Olivier Humbrecht

In part one of his presentation on minerality, Oliver Humbrecht said what minerality is not, and explained the need for a soil full of microbial life to bring the mineral fraction into contact with the organic fraction of the soil. Plants need minerals to grow properly.

Will this mineral fraction give a taste to the wine? “I can’t answer that” he said “this is a subject for the next few decades. It’s very hard to say that because your soil has this mineral fraction, its wines will taste more complex.”

However, “finding a wine with a high mineral content is always a sign of a soil that functions properly and a sign the vine is capable to transfer these minerals from the soil.”

Humbrecht explained that the extraction and transfer is done by different microorganisms in the soil. “A vine that has a high mineral extract also has mycorrhizae on the roots functioning perfectly, able to absorb those minerals.

“So minerality in a wine is a sign that the vine is working properly. But it’s a dangerous statement to [suggest] minerality affects the taste of the wine in terms of flavour. We don’t have the research to clarify that.

First steps, he said, are that “you must learn to recognise minerality on the palate. This very small amount of minerals may not smell of something, but they will taste. Very often it’s associated with acids in the wine especially tartaric. And it will modify the structure of wine in terms of acidity, pH, salinity of wine. A wine with a high mineral content, with lots of ashes, will for sure be a wine that makes you salivate.”

Part of this learning is to avoid confusing “true minerality or true salinity with green acidity.  People have to learn how to distinguish. A big mistake is to confuse unripe characters with actual salinity/minerality.”

Root activity is key to understanding minerality, he said. “Everything in non-organic cultivation favours the development of the green parts of the plant [branches, leaves]. It neglects the root activity and flowering process.” So when you increase the vegetative part of the vine by augmenting photosynthesis, you diminish the importance of root activity and dilute minerality.

Checking to see if a vineyard is managed properly can be done by digging a hole and cutting a piece of fine root.  Under the microscope, Humbrecht said “in vineyards with good organic metabolism, you find lots of mycorrhizae, like a veil of white mushroom filaments. These mycorrhizae are in symbiosis with the roots, using vine sap to satisfy their own sugar and carbohydrate needs.  And they help to degrade the soil around the roots, liberating minerals” in this zone.

But when mycorrhizae are not working properly, for example where soil is compacted or where chemicals have been used, he said, fertilisers are needed so vines get the minerals they need.

Whether your mycorrhizae are working properly or not, all soils are not equal in the minerals stakes. “Not every soil has the capacity to produce high quality clay” he said “and therefore have the capacity to fixate minerals in the soil.

“You can measure the mineral capacity fixation ratio.  It depends on the capacity of the mother rock to degrade into particles small enough. Limestone, calcareous [soil], schist, marl, ferruginous clay and basalt are all soils that have this capacity to produce these interesting elements. But some soil types do not have the capacity to produce minerals and these are usually sandy soils, sandy loam, silt, gravelly soils that are not mixed with marl or richer content.”

Grape varieties, too, can influence the sensation of minerality. Humbrecht said “probably there is an inference that varietal aromatics of a wine can hide minerality. I often say that minerals don’t smell. But some aromatics are often associated with a mineral quality. For example iodine is a volatile compound so you can smell iodine.  If I smell iodine it brings a notion, an association, of minerality to my mind.  But you have to teach your brain not to fall into certain traps, the most common one is not to associate reductive character in wine with minerality or unripe character such as high malic content.“

On the question of high alcohol and lots of new oak, Humbrecht said “anything that detracts from the fundamentals of the wine may hide the minerality. New oak, a very aromatic grape variety: for example many people say riesling is more mineral than gewürztraminer but this is because we look at things from the aromatic point of view. Yet once you dissect the taste, not the flavour, on the palate, you understand what makes you salivate. It’s a tasting exercise.”

He reiterated “minerality is not acidity. Acidity is not minerality”. However biodynamic practitioners report a rise in analytical acidity, anything from 0.5g/l to 2g/l, though it’s still not fully understood why this happens. Humbrecht did say “wine is based on tartaric acid, a strong acid, with two acid radicals which each can combine with minerals. [Biodynamic growers] have seen a change from malic-dominated wine to tartaric-dominated wine, and tartaric acidity is capable of fixing more minerals which are in the wine.”

So minerality is by no means a preserve of biodynamic producers, but the inference is that they get more of this elusive palate sensation.

Olivier Humbrecht

In London earlier this month, Olivier Humbrecht, of Alsatian Domaine Zind-Humbrecht, discussed minerality in wine.

His presentation was part of a tasting of biodynamic wines from members of Biodyvin Syndicat International des Vignerons en Culture Biodynamique, the organisation of which Humbrecht is president, though his discussion was not uniquely about minerality in biodynamic wines.

He kicked off by dispelling some commonly held mis-perceptions: “for most people minerality is reductive, or a certain green flavour, it doesn’t taste fruity or floral, and you end up calling the wine ‘mineral’. Minerals don’t smell.  If stones, or water, or salt smell of something, it’s because it’s associated with an organic compound that is volatile.”

The organic compound commonly associated with minerality is sulphur, about which he said “sulphur is a very broad component in nature, it’s found in very many organic molecules. It smells a lot.  At worst, think of wet dog, mercaptan, H2S.

“These sulphur compounds can be linked into more complex molecules, not smelling obviously like sulphur, and these elements might be associated with some kind of minerality. And the most common mistake is to associate reductive character with minerality. [Another mistake] is to associate certain forms of organic acidity with minerality, if the wine is tight, with green acidity.  All these are not minerality.”

Minerals are present in soil, coming from the degradation of rock by erosion, weathering, frost action, as well as the activity of microorganisms, all of which break down larger particles to smaller particles.  When the size of these particles is smaller than two microns, it is called clay.

Humbrecht said “the finer the structure, the more it can trap minerals in the soil. And minerals are necessary to the plant. But will the minerals in the soil give a taste in the wine, that is questionable” though he did say “the mineral fraction in the soil will be represented in the wine as a mineral fraction.” And it is this that is interesting to analyse in a wine.

“Often people analyse minerality of a wine by analysing dry extract, or reduced dry extract” he said. “This consists of evaporating all the liquids, then burning all the organic elements. Or by calculating the reduced dry extract.  It’s good to have a high reduced dry extract as it shows wine is more concentrated.

“But the organic fraction of a wine is expendable, according to physiology of the plant – you can easily have more sugar, more organic acids, as the vine continues to function. [Dry extract] is something the vine is continuously producing, so it can change with time. It can also be altered if you acidify a wine or add sugar to a wine.

“So when we talk about minerality we should talk about the ashes. Take a wine and burn it till you have only dust left. You end up with few milligrams of dust which directly comes from the earth. It’s the only solid fraction in a wine that you can directly link to the earth, everything else comes from photosynthesis – 99.9% of wine is made from heat, air and light.

“The fraction of minerals is a very, very small quantity. Whether the wine is very acid, or high or low alcohol, it doesn’t really change the mineral fraction.”

And, he added “we don’t analyse the mineral fraction in a wine very often because it’s very expensive. But it’s the best way to see if a wine has been produced from a high or low yield.  The reduced dry extract could be the same for a wine made from 25 or 100hl/ha, but the mineral fraction will be divided by 4.”

Digging deeper into the issue to understand the soil, Humbrecht said “a soil should be able to feed a plant without doing anything. For us having a living soil means having a soil that is able to supply all that the plant needs at different moments in the year. And this is something modern agriculture has forgotten.” He spoke of forests that have survived centuries in a sustainable fashion without man’s interference in the form of soil additions, be they fertilisers or chemicals.

But even biodynamic producers add composts to their soils. Humbrecht said “it’s not really to bring fertilisers to the soil, but to bring something alive, microorganisms, and the elements of humus to stabilise the mineral fraction in the soil and bring energies to bring back harmony into our wines.

“We want our soil to be alive, with worms, fungus, micro-organisms, everything it takes to allow the mineral fraction to combine with organic fraction in the soil. If you don’t have this link the soil will fall apart” for example being eroded after rain, or compacted from repeated machinery passes.

This is so important, he said “because the very small mineral fraction is absolutely necessary for the vines to grow properly.”

Will this mineral fraction give a taste to the wine? Find out what Humbrecht said in part two.

Fred Pizzini, proprietor of Pizzini Wines, King Valley, Victoria, October 2010
“Flavours of the earth. Acidity steeliness, with maybe some phenolics.”             

Katrina Pizzini, co-proprietor of Pizzini Wines, and runs cooking classes at the cellar door, on minerality in food, October 2010
“kangaroo meat; salt bush lamb. It makes you salivate; metallic, mineral salts without being salty. Moist.”

Keppell Smith, proprietor of Savaterre, Beechworth, Victoria, October 2010
“a tactile sense in your mouth. A clean, slatey, non-cloying sensation, different from straight acid. You get it more in pinot noir than chardonnay. Almost like a bit of bitterness in our wines which gives a savoury character, makes them nice with food.

“Everyone’s jumped on the minerality gravy train.  But you can taste it. It’s definitely not acid, but it’s linked with acid.  It’s something of terroir. It‘s not something you have a choice about it. You can’t make minerality in a wine. It’s slightly metallic.”

Ron Laughton, proprietor of Jasper Hill, Heathcote, Victoria, October 2010  
“Minerality doesn’t mean salt. It’s a descriptor about the earth itself. Emily’s Paddock has a creaminess about it, not minerality.  Minerality is earthiness. Georgia’s Paddock has mineral-ness. Different stones have different flavours, rocks are not totally inert. Maybe I’m swayed by knowing there’s a difference, there’s a major difference in the subsoil. Minerals are expressing themselves in a different way.”

Alan Cooper, proprietor of Cobaw Ridge, Macedon Ranges, Victoria, October 2010
“A lot of minerality is acidity; natural acidity. Sure it’s coming from the soil, it’s the whole combination of terroir.”

Roger Harris, proprietor of Brindabella Hills, Canberra District, New South Wales, October 2010
“Minerality is backbone in riesling; a combination of acidity and phenolic characters in the grape – firmness, tightness.”  

Ken Helm, proprietor, Helm Wines, Canberra District, New South Wales
“Minerality from volcanic ironstone. Minerality is clean, fresh, it exhibits characters of the vineyard.  A ferruginous minerality.  Minerality is a balance, no element stands out.”

Michael Walker, winemaker, Faisan Estate, Orange, New South Wales
“Acidity gives a crushed rock, flinty minerality.”

Plus one contribution from
Louisa Rose, chief winemaker, Yalumba, Barossa Valley, South Australia, November 2010, in London. 
Minerality is “a textural thing, a dryness to the palate. It can look a bit like phenolics. It’s a pebbly, wet stone texture.”  

My research visit to Australia in October 2010 was sponsored by Wine Australia.

Minerality in wine is one of the trendiest tasting terms of our times. Science is establishing that it does exist, at least sensorially, but identifying potential responsible compounds or complex of compounds working in combination, and that can be chemically analysed, remains elusive at best.

No minerality directly from rock

Professor Alex Maltman of the Institute of Geography and Earth Sciences at the University of Wales, Aberystwyth explained: firstly “there is a whole series of complicated ways in which the parent geological minerals decay to yield nutrient minerals”, and “for roots to pick up nutrient minerals, such as potassium and calcium, these elements have to get into solution. Then there is a whole series of complicated ways of those elements getting into the vine roots – a complicated series of distancing reactions between geological minerals and getting nutrients into the vine.

No route from root to wine

“When you start making wine, yeast takes some of those nutrients from the fermenting must, making the connection between mineral nutrients and geological minerals even more remote and complicated.”  He added “whatever minerality is, it is not these elements that ultimately came from the vineyard. They’re last in all the things that give wine its flavour.”

With minerals comprising just 0.2% of wine, Maltman said you cannot taste the minerals, especially with all the organic compounds that do give wine its flavour.  

Semantic confusion

Though, Maltman explained, “I’m not saying the taste attribute doesn’t exist in wine. But it’s given the label that gives a connotation of origin, of coming from vineyard. People used to talk of austere, lean, steely, even. As soon as people say minerality, people assume minerals are in the wine.“

To geologists minerals are complex compounds – collections of minerals/elements bonded together, such as feldspar. To nutritionists minerals are single elements – zinc, calcium, potassium.  To wine people minerality seems to elicit a direct causal link with vineyard rocks despite this being an untenable thesis.  All of which creates confusion: of description, of accuracy, of communication.  This is not to say that soil, geology, drainage and water holding capacity are not important influences on the flavour of wine.

Mosel slate

Which leads us back to minerality by association: this is Mosel riesling therefore I’m tasting slate’ or ‘this is Sancerre therefore I’m tasting gunflint’.  Minerality has relatively quickly become a literal and emotive ‘beam-me-up Scotty’ of rocky allusions which create vinous illusions.

Winemakers’ words

Even winemakers worry for words when trying to explain the ‘minerality’ in their own wines. The ‘reductive’ sulphide connection is often mentioned, as well as other perceptions – a palate texture, tension, tautness, a tingle on the tongue, a cleanness, purity and freshness, an integrative feeling.

Dr. Tony Jordan, of global consultancy Oenotec, said minerality is a “taste sensation. People have talked the talk in the last ten years. It’s one of the buzz words, everything has to have minerality. I tend to associate it with wines that have a finer, tighter, long flavour spine, good spice,  that have a distinct play of acid in the balance; occasionally an effect of sulphide, and may even be other chemistry in the wine, both organic and inorganic components.”  

This relationship with acidity is a common thread. Martin Aurich, general manager of Weingut Unterortl in Italy’s Alto Adige said: “minerality is a certain amount of acid, acid which is not sour; a positive acid which requires another sip. It’s like a game in your mouth – acid, tannin, sugar.”

Bevan Johnson, managing director of family winery Newton Johnson in South Africa described minerality as “the poise of the finish. It brings a freshness from the mid palate to the finish; a freshness that’s not just acidity. A harmonious finish that’s fresh.”

Pfalz basalt

And Ernie Loosen, of the Mosel’s Dr. Loosen, was emphatic, saying “minerality always has something to do with acidity. Acidity expresses minerality, just as sweetness brings out aroma structure in our wines; as alcohol carries the aroma. A wine without acidity doesn’t show minerality as strongly as wine with the right amount of acidity.”  

At Loosen’s JL Wolf estate in the Pfalz, when they taste the wines blind “with its black basalt soil the Pechstein is the most mineral driven. It is more grippy, with a stony edge.  The Ungeheuer, with its loamy, weathered sandstone soil, is softer even with the same analytical acidity. Minerality is the acidity and soil together. At the end of the day you can only describe minerality by tasting it.”

Cooler climate

If the acidity thesis gains ground, must minerality be a cooler climate phenomenon?  Loosen said he saw less minerality in the hot 2003 than the classic 2007 German vintage.

Climate change specialist Professor Gregory Jones, of the geography department at Southern Oregon University, agreed, saying “grapes grown in cool climates tend to express themselves differently than those grown in warmer climates. Also, cool climate wines are much more likely to be single variety wines than the blends we find in warmer climates. Single variety wines grown at or near their cool climate margin will always show more finesse and character than those grown in warmer climates. A good example is chardonnay, which is grown in cool to fairly warm climates. In a warmer climate there is less finesse and more need for oak to bring out other characteristics. Also a good test is to try the chardonnays grown in the same region in a cool versus a warm vintage … the warm vintage will lack the supposed ‘minerality’ and finesse. So climate does play a role.”

Priorat schist

But what about places such as Priorat, where notes of minerality/graphite are commonly reported in the wines?  This is a warm to hot Mediterranean climate where big, alcoholic, blended reds are made. In his inimitable style, Alvaro Palacios of his eponymous Priorat property said “minerality is exactly as you see in the slate or granite soils. There are huge levels of minerals and metals. When you lick them you can feel that. Vegetal tannins are normally very fat, and mild, gentle, soft. Minerality is different; something tiny and vertical that dries out, micro particles.”

Over at Celler de Capçanes, in neighbouring Montsant, winemaker Jürgen Wagner upheld the acidity paradigm, saying “minerality adds some astringency. It gives a feeling of a higher level of acidity. It is a certain saltiness, the graphite of lead pencil for me means nerviness, liveliness, even astringency.”  

Scientific speculation

All of which means we are left with supposition and suggestion.  Jones suspects “there are chemical pathways via fruit to wine transformation that create aroma/flavour components that spark sensual characteristics that lead us to our cues of certain, remembered qualities.”

Maltman makes it clear he doesn’t know “what minerality is actually due to. I think acidity in wine is relatively well understood so I’m not sure it’s primarily that; my guess would be some combination of organic compounds (secondary metabolites), possibly, as has been suggested, involving sulphur” adding “complex organic molecules could be influencing minerals, promoting some, and buffering others. The effect could be important. I’m saying you cannot taste vineyard minerals. But these tiny amounts could have a chemical role. “

But we are left with more than poetic allegory. Jean Trimbach, of Maison Trimbach in the Alsace, said: “It is there. It exists. It’s the philosophical part of the wine; the most intellectual part of the wine, which has yet to be better analysed, and quantified.”  

Wine needs the scientists to get a hurry-on, so we can use the term correctly and consistently as a meaningful communicator of wine quality, composition and style.

The first article looks at where the scientists are at with minerality.  The second one speculates scientifically, if such a thing is possible.

What follows are some thoughts of winery people I have quizzed on my various research visits, along with dates, so the comments can be put into the perspective of our evolving knowledge on the subject of minerality in wine.  These comments are unfined, unfiltered, uncategorised, not that we yet possess the knowledge to categorise minerality.
 

A few developing themes, make of them what you will, not all highlighted in the following quotes, include

• linking minerality and acidity.
• linking minerality and ageworthiness.
• linking minerality and (bed)rock.
• linking minerality and complexity.
• linking minerality and freshness.
• linking minerality and tannin.
• linking minerality and terroir.
• suggestions that not all grape varieties have the potential to express minerality.

Olivier Humbrecht, Domaine Zind-Humbrecht, Alsace, France. November 2009
“You cannot smell minerals as they are not volatile. Salt is associated with other molecules, for example iodine, which is volatile.  Minerality is more a palate sensation than an actual smell.  If a wine is going towards more undergrowth, earthy, it goes to more mineral. The brain does not associate fruit with minerality.”

Minerality “leaves your palate more salty than sweet. And it’s more difficult to see it on sweet wines than dry wines, as sugar will hide it.  Also the tannins of oak will cover or overpower a sense of minerals on the palate.”

It’s a “sensation on the palate.  You can also sometimes detect it in a way of pH. Acidity potential might reflect how minerals have reacted with the wine.  A higher pH, if not caused by a fault, such as rot or dilution, for me, is that soil is more present in the wine. The more minerals in the wine, pH increases.”

Wolfgang Klotz, marketing and sales manager at Cantina/Kellerei Tramin, Alto Adige, Italy, November 2009.
“If I smell stony, chalky, and stones banging together, and the wine is dry and crisp, this I think of as minerality.  The topsoil is chalky, and 1-2 metres below is volcanic porphyry.  Porphyry gives lot of minerality. You could age wines up to ten years and more.”

Klaus Gasser, sales director at Cantina/Kellerei Terlan, Alto Adige, Italy, November 2009.
The mountain “Tschögglberg is porphyry, a quartz porphyritic rock, high in minerals, with a high silicate concentration, like in Pouilly-Fumé with silex. There’s a high mineral concentration in the soils. Minerality in the wines is a salty note, and great ageing potential.”    

Martin Aurich, general manager at Weingut Unterortl, Alto Adige, Italy, November 2009.
“Minerality is a certain amount of acid, acid which is not sour; a positive acid which requires another sip. It’s like a game in your mouth – acid, tannin, sugar.”

Franz-Joseph Loacker, sales manager at Tentute Loacker, Alto Adige, Italy. November 2009.
“Minerality comes from the stones and from the power of the soil, from the terroir, and what we have in the soil. Some grapes such as sauvignon blanc have minerality; other grapes do not, such as gewürztraminer, which goes more in the sweet direction.”

Willi Bründlmayer of Weingut Bründlmayer in Kamptal, Austria, June 2009.  
“In spring, the terraces are soaked with rainfall. Water remains hidden in clefts of the rock, and takes up minerals. Vine roots need water. But the taste is something different.  For me, the wines are not too alcoholic, they lack creaminess and softness. I feel a slight roughness, a substance and structure but different from the substance and structure tannins give.”

Hannes Hirsch of Weingut Hirsch in Kamptal, Austria, June 2009.
“Minerality is like an extra layer of Maldon sea salt, which bubbles and explodes on your tongue. Heiligenstein has a smokey nose, like banging stones together.  As grüner veltliner  and riesling wines get more powerful, they lose their fruit definition. Minerality comes through as a tension on the tongue.”

Andi Kollwentz of Weingut Kollwentz-Römerhof in Burgenland, Austria, June 2008.
“Minerality comes from the soil but it’s not a chemical influence, it’s a physical influence, it’s stoney. If you get the grapes in the right state, and you don’t interfere with the wine in the cellar, you get an impression of minerality: fine, fragrant fruit, but not bold, and a spiciness, not from oak.”

Alvaro Palacios of Alvaro Palacios in Priorat, Spain, April 2009.
“Minerality is exactly as you see in the slate or granite soils. There are huge levels of minerals and metals. When you lick them you can feel that. Vegetal tannins are normally very fat, and mild, gentle, soft. Minerality is different. It’s something tiny and vertical that dries out: micro-particles. It’s a blend of tannin and minerality.”  

René Barbier of Clos Mogador in Priorat, Spain, April 2009.
For Barbier, minerality “is all to do with terroir.” Of his Clos Manyetes wine, he said the “wine is built on the basis of terroir; the minerality and tannins are interwined. When wine is created on a more technical basis, the tannins are clearly defined. With terroir and minerality the tannins are intertwined.”

Sara Pérez of Mas Martinet in Priorat, Spain, April 2009.  
“Minerality in Priorat is complicated to understand sometimes. Minerality is all the aromatic components of the soil – liquorice, iron, non-organic things that you can find in wine. You never have liquorice or iron on calcareous soil. The floral and fruity elements are the climate and the grape variety.”

Jürgen Wagner, winemaker at Celler de Capçanes, Montsant, Spain, April 2009.
“Minerality adds some astringency. Minerality disguises. It gives a feeling of a higher level of acidity.  It is a certain saltiness; the graphite of lead pencil. For me it means nerviness, liveliness, even astringency.”  

Duncan Savage, winemaker at Cape Point Vineyards, South Africa, March 2009.
“Minerality is the most abused tasting term. It’s a perception, an holistic picture. You identify with the soil, and feel like you’re tasting what you see in the soil. This is minerality by association.”  

Neil Ellis of Neil Ellis Wines, South Africa, March 2009.
“Minerality is a term to describe a certain feel in a wine, not massive, not big, more elegant. On chardonnay I use ‘restraint’.”

Andrew Gunn of Iona, South Africa, March 2009
“Minerality is flintiness, wet stones, chalk rocks.”

Bevan Johnson, manager of Newton Johnson Wines, South Africa, March 2009.
“Minerality is the poise of the finish. Minerality brings a freshness from mid palate to the finish; a freshness that’s not just acidity. An harmonious finish that’s fresh.”

Anthony Rawbone-Viljoen of Oak Valley Wines, South Africa, March 2009.
“Minerality is a product of the soil, and is something at the back of the wine, a flintiness, a complexity lurking at the back.”

Heiligenstein vineyard, Kamptal

This hillside vineyard was first mentioned in the Zwettl abbey register of 1280 as “Hellenstein”, or hell stone, because it was a mountain on which the sun “burns like hell”.  It was later renamed Heiligenstein, or “holy rock”, in possibly in an early form of political correctness.

The Heiligenstein is a unique geological formation – a geological island – within Europe, dating to the Permian period some 250 to 270 million years ago, comprising an extrusion of desert sandstone with volcanic and carboniferous conglomerates.

Digging deeper into a more detailed meaning of ‘primary rock’ or ‘urgestein’ reveals many layers.  “In ancient times there were very high mountains here.” explained Willi Bründlmayer of the eponymous Kamptal estate Weingut Bründlmayer. “There was an erosion of 300-1,000m, which left some rock stumps.  These rock stumps are primary rock.  The rocks are silicate, gneiss, granite, amphibolites. Then 250 million years ago, erosion residues and volcanic material and vegetation residues had built up. Later this mixed material compressed over a long time, and changed to soft rock. This was then pushed up again tectonically. What remains are Heiligenstein and Lamm vineyards.

Willi Bründlmayer holding primary rock

Hannes Hirsch of the eponymous estate Weingut Hirsch, added that after the “volcanic activity there was consistent vegetation 250m years ago which left roots and leaves, layers and layers of which built up. A shallow ocean then came in, then tectonic movement which pushed out the Permian material again.”

This complex ancient geology plus centuries of viticulture have resulted in a detailed map of vineyards matched to grape variety, mostly either riesling or grüner veltliner, which now account for 80% or more of plantings in Kamptal.  Bründlmayer said “Heiligenstein is more to the west, cooler, poorer, and better adapted for riesling. There’s no grüner veltliner.  Lamm has a layer of chalk-rich loess and loam, it’s a richer soil, warmer.  It’s suited to rich styles of grüner veltliner.” The Lamm vineyard, lying on the lower slopes below the Heiligenstein vineyard, has a primary rock base underneath the loess and loam. 

Bründlmayer added “riesling is better planted directly in the primary rock, and grüner veltliner prefers the addition of some rich material – sediment, loam, loess.”

Detail of Kamptal vineyards

The Gaisberg vineyard, to the immediate south-east of Heiligenstein, marks the end of the ancient massif coming down from the north, and is founded on primary rock of gneiss and mica-schist. Hirsch said: “you can break it up, it’s schistous with a brown earth layer. And the eastern part of the vineyard has a loess covering, which came from the east”.  Gaisberg is often planted to riesling.

Heiligenstein and ‘primary rock’ are only ever spoken in the same breath, but primary rock is a term used elsewhere for soils coming from this very old rock. Much of nearby Wachau has granite and gneiss primary rock at its foundation, and the primary rock soils have been divided into the three main camps of granite, gneiss and slate.

Over the geological time of millennia, rocks have been variously heated, cooled, compressed and tectonically moved. Granite is a mineral-rich rock formed of molten material. Gneiss can be formed by changes in heat and pressure. Slate can be the product of sedimented erosion material which has been metamorphosed by heat or pressure.

Soils derived from primary rock are often thin and low in organic matter and fertility, a layer of crumbly rock at the surface with the bedrock 20 to 30 cm below.

The importance of primary rock is the structure and flavour profile found in the wines.  Primary rock is strongly argued to confer ‘minerality’ into the wines.  Bründlmayer said: “On the rocky hillsides, grape berries are smaller. It’s not about the 3, 4, 5 principal elements, it’s about the hundreds of elements.  Heiligenstein is silicate with an acidic element and 250 million year old organic matter.  Roots take many different minerals in many different micro-doses.  It contributes to a wine.”

As yet though, exactly, scientifically, how those mineral-laden rocks confer minerality in wine is yet to be unearthed, as it were. Read here for a discussion about minerality.

The new wine game:  animal, vegetable, mineral.

The term minerality is bandied around with gay abandon by winemakers and industry alike, who regularly struggle to define it precisely when probed. But “minerality in wine is difficult to define” said Kees van Leeuwen, Professor of Viticulture at ENITA – Bordeaux University, precisely “because it does not refer to a specific substance present in wine.”

This leaves us floundering with an imprecise language to describe the term. Among many, Andrew Jefford has described it as an “absence of fruit, animal, wood.” Others intone the chalky, flinty paradigm. So if it’s not animal, nor fruit nor vegetable, must it be mineral?

Minerality implies a quality innuendo

In trying to unravel minerality, we have to overcome ‘tasting by association’ which is trained into our understandings.  Professor Ulrich Fischer, at the department of viticulture and oenology at Neustadt in Germany said minerality is a “self fulfilling prophecy – you learn Chablis is flinty; Mosel is wet slate. You know you have heritage and you pick it up.”  But if you lick that flint or that piece of Mosel slate, there’s not a lot of direct flavour.

One thing’s for sure. It’s trendy. And there’s an implied quality innuendo when minerality is mentioned. So there is a responsibility not to abuse the term.

For analytical study, certain chemical compounds are attributed to certain aromas, for example the floral character of monoterpenes or the green pepper of methoxypyrazines. The chemical compound can be analysed to study how the character is formed. Yet no one compound has yet been attributed to mineral character, which explains why there is no consensus on its use.  

Sensory analysis

We move from analytical study to sensory study, where studies of sauvignon blanc by Dr. Wendy Parr, sensory scientist at Lincoln University in New Zealand, using experienced wine tasters and winemakers from both NZ and France identified “an aroma and flavour characteristic that they term ‘flinty’, ‘smoky’ (but not smoke ’smoky’), or ‘minerality’.” She added “French people also use the word ‘silex’ to describe this note.”

In an ongoing study of the terroir of riesling in the Mosel, Nahe, Rheinhessen and Pfalz, Fischer and his team “do descriptive analysis, evaluating wines on the intensity of ten aromas, such as citrus, pineapple and floral, and taste. People can perceive smell of mineral wine.  In order to be scientific we have to produce a standard, which is reproducible, so we took small stones, wet them, and we look for a smell which is reminiscent of wet slate, wet pebbles. For the taste we couldn’t yet find a standard, however.”

“The standard for minerality is wet pebbles, wet quartzite” Fischer added, “above all it is a smell. Also think about iodine smell at sea and maybe think about fresh oysters. Ozone is maybe coming close, it fits into the concept. “

The terroir connection

You can have terroir without minerality, but can you have minerality without terroir-expression?  Fischer thinks not, saying “minerality is appreciated by people because it relates to the character of the soil. Since the turn of the century, we’re wanting wines with more individuality . One way is to look for more specific terroir wines; another is to use more spontaneous fermentation. This is why wines are getting more mineral. Many wines are fermented warmer [above 18°C]. The fermentation esters are reduced, and other properties of wine are getting stronger, and one of these seems to be the mineral character.”

Parr concurs. “From our data, it is related to the wines from specific areas. All the wines in our studies are tasted blind in opaque glasses and yet the wines from Loire and Saint Bris, near Chablis, always show up with higher intensity ratings to the flinty notes.“

Another area that scientists so far agree that the root route does not exist, in that minerals taken into the plant are not replicated in the form or proportions they’re represented in the soil and bedrock.

And vines have pretty much the same requirements to photosynthesise wherever they are, and soil can be managed to provide these: liming an acid soil, adding drainage to soil in a region of high rainfall. Van Leewen said: “If wine quality was related to specific minerals such as potassium, phosphorus, iron, trace elements, then quality could be improved by addition of these elements. But viticultural practice shows that, except for the correction of severe deficiencies or the application of excessive fertilisation, wine quality is not easily manipulated in either way by these practices.”

The sulphide connection

Nonetheless, many nutrient-poor soils exist. Indeed the heritage of viticulture is on soils that were too poor or mountainous to grow other crops. An indirect relationship between poor soils, stressed vine growth, and winemaking may come into play, with winemaking accentuating or accessing a terroir effect.

Winemaking consultant Sam Harrop MW said “In Pouilly-Fumé, if you bang two bits of silex together, you get an aroma reminiscent of gunflint. Locals believe these flavours come through in the wine and I’ve tasted plenty of wines from this region with such aromas.  But a sulphide is responsible for this aroma, which occurs during fermentation, so the relationship of terroir and minerality is an indirect one. You can’t get the smell of silex banging together directly into the final wine.”

In addition, he said, winemakers in the classic Loire sauvignon blanc regions “have a less interventionist approach – for example, spontaneous fermentation, extended lees contact, not using nutrient supplement – and working with more turbid juices, which offer a greater concentration of precursors for thiol production. All of these work towards greater sulphides some of which can be really positive, and others not quite so tasty. For example I see guava-like thiol expression from ferments of well-managed turbid musts.”  So thiols are terroir-originated, and expressed by a well-managed fermentation process.

Fischer agreed, adding minerality is “more related to terroir than winemaking, though winemaking has an impact.  It seems to be a reductive character, so keeping wine longer on lees enhances the mineral character.”

A thiol called benzenemethanethiol has been reported by Denis Dubourdieu and colleagues at the University of Bordeaux as one source of a mineral/flinty note in sauvignon blanc. Parr said: “It is assumed that these thiols develop their flavour characteristics during fermentation as the precursor compounds in the grape itself need yeast to produce the thiol and the volatile aspects.”   

While there’s a long way to go, minerality clearly does exist sensorially, though current industry usage of the term is highly individual, and without shared meaning. Until more is known, its use as a means of communication may advisedly be used only under caution.