid over-extraction. Jérôme Poisson aims to prevent overly extracted wines. Musts with high pH levels have sometimes regained balance during fermentation, with better acidity. This phenomenon is beginning to be better understood.

Acidity and wine stability

Preserving acidity under heatwaves is not only about freshness but also about the wine's stability over time. The rise in acidity during fermentation is a recent discovery, prompting calls for caution in acidification before fermentation.

Achieving freshness in wines

The much-anticipated freshness by consumers is achieved through various factors, including soil management, foliage, harvest timing, and winemaking restraint. However, the question of how wines with low acidity can still appear fresh remains an enigma, to be explored in a future discussion.