Busting terroir myths: The science of soil and wine taste

Me too. However, John said he thinks many dry Rieslings have very little aroma, and my experiences really don’t corroborate that. I’ve also had dry Rieslings and other aromatic varieties that have been made into surprisingly un-aromatic wines, but I do not find that many Rieslings are made into such style nor many dry Rieslings (no matter the style they are made into) have very little aroma. Some, yes, but from my experience they are a small minority.

And for example many Clare and Eden Valley Rieslings can be very lean and almost painfully austere, bordering on green, yet I haven’t noticed they’d be lacking in aroma department.

Interested parties are invited to pore over the following study evaluating the various terroir-affected elements in wines:

Oeno One, Vol. 54 No. 4 (2020)
“Recent Advancements in Understanding the Terroir Effect on Aromas in Grapes and Wines”

Cornelis van Leeuwen; Jean-Christophe Barbe; Philippe Darriet; Olivier Geffroy; Eric Gomès; Sabine Guillaumie; Pierre Helwi; Justine Laboyrie; Georgia Lytra; Nicolas Le Menn; Stéphanie Marchand; Magali Picard; Alexandre Pons; Armin Schüttler; Cécile Thibon
November 5, 2020

"Table 1. Effect of four terroir factors (air temperature, radiation, vine nitrogen status, vine water deficit) on aroma compounds in grapes and wines."

“Red colour indicates that the aroma compound (or family) increases with increasing terroir factor, blue colour that aroma compound (or family) decreases with increasing terroir factor. Grey colour indicates no effect was shown. In references in bold the terroir factor was investigated without interference from other factors. In references not printed in bold the effect of several factors cannot be easily disentangled (e.g., light and temperature in a leaf removal trial).”

I am not an environmental scientist. Nor am I an expert in biochemistry, botany, or wine production. Having said that, I have enjoyed perusing recent research articles on the influences of various factors on a finished wine.

Frontiers In…
Frontiers in Earth Science
, 06 November 2020
Opinion: “Unbiased Scientific Approaches to the Study of Terroir Are Needed!”
by Luca Brillante, Antonello Bonfante, Robert G.V. Bramley, Javier Tardaguila, & Simone Priori
"…According to OIV, 2010, which should be considered an accepted definition, terroir is a loose interpretation of a protected designation of origin (PDO), thus questioning the need for a wine-specific term. For example, in the regulation of the European Union (EC No. 510/2006 Art. 2.1(a), Council of the European Union, 2006), in order to benefit from PDO status, an agricultural product needs to:

i) originate and be produced, processed and prepared in the defined geographical area and

ii) have ‘quality or characteristics essentially or exclusively due to a particular geographical environment with its inherent natural and human factors.’

“The concept of geographical origin can be used in all crops and foods, and PDOs are defined and regulated. Conversely, the terroir interpretation applies mostly to wine and is not regulated, which leaves it open to abuse and self-assessment without control, scientific evidence or socio-historical recognition (Matthews, 2016). As a result, in the current popular use, the term terroir has erroneously become jargon for vineyard site.”

“…Reverse engineering of geographically designated products may be straightforward, but it is definitely harder to recreate the collective knowledge, the human and cultural aspects, which are crucial to the past but also the future developments of food.”

"…The science of grapes and wines risks entering a seIf-referential bubble if it does not acknowledge that other crops are doing the same with different names. It is important to keep in mind that what really matters is the idea that variability in the environment affects agricultural production. This variability can be identified and managed to smooth differences when the goal is uniformity and consistency across vintages or to enhance differences when trying to produce distinctive wines. This is possible only through the development of fundamental, objective and unbiased understandings of vine-environment relationships and their application through precision agriculture techniques. That is, both wine research and wine production should rely on science rather than myths. Accordingly, communication of terroir to consumers should be based on evidence. Such an approach can only reinforce the concept of terroir and ensure its persistence and utility, even in instances where this relates primarily to the marketing of wines."Article Link:

Frontiers In…
Frontiers in Environmental Science
, 17 June 2020
“Microbial Functional Diversity in Vineyard Soils: Sulfur Metabolism and Links With Grapevine Plants and Wine Quality”
by Stefano Mocali, Eiko E. Kuramae, George A. Kowalchuk, Flavio Fornasier, & Simone Priori

“The quality of the vineyard soils has a direct impact on grapes and wine quality and represents a key component of the ‘Terroir concept’. However, information on the impact of soil microbiota on grapevine plants and wine quality are generally lacking. In fact, over the last few years most of the attempts made to correlate soil microbial communities and wine quality were limited by overlooking both the functional traits of soil microbiota and the spatial variability of vineyards soils.”

"In this work, we used a functional gene microarray approach (GeoChip) and soil enzymatic analyses to assess the soil microbial community functional potential related to the different wine quality. In order to minimize the soil variability, this work was conducted at a ‘within-vineyard’ scale, comparing two similar soils (BRO11 and BRO12) previously identified with respect to pedological and hydrological properties within a single vineyard in Central Tuscany and that yielded highly contrasting wine quality upon cultivation of the same Sangiovese cultivar (BRO12 exhibited the higher quality).

“Our results showed an enrichment of Actinobacteria in BRO12, whereas Alfa- and Gamma-Proteobacteria were more abundant in BRO11, where an enrichment of bacteria involved in N fixation and denitrification occurred. Overall, the GeoChip output revealed a greater biological activity in BRO11 but a significant enrichment of sulfur-oxidation genes in BRO12 compared to BRO11 soil, where a higher level of arylsulfatase activity was also detected. Moreover, the low content of sulfates and available nitrogen found in BRO12 suggested that the reduced availability of sulfates for vine plants might limit the reduced glutathione (GSH) synthesis, which plays an important role in aroma protection in musts and wines. In conclusion, in addition to nitrogen availability, we propose that soil microbial sulfur metabolism may also play a key role in shaping plant physiology, grapes and wine quality.”
“Overall, these results support the existence of a ‘microbial functional terroir’ effect as a determining factor in vineyard-scale variation among wine grapes…”.

Article Link:

Research Topic Series:
“Biogeosciences and Wine: the Management and Environmental Processes that Regulate the Terroir Effect in Space and Time” (13 articles in series, including the above articles).

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South African Journal of Enology & Viticulture, Vol.35 No.1
“Effects of Weathered Soil Parent Materials on Merlot Grapevines Grafted onto 110 Richter and 101-14Mgt Rootstocks”

by J. Wooldridge; M.P. Olivier


"In a trial under semi-controlled conditions, Merlot grapevines on 101-14Mgt and 110 Richter (110R) rootstocks were grown in virgin soils developed in highly weathered parent materials derived mainly from granite and metasediment (shale). Each soil was irrigated at c. -0.075 MPa. The clay fractions of both soils were dominated by kaolinite. Lime and P were supplied, but no K. Bray II soil K levels from both parent materials were similar in the field state, but lower in the shale than in the granite when averaged over the trial period.

“Petiole K concentrations did not differ between rootstocks on the granite, but on the shale soils were higher in the vines on 101-14Mgt than on 110R. The granite x 101-14Mgt treatment significantly promoted (p < 0.05) greater trunk circumferences, cane mass, leaf areas and overall wine quality than the shale x 110R treatment. Yields from grapevines in the granite x 110R and granite x 101-14Mgt treatments did not differ significantly. However, the granite x 101-14Mgt treatment produced higher yields than the shale x 101-14Mgt and shale x 110R treatments. These differences were attributed to an interaction between the soil and rootstock, with K availability and uptake as contributory factors.”

Proceedings of the National Academy of Sciences, Vol.111 No.1
“Microbial Biogeography of Wine Grapes is Conditioned by Cultivar, Vintage, and Climate”

by Nicholas A. Bokulich, John H. Thorngate, Paul M. Richardson, & David A. Mills
January 7, 2014
Alternate Link: https://doi.org/10.1073/pnas.1317377110


"These results represent evidence that grape-associated microbial biogeography is nonrandomly associated with regional, varietal, and climatic factors across multiscale viticultural zones. As the most dominant and discriminant taxa between regions and varieties have well-characterized impacts on grape and wine qualities, these differences may help explain regional patterns in wine chemicosensory properties (29–33). Whether these regionally differential microbiota actually modulate wine sensory qualities must be experimentally tested, as do all putative features of wine terroir.

"This prospective study also reveals several promising applications for grapevine and wine-fermentation management, with the opportunity to develop tailored strategies for improving grape and wine quality of individual varieties and predictive models for microbial community responses to climatic conditions.

“These exploratory findings pose a paradigm shift in our understanding of food and agricultural systems beyond grape and wine production, wherein microbial communities play active roles in product quality characteristics. Elaboration of the interplay between production region, climate, microbial patterns, and quality outcomes may enhance biological control within these systems, improving the supply, consumer acceptance, and economic value of important agricultural commodities.”

Figure #2: “Varietal variation in bacterial (Left) and fungal (Right) communities of Zinfandel, Cabernet Sauvignon, and Chardonnay grape musts.”

"(A) LDA effect size taxonomic cladogram comparing bacterial communities in all Sonoma Cabernet Sauvignon, Chardonnay, and Zinfandel musts. Significantly discriminant taxon nodes are colored and branch areas are shaded according to the highest-ranked variety for that taxon. For each taxon detected, the corresponding node in the taxonomic cladogram is colored according to the highest-ranked group for that taxon. If the taxon is not significantly differentially represented between sample groups, the corresponding node is colored yellow. Highly abundant and select taxa are indicated: C, Citrobacter; E, Erwinia; G, Gluconobacter; H, Hymenobacter; J, Janthinobacterium; K, Klebsiella; L, Lactococcus; M, Microbacteriaceae; P, Pseudomonadaceae; S, Sphingomonas; U, Leuconostocaceae; X, Moraxellaceae; Y, Methylobacterium.

"(B) Weighted UniFrac distance PCoA of bacterial communities in all Sonoma Cabernet Sauvignon, Chardonnay, and Zinfandel musts.

"(C and D) One-way ANOVA of select bacterial (C) and fungal taxa (D) exhibiting significant differences between grape varieties. The x axes represent relative abundance (maximum 1.0). Bonferroni-corrected and false-discovery-rate (FDR) corrected P values are shown.

"(E) Bray–Curtis dissimilarity PCoA of fungal communities in all Cabernet Sauvignon, Chardonnay, and Zinfandel musts. (Inset) Same plot categorized by vintage. The x axis represents relative abundance (maximum 1.0).

“(F) LDA effect size taxonomic cladogram comparing fungal communities in all Cabernet Sauvignon, Chardonnay, and Zinfandel musts in all regions. Significantly discriminant taxon nodes are colored and branch areas are shaded according to the highest-ranked variety for that taxon. Highly abundant and select taxa are indicated: A, Aureobasidium pullulans; B, Botryotinia fuckeliana; C, Cladosporium; D, Davidiella; G, Rhodotorula glutinis; H, Hanseniaspora; M, Erysiphe necator; N, Sclerostagonospora opuntiae; P, Penicillium; R, Rhizopus oryzae; S, Saccharomyces cerevisiae; T, Lachancea thermotolerans; U, Aspergillus; Y, Cryptococcus; Z, Candida zemplinina…”.

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I saw that today Alan and first person I thought of was you. Interesting article. I’d like to talk to her. The article wasn’t that deep and from what I’ve read, I don’t think it proves/disproves anything discussed in this thread. It is more information that could be interesting though. I’m going to show it to a geologist friend of mine tomorrow and see what he thinks.

Just posted as an interesting read. I don’t think there’s anything controversially here. Things grow differently in different soils, the surprise would be if that wasn’t true. If she’s really the first to study soil, stratification, micro geology (my term) in different plots, hopefully she and her employers will start to put together links between different soil types and the end product. I suspect there are some growers who have done at least some of this kind of work already.

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Below is a study of non-Saccharomyces yeast found in vineyards across three Spanish appellations.

A survey of strains (and their respective isolates) found in four plantings was performed in order to quantify populations and their diversity over the span of several vintages.

Yeast demonstrate a capacity to influence wine quality from the earliest stages of production. It is essential to understand which genera/species of fungi will thrive in specific vineyards. Thus, “aiming to predict the most suitable application for the current non-Saccharomyces strains, as well as the potential future applications of new strains,” is a worthy pursuit.

Frontiers in Microbiology volume 7, 12
“Unraveling the Enzymatic Basis of Wine ‘Flavorome’: A Phylo-Functional Study of Wine Related Yeast Species”
by Ignacio Belda, Javier Ruiz, […], and Antonio Santos
DOI: 10.3389/fmicb.2016.00012

"Introduction: …This paper explores the knowledge established between the concepts of wine microbiome and microbial terroir, linking the phylogenetic data provided with the enzymatic characteristics determined in a wide yeast collection. These results have allowed us to establish a general enzymatic phenotypical characterization of several wine-related yeast species and their intraspecific variability, predicting the impact of yeast microbiome on wine flavor.

“Thus, since the wine microbial terroir has been defined as the distinctive autochthonous microbiome of a wine region and it has been experimentally demonstrated as a determining feature of wine qualities (Bokulich et al., 2014), this work provides a compelling basis to understand the influence of these microbial differences on the wine flavor identity, developing the new concept of wine yeast flavorome and also providing some of its enzymatic basis…”.

Related Research Papers:

mBio, March/April, 2015; vol.6, no.2 e02527-14
“The Soil Microbiome Influences Grapevine-Associated Microbiota”
by Iratxe Zarraonaindia, Sarah M. Owens, […], and Jack A. Gilbert
DOI: 10.1128/mBio.02527-14

Molecules February, 2017; vol.22(2): 189
“Microbial Contribution to Wine Aroma and Its Intended Use for Wine Quality Improvement”
by Ignacio Belda, Javier Ruiz, […], and M. Victoria Moreno-Arribas
DOI: 10.3390/molecules22020189

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