John Szabo’s Free Run – Digging for Minerality

By John Szabo MSAugust 24, 2015


John Szabo MS

John Szabo MS

There’s ample anecdotal and empirical evidence that soils affects the smell, taste and texture of wine. Scientists, however, still struggle to pinpoint exactly why and how these differences arise – the direct and indirect effects of soil chemistry on wine are challenging to identify and even harder to quantify with scientific certainty. It’s nearly impossible to isolate soil mineral content alone as the difference between the chemical content of wines, as the number of variables is staggering. But knowing empirically that soils play an important role, it seems impossible not to attribute and connect differing characteristics to a wine’s geological origins, sketchy science and all.

Under the umbrella of minerality, myriad geological formations such as slate, shale, schist, granitic, basalt, tuff, limestone, chalk, river bed and countless more have been called into action to explain the unique flavor profile that certain, invariably much admired, wines have. How else to distinguish the very good from the very best in an ever-increasing worldwide offering? Wines with minerality have a sacred link to their place of birth, presumably thanks to the special geology of their origins, and are thus more valuable than other wines. The trouble is, there’s very little evidence to support this. Yet scientists be damned. So far, their efforts to explain wine character have been as effective as the laws of physics have been to explain psychology. Minerality does exist, but perhaps not in the way you thought.

Defining Minerality

The main trouble with the term minerality is that it has no definition. There’s no consensus among either winemakers or wine tasters on what exactly constitutes minerality. Researcher Jordi Ballester at the Centre des Sciences du Goût in Dijon among others has studied the use of the term, and found widespread differences in a large sampling of tasters in when and how it was applied. For some it’s an aroma (flint, wet stones, riverbed, oyster shell, etc.), for others it’s a taste (salty, metallic, or a particularly vibrant type of acidity). Yet others claim to detect minerality in the texture of a wine, offering supporting terms like chalky or granitic, which evoke additional geological mental images.

What it Isn’t

What is abundantly clear is that minerality doesn’t exist in the literal sense. The above-mentioned characteristics don’t arise directly from geological minerals in wine, as nice and neat as that would be. Alex Maltman, Professor of the Institute of Geography and Earth Sciences at the University of Wales, is a well-known debunker of the minerality myth, and has written convincingly on the impossibility of actually tasting minerals in wine. “Whatever minerality is, it cannot literally be the taste of minerals derived from the vineyard geology”, he concludes. Minerals themselves have no taste. According to Maltman, the levels of even the most abundant elements in wine like calcium, potassium, sodium and magnesium are present at sub-threshold levels: “Potassium rarely exceeds a few hundred parts per million (ppm) with a few tens of ppm for calcium and magnesium… these are tasteless anyway and their concentration in wine are below sensory thresholds measured in water. In fact, the total inorganic content of wines typically ranges between only 0.15 and 0.4%”, he continues. Categorically, says Maltman, there is no direct link between rocks and wine flavour.

Professor Alex Maltman

Professor Alex Maltman excitedly debunking minerality at the i4c conference in Niagara this past July 2015. Photo credit: Steven Elphick (L) @TheWineSisters (R)

As he and others quite rightly point out, the aromas and flavours associated with minerality – seashells or gunflint or wet stones or whatever – are due to organic compounds, not the minerals these things are made of. But unlike, say, descriptions such as “vanilla” or “butter” or “green pepper” for which scientists have identified the main source compounds that cause these sensations in wine (vanillin, diacetyl and methoxypyrazines, respectively), the compounds responsible for “minerally” flavours aren’t as clear. Plenty of suspects have been put forth, such as volatile sulphur compounds derived from reductive winemaking (flinty, matchstick), or the esters formed by the interaction of alcohol and organic acids, or volatile thiols, the precursors for which are naturally present in certain grapes (such as Benzenemethanethiol (BMT) in sauvignon blanc, which apparently smells like gunflint). Of course none of these derive directly from soil. And logically, until everyone agrees on what minerality is, a single cause for it can’t be found.

So really, it’s time to redefine minerality. It doesn’t arise from a collection of measurable inorganic chemicals, sucked from rocks through vine roots and finishing up in a glass of wine to give it a special taste.

Metaphorical Minerality

But scientists have missed the point, missing the forest for all the trees. Minerality needn’t be taken so literally. All wine description is based on metaphor and analogy – there’s no other way to describe a sensory experience. And science is incapable of expressing such things in a helpful way. When a wine is described as floral or peachy, no one thinks for a moment that flowers or peaches were used in its production. Similarly, “minerality” and all its variations are helpful to describe and convey differences, and even suggest the quality associated with a distinctive personality, without implying that geological minerals somehow ended up in the wine.

Minerality is a useful umbrella term to describe wines that don’t fall into basic fruity, floral or spicy categories. There will probably always be multiple definitions. Its derivatives help further express even finer nuances. Used metaphorically, it’s as valid and useful at expressing the essence of a wine as any other descriptive term. Just be clear on how it’s used.

And Besides, Minerals do Affect Flavour!

Although the connection between a sensation of minerality in wine and vineyard geology cannot be literal and direct, we shouldn’t give up on minerals affecting wine flavor just yet. Not even Maltman closes the door on the role of mineral nutrients: “It may turn out with further research that the nutrient minerals of geological origin in vines and wines − minuscule in concentration and virtually flavourless though they may be themselves – are pivotal in determining wine character and flavour.” I know a thousand winemakers who would agree.

Citing just one of the possible ways in which minerals might influence flavour, Dr. Jamie Goode points out that it seems plausible, even likely, that varying concentrations of mineral nutrients could alter gene expressions in the vine, and hence the chemical composition of its grapes and the wines made from them.

I’d argue, contrary to Maltman, that there are cases in which elements like potassium, magnesium and iron do affect wine taste and flavour, and likely texture, too. In my travels and research for my upcoming book on wines from (invariably mineral-rich) volcanic soils, I’ve come across many examples of notably salty wines, my personal signature for minerality, a sensation too temptingly linked to particularly high levels of soil potassium. And I’ve seen the chemical analyses that also show shockingly high levels of potassium in the finished wines. Could the saltiness be potassium in its salt form, even if some would precipitate out during winemaking? It’s worth further investigation. (In some cases, admittedly, the salty sensation comes from run-of-the-mill sodium chloride from high water tables, or comes right out of thin air, deposited directly on grapes in seaside vineyards.) In another interesting twist, high potassium in soils is known to buffer wine acids and raise pH, yet the best of these wines remain fresh, thanks at least in part to their salinity – perhaps it’s that tangy, electric acid sensation that many associate with minerality.

Chemical analysis on Olivier Humbrecht’s masterful Riesling Rangen de Thann Grand Cru from Alsace, a “terroir” wine if there ever was one, also had measurably more mineral ash (sugar-free dry extract) than rieslings from his other sites. Is the wine distinctive? You bet. Does the mineral ash play a role? Unquestionably.

The influence of soil chemistry is surely complex and circuitous and much research is needed, but in the end “minerality” makes its contribution. There’s simply too much evidence to ignore. All those winemakers and wine tasters claiming that the geology influences flavour may one day be scientifically vindicated after all. But in the end, who cares. Let’s just go and have a glass of singular, minerally wine.

Szabo’s Guide to Minerally Wines:

Maximin Grünhäuser Herrenberg Riesling Kabinett 2012

Benjamin Bridge Nova Scotia Brut 2009

Benjamin Bridge Nova Scotia Brut 2009, Gaspereau Valley, Nova Scotia, Canada – Yes, Nova Scotia does minerality, especially in the careful hands of Benjamin Bridge, one of Canada’s most serious bubbly producers. Each year the vineyard team turns in grapes with the sort of analytical numbers that are dreamed of in champagne. Even this, their non-reserve brut, has surprising weight and even a touch of fat – call it vinosity – to soften the stony impact.

Maximin Grünhäuser 2012 Herrenberg Riesling Kabinett, Mosel, Germany – A dazzling Mosel Kabinett from arch-traditionalist Maximin Grünhäuser, barely off-dry but balanced by crackling acids, driven more by honey-slathered wet slate than mere fruit. Best 2015-2027.

Argyros 2014 Santorini Assyrtiko, Greece – A superb Santorini, bone dry with electric acids, and a finish that shows the future salinity that will dominate this wine in time, in another 1-3 years, along with the ash taste that marks so many volcanic wines.

Domaine Laroche 2013 Chablis Saint Martin, Burgundy, France – Regionally accurate and representative wine here from Domaine Laroche, on the broader side of the Chablis spectrum, fullish and ripe, but still sufficiently tight and minerally to satisfy purists.

Domaine Drouhin 2012 Pinot Noir, Dundee Hills, Oregon, USA – A fleshy and fullish, well-balanced and generously proportioned pinot noir from the iron rich, red volcanic soils of the Dundee Hills, with distinctive sanguine tang and salinity.

Argyros Santorini Assyrtiko 2014 Domaine Laroche Chablis Saint Martin 2013Domaine Drouhin Pinot Noir 2012Aglianico del Vulture Elena Fucci Titolo 2011Fontanafredda Barolo 2010

Elena Fucci 2011 Aglianico Del Vulture Titolo, Basilicata, Italy – Titolo, the sole wine made from Fucci’s 6 hectares – among of the highest and oldest vines on Mount Vulture, an extinct volcano – is an extraordinarily dense and complete wine, with a staggering streak of iron-graphite like minerality and palpable saltiness. Don’t touch for several years. (The equally excellent 2012 is available in consignment in Ontario through Le Sommelier).

Fontanafredda 2010 Barolo, Piedmont, Italy – A terrific buy for Barolo fans, and indeed for fans of all savoury, firmly structured, minerally, complex and succulent reds. This is the best yet from Fontanafredda.

Bonus Round

I asked several Oregonian winemakers for their thoughts on minerality. Here are a few of the more interesting answers:

“I use the term minerality to describe aromas and tastes that remind me of rock (flint, chalk, crumbled stone). Unlike “earthiness,” which is deeper in tone, minerality is a high note that is often accentuated by a resonant “electricity” in the wine, often (but not always) related to the acid backbone.” – Anthony King, (formerly of Lemelson Vineyards)

“It smells like minerals/stone. Sometimes it is almost dusty and sometimes it smells like the first rain on dry rocks. Elusive. Am aware of a growing number of voices declaring that there is no such thing. I think that there is-I can smell it and I know what minerals and rocks smell like, but like so many words, it has been overused ad nauseam. There is no way words can accurately describe this quality.” – Kelley Fox, Kelley Fox Wines

“One aspect of complexity is certainly minerality, though I admit that the word is probably used to describe many different things.  Some sites are generally fruit-driven, but many of our vineyards show earthy aromas and flavors that range from dark, loamy earth to wet stones.  We tend to use the word minerality to describe the more ‘wet stone’ style of earth.  We see it in many varieties, usually from volcanic sites. It seems to be more than just an aroma or flavor.  At its best, it seems to also be part of the structure and texture of the wine, a quality that you can feel as well as taste.” – Dave Paige, Adelsheim

Keep digging.

John Szabo, MS

John Szabo, Master Sommelier

NOVA 7 - The Toast of Nova Scotia

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