Bordeaux winemakers rethink heat strategy after hot-vintage wines stay fresh despite low acidity

In Bordeaux, winemakers and researchers working through another heat-affected vintage say the sense of freshness in wine cannot be explained by acidity alone, a finding that is pushing the region to rethink how it responds to rising temperatures.

The issue has become more visible in very hot years such as 2022 and 2026. In those vintages, grapes often showed low acidity and high sugar levels, conditions that usually point to heavier wines with more alcohol. Yet some finished wines still tasted bright and lively. That gap between laboratory analysis and what people actually taste is now driving new work in vineyards, cellars and research labs.

Acidity remains a major part of the picture. It gives wine shape, stimulates saliva and helps prevent a flat impression on the palate. But several Bordeaux professionals told Terre de Vins that freshness and acidity are not the same thing. Jérôme Poisson, general manager at Château Giscours, said a wine can have enough acidity and still fail to taste fresh if its aromas are cooked or jammy. By contrast, he said, a wine with slightly less acidity may seem fresher if it shows red fruit and more vivid aromas.

That aromatic side of freshness is one of the main lessons from recent hot vintages. Axel Marchal, a professor at the Institute of Vine and Wine Sciences in Bordeaux, said he has found relatively few 2026 wines marked by cooked-fruit notes, far fewer than in the extreme heat of 2003. He linked that, in part, to changes in vineyard practice. Growers now do more to protect grapes from direct sun, and they have become more precise about harvest timing. Antoine Médeville, an enologist at Oenoconseil in Pauillac, said morning and night harvesting can also help by preserving fruit character even if those steps do not directly increase acidity.

The role of alcohol adds another layer. Hot weather raises sugar levels in grapes, and more sugar generally means more alcohol after fermentation. Consumers often associate higher alcohol with heat on the palate, which can work against any impression of freshness. But several specialists said the number alone does not tell the full story. Marie-Laurence Porte, an enologist at the Oenosens laboratory, said some 2026 wines with high alcohol levels did not necessarily taste alcoholic. Julien Viaud, an enologist at Rolland & Associés, said the way alcohol is perceived may also depend on pH and on the broader balance of the wine, though he said that link still needs more scientific work.

That means a wine at 14% alcohol does not automatically taste hotter than another wine at 14%. The surrounding elements matter, especially texture and tannin structure. Poisson said that when acidity drops, a well-judged tannic structure can restore energy in the middle of the palate. But he and others also warned that the same hot conditions that concentrate grapes can quickly produce overly dense wines if extraction is pushed too far during fermentation.

Médeville said that concern has already changed cellar practice in the Médoc. He said the older approach of seeking ever more tannin no longer fits warmer conditions. Instead, producers are looking for finer, rounder tannins. That has led some wineries to start fermentations at cooler temperatures, sometimes after a cold pre-fermentation phase, reduce pump-overs and stop extraction earlier so they do not pull harsh seed tannins late in fermentation, when alcohol can act as a stronger solvent.

Researchers are also exploring whether freshness can come from sources that are not yet well defined. Marchal said there may be a gustatory form of freshness tied to certain mineral species or to other molecules that remain poorly identified. In highly concentrated grapes, he said, those compounds could also be more concentrated and may contribute to the salty sensation that tasters often associate with freshness. He also cautioned that the scientific basis is still uncertain, especially regarding the contribution of mineral ions to overall balance.

Another complication is that grape analysis does not always predict the final wine. Marchal said he observed musts in 2026 with high pH and low acidity that later regained better balance during fermentation. In those cases, acids were released from the grapes during the winemaking process. That is why he urged caution before adding acid early, since the wine’s chemistry can still shift on its own.

Some of the most closely watched trials involve microbiology. Médeville said he has been testing yeast strains that can divert part of the grape sugar away from alcohol production and toward malic acid. In some trials, he said, that approach delivered about 0.5% less alcohol and nearly 1 gram more malic acid. The idea is especially relevant in hot years because malic acid tends to fall sharply as temperatures rise. Even so, he said the key question has not been settled: whether that analytical gain produces a clear sensory benefit in the glass.

Porte is studying another route, using yeasts that produce lactic acid and examining certain enological tannins that, in her view, may add tension and a feeling of freshness without raising measured acidity. She said those effects still need stronger scientific documentation.

The work matters beyond a technical debate over tasting language. For wine producers, and potentially for other beverage makers adapting recipes and production methods to warmer conditions, it points to new ways to manage alcohol, acidity and texture as climate pressures increase. It also suggests that laboratory acidity alone may be a poor guide to the final sensory result, which could affect how new tools are judged and adopted across the drinks sector.

The broader challenge now facing Bordeaux, Burgundy and other warming wine regions is to protect acidity where possible while also looking past it. Vineyard protection from sun, harvest timing, extraction choices, yeast selection, aroma preservation and the interaction between tannins, alcohol and pH are all becoming part of the same response as producers prepare for more frequent hot vintages.