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Minerality: Ioning It Out

In this personal exploration of minerality I started here with a look at how rock minerals, such as feldspar (an important constituent of slate, gneiss, and countless other familiar rock types) might be transported into the root and then up to the fruit, giving us a fabulously mineral sensation when drinking the wine. My conclusion, in short, was that such a concept is nonsense (to be fair, this is what many others have also concluded, including many with greater knowledge of plant biology than I). You don’t have molecules of feldspar and quartz, imparting subtle suggestions of slate and gneiss, in your most recent glass of Muscadet regardless of how appealing the thought might be.

There are other much more likely candidates which might account for our perception of ‘minerality’ in wine. And we also need to explore exactly what I (and you) mean when we use the term; is it, for example, an aroma (or flavour) within the wine, or is it a comment on its texture? Or something else? Before getting on to these questions though, I wanted to return briefly to something raised in my first post. And that is the suggestion that, if minerality is not down to these large ‘geological’ minerals which are far too large to be transported into the root cells, could it be down to the ‘chemical’ minerals, the more elemental constituents of these ‘geological’ minerals, i.e. the ions of calcium, magnesium, potassium and so on that certainly are actively taken up by the roots.

Of all the nutrients the vines require, only three – carbon, hydrogen and oxygen – come from the air, being permitted to enter the tissues through open pores on the underside of the leaves. All other substances essential for life, health and growth – including nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, iron, manganese, copper, zinc, chlorine, boron and molybdenum – are absorbed through the roots. The notion that these ions might have a role to play in ‘minerally’ sensations seems, on first inspection, a tempting idea, as some of those ions – calcium, for example – look like good candidates for engendering such a characterictic. Surely, calcium has to taste at least a little chalky, you might think?

My experience with a variety of mineral waters suggests that different concentrations of ions dissolved in the water can influence its flavour; presumably, this is why the water from one spring tastes different to water from another. One of my favourites is San Pellegrino (a bit of a cliché I know, but I hope you will forgive me) and a glance at the label tells me that there is, for example, 52 mg/l of magnesium and 179 mg/l of calcium in the bottle I’m just about to open to accompany my lunch.

Minerality in wine - schist, Clos des Allées, Domaine Luneau-Papin, June 2013

Even so, my pre-existing prejudice was that the metal-ion concentrations in wine would be too low to have any influence on flavour. I didn’t feel that these ions were likely to be the explanation for minerality, a term which has only been a common part of the wine writing lexicon for 10-20 years, when mankind has been drinking presumably ion-rich wines for millennia. I still think ions are not the answer to the ‘minerality’ question (it just couldn’t be that simple!) although as it turns out I was wrong about their potential impact on wine flavour. The ion concentrations in many wines match or exceed flavour thresholds, which means it is conceivable that these ions may have some influence on flavour.

Published flavour thresholds vary, this variation the result of differing temperatures of the solution, what salts the metal might be bound within, the sensitivity of the individuals (some authors having claimed 6400-fold variation in sensitivity between tasters), and so on. In addition, published concentrations in wine also vary (from wine to wine, obviously), so here are a few typical figures (some sources are listed at the foot of the article):

  Sodium: reported threshold up to 200 mg/l, concentrations in wine can be higher, varying from 10 to 300 mg/l.

  Potassium: reported threshold up to 680 mg/l, concentrations in wine can be higher, varying from 200 to 2000 mg/l. It is no surprise that potassium concentrations go high, this being the major intracellular ion of living organisms, and those grapes were alive once!

  Magnesium: reported threshold 100 mg/l, concentrations in wine about this level, so possibly detectable.

  Calcium: reported threshold up to 125 mg/l, concentrations in wine probably lower, up to 125 mg/l, one of the few relatively commonly occurring ions that doesn’t seem to hit the threshold.

  Iron: reported thresholds are very variable, but range up to 0.3 mg/l (I’m sure there are some very different numbers out there), but concentrations in wine can be higher, varying from 1 to 10 mg/l.

  Copper: reported threshold perhaps 1 to 2 mg/l, concentrations in wine thankfully generally lower at 0.1 to 0.3 mg/l

So are minerals such as these simple metal ions responsible for minerally sensations in wine? I doubt it very much, and even if they contribute a little, they surely aren’t the whole story. My doubt about a potential role for ions in minerality is based on a number of holes in this theory. First, if these ions were responsible then wines have always been ‘minerally’, we would have been talking of minerality for centuries, not the last one or two decades. Second, it would be easy to test, as classically ‘minerally’ wines – Muscadet, Chablis, Sancerre, and so on – would have high levels whereas non-minerally wines – big, blobby Châteauneuf du Pape and other turbocharged ooze-monsters – would not. And studies don’t seem to bear this out, as all wines seem well endowed with these minerals, even from warm climates such as Greece and Australia.

There is one fly in the ointment, however, which comes from some research correlating ion concentrations and tasters’ perception of the mineral character of the wine. The work, by Oze, Horton and Beaman of the University of Canterbury (in New Zealand), has only been published in abstract form (and thus not in a peer-reviewed journal) following a meeting of the American Geophysical Union in 2010, nevertheless their results still pique my interest. First, there was no significant correlation at all between perceived minerality and the concentrations of aluminium, silicon, potassium, sodium, calcium, magnesium, sulphur and iron, in keeping with my thoughts above. There was, however, a tantalising result for kaolinite (a clay mineral) and gibbsite (a form of aluminium hydroxide), both of which may form in the wine depending on the pH, or possibly even in the mouth under the influence of the much higher pH of saliva compared to the wine. There was a strong correlation between these compounds and the perception of minerality in the wine. However, the finding that minerality might be engendered by the creation of minerals in a higher-pH, less acidic milieu seems at odds with the general perception that it is the acidic, cool-climate wines that are more likely to display minerality. For the moment, I think this isolated result remains an acaemic curiosity, one that certainly doesn’t offer a convincing or conclusive answer (but which perhaps deserves further exploration). For the moment I will put these results to one side, and continue my search to uncover the cause of minerality in wine.


Boulton, R.B., V.L. Singleton, L.F. Bisson, and R.E. Kunkee. Principles and practices in winemaking. Chapman & Hall, New York (1996).
Lockhart, E.E., Tucker, C.L. and Merritt, M.C. The effect of water impurities on the flavor of brewed coffee. Food Res., 20: 598 (1955)
Lazos, E.S., ajd Alexakis A. Metal ion content of some Greek wines. International Journal of Food Science and Technology., 24,39-46 (1989)
Cohen, J.M., Kamphake, L.J., Harris, E.K. and Woodward, R.L. Taste threshold concentrations of metals in drinking water. J. Am. Water Works Assoc., 52: 660 (1960)

Minerality: Gneiss-y Nonsense

There has been a lot of words written on minerality over the past few years; what it means, where it comes from, is it real, and so on. I think the terms minerally and minerality are useful descriptors for wine; I accept, however, that it can be difficult knowing exactly what someone (including me) means when we use one of these terms in a tasting note. I wanted to share some of my own thoughts on minerality over the next few days. In particular I will try and explain my own take on the term, although I will warn you now I’m not going to be as precise as you might be hoping.

Before I get to that though, I first wanted to consider the notion that minerality in wine reflects minerality in the soil.

The major problem with minerality is that some may have assumed that its presence in a wine reflects a direct relationship between the wine and/or fruit from which it was made, and the soil or rock in which the vines are planted. In other words, minerals from the ground somehow find their way into the grapes, and then to the wine. This has always seemed like nonsense to me. We probably all know that plants absorb water, nutrients and minerals through their roots; this is why the health and growth of plants can be influenced by adding fertiliser to the soil. The fertiliser contains nutrients and minerals valuable to the plant, which can be absorbed across the huge surface area offered by its extensive network of fine, branching roots. It is important to understand exactly what we mean by ‘minerals’ though. It is tempting to think they are rock minerals, a molecule of gneiss here, a granite molecule there. That’s always seemed like nonsense to me, for several reasons. Take gneiss – a commonly encountered metamorphic rock in the Muscadet region – as an example; this is made from a variety of minerals, but is likely to be a mix of the following:

  Feldspar, chemical formula : (Ca,Na)AlSi3O8 or KAlSi3O8

  Quartz, chemical formula : SiO2

  Muscovite, chemical formula : KAl2(AlSi3O10)(F,OH)2 or (KF)2(Al2O3)3(SiO2)6(H2O)

  Biotite, chemical formula : K(Mg,Fe)3(AlSi3O10)(OH)2

Gneiss, as an aside, is not defined by a specific mineral composition (so it can be a mix of the above, and other minerals too) but by a texture; it is a metamorphic rock, often granite-derived in the Muscadet region I believe, where the minerals are banded into dark and light strands a result of extreme heat and pressure.

No, I haven’t surreptitiously pulled out a geology degree you never knew about; I simply pulled these formulae off Wikipedia, which only seems fair as they have been mining Winedoctor for wine-related facts ever since a wiki author decided that Latour and Le Pin warranted entries just as much as Miley Cyrus and all the episodes of South Park and The Simpsons ever made did.

Looking at the above minerally formulae, several things spring to mind:

  1. Gneiss is made up of some huge molecules; it would be very difficult (impossible I think – but I’m not a plant scientist and I’m trying to remain open and balanced) to transport them across a cell membrane.

  2. There looks as though there is a lot of potential toxicity there – do plants really want to be hoovering up Aluminium-containing minerals?

  3. Active transport into the cell requires energy – why would the plant use energy to absorb such huge molecules, when it is the constituents (iron, manganese, etc.) that might be useful. Why not just transport in iron and manganese ions from the surrounding soil?

  4. Transport into the cell requires the nutrient or ion to be water soluble; any gardener knows this. In high-pH (alkaline) soils plants suffer from chlorosis. This disease was a big problem for those planting experimental grafted vines in the early years after phylloxera, as some rootstocks when planted on limestone couldn’t handle the conditions. In such conditions much-needed iron is sequestered as a solid, bound with calcium. Solids cannot be absorbed by roots, the ‘minerals’ need to be dissolved. There are two solutions; alter the pH, for a long term solution, or add chelated iron (iron in soluble compounds) for a quick fix. It is impossible to imagine the molecules of stone, described above, dissolving in water and being absorbed. Gneiss, and other rocks, just aren’t water-soluble. They erode, yes, but they don’t dissolve into water like sugar.

  5. Discount all of the above; assume gneiss is soluble, and magically taken up by the roots. How and why would this gigantic minerally molecule be ascended through the structure of the plant to be deposited in the grapes. Would the normal xylem channels achieve this? What would be the purpose of this energy-expensive process?

It all seems like gneiss-y nonsense to me, and seems to discount both the notions that ‘minerality’ originates with the absorption of minerals, and also – on a related issue – that a particular terroir might be expressed in a wine through the absorption of the very minerals that comprise that terroir.

More minerally thoughts on another day.

Rayne-Vigneau: Visitors Welcome

Bordeaux hasn’t been renowned for welcoming wine-interested visitors; buyers, merchants, journalists and other professionals, yes, but it wasn’t that long ago Bordeaux châteaux were forbidden fruit for wine drinkers. This, in an era when many New World estates offer visits, tours, on-site sales, dining experiences (I cringe when I write “dining experience”, but dining on the terrace overlooking the vines is certainly about more than just the food for us wine geeks) and even functions, everything from concerts to weddings, seems increasingly anachronistic.

Times are changing though, and more and more Bordeaux is realising the importance of welcoming the wine-buying and wine-drinking public. With this in mind, Château de Rayne-Vigneau (pictured below) has recently begun welcoming visitors to the estate.

Following an expensive refurbishment of the cellars, the team – led by Vincent Labergére who runs the estate on behalf of owners Crédit Agricole Grands Crus – now welcome visitors who can receive a guided tour of the cellars before making their way to the tasting room to try a small selection of the wines. More importantly, the wines are available for sale on-site – something quite rare in Bordeaux with its long-established system of selling through the Place de Bordeaux, with all its courtiers and négociants, and there is also the option to dine on-site (no doubt with a glass or two of Rayne-Vigneau, or perhaps the dry Sec de Rayne-Vigneau, to wash it all down). The tours are overseen by the newly appointed Élodie Vargas.

One thing that won’t be available is a tour of the rather attractive château, which has remained in private hands ever since 1961, when the proprietor at the time – Vicomte François – sold his vineyard.

The tours cost €7, and this includes a tasting of three wines.

Wine: Not the same as Fishing

I came home later than expected one evening this week and slumped down on the sofa, exhausted. Two of my three teenage children had occupied the room before my arrival, and had therefore staked a claim on the television. Their choice of viewing? Extreme Fishing with actor and UK television sleb’, Robson Greene.

To me, fishing seems like the antithesis of what might make good television. Sitting on a riverbank waiting for the bite that might never come is, to my mind, a fine way to ruin an otherwise potentially enjoyable day. The idea of watching somebody else do this is surely the televisual equivalent of me drilling holes in my head. But the programme works; having sat through nearly 60 minutes of it perhaps I now understand why. And why, conversely, wine on TV doesn’t work.

1. The presenter; Robson Greene is expert (a keen fisherman) and novice (he travels the world to take up new fishing challenges) combined. He has a down-to-earth approach, and never talks down to the audience. Perhaps this is why the UK television audience find him so endearing? How could you do this with wine? Finding a novice and expert in one would be difficult; wine drinking isn’t a sport that requires some knowledge such as fishing, and somebody who merely drinks wine – that’s most people – rather than obsessing over variety, terroir and closures doesn’t count. This is perhaps why two of the most successful ‘light entertainment’ wine programmes I can think of featured “novice-expert” pairings (Oz Clarke and James May, Jonathan Pedley MW and Keith Floyd). Is there a TV sleb’ in existence who could fill the novice-expert role? Wine also suffers from having an instant snob-feel to it. It’s easy to be “down to earth” with fishing – it’s easy to avoid too much detail, for fear of coming across as a snob, with wine.

2. The action; extreme fishing doesn’t mean sitting on a riverbank. It means diving in cages for abalone in shark infested waters, trying to catch crabs with huge pincers with just a stick and your bare hands, deep-sea fishing for octopus which must be beheaded by the presenter as soon as the cage comes on board, fishing for shark which attack as soon as they hit the boat deck, you get the idea. Suddenly, fishing isn’t so boring. How do you replicate this with wine? The excitement of the wind rustling through the leaves in the vineyard? The thrill of a vertical press in action? Worse still, watching people taste wine?

3. Comedy; there is plenty of opportunity. Those octopus cages are on a line and are arriving at the rate of 10 per minute, so mishaps and the ultimate failure of the presenter after “having a go” provides a laugh. The octopus, prior to decapitation, quite sensibly went on the offensive – “it’s grabbed me knackers“, as Robson put it. This is clearly why my teenagers watch a programme which, superficially, I thought was going to be aimed at middle-aged men who spend a lot of time thinking about rods and bait. And then there’s the eating – of octopus (raw), abalone (raw and cooked), gummy shark (cooked). Not only is the transition from just-landed fish to cooked meal interesting to watch (part of why cooking works on TV, and wine doesn’t) there is plenty of opportunity for disgusted face-pulling and near-retching. How could you do any of this with wine? Bottling line mishaps? They aren’t going to be funny. And which producer will stand by while wine’s Robson-equivalent tastes his Shiraz, retches, spits it out and exclaims “and people pay to drink this“?

4. Travel; exotic locations count for a lot here, as Robson travels the world to fish. This is one where wine does at least stand a chance – but it certainly pushes the budget up.

There may be other facets, but these are the big four I think – affable presenter with right level of knowledge + comedy + action + travel = appealing light entertainment show from which viewers will, without realising it, perhaps learn something about the subject matter. In fact this is perhaps the basic premise for many successful television shows – Michael Palin’s travelogues seem to fit a similar scheme. With wine, it doesn’t seem likely to work. How do you make wine work on television?