Abstract/overview: The word and concept of "terroir" has come to represent winegrowing traditions and beliefs, some of which date back 7,500 years to explain how grapevines grow, what wine contains and why it tastes the way it does. Adherence to such beliefs (acceptance of something as true or real) and myths (widely held tradition, story, exaggerated or false belief) to explain winegrowing (the growing of grapes and finishing them to wine) prevents and/or hampers objective and open-minded investigation of grapevine physiology and wine sensory analysis (Matthews, 2015). Recently, "terroir" has been used as a marketing ploy (especially following the 1976 Paris wine tasting at which French judges determined that California wines were superior to French wines, in a blind side-by-side comparison). This essay provides a case study and peer-reviewed research into the effects of selected elements of "terroir": climate, soil , yield and vine spacing on grapevine performance. An application of sensory science, called 'descriptive analysis', used to explain how wine is perceived, is also presented.
A working definition:
Terroir (“tair-wahr”):
an ecosystem, in a given place, including many factors including: climatic
conditions, cultivar and rootstock, geography and topography, soil
characteristics such as mineral nutrition and water supply (Seguin, 1986)
In contrast to the Seguin's definition, many who try to explain or apply 'terroir' often resort to complex, contradictory, subjective opinions, relying on tradition, unsubstantiated intuition and antidotal observation. Since the 1300's, winegrowing Cistercian monks in Burgundy, France have been credited with the concept of terroir as a 'sense of place' that imparts uniqueness and 'quality' to a wine form a specific region or vineyard (Patterson and Buechenstein, 2018). But is 'terroir' a 'sense of place' or a concept, a culture, a soil-based production system, a marketing ploy or all of the above? Whatever it is, many winegrowers, writers, critics, sommeliers, marketers and consumers 'believe in it' and embrace it (Morris, 2018). Thus 'terroir' seems the antithesis of empirical science and many viticulture scientists's view of it is summed up in quote from Dr. Marcus Keller or Washington State University: "... the concept of terroir is mostly meaningless, because something that explains everything (in one word!) ends up explaining nothing." Nonetheless, many consumer attitudes and their wine purchases are based on a language of 'terroir'.
When one Googles the word 'terroir' many articles surface that provide many general 'terroir' categories, such as climate, soil, topography, grapevine genetics, human culture, and the microbiome of fermentation. Faced with these myriad factors, it is convenient to break 'terroir' into two broad realms: the physical, or vineyard site characteristics, and the sensory aspect of wine from a given site, Zoecklein (2019). Physical site characteristics with assigned numeric values, calculated as 'natural terroir units' (NTUs), are used in some wine regions to assign value or rank to vineyard sites and their wines (Table 1). From the NTU list we consider: climate, soil and yield. Both climate and soil have been amply documented to drive all vine performance (Jackson and Lombard, 1993) and yield is important across all agriculture endeavors.
Although
climate is presented as single entity in the NTU listing, as it affects
agriculture, inclusive of vineyards, climate is best understood on three
levels (Figure 1): ‘microclimate’, the climate within the grapevine canopy (or any plant
canopy), ‘mesoclimate’, within a particular vineyard,
farm or agronomic field and ‘macroclimate’ or regional climate, categorized as either
maritime or continental (Geiger, 1927, as cited in Patterson and Buechenstein, 2018).
|
CATEGORY
‘Natural Terroir Unit’
|
MAXIMUM VALUE
|
|
Location
|
600
|
|
Aspect
|
250
|
|
Altitude
|
150
|
|
Gradient
|
100
|
|
Soil
|
100
|
|
Microclimate
|
60
|
|
Varieties
|
150
|
|
Vine age
|
60
|
|
Vine density
|
50
|
|
Yield
|
150
|
|
Maintenance
|
100
|
Table 1. Physical parameters or Natural
Terroir Units (NTUs), used to classify a vineyard site’s ‘terroir’ and the wine it is likely to produce. Adapted from, Carey (2001).
Figure 1. Three levels of climate impacting plants/grapevines.
Next,
lets briefly consider soil and its role in ‘terroir’.
Notice that within the NTU list (Table 1) ‘aspect’ (compass direction) is ranked over
soil, despite soil's geology and proven agronomic impact on most all agricultural
crops. However, Van Leeuwen et al. (2004), elegantly investigated ‘terroir’ in Bordeaux, France by
comparing yield and berry composition of three vineyards, all exposed to a
similar climate and the planted to the same cultivar, Cabernet Franc, but, each
having a distinct soil type (Figure 2). Van Leeuwen et al. found that the soil’s water holding capacity, contingent
on its texture, was the factor with
the greatest effect on vine vegetative growth that indirectly impacted berry
composition, and finally, the wines from each site. In another soil-centric
study in Australia, withholding irrigation water
pre-fruit-set to veraison
(onset of ripening: grapes soften and develop color, flavor and aroma),
restricted vine uptake of nitrogen, and improved berry composition without
significantly reducing Brix level (sugar %) or yield (White et al., 2007). Unsurprisingly to
agrarians, these studies showed that water and its availability dependent on
soil type, along with the mineral nutrient, nitrogen, are the main drivers of plant
growth, including grapevines. These two components influenced by the vineyard soil, invariably and substantially,
impact the physical realm and result of ‘terroir’.
Figure 2. Percentage of clay, loam, sand
and gravel in the root zone of (A) gravelly soil, (B) clayey soil and (C) sandy
soil. (Van Leeuwen et al., 2004).
Next within the NTU list, consider that yield is assigned greater weight than
‘maintenance’, i.e., all viticultural operations:
pruning, leaf removal, trellis design, fertilization, cultivation, cover crops,
irrigation, and spraying. This ranking of yield over maintenance, is
interesting in light of the widely cited and classic paper by Jackson and
Lombard (1993), who review and explain the impact of site and viticultural
operations, i.e. ‘maintenance’ on grape composition and yield, without mention
of the word ‘terroir’. To this point
of maintenance or cultural impact, Dr. Mark Matthews, (2015) presents several ‘terroir’
‘beliefs’ that he classifies and
explores as ‘myths’ and then systemically debunks. One of these myths is: ‘high yield equals low quality’ and its
accompanying tenet: many small vines with
a small yield is superior to few large vines with greater yield.
I
have first-hand experience with this ‘tenet
of terroir’. As a vineyard consultant working in the humid, southeastern
US, I was presented with a vineyard planted to a ‘high-density’ European model,
with meter x meter vine spacing and ~ 4,400 vines/acre. Research based recommendations
for the eastern US at the time, were for a much wider row and vine spacing, with
~ 800 to 1000 vines/acre. The high-density planting presented problems: increased
fungal disease, low yields, poor quality fruit (reduced light exposure and
increased bunch rot), increased labor for: canopy management, mowing, spraying
and harvest as ‘normal’ tractors could not navigate the ~ 39 in. rows (Figure 3).
Figure 3. Meter x meter vineyards: Chablis
France (left) and North Carolina, US (right).
It was not
my personal opinion, but peer-reviewed research (Intrieri
and Filippetti, 2000) that informed my recommendation
that two thirds of the rows, and every other vine within a row be removed, to
achieve a ~9’x 6’ spacing and ~ 840 vines/acre. Fewer vines/acre actually increased yields (from 1 to 2 tons/acre
the next year) and quality, reduced operating costs, and refuted the low yield
= high quality ‘belief’. Obviously, this one case study does not explain the entire
concept of ‘terroir’, but it did shed
a degree of empirical light on one aspect of it…in that one place.
The
second realm of ‘terroir’: sensory
impact, has relatively recently been explained beyond the subjective, in a
classic paper by Dr. Ann Noble, the first woman food scientist at UC Davis. Dr.
Noble applied descriptive analysis and comparative statistics to compare and
differentiate wines (Noble et al., 1984).
|
Term
|
Composition of reference standard
|
|
Berry
(black/raspberry)
|
10 ml liquor from
canned blackberries, 2-3 thawed frozen raspberries, 5-6 g strawberry jam, 5-6
g raspberry jam
|
|
Black
currant (canned/ “Ribena”)
|
7-10 ml liquor from
canned black currants, 2-4 ml Sainsbury’s black current drink
|
|
Synthetic
fruit
|
5 ml cherryade (Corona drinks), 1 pear drop
|
|
Green
bean/green olive
|
4-5 ml liquor from canned
green olives, 8-10 ml liquor from canned green beans
|
|
Black
pepper
|
4 particles black
pepper (fine ground)
|
|
Raisin
|
10 raisins
|
|
Soy/
“Marmite”
|
0.5 ml soy sauce,
0.5-1 g “Marmite” yeast extract
|
|
Vanilla
|
0.25 ml vanilla
flavoring essence
|
|
Phenolic/spicy
|
5-10 ul 4-ethyl guaiacol
|
|
Ethanolic
|
5 ml (950 ml liter-1)
ethanol
|
Table 2. Aroma terms selected for the
descriptive evaluation and composition of the reference standards created to
define them (Noble et al., 1984).
Descriptive
analysis protocol required that a trained a panel of tasters assess (describe)
the wines (24 wines from four different Bordeaux producers) using commonly
discovered and agreed upon aromas and flavors, benchmarked with common
‘reference’ standards (Table 2). The wines’ quality was further compared by
certified Masters of Wine (MW). The
major differences between the wines was in variation of the intensity of the
‘green bean/green olive’ character and astringency and bitterness by mouth,
determined by canonical variates analysis (CVA). The wines did not differ
between producers and MWs were unable to differentiate the wine’s quality.
Recently,
wine writers and critics have taken to describing a ‘direct connection between wines and their terroir’, via the flavor
descriptor referred to as ‘minerality’ (Maltman,
2013). Despite the physical difference
between mineral compounds that occur
in soil, and mineral nutrients that
occur in grape juice and wine, many wine writers and winemakers, claim to taste
the vineyard soil in wine. A wine’s ‘minerality’
is not only ‘detected’, but celebrated! What exactly are they tasting? For
example, if the mineral nutrients of potassium, calcium or sodium actually
occurred at levels within the human sensory threshold and thus, were detectable
to the palate, they would likely be toxic! In this instance ‘minerality’ is a
subjective descriptor, not an actual measurable factor. ‘Minerality’ may well
exist…however, it is just not the case that actual mineral compounds are
absorbed by the vine’s roots, transported to the grape berries, directly
deposited in one’s wine glass and consequently are available and tasted as ‘minerality’ (Maltman, 2013). ‘Minerality’ then, as a descriptor,
appears well-positioned to occupy the tension between the physical and sensory
realms of terroir and that of unsubstantiated beliefs.
Obviously,
there is something going on with winegrowing, wine consumption and “terroir”. Terroir’s factors, as defined by Seguin at the beginning of this
essay, can be investigated and measured, wine is an agricultural product after
all. However, few agricultural products have gods dedicated to them, as
provided by the Greeks and Romans. There remains something unexplained about a
wine’s ‘terroir’, something akin to
Chinese acupuncture, or Polynesian ocean navigation, each of which is
documented to actually ‘work’ (Patterson and Buechenstein,
2018). ‘Terroir’ as an overarching
explanation of winegrowing seems to ‘work’ for many…and to those of us who
doubt, question, test and document…it extends an invitation of exploration and discovery
into what makes grapes transformed to wine so unique and special to us.
References:
1. Carey, V.A., 2001. The Spatial
Characterization of Natural Terroir Units for Viticulture in the Bottelaryberg-Simonsberg-Heiderberg Winegrowing Area. MS
Thesis, University of Stellenbosch.
2. Intrieri, C., and I. Filippetti.
2000. “Planting Density and Physiological Balance: Comparing Approaches to
European Viticulture in the 21st Century.” Proceedings of the
American Society of Enology and Viticulture 50th Anniversary Annual
Meeting, June 19-23, 2000 Seattle, Washington, 296-308.
3. Jackson, D. and P. Lombard. 1993. Environmental
and management practices affecting grape composition and wine quality—a review.
Amer. J. Enol. Vitic. 44: 409-430.
4. Maltman, A. 2013. Minerality in
wine: a geological perspective. J. Wine Res. 24:169-181.
5. Matthews, M. 2015. In, Terroir and Other Myths of Winegrowing.,
Univ. of Calif. Press, Oakland, CA.
6. Morris, R., 2018. Does terroir
matter? https://www.winemag.com/2018/11/13/does-terroir-matter/
7. Noble, A.C., A. A. Williams, and
S.P. Langron. 1984. Descriptive analysis and quality
ratings of 1976 wines from four Bordeaux communes. J. Sci. Food Agric.
35:88-98.
8. Patterson, T. and J. Buechsenstein. 2018. In,
Wine and Place., Univ. of Calif. Press, Oakland, CA.
9. Seguin, G. 1986. ‘Terroirs’ and
pedology of vinegrowing, Experientia,
42:861–873.
10. Van
Leeuwen, C., Friant, Ph., Chone, X., Tre’goat, O., Koundouras, S. and Dubourdieu, D. 2004. The influence of climate, soil and
cultivar on terroir. Amer. J. Enol.Vitic., 55:207-217.
11. White,
R., Balanchandra, L., Edis,
R. and D. Chen. 2007. The soil component of terroir. J. Int. Sci. Vigne
Vin. 41: 9-18.
12. Zoecklein,
B. 2019. What defines your wines? Wine Business Monthly, Dec. 62-69. www.winebusiness.com
Suggested
reading:
1. Keller, M. 2010. In, The Science of Grapevines: Anatomy
and Physiology., Academic Press, Burlington, MA.
2. Van Leeuwen, C. and G. Seguin. 2006.
The concept of terroir in viticulture. J. Wine Res. 17:1-10.
3. Van Leeuwen, C., Roby, J-P., and L. Rességuier. 2018. Soil-related terroir factors: a review.
Oeno-one. 52: https://oeno-one.eu/article/view/2208
4. White, R. 2020. The value of soil
knowledge in understanding wine terroir. Front. Environ. Sci. 8:1-6.
https://www.frontiersin.org/articles/10.3389/fenvs.2020.00012/full
