Global Warming: The Issues in Winemaking

Scientists, oenologists and wine professionals from around the world gathered on May 10 at the Relais de Margaux (France) to discuss the impact of climate change on vineyards and winemaking. This conference, held under the auspices of Lallemand, a producer of wine yeast and bacteria, brought together nearly 150 vine and wine specialists to talk about the issues raised for the profession by the advent of global warming. Following a report on global wine markets by Patrick Aigrain (Viniflhor – OIV), Jean-Pierre Gaudillère (INRA Bordeaux) outlined the consequences of different climate change scenarios on vineyards and the quality of wine. French and foreign researchers specialized in oenology then presented their research in the perspective of responding to problem situations, particularly by relying on the control of fermentation. Indeed, as summarized by Mr. Gaudillère, “Climate change inevitably results in higher levels of sugar in the grape juice, and consequently higher levels of alcohol in the wine, as well as a decrease of the acidity of the must, which can result in the proliferation of undesirable microorganisms and a decrease in phenolic maturity. This tendency – observed since the 1970s – is now a certainty.” In order to respond to the problem of high concentrations of sugar in the grapes, one of the approaches suggested by the INRA in Montpellier is to select yeast strains that produce less ethanol during alcoholic fermentation. As Sylvie Dequin, Director of Research, explained, “We are observing increasingly higher sugar levels. As yeast is responsible for transforming sugar into alcohol during alcoholic fermentation, we have been working for more than a decade on this problem, notably by trying to develop yeasts that produce less alcohol while transforming the sugars into other compounds. One of the main challenges is to do this without altering any of the sensory characteristics of the wine. For instance, increasing the proportion of sugar transformed into glycerol allows us to lower the alcohol level while bringing a certain roundness to the wine.” Ms. Dequin’s team is working on this approach in partnership with Lallemand. Ramón Mira de Orduña, from Cornell University in the United States, addressed the impact of global warming on lowered acidity in grapes, which could compromise proper fermentation. He advocates utilizing winemaking yeast selected from the vineyard and produced commercially to better master the malolactic fermentation (the secondary fermentation by lactic bacteria, which allows the winemaker to rework the acids in the wine and guarantee its stability), and thus the final quality of the wines. Based on observations that the wine harvest is occurring earlier and earlier, Fernando Zamora, from the Universitat Rovira i Virgili in Tarragona, Spain, noted, “Global warming accelerates the accumulation of sugar in the grape. However, the grape skins and seeds may not be sufficiently mature (the phenolic maturity), resulting in unbalanced wines that are too bitter and astringent, with herbal aromas. The possible solutions include harvesting the grapes as soon as the sugar level is optimal, adapting the winemaking technique to extract less tannin from the seeds, or waiting until phenolic maturity is reached and applying techniques that allow us to control the level of alcohol and acidity.” ABOUT LALLEMAND Lallemand – a leading producer of wine yeast and bacteria, and their nutrients, and a distributor of oenological enzymes – is a privately owned Canadian corporation with divisions operating around the world. The Oenology Division, based in Toulouse, France, has a major focus on research and development, both in-house and in collaboration with renowned research institutes. Each year, the company organizes the “Entretiens Scientifiques Lallemand” technical meetings in a winemaking region of the world, bringing together scientists and winemaking professionals to discuss issues related to winemaking processes. This year, the 19th meeting took place in Margaux, France.