Terroir: How Microbes Affect Wine
A major part of terroir is the microbes
Wine seems to be so complicated. It can be, but it doesn’t have to be. Watch Bottle Shock, Somm, or Sideways, and you’ll get a hint of the many dimensions of wine. Wine is a huge industry. The US wine market sold over $107 billion in 2023, and wine sales are on the rise globally. (Thatch, 2024)
It seems like a lifetime ago that I was working in a French restaurant, learning about wines, how to cook with them, how to pair them with food, how to serve them, and eventually, how to buy them for the wine list. I went to tastings and learned from the people selling the wines, eventually concluding that what really mattered was if you liked the wine or not. As Jacques Pépin said on Julia Child’s show, “Never cook with a wine you don’t like!”
The soil is credited with imparting flavor to the wine. It is called “terroir.” Each location has a unique profile. Discovering and managing that profile is a great art that comes through the grapes.
Terroir refers to the distinct blend of environmental elements influencing wine quality in a certain area. These elements include climate, soil composition, geography, and, more recently acknowledged, microbiological populations. These microorganisms, including bacteria, yeasts, and fungi, have a vital impact on the overall health of the vine and the fermentation processes and ultimately determine the flavor and fragrance of the wine.
Bacteria, namely lactic acid bacteria (LAB) such as Lactobacillus and Oenococcus oeni, play a crucial role in the process of malolactic fermentation. This fermentation process reduces the acidity of the wine and imparts rich buttery tastes. This procedure converts the sharp malic acid into milder lactic acid, enhancing the wine's intricacy and texture.(Lorentzen and Lucas, 2019) Acetic acid bacteria, commonly linked with causing spoilage, can contribute pleasant vinegar-like odors when present in regulated amounts. Nitrogen-fixing bacteria in the soil increase fertility by transforming atmospheric nitrogen into plant-accessible forms, enhancing vine health and boosting the quality of grapes.
Yeasts, namely Saccharomyces cerevisiae, are the main catalysts of alcoholic fermentation, transforming sugars found in grapes into ethanol and carbon dioxide. This yeast strain also generates esters and other chemicals that add to the wine's fruity and flowery aromas. Other yeasts, such as Brettanomyces, can enhance the complexity of wine by imparting earthy and spicy smells. (Australian Wine Research Institute, n. d.) While wild yeasts may be undesirable because of their unpredictable behavior, they can contribute distinctive qualities that are much appreciated in specific wine varieties.
Fungi also have a notable impact on the grapevine ecology. Mycorrhizal fungi establish symbiotic associations with grapevine roots, thus increasing the absorption of water and nutrients, especially phosphorus. This mutualistic relationship is essential for the vine's overall well-being and can enhance the quality of grapes. (Trouvelot et al., 2015) Botrytis cinerea, mostly known as a plant pathogen, also referred to as noble rot, has the ability to enhance the concentration of sugars and tastes in grapes, resulting in the creation of highly esteemed sweet wines such as Sauternes and Tokaji. (Negri et al., 2017) These wines are distinguished by their opulent, honey-like taste and intricate smells.
Microbial communities exhibit substantial variation among areas as a result of disparities in temperature, soil composition, and vineyard management techniques. Climate impacts the composition of microorganisms; higher temperatures promote specific yeasts and bacteria that impact fermentation and taste characteristics, whilst lower temperatures encourage various microbes that influence the retention of acids and the complexity of aromas. For example, Napa Valley's warmer temperature fosters a microbial community that enhances the region's robust and fruit-driven wines, while the colder environment of Burgundy promotes microorganisms that aid in maintaining acidity and creating delicate and complex flavors.
The makeup of the soil also influences microbial diversity. Soils with high calcium carbonate, known as calcareous soils, have different microbial communities than volcanic or sandy soils. This difference in microbial communities affects the availability of nutrients and the growth of vines. For instance, limestone's presence in Champagne's soils creates a specific microbial ecosystem that enhances the region's unique mineral qualities and refreshing acidity.
Vineyard management strategies have an additional impact on the variety of microorganisms. Organic and biodynamic techniques promote microbial variety by reducing the use of artificial substances, which helps maintain a harmonious soil environment. Organic farming uses natural fertilizers and compost while abstaining from the use of synthetic pesticides. This method encourages the development of a varied and well-balanced community of microorganisms in the soil, which improves the overall health of the vines and enhances the diversity of flavors in the grapes. Biodynamic farming incorporates organic principles and holistic methods, such as the use of biodynamic preparations, compost teas, and moon cycles, to cultivate a highly diverse and productive soil microbiome. These measures enhance the vitality and durability of the vineyard environment, leading to grapes with richer and intensified tastes.
Conversely, conventional farming frequently depends on artificial fertilizers, pesticides, and herbicides, which can diminish the variety of microorganisms in the soil and affect its structure. Although these methods might provide abundant harvests, they can lead to grapes with diluted tastes as a consequence of gradual soil deterioration. Traditional methods can result in a more uniform vineyard microbiome, affecting the intricacy of the wine. (Hasanaliyeva et al., 2021; Delmar et al., 2016)
Organic and biodynamic wines sometimes utilize indigenous or spontaneous yeasts found on the grape skins and within the winery surroundings throughout the winemaking process. The spontaneous fermentations enhance the distinct and varied taste profiles, showcasing the inherent qualities of the grapes and terroir. This methodology frequently yields wines with a heightened sense of terroir, showcasing the distinct characteristics of the vineyard's environment. (Meissner et al., 2019 and Ross et al., 2009)
Traditional wines commonly employ specifically cultivated yeasts selected for their capacity to provide reliable and anticipated outcomes. Although this approach guarantees dependability and regulation throughout the fermentation process, it can result in more consistent taste profiles that may lack the complexity and distinctiveness seen in spontaneously fermented wines.
Organic and biodynamic wines restrict the utilization of chemicals and processing aids, such as fining agents and sulfur dioxide (SO2), different types of fertilizers (synthetic vs not synthetic), and lack the applications of synthetic pesticides like glyphosate vs. conventional wines. The primary objective of this concept is to maintain the inherent tastes and aromas of the wine, producing a more authentic representation of the grape and terroir. In contrast, conventional wines may include a broader array of chemicals and processing aids to stabilize the wine and augment certain characteristics. Although these additions have the potential to enhance the clarity and longevity of the wine, they may also diminish its distinctiveness and ability to convey its specific regional characteristics.
The discernible variations in taste among organic, biodynamic, and conventional wines can be significant, depending on the variety and area where they are grown. Organic and biodynamic wines typically exhibit more distinct and diversified tastes due to the complex vineyard microbiota and the use of minimum intervention techniques. (Messiner et al., 2019) These wines frequently have a heightened expression of their origin, known as terroir, with intricate and multifaceted characteristics that reflect the distinctive environmental factors of their source. Conventional wines, while sometimes of excellent quality, tend to have more uniform taste profiles due to the employment of certain yeasts and chemicals.
Organic and biodynamic wines sometimes exhibit enhanced textures and vibrancy in their scents and mouthfeel due to natural winemaking techniques. These wines possess a broader spectrum of fragrances, ranging from flowery and fruity to earthy and mineral, and have a more vibrant and lively flavor profile. Traditional wines often have a smoother and more refined character, characterized by constant scents and a clear, polished profile. However, they may not possess the same taste complexity and distinctiveness level.
Organic and biodynamic wines frequently have a vibrant and invigorating acidity resulting from the natural maturation process and meticulous vineyard supervision. These wines might possess a livelier and more energetic flavor profile characterized by a refreshing and pure aftertaste. Conventional wines have carefully regulated acidity levels and provide a reliable but less lively flavor profile.
Microorganisms play a crucial role in the idea of terroir, impacting the well-being of grapevines, the process of fermentation, and the sensory characteristics of wine. The agricultural techniques, whether they are organic, biodynamic, or conventional, have a substantial influence on these microbial populations, which in turn affects the taste and characteristics of the wine. Although temperature and soil are still vital, comprehending and controlling the vineyard microbiome is becoming increasingly crucial to producing top-notch wines that reflect the region's unique characteristics. Organic and biodynamic processes, via the promotion of microbial diversity and limited intervention, frequently provide wines that exhibit heightened complexity, distinct aromas, and a more pronounced terroir than those produced using conventional methods.
Conclusion
Ultimately, the interaction of microorganisms, terroir, and agricultural methods determines wine's distinct qualities. By using the wide range of microorganisms and natural processes in organic and biodynamic farming, it is possible to amplify the unique characteristics of the land, resulting in wines that genuinely represent their origins and provide a more intricate and diverse sensory encounter. As the wine business further investigates and comprehends these connections and consumers choose to purchase organic or biodynamic wines, the recognition for organically produced wines that accentuate the genuine tastes of their specific region is expected to increase.
References
Australian Wine Research Institute (AWRI). (n.d.). Bretanomyces. https://www.awri.com.au/industry_support/winemaking_resources/frequently_asked_questions/brettanomyces-faq/
Delmas, M. A., Gergaud, O., & Lim, J. (2016). Does organic wine taste better? An analysis of experts' ratings. Journal of Wine Economics, 11(3), 329-354. https://doi.org10.1017/jwe.2016.14 https://www.wine-economics.org/wp-content/uploads/2016/12/Vol11-Issue03-Does-Organic-Wine-Taste-Better-An-Analysis-of-Experts-Ratings.pdf
Lorentzen, M. P. G., & Lucas, P. M. (2019). Distribution of Oenococcus oeni populations in natural habitats. Applied Microbiology and Biotechnology, 103(7), 2937-2945. https://doi.org/10.1007/s00253-019-09689-z
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Meissner, G., Athmann, M. E., Fritz, J., Kauer, R., Stoll, M., & Schultz, H. R. (2019). Conversion to organic and biodynamic viticultural practices: impact on soil, grapevine development and grape quality. Oeno One, 53(4). https://doi.org/10.20870/oeno-one.2019.53.4.2470
Negri, S., Lovato, A., Boscaini, F., Salvetti, E., Torriani, S., Commisso, M., Danzi, R., Ugliano, M., Polverari, A., Tornielli, G. B., & Guzzo, F. (2017). The Induction of Noble Rot (Botrytis cinerea) Infection during Postharvest Withering Changes the Metabolome of Grapevine Berries (Vitis vinifera L., cv. Garganega). Frontiers in Plant Science, 8. https://doi.org/10.3389/fpls.2017.01002
Ross, C. F., Weller, K. M., Blue, R. B., & Reganold, J. P. (2009). Difference Testing of Merlot Produced from Biodynamically and Organically Grown Wine Grapes. Journal of Wine Research, 20(2), 85–94. https://doi.org/10.1080/09571260903169423
Thatch, L. (2024, May 15). U.S. Wine Industry Surpasses $107 Billion In 2023 Sales, Report Reveals. https://www.forbes.com/sites/lizthach/2024/05/15/wine-triumphs-us-wine-industry-surpasses-107-billion-in-2023-sales-report-reveals/
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