Mouton Noir

I understand winemaking is more art than science, but (unfortunately) I'm closer to a scientist than an artist at the time of this writing.

My original intention for this post was to develop a “scientific” framework¹ to understand the concept of “terroir” by examining the intricate relationship between a vine's physical environment and the resulting wine.

However, I'm thinking about changing the direction of the research. After reading about five (highly-cited) academic papers on this topic, I realised two things:

• I had picked a wrong branch of science for my research: I should have picked biology, not geology.²
• I will have to continue my research on this topic as long as I'm making wine.

I will write about the science of terroir whenever I come across an interesting article or paper.

But first, I'm going to look for an old article on the topic of terroir and examine how the concept was viewed back then, hopefully, without forcing any scientific lens.³

Below are the summaries of the two papers I found interesting as they point towards my current hypothesis: the transfer mechanism is us.⁴

I also found it fascinating that altitude affected the chemical compositions of wines more than precipitation or growing degree days. Further research on the altitude and/or the atmospheric pressure on the physiology of vines and winemaking process is warranted.

Here's the first paper: The Value of Soil Knowledge in Understanding Wine Terroir By Robert E. White from The School of Agriculture and Food, The University of Melbourne

Introduction:

• The concept of wine terroir encompasses natural, human, and historical factors.
• The focus of this paper is on natural factors, especially the interaction of the vine with its environment.
• Key natural factors include climate, soil, and vine cultivar.
• Soil properties play a crucial role in vine phenology and grape composition, influencing the sensory characteristics of wine.
• Terroir recognition is based on consistent wine sensory characteristics over time, integrating historical and human factors.

Concepts of Terroir:

• The Bordeaux school defines terroir as an ecophysiological concept linking wine's sensory characteristics to its geographical origin.
• Terroir appreciation varies among consumers, ranging from experienced tasters to casual drinkers.
• Numerous factors contribute to terroir, including climatic conditions, microclimate, cultivar, yield, topography, soil properties, and the ecogeopedological milieu.
• The scale of these factors varies, affecting the precision of terroir identification and the cost of analysis.
• Technological advancements enable the mapping of viticultural terroirs at various scales, aiding in viticultural management and adaptation to changes such as climate change.

Physicochemical Factors – Water, Nitrogen, and Temperature:

• Water supply, nitrogen availability, and soil temperature are primary soil determinants of terroir.
• Moderate soil water deficits, controlled nitrogen supply, and optimal soil temperature timings are crucial for high-quality wine production.
• Management practices, including deficit irrigation and vine training systems, are adjusted to optimise terroir expression.
• The combination of these factors varies among sites, grape varieties, and vintages, highlighting the uniqueness of each wine terroir.

Physicochemical Factors – Soil Nutrients:

• While no direct correlation between wine quality and soil nutrient content has been established, soil nutrient management is vital for vine health and wine quality.
• Variations in nutrient bioavailability, vine nutrient demand, and climate fluctuations complicate the quantification of soil property–terroir relationships.
• Advanced analytical techniques are used to explore the relationships between wine composition, soil, and parent rock composition.

Microbiological Factors:

• Microbial terroir is an emerging concept focusing on the unique soil microbiome and its impact on wine characteristics.
• Research on natural yeast populations, soil microbial communities, and arbuscular mycorrhizal fungi (AMF) explores their contributions to wine terroir.
• Advanced genetic-based techniques are used to study the soil microbiome's influence on fermentation and wine sensory properties.

Other Questions:

• The influence of vineyard management on site terroir and the independence of soil–terroir relationships from vintage variations are areas of ongoing research.
• Climate change poses challenges to traditional wine terroirs, necessitating adaptation in viticultural practices and potentially altering consumer preferences.

Conclusion:

• Quantitative relationships between soil properties, vine phenology, grape composition, and wine sensory characteristics are still being explored.
• Future research may enable the manipulation of the soil microbiome to enhance soil quality and wine terroir.
• Despite technological advancements, the definition of wine terroir continues to rely on historical tradition, sensory perceptions, and evolving consumer preferences.

And here's the second paper: Taste, terroir, and technology By Roger Pinder from International Journal of Wine

Complex Interplay of Terroir and Taste:

• Recognises the established connection between wine flavour and the specific vineyard environment (terroir).
• Highlights the historical debate and emerging clarity brought by advancements in “neuroenology” and wine chemistry.

In-depth Chemical Analysis:

• Utilised advanced techniques like gas chromatography-mass spectrometry and selected ion monitoring to analyse wine composition.
• Found direct correlations between specific chemical components in wine (e.g., α-terpinene, limonene, α-pinene, eugenol, 4-methylguaiacol) and flavour profiles.

Regional Sensory Distinctions:

• Identified clear sensory and chemical distinctions between Malbec wines from Mendoza, Argentina, and California, USA.
• Noted that regional differences were more pronounced than variations due to vineyard practices like rootstock, vine age, or trellising systems.

Influence of Altitude and Winery Processing:

• Determined that altitude played a significant role in the chemical composition of wines, more so than factors like precipitation or growing degree days.
• Acknowledged the impact of winery processing on the wine's chemical makeup, sometimes overlaying the terroir signature.

Perception and Flavour Creation:

• Explored the concept that wine flavour may not solely reside in the wine itself but is also created in the brain through complex sensory, cognitive, and emotional processes.
• Suggested that terroir might not only be a physical phenomenon but also a perceptual experience, influenced by anticipation, sensory analysis, and post-ingestion effects.

Conclusion and Future Directions:

Concludes that the notion of terroir involves both tangible factors (soil, climate, altitude) and intangible aspects (perception, processing methods).

Notes:

1: As I'm proofreading my post, I feel what I mean by “scientific” is actually quantitative. 2: I was too linear in my thinking when linking the soil and the grape in my mind. 1 – 0 to Mother Nature. 3: That's going to be Part II. 4: I need to fine tune my hypothesis but I think we are the conduit for translating the environment to the grape (by influencing two fundamental factors: sunlight and access to water.)