In recent years, global winters have become warmer and summers have turned into periods of extreme heat. Daily life that once considered 30°C hot has shifted to a reality where 40°C is now the standard for hot weather.
The terms “global warming” and “climate change” have become increasingly prevalent in discourse. These climate shifts are no longer “abnormal” phenomena but are becoming distinctly “normal” aspects of daily life. This persistent climate change is definitively transforming winemaking practices.
Consider the case of France. AOC (Appellation d’Origine Contrôlée) Bordeaux, which maintains strict regulations on permitted grape varieties, officially authorized the use of new grape varieties in 2019. The reason for this authorization was climate change adaptation.
Warmer winters advance the timing of bud break in grapevines. Hotter summers accelerate grape ripening. The time required for grapes to accumulate sugars becomes compressed.
In viticulture oriented toward winemaking, grape ripeness and sugar accumulation do not necessarily progress in tandem. Situations can arise where grapes have accumulated sufficient sugars but remain physiologically immature. Climate warming accelerates this decoupling between sugar accumulation and physiological maturation.
Grape sugar content demonstrates a strong positive correlation with wine alcohol content. Grape maturity demonstrates a strong positive correlation with wine flavor development. Wines produced from grapes that are high in sugar but physiologically immature result in wines with elevated alcohol content but lacking aromatic complexity. Conversely, wines made from fully ripe grapes with extreme sugar accumulation produce wines with exceptionally high alcohol content and rich flavor profiles. In cases of excessive maturation, wines can develop jam-like flavor characteristics.
When presented this way, the situation appears to present a binary choice. However, winemakers worldwide are declining to select either of these options. Winemakers are employing various strategies to pursue alternative pathways.
One such approach is the addition of water to must prior to fermentation. Water addition is a relatively common technique for alcohol adjustment in regions such as the United States.
In contrast, within the European Union, legislation prohibits the addition of water for alcohol adjustment regardless of whether it occurs before or after fermentation. Ongoing discussions continue regarding water addition, making future developments uncertain. However, at present, wineries within the EU cannot implement this straightforward water addition strategy.
Consequently, the method that has been implemented within the EU involves physical techniques using equipment capable of separating water from finished wine.
However, water separation equipment is prohibitively expensive for small-scale wineries to adopt. For all but a limited number of large-scale operations, physical equipment-based solutions have not proven to be viable solutions. Additionally, many wineries reject solutions that rely on excessively industrial methodologies, and alternative approaches continue to be explored.
The objectives of climate change adaptation strategies differ somewhat between viticultural and enological aspects. Furthermore, even within enological approaches, multiple initiatives target different parameters. These various initiatives may be interrelated in some cases and completely independent in others.
This article focuses specifically on wine alcohol content among the various targets of these strategies. The focus is on methods that neither rely on physical techniques nor involve water addition. This article examines new approaches for reducing wine alcohol content in the era of climate warming.
Conceptual Approaches to Alcohol Reduction
Two conceptual approaches exist for reducing wine alcohol content. The first approach prevents alcohol formation in the first place. Methods that reduce must sugar concentration fall under this conceptual framework. The second approach involves removing alcohol after it has been produced. Most of the physical techniques mentioned previously fall under the alcohol removal concept.
Both methods ultimately reduce wine alcohol concentration. However, approaches that attempt to remove alcohol after it has been produced require greater labor and cost. Additionally, these approaches carry higher risk of significant impacts on wine composition.
Consider the scenario where milk has been added to coffee and someone subsequently requests black coffee. Attempting to somehow remove the milk from that coffee to restore it to black coffee would be far more difficult than simply brewing fresh black coffee. The same principle applies to alcohol content adjustment.
From the perspective of minimizing unnecessary labor and costs, the appropriate choice of strategy becomes clear. However, the most straightforward and reliable method—water addition—is prohibited within the EU. How then can wineries reduce must sugar concentration? The majority of low-alcohol initiatives attempt viticultural solutions.
Reducing Must Sugar Concentration
Two methodological approaches exist even when reducing must sugar concentration. Recall the formula for calculating concentration, likely used for salt solution calculations in elementary school:
Salt concentration = Salt mass / (Salt mass + Water mass) × 100
This formula reveals that reducing salt concentration requires either decreasing the salt mass in the numerator or increasing the total mass in the denominator. The same conceptual framework applies when considering must sugar concentration. Specifically, either reduce the sugar content in the must or increase the water content. Water addition is the archetypal strategy for increasing water content.
Viticultural strategies aim to reduce the absolute quantity of sugars.
The relaxation of variety restrictions being considered in various regions takes a different approach rather than reducing grape sugars per se. The objective is to reduce sugar content in the must by harvesting before sugar accumulation reaches its peak. With currently authorized varieties, harvesting at this early timing results in pronounced grape immaturity. Immature grapes negatively impact wine flavor and aroma. However, employing early-ripening varieties can eliminate the temporal gap created by early harvesting.
Certain varieties are being adopted based on their slow rate of acid degradation. However, the adoption of varieties with slow acid degradation rates addresses acid loss rather than alcohol content, representing a somewhat different perspective. The style of wines with elevated alcohol content but also high acidity, resulting in balanced overall flavor profiles, likely represents one of the standard wine styles that will emerge in the future.
Alternative approaches exist within viticultural strategies. Methods such as second crop cultivation deliberately delay vine developmental stages. These cultivation methods aim to prevent temporal overlap between the hottest summer period and grape maturation. Another approach involves intentionally retaining growth points and clusters that would traditionally be removed. Retained clusters and growth points enable distribution of sugar consumption and accumulation, thereby diluting sugar accumulation per individual cluster.
In terms of novel approaches, viticultural strategies predominate, which explains why these approaches receive considerable attention. However, various investigations are also being conducted regarding enological approaches. One novel enological approach involves dilution without water.
Wine Dilution Without Water
A common problem when reducing alcohol concentration through dilution involves the disruption of overall wine balance accompanying dilution. Logically, when water is added to must, sugar concentration is not the sole component that becomes diluted. All components contained in must or wine become equally diluted. Consequently, the probability of producing watery wines increases. In this sense, reducing alcohol concentration through water addition cannot be considered an ideal method.
Therefore, wine dilution using wine itself is being explored.
Blending wines to adjust flavor and aroma has long been common practice and represents no particularly unusual technique. For example, under German wine law, blending wines of different grape varieties, vineyards, or vintages in proportions not exceeding 15% does not affect label declarations. In actual winemaking operations, such minor blending occurs frequently.
However, when attempting to reduce alcohol content, blending at approximately 15% proportions is often insufficient.
The method for blending wines without deviating from the so-called 15% rule is straightforward. Blend wines of identical grape variety, identical vineyard, and identical vintage. When these conditions are satisfied, even if fermentation vessels or yeast strains differ, the wines are fundamentally considered identical. Therefore, any blending proportion does not violate the 15% rule.
Obviously, blending wines harvested and vinified on the same date cannot achieve the objective of alcohol adjustment. To reduce excessively high alcohol content, the blending wine must possess sufficiently low alcohol content.
However, conversely, this means that preparing two wines with different alcohol contents enables reduction of wine alcohol content without requiring modifications to viticultural practices.
Advantages of Alcohol Adjustment Using Wine
A method exists for reducing the alcohol content of finished wine by blending two wines with different alcohol concentrations. The primary advantage this technique offers compared to water-based adjustment is the ability to maintain wine balance to a reasonable degree.
Water-based adjustment uniformly dilutes the concentration of all wine components. This problem arises because water contains none of the components that constitute wine, such as acids or phenolic compounds (chemical compound groups that contribute to wine color and flavor).
In contrast, when diluting with wine, these components are present, albeit in varying quantities. Consequently, wine-based dilution does not result in unilateral dilution, and wine balance is preserved.
Findings from validation studies conducted to date have yielded the following insights. Comparing wines produced from grapes harvested at appropriate timing from an alcohol concentration perspective with wines adjusted by blending two wines revealed no difference in total acidity. Reports actually indicated increased concentrations of phenolic compounds, particularly anthocyanins (pigment components in red wine).
Additionally, sensory evaluation (quality assessment using human sensory organs) results showed that alcohol-adjusted wines produced results equivalent to wines made respecting appropriate harvest timing. No statistically significant discrimination occurred between these two categories.
In other words, while increased phenolic compound content did not produce positive sensory evaluation, these findings demonstrated that the method is at minimum effective as a means of maintaining current quality standards.
Summary | How Should Wineries Address Climate Change
Recent climate change represents a significant challenge for wineries. Of course, viewing the situation across a multi-decade timescale, current warming could be considered transitory. From geophysical perspectives, arguments exist claiming that a minor ice age will arrive within several decades, substantially reducing global average temperatures, rendering current moderate warming inconsequential.
However, wineries must continue producing wine throughout those intervening decades. During this period, many traditional methodologies are becoming increasingly untenable in their current form.
The fundamental solution to problems originating from climate change involves relocating grape cultivation sites and changing varieties. Locations historically considered optimal based on accumulated experience are no longer appropriate.
Certainly, strategies such as site relocation and varietal changes are necessary. However, these require both time and capital. Changing one’s foundational location in a profession rooted in place is far from straightforward. Consequently, wineries must implement multiple strategies in parallel. Resources, including capital, must be allocated across these various strategies.
Considering this context, alcohol concentration adjustment techniques requiring minimal capital investment possess substantial value.
The advantage of wine-based dilution over water-based dilution is preservation of wine balance. However, within the EU where water addition is already prohibited, this aspect does not constitute an advantage. What holds far greater significance for EU wineries is that dilution through blending two wines requires virtually no capital investment or labor.
As previously demonstrated, wine blending methodology does not unequivocally improve wine quality. At best, it maintains current standards. Moreover, no guarantee exists that the same technique will enable continued production of elegant wines in the future.
However, if elements known to become increasingly problematic can be maintained at current levels with virtually no cost investment, this effectively represents substantial positive value. Wineries can redirect the time gained and capital saved toward fundamental adaptation strategies. Currently, securing time and resources for decision-making and implementation of countermeasures is critically important.
A method exists for adjusting alcohol concentration by blending two wines. While conceptually straightforward, actual implementation requires extensive trial-and-error and informed judgment. Furthermore, the knowledge and technical expertise required differs from conventional winemaking techniques and resists standardization.
The implementation of alcohol adjustment using wine carries no mandatory labeling requirements in principle. Consequently, consumers have virtually no means of knowing whether such adjustment has occurred. Moving forward, winemakers are being called upon to advance their practices to yet higher levels behind the scenes in order to continue providing consumers with elegant wines of traditional character.
