Thursday, April 06, 2006

Minerality: mythos and reality

Mineral notes in your wine - minerality, if you will - what causes it? Classic viticulture states plainly that it's due to the soil type your vineyard is situated upon. But is that true?

Mineral content of the soil is largely inconsequential to perceptions of 'minerality' in the finished wine. Take the variations in mineral content in Sonoma and Mendocino Counties for calcium (Ca)[8~23 ppm], potassium (K)[1~3 ppm], and magnesium (Mg)[1.5~16 ppm] from vine growing areas. At first we see what looks to be a rather large range of these minerals, but when looked at on larger scales aren’t very significant at all...

That calcium range, the largest of the 3 minerals mentioned, is just 0.008 g to 0.023 grams per kilogram of soil...which really isn't much variation at all, as well as being very low levels initially. How can such a small range for that mineral be responsible for such a large variation in the resulting wines? - the grapevines would have to be phenomenally responsive to those minerals, as would our taste buds (neither of which is the case).

Couple that fact with what has to be a very inefficient translocation mechanism of the minerals into the fruit, and you have even lower variation in the fruit than you do in the soil to start with. Also on point is that there are similar soil compositions in areas of Sonoma and Mendocino Counties which produce such different finished wines, in regards to minerality, that it leads one away from the (romantic) notion of soil as the defining factor in the finished character of a wine. This again is one of the reasons I feel that appellations based on prevailing climate are more important (read 'accurate') than those based predominantly on soil types (Tom, please forgive my love of the 'Sonoma Coast' appellation!).

Historically soil was linked to blood lines, nobility, ancestry & heredity, etc., and it was an easy extension to apply those ideas to wines as well...even though only anecdotal reasons were available to do so. (Witness the use of the term "Noble" varietals when discussing grapevines...more popular vines were thought to have better qualities, more 'pure' and 'noble' in nature than the 'coarse' 'common' varietals...)

The following is from Jamie Goode's
Wineanorak [2003 Harper's article] regarding the 'minerality' of the soil being deposited into the fruit:

...Scientific views of terroir
While in some circles it is quite common to hear such literalist explanations of terroir, they are treated with a degree of incredulity by many new world viticulturalists. I asked viticultural guru Dr Richard Smart what he thought of popular notions of terroir which propose direct translocation of flavour molecules from the soil to the grapes, and hence the wine [which is exactly what would have to happen for the 'minerality' of the soil to be tasted].
‘This is an absolute nonsense’, he replied. ‘I have never heard this, yet you say it is popular. Who on earth postulated this?’
[Damn, that quote just kills it! Think back again to the romantic notions of land and 'nobility'...hmmmmm, where could that idea have come from?]

Dawid Saayman, a South African viticultural expert known for his work on terroir, adds that, ‘I don’t believe that the minerals taken up by the vine can register as minerality in the wines. Minerality appears to me to be more the result of absence of fruitiness.’ But it’s pretty much a given that wines that [are] made from grapes differing only in the soil in which they were grown taste different.
[True, but what's not 'a given' is that those differences are soil derived...too many variables are involved for a fermentation to be reduced to just a difference in the soil...and this ignores the fact that if one splits those grapes harvested from a single block, picked on the same day, by the same people, and fermented by the same winemaker & crew into two tanks right next to each other, that more often than not they have somle differences between them...how can that be? Why aren't they the same? They were grown on identical soil under identical conditions, no? Also I think that minerality is not necessarily due to the 'abscence of fruitiness', but rather it's a subtle effect which is sometimes swamped by wines with more apparent fruit aroma...and is therefore easier to detect in less 'fruity' wines.]

So just what is the scientific explanation for these terroir effects? It is an important question, because providing a sound scientific footing for terroir is a worthy cause. Not only will it lend credibility to the concept in the eyes of sceptics [sic], but it will also help the already converted understand and therefore better utlilize [sic] terroir effects....
***


I just can't see the argument for soils affecting 'minerality' as a plausible explanation.
And unfortunately for terroiristas everywhere, if the soil portion of the terroir argument falls, then so a good portion of the foundation of the current definiton of what terroir even IS is weakened nearly to failure...

delenda est terroir...?

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7 Comments:

Anonymous Mithrandir said...

Before we can discuss the viticultural causes of minerality, we must first determine the chemical basis of the experience of minerality.

Is it really based on Ca, K and Mg? Is Na a significant factor? Cl? F? What about Fe, P or S? Or is it a complex organic molecule we're sensing?

This is, I'm relatively certain, known information, at least in some lab in New Jersey where they specialize in artificial flavors and purfume. I'd be surprised if you couldn't buy a bottle of artificial "wet stones" from one of these places.

Second, your statement that these differences in concentration are minor is pure bunk. We have factors of 4, 3, and 10 - an order of magnitude! Those are not small differences.

A vine is not a medium for simple diffusion: energy is expended to concentrate certain substances, and arrage them in certain ways. I assure you, the arrangement of these highly reactive elements in the reproductive organs of the vine is not random. Vines are not inefficient in transporting trace nutrients from the soil into the leaves and fruit: it is their entire purpose in life.

Do you actually have any scientific basis for this argument (sound bites don't count), or are you talking out of your ass the same way the "terrioristas" do?

April 06, 2006 12:47 PM  
Anonymous Dino said...

I agree with you that “tasting” minerality is unlikely and for a very simple physico-chemical reason. The vapor pressures of minerals are nil at ambient temperatures and pressures, you can’t taste them because there is no vapor to smell. Smell being the predominant sense involved in human perceptions of taste. The human tongue is rudimentary sense organ. Even if ionic calcium had a taste, it is unlikely that a human could taste it at the <25 ppm concentrations. Any perception of taste results from the pH of the salt in aqueous solution not any inherent taste. The physiology of taste is straightforward. The psychology of taste is something else. The human mind complicates the psychology of taste and at the same time is not consciously aware of the differences between the physiology and psychology of taste.

I am reminded of an incident at a local post office, some years ago. A clerk sorting the mail discovered a package, addressed to a local chemical company, was leaking. Soon the enter shift of postal workers was in the local emergency room complaining of headaches and nausea. I know of the incident because I was a chemist at nearby company, and the wife of one if my colleagues was an emergency room nurse, called into to help deal with the mass poisoning. The ER staff needed to know what to treat, now. It couldn’t wait for the company to figure out what the chemical was because lives could be at stake. While other ER personnel were running around conducting medical examinations, the wife of the chemist began asking, “What did it smell like? Could you ‘taste’ it?” It turned out the leaking sample had no perceptible order or taste. It was water. The company was in the business of providing water treatment chemicals. A potential customer had sent in the water sample for analysis. The physiological responses were induced by the psychological response. We perceive the taste of mineral because we have “smelled” them in nature, where they are the result of rotting organic matter. Still we think of it as smelling the earth.

So how does the “typicity” of great wines arise? How do you do the controlled experiments? No sane grape farmer would allow you to experiment with his vineyards (at least unless you paid him more than the going rate for the grapes). The best I can think of is to rank the independent variables by importance. That’s hard to do in Europe where the government regulations tell you what grape to plant, where to plant it, how to layout the vineyard, how to trellis and prune the vines, when to prune and pick, and what vintification practices are allowed. All this is overlaid with the Naturalistic fallacy, “The way things are is the way things must be,” and the Nativist fantasy, “The way things are is the way things always have been.” I think the clues are in France and especially in the 2004 vintage.

Let me begin with a caveat. I am not in the wine business; my tasting experience is neither systematic nor comprehensive. I am, however, a scientist (chemist) who was employed by a major corporation for thirty years. I was a problem solver. The one called in to figure out why a product, which had been oversold to management, wasn’t working like it should and figure out what could be done about it; essentially, to that product out of the laboratory and into the marketplace or kill it. So I think I can say that I know how to think clearly about problems and devise straightforward, robust experiments to get to the important issues. I also recognize that truth in the scientific sense is provisional. I have little doubt that much of what I say below will prove incorrect, at least for the reasons stated. But, hey, that is part of the fun in armchair speculation. All I need is a computer, a web browser, and an Internet connection to put my 2 cents in!

The salary and travel perks associated with my position allowed me to indulge my tastes in wine. I stumbled on Burgundies early on in graduate school, ca. 1970 and have been in their thrall ever since. Grand Crus from cote de Beaune could be had for $6 a bottle, but that princely sum also represented 2% of my monthly stipend. I haven’t spent that much on a wine since. That explosion of taste in your mouth and throat of a good pinot noir is one of the reasons I drink wine. Janice Robinson has called it “Tasting Pleasure.”

Over the last twenty years or so, there has been, to my palate, a perceptible improvement in the typicity (and quality) of village and country wines from regions such as Burgundy and the Rhone. What’s changed in that time? Certainly not the terroir of the vineyard. The age of the vines? Perhaps. The clones, the vintification techniques and technologies? Probably. A simple experiment, Domaine Leflaive began adopting bio-dynamic cultivation techniques in the late 1980’s. Have their wines gotten worse? Certainly not. Have their wines gotten better? Yes. Have they become transcendently good? Certainly not. The improvements can be accounted for by older vines, clonal selections, vilification techniques, and more rigorous selection of the barrels that comprise the cuvee (this is their Bio-Dynamic wine, after all).

Then came 2004, the experiment in the effects of climate on wine typicity in Europe. I buy a case of Raspail-Aye most every year, its my favorite Gigondas. I bought the 2004. Is it typical? No. Is it good? I think so. Chablis? Good? Yes. Typical? Not to my palate, the grapes are ripe! But Burgundy and Rhone brands will survive, at least until global warming has a large enough influence on the local climate to influence the behavior of the vines. That should happen first in Burgundy where there is no Ocean nearby to act as a thermal sink.

April 06, 2006 2:34 PM  
Anonymous Dino said...

Ah, the tyranny of low concentrations -- 1 mg/Kg (1 ppm) is 99.9999% something else while 100 mg/Kg is only 99.99% something else.

April 06, 2006 2:45 PM  
Blogger David Ogilvie said...

I come from a farming background and after studying viticulture and working in many wine-growing regions I have a hard time with the whole Terroir idea too. the character of "Minerality" in wine is a common descriptor and I don't doubt that something is in the wine that gives it that character. But I don't think it comes just from growing a vine on calcerous soil. Climate in my opinion has a much greater affect mainly through natural acidity and the perceptions of fruit foward flavors. Not only is the climate important but vine balance aswell. A well balanced vine is one in which the canopy and fruit ratio is balanced with the soil and climate. In vigorous fertile soils, cutting your Pinot Noir yields down to 2-3 tons/acre will give fruit that is unbalanced and giving too many green characters. Growing on Calcerous soil has its own "balanced" fruit character, maybe this is the "minerality" we taste.

April 06, 2006 3:29 PM  
Blogger St. Vini said...

Mithrandir ~

First, I’ll thank you for holding me to the same standards that I’d like others to strive for…so I’ll try this without any sound bites which are left hanging by themselves…

Mg, Ca, & K are indeed the major contributors to the mineral content of a wine. There are others present, but the phenomena is much more likely due to the level of organic acids (tartaric, malic and citric) in the fruit. As Dino points out, pH as well as acid levels play a part in the experience. He also points out
the difference in small concentrations really isn’t affecting the mineral perception – it’s still too damned low to account for the differences in wines – and even an order of magnitude isn’t significant in this case because we’re still so far from a level where it could plausibly make such differences.
I brought Ca, K, & Mg into the discussion because even as they are the principal constituents their range is too small to account for the vast differences observed in the final wines, thereby illustrating the fallacy of declaring that soils are primarily responsible for the perception of minerality.

Let’s back track a little: It’s been observed for decades now that ‘vintage years’ occur over large areas, not just vineyards with specific soils types. Those vintages are due to weather, and riper fruit. Quite a winning combination, at least by most accounts.

My comment about translocation was in refuting the idea that vines concentrate enough of the mineral components from the soil to produce the perception of ‘minerality’, and in that sense they are inefficient.

Dino,
Those were some well measured observations and an interesting story. Welcome!

David,
I agree that it’s got to be more than just a specific soil type (OK, like that wasn’t already apparent…), and I think it’s interesting to note that while the French proclaim the benefits of lime soils, and in some of the coldest growing areas this may have an ameliorating effect on the acidity of the fruit – especially if the vines are on their own roots. In any other than cold areas this view really doesn’t hold as well. However, the Italian view doesn’t really give lime soils too much special treatment.

Cheers!
Vini

April 06, 2006 11:27 PM  
Anonymous dino said...

There is a simple experiment you can do to understand what minerals in wine might taste like. The experiment is to drink some mineral water, either bottles or from a well (aka hard water) and compare it to a RO (reverse osmosis) bottled water (pick your favorite Brand) or softened tap water. The minerals in hard water (Ca, Mg, soluble silica, Fe and trace metals) are similar to the minerals in vineyard soil. They have a similar geological origin, rock, and their concentrations are similar because Ca, Mg, and some others have low solubility in water at neutral pH. The hard water has a taste, but I don’t get the sensation of minerality that I get from a good Chablis, for example. The taste is on the tip of my tongue, not the back of the throat and it can be unpleasant if there is enough iron in the water.

I think the minerality in wine is due to a mixture of aromas we have come to associate with “minerality.” An aroma derives from volatile organic compounds with a finite vapor pressure. Because is I said yesterday, the vapor pressure of minerals is nil at ambient temperatures and pressures and, therefore, there is nothing to smell.

April 07, 2006 10:22 AM  
Blogger Vintner said...

Ahhhh...it is so plainly obvious as to what causes minerality in wine to one who is trained in many sciences.

Have you ever thought that perhaps "terrior" has more to do with what isn't in the soil than what is?

Where do the boldest and notable wines in the world come from? Vineyards full of shale in Southern France, limestone rich soils in Burgundy, steep infertile hillsides of the Rhine and Mosel Rivers, or the poor tilth of the Rutherford District of Napa Valley?

The truth is all of the above. Where the soil lacks, the vine struggles and just like when we human beings are stressed we produce stress hormones i.e. Cortisol. In response we become irritable and may even gorge our selves into obesity. When honey bees are exposed to smoke they gorge themselves as well. This is simple stimulus response of a living organism to the environment. We see this in the research behind the origin of phytonutrients that may explain the health benefits of consuming wine. Q: Why do grapes grown in cool damp climates produce more Resveratrol? A: to fight off fungus. No need to do so in dry arid wine regions.

Minerality is not a literal expression of the obvious minerals found in the soil of a wine growing region. Why is it then expressed in the wine? Soil and climates effect on the grape and ultimately certain compounds produced by the grape or the lacking/additional nutrients present in the must. How the biological pathways (Kreb's Cycle) the yeast utilize for energy and protein synthesis ultimately builds a wine.

To make a “fruit bomb” of wine we use nutrient supplementation, antiseptic stainless steel fermenters, and cool ferment the wine with ideal conditions for yeast to only produce ethanol and CO2 not Hydrogen Sulfide and so on.

So consider this next time. Maybe it's what is not in the soil and conversely what is or isn't in the grape and as a result this ultimately defines "terrior"!

September 17, 2008 11:48 AM  

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