Minerality in wine : beliefs and explanations

Last night I had a terrible nightmare: I was in a room full of wine geeks of the worst kind and had to stand around while listening to their tasting comments. A particular group was busy describing a young Sancerre from the Domaine Vacheron. One after the other, after having sniffed their glasses with love, declared in the most highfalutin manner: « well, how chalky! », « can you not smell the flint? », « and this rocky taste, my God ! ». Suddenly, they ended on their knees and started licking stones from the ground. How odd… Eventually, I woke up, after having heard the word « minerality » in wine more than I could bare.  

“Mineral wine! isn’t it?” What does it mean?

Let us try to define this term: it derives from “mineral” which relates to the minerals, that is, any inorganic matter. In relation to wine, it seems to have appeared over the last 15 years, and it is now encountered in every other tasting notes. However, one could criticize its “catch-all”, abstract side, the fact that it does not describe anything in particular and seems to be used and re-used whenever wine escapes us, a little like the word “terroir” is sometimes used to justify an aspect or an other in wine which can not be explained. Moreover, from a chemical point of view, the use of this descriptor is incorrect.

As a matter of fact, unless they are robbed, scratched, warmed, pounded, minerals do not have a smell, except maybe for whatever organic matter they may have soaked in. Luckily, rocks are not soluble in water, otherwise what would become of the Pyramids, the Great Wall of China or any other of the world’s architectural masterpieces? If minerals are not soluble, then they cannot have aromas for us to smell or taste.

All the more surprising, wine often contains less than 2g per liter of mineral components (calcium, magnesium, sodium, a little iron and copper) against 100-200g of organic compounds. As for the aromas themselves, they are organic compounds and therefore do not contain minerals.

The great difficulty about the art of tasting is its subjectivity, relying on physiological differences, the memory and olfactive library of the tasters, on their vocabulary. Consequently, and in order to overcome this complexity, shall we not use a terminology as accurate, as communicable as possible? One should not lose along the way the layman, because of a pompous lingo.

There is nothing surprising however, in describing wine using terms linked to fruits, flowers, spices, everything nature has to offer. Science knows well the aromatic composition of many grape varieties, such as Sauvignon blanc, thoroughly studied by the University of Bordeaux, under the supervision of Denis Dubourdieu. It is known for example, that the grapefruit character often associated to Sauvignon blanc is due to the presence of an aromatic molecule identical in the fruit.

You have to understand that it is much more appealing to the ear to use of metaphors and associate a smell to a fruit rather than to its actual chemical composition. It would be rather unsexy to communicate as follows: “lovely nose of benzenemethanethiol and of 4-mercapto-4-methylpentan-2-one”. The world of wine would be deserted in no time!

However, in the same way that a comment such as “this wine reminds me of my dog’s breath” can only speak to its author, the smell of “minerality” is left to everyone’s interpretation.

Science can answer about minerality in wine. Enough to understand?

For many, the minerality of a wine is linked to the soil or rather, it would come from the soil, the essential source of minerals for wine. Yet it has been observed that the soil’s content in minerals does not reverberate clearly into the wine’s composition. Minerals not being soluble, they can not directly penetrate the root system of the vine. It was also noticed that soils with the highest limestone content (therefore the most basic, the less acidic), were also the ones cropping the most acidic wines, and that there will not be more calcium in the wine.

This concept of minerality in wine has resulted in many researches and questioning. In 2003, a group of researchers has identified an aromatic compound from the thiol[1] family as being responsible for this “mineral” smell, especially in Chardonnay: the benzenemethanethiol. It was noted that this “minerality” is often associated to wines made on soils that are poor in nitrogen (a mineral!). As a matter of fact, when the must is poor in nitrogen, it seems that the yeast synthesizes more sulfur compounds, which can then be described as smokey, “mineral”.

One could notice that the word is often associated to rather austere wines, which do not have obvious aromatic character. Importantly enough, « minerality » in wine is almost always linked to an idea of quality, something discreet, yet elegant in wine. It is all the more amusing if we think of another expression, today considered old fashioned: “le goût de terroir” (“the taste of terroir”). It also relates to the soil, but was often used in a very pejorative way, referring to rustic wines, sometimes even faulty, such as volatile phenols which are responsible for unpleasant (for most people) farmyard, sweaty horse, or goat leather smells.

Having said all that, what alternatives to describe a “mineral” wine without using this rather vague term? Some more accurate descriptors can be used: a “smoky » wine, which reminds of seashore, “sea spray”, a “petrol-like” aroma, “cold ash”, a salinity on the palate. Studies have also highlighted the fact that this word is often associated with acidic, crispy wines. Those can be described as “sharp”, “bright”, “nervy”.

If we can all agree over the smell of violet, pear, green pepper, there is no consensus over the idea of “minerality”. Until it is a universal notion, it is too abstract a word and does not allow to precisely describe an impression or another. What remains clear however, is that it is still widely used, and causes a certain fascination amongst professionals and amateurs, and is often the occasion of discussions, debates, articles. At this stage of my writing I must admit, not without a sense of guilt, to resorting to using it (very rarely) when my senses or vocabulary fail me.

[1] Thiols are sulfur molecules responsible for the varietal profile of some wines, notably those of Sauvignon blanc.

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Written by our wine specialist Annabelle Mispelblom Beijer