Malolactic Fermentation: A Double-Edged Sword in a Warming World

Climate change and evolving market preferences are creating opposing pressures that winemakers must address with innovation. As rising temperatures lead to riper grapes with rounder flavors and lower acidity, both consumers and winemakers continue to seek fresh wines with intense profiles and notable acidity. This divergence presents challenges for wine producers, who are exploring vineyard and cellar strategies to balance climate effects with market demands.

One essential aspect of these strategies is the management of malolactic fermentation (MLF). This process converts malic acid to lactic acid, reducing perceived acidity and softening the wine's flavor profile. While MLF is common in red wines and some cool-climate whites, using it in increasingly warm regions can reduce a wine's freshness. Beyond lowering acidity, MLF changes the wine's chemical and sensory characteristics, requiring a careful assessment of its use.

Climate change has also altered the bacterial landscape that drives MLF. A 2022 study published in Microorganisms highlights how bacteria like Lactobacillus and Pediococcus—previously less prominent compared to Oenococcus oeni—are becoming more important in fermentation, especially in warmer regions. These shifts in microbiota complicate spontaneous MLF, which can risk wine quality if not carefully managed.

In response, many wineries have adjusted their vineyard and winemaking practices. Some, aiming for rounder profiles and fuller textures, have reduced MLF use by sourcing grapes from cooler areas where natural acidity is higher. This strategy allows wines to maintain a balanced structure without a full MLF that might overly soften the profile.

In contrast, some Chardonnay producers in regions like the Pacific Northwest value the mouthfeel that MLF provides. Focusing on vineyard management, these winemakers use canopy techniques and control sunlight exposure to preserve acidity, reducing the need for cellar adjustments. In warm climates, careful light and wind management helps avoid tropical flavors that could overwhelm desired freshness.

Other producers decide on MLF after harvest. By assessing the grapes' pH, some wineries adjust the level of MLF according to each vintage's conditions. This adaptable approach means more MLF in warmer years, where grapes show heightened ripeness, compared to cooler years.

Some vintners have also turned to grape clones that allow for later ripening, retaining good acidity and concentrated flavors, especially for Chardonnay. Using these clones, winemakers achieve physiological ripeness without overly high pH levels, allowing MLF to enhance the wine's profile without sacrificing freshness. Certain older French clones have proven successful in warm regions, where they maintain a lower pH at harvest, facilitating a controlled and balanced MLF.

Bacterial management is another area undergoing change. In New Zealand, some Chardonnay-focused wineries select specific bacterial strains for MLF based on the desired wine profile. For wines aimed at a broader audience, strains that produce more diacetyl, which gives buttery notes, are often chosen. However, for premium wines, these wineries prefer strains that support lighter, spontaneous MLF, helping maintain a fresh profile.

In parts of Europe, shifting market preferences have also reduced MLF use in Chardonnays, with a focus on citrus and fresh profiles rather than the brioche notes a full MLF can produce. In regions working with varieties like Sauvignon Blanc, commercial bacteria strains are selected that add mouthfeel without compromising the wine's fresh character. This careful selection meets market expectations and preserves the desired freshness, even in hot years.

In a climate change context, vineyard and cellar decisions are essential to adapt to each vintage's character and market demand. Continuous adjustments, detailed analyses, and experimentation with techniques and bacterial strains enable winemakers to create balanced wines representative of their terroir. Despite the challenges of shifting conditions and consumer tastes, producers are working to ensure the freshness, acidity, and character that distinguish quality white wines worldwide.