Minerality and geology
David Lefebvre and MINERALITYSecond interview of David Lefebvre on Minerality, published in the R&B N° 112
R&B In 2011, you called for a way to measure minerality. Has this happened ?
David Lefebvre: Scientists are not interested in salinity or the harmony of taste components as such because they cannot quantify them. For persistence, though, they have more easily quantified reference values: the "caudalies" measure of persistence, as well as the analytical data for acidity.
For me, the semantic definition of minerality as "the property of what is mineral" is perfectly appropriate. However, building an analytical frame of reference for minerality is considerably more complex. To explain it concretely in relation to the way tasters react to wine, I rely on the way the mineralization is expressed in the wine: the decomposition of the organic matter as it evolves towards a stable state. In fact, as winemakers break down the grape’s substances, they mineralize it. Agronomy - not oenology! - gives a very precise definition: the mineralization of organic matter (which is the basis for the wine) is its decomposition to a more stable state. Initially, the juice is biologically unstable; pressing, settling, fermenting or punch-down (pigeage) are all steps in the mineralization of this organic matter. The molecules decompose and evolve towards thermodynamically more stable molecules than their initial state.
There are three types of mineralization: biological, chemical and physical.
Biological mineralization corresponds to the action of the yeasts, which digest macromolecules to turn them into smaller and more stable molecules. The different fermentations, foam making, rearing under veil, all follow this same principle.
Chemical mineralization includes oxidation: the oxidized molecule is always more stable than its counterpart in the reduced state. The mild oxidation of a wine is therefore a chemical mineralization.
Finally, crushing a grape in one's fingers is a type of physical mineralization.
As the wine evolves, all three aspects are present and can combine to give rise to biochemical, biophysical or physicochemical phenomena. For example, during settling (débourbage), enzyme action is an example of chemical mineralization that combines with biological mineralization because the enzymes can come from the yeasts.
R&B Can it be measured ?
Yes, there is objective data; for example, the average molecular weight of all the compounds of a wine. Let's go back to mineralization: the decomposition of the initial macromolecules of the grapes, their most highly organized form, (this would really be ‘the grape flower’- the flower of the vine, since it has the greatest molecular complexity). The juice also contains macromolecules such as pectins which enzymes break down into simpler molecules. The other results of fermentation - ethanol, fructose ... – become objective chemical data of this level of mineralization. Note that Jura vine growers go even further when they raise their wines under veil; they mineralize the ethanol to reach a more stable substance: its oxidized counterpart, ethanal. The latter is not a breakdown of ethanol but an oxidation, thus a biological mineralization. To evaluate molecular weights, we use advanced chemical investigation techniques such as liquid or gas chromatography.
R&B What is your view of salinity?
In grapes, minerals are embedded in molecular matrixes. Calcium, for example, is bound in branched chains of relatively complex pectins. Tightly linked, it is hardly noticeable as a taste. However, during mineralization, it changes matrixes and is then surrounded by much smaller molecules. The saline dimension can then appear, the salts are liberated from their initial matrices.
To check this, tests were carried out on cheese with relatively neutral caseins. By modifying their molecular weight and using blind tastings, it was shown that salt of equal concentration is much more noticeable in caseins of lower molecular weight. This organo-mineral observation deserves to be investigated in oenology.
Notice that these minerals do not come from photosynthesis, but from the soil. This is why they are interesting, and wine growers are well aware of this. Tillage, grassing, healthy agriculture, all contribute to this interaction. When soil pits are dug in conventional vineyards, the subsoil is characterized by clearly defined horizontal layers and diminished porosity due to compacting by machinery. But in healthy vines, such as those seen at Patrick Meyer’s vineyard (see R & B No. 101), there is gradual change between layers. This structural continuity of the soil links the bedrock and the upper layers and favors capillary rise during the dry season. It is in this sense that I suggested, in 2002, adapting "rolofaca " as used in TCS (simplified cultivation techniques) to wine growing. When a vine is in a pedological environment conducive to capillary rising and protected from the sun, it is always supplied with water and minerals. The verticality of a soil thus gives us the verticality of a wine!
R&B Why isn’t oenology interested in the mineral aspect?
Primarily because the organic (as opposed to mineral/inorganic) aspect is the one that most interests the wine business. Quantifying and qualifying this organic aspect leads to “additive “oenology. Since it is possible to mineralize a wine with additives, this creates new product lines. For example, there was an additive powder on the market called "Reminéral"!
Organic compounds - acids, alcohol, sugars, polyphenols, proteins ... - are the frame of reference for oenological laboratories and oenological research in general. This is reinforced by writers and bloggers who suggest that 2 or 3 grams of salt per liter have no significance when compared to 10 or 15% ethanol or 25 grams per liter of dry extracts and sugar. This is false, because we know perfectly well that a few milligrams of salt completely modify the taste of food! The subject is widely debated. For Patrick MacLeod, neuroreceptors can only perceive the effect of sodium, so salinity could be considered as sodium. Yet, I remember perfectly well from my childhood that my father gave magnesium chloride to the horses. Having tasted it, I know it has a characteristic salinity which even adds a sensation of bitterness.
R&B If salt is added in any form, would it be detectable?
Winemakers fall into two categories: those who consider that the only interesting minerals come from the soil and the others, the vast majority, who look for oenological recipes. However, additive oenology cannot be a sustainable solution for the wine industry, because by definition it uses reproducible recipes that can be exported for wines destined for global competition. I worked in California where additive oenology was the norm, though it varied widely in practice.
Minerality is not so much the quantity of mineral salts (the weight of the ashes) contained in the wine as the expression of the organo-mineral interactions. Of course, the salts play a role as enhancer, but the effect of the mineralization also implies a harmonization of tastes and can go further: wine growers speak of the ‘tactile’ aspect of wine. Even were one to add salt, this would not produce the same interactions. For AOP wines, salinizing the wine is not allowed because it is forbidden to modify the taste of the product; one wonders about the practice of modifying aromas with the barrel and chips. Unfortunately, winemakers who do boost salinity may be trying to compensate for an absence of minerality, in the same way as adding gum arabic tries to correct for absence of body.
R&B How can we characterize and measure these organo-mineral bonds?
Since June 2013, the Duo Oenologie - a lab in Châtenois (Bas-Rhin) - has been using Ehrenfried Pfeiffer's tests. Pfeiffer, a pupil of Steiner’s, developed a method to visualize soil quality which is accepted by conventional agronomy. Compost manufacturers use it as a reference method to measure maturity, and thus the level of mineralization.
Wine can be tested with this method. In the past (cf. Jean-Paul Gelin), this has given good results, but only for red wines. What is the difference between red and white wines? The tannins, i.e. the polyphenols. Though the Ehrenfried test highlights the mineralization of polyphenols and works well on red wines, the protocol for white wines still needs to be defined - to assess the level of mineralization and the harmony of alcohol and sugars thus induced. The greater the visual pattern (on the blotter), the more mineralized the product.
Further work on these methods could result in a protocol that visualizes and differentiates a highly decomposed wine from a less evolved wine. This would be a revolution!
R&B If the winemaking, varietal, and grower are the same, can we distinguish between wines from vines planted on limestone and those planted on shale?
With chromatography, we can hope to document and compare the visual profile of a wine from a shale terroir with one from a calcareous soil. MacLeod points out that our olfactory and taste memories are very limited in range. Dogs far outperform humans. Our sight, on the other hand, is far more developed. Humans recognize one face from among thousands.
Pfeiffer’s idea was to get a taste and smell image of an "individual" (soil for example). Building a profile by smelling and tasting while visualizing the chromatography may make it possible to differentiate classes of "individuals", and thus differentiate wines from shale, limestone or sandstone. This has historically been the goal of gourmets. They did not characterize by the aromas but by the tactile aspect of the wines.
At the Université des Grands Vins en Alsace, tastings are held by candlelight, which completely modifies sensory perception mechanisms. When tasting in the dark, we ignore the aromas. Tasting becomes an introspective phenomenon, a kind of meditation on the texture or the persistence in the mouth for example, which changes our reference points. Those who identify a terroir of shale or limestone are remembering the physiognomy of a wine they have previously tasted.
Even admitting that that there are specific tastes linked to a specific terroir, human abilities are too limited to recognize them. But, in my opinion, this is not the point. What is important is the wine’s personality, in particular, the fact that it is inimitable.
MacLeod is right when he proclaims that the taste of terroir does not exist! Our neurosensory capabilities are physiologically too limited to recognize one.
R&B Minerality is thus the result of mineralization?
Yes, it is the stage of the mineralization process that gives minerality. For example, let’s start with the same initial juice. Assume one half undergoes oenological operations (racking, sulphiting, filtering ...) in January. The other part ferments on lees for 12 months or more. Then compare the two. The gustative difference, i.e. the salinity and the harmony of the components, corresponds to the true definition of minerality!
If there are residual sugars, the sweetness of the long-fermented wine will be much more harmonious, not drying. The same is true for the for acidity, alcohol, and tannins. We could correct the astringency of a wine by modifying the organic matter using collage or micro-oxygenation, but the salinity has the effect of erasing the astringency. For me, this is a discovery! Try this simple experiment: put the same quantity of tannins and pips in fresh water and in mineral water and compare the results
R&B If, after some aging, it is difficult to distinguish the constituent grape varieties of wines, does this mean that the mineralization tends asymptotically to standardize the flavors?
Mineralization leads to the loss of varietal characteristics. For example, a flower will lose its colored pigments over time (actually its anthocyanins). However, two dissimilar roses that have lost their pigmentation will remain morphologically different.
All living things age and mineralize (decompose).
Our faces evolve over time. Do all old people look alike? Individuals are always different, whether young or old. For wine, organic matter certainly contributes to the diversity of individuals, but over time, this diversity is less related to organic matter, and more to the tactile dimension, to persistence. It’s another type of individuality. The varietal dimension (citrus fruit, mint ...) is transformed.
The important thing is that the wines’ starting points are different. A parcel of dead soil, with an army of cloned vines which don’t communicate with each other produces only organic matter with no mineral structure (comparatively unevolved plant matter). In comparison, there is more complexity when there are complants, grape varieties with genetic variants, which communicate by exchanging genes though the mycorrhizomes. The more complexity present at the start, the more complex the resulting wine
R&B Does this mean that a mineralized wine would become somehow "ultra-organic" and would not have stopped being organic?
If it has become mineralized, it is because at some point it was at an organic stage. For any two wines (two stages of the same wine or two different wines), one is always more mineralized than the other. Organic (initial unevolved) and mineral (evolved) are opposite poles and wines are always between the two. The fully mineral pole corresponds to completely decomposed matter; in its final stage this corresponds to water, carbons transformed into carbon dioxide and precipitated or dissolved salts. This is as stable as things can get.
R&B What could be ‘practical’ results of a mineral approach to wine?
For example, Alsatian law currently regulates the sweetness of Riesling by adopting an organic structure approach, that is to say by the sugar / acid ratio. A mineral approach would give legislation based on yield. A low or reasonable yield, even with conventional growing, modifies the ratio between grapes / root quantity. Lower-yield Rieslings tolerate much more residual sugar.
R&B You talk about two conceptual visions of wine that give rise to two types of wine: organic and mineral. Can you enlarge on this?
It's an observation, I do not want to set them up as opposites. 90 to 95% of wine growers produce short-term wines using a set of technological and chemical tools: racking, stabilization, sulphiting, sticking, filtering ... This is understandable, the financial aspects are important, to age wine is to tie up cash, and it is expensive to take the time for mineralization.
Despite some local terroir characteristics, these wines are very easily shaped with “high performance” oenology. In contrast, mineralization’s effects need time, and time is money. Fermentations that take 24 months, as practiced by Jean-Pierre Frick (see R & B No. 78), cannot be replaced by additive processes. Oenology can’t condense 20 years of bottle aging into one year, even with techniques such as micro-oxygenation. What’s more, using sulfur is the very opposite of the mineralization process, since it plays a role of chemical blockage. It freezes organic material by combining, for example, anthocyanins. The wine keeps its brightness (éclat), but the underlying material does not evolve anymore. It is the same with physical membrane processes - they work against mineralization.
These aspects are intuitively understood by winemakers like Patrick Meyer. I’m just a mirror. Meeting with these winemakers allows me to understand, formalize and document their experience and intuition.
R&B You talk about ‘oxidative stress’. What is this?
Winegrowing, like any farming, leads to oxidative stress: stripping, suckering, pruning ... Pruning the vine hurts it, this inflicts oxidative stress. When the vines are "bludgeoned" by inappropriate growing methods, the resulting grape juice, the living matter, is a record of all these stresses. This makes it more sensitive to oxidation. This is shown in the work of Louis-Claude Vincent on micro-organisms (fungi, algae ...). For example, strawberry juice, made in the conventional way oxidizes during fermentation because the supporting medium selects oxidative strains of micro-organisms. However, the same juice, when made from fruit grown to preserve vitality, selects microorganisms such as Saccharomyces cerevisiae yeast which are more “reducteur” (poor in oxygen).
Increasing mineralization means excluding sulfur. This in turn means minimizing oxidative stress upstream, and thus requires a soil full of life with few aggressive treatments against downy and powdery mildew.
Sulfur, used to protect the initial berry material during pressing is not needed if the latter has the necessary vitality to protect itself. Another important point, as developed by Bruno Schloegel in Wolxheim (Domaine Clement Lissner), is the level of organic complexity. If we look at a parcel as a living thing, the more complex its biodiversity, and the more interdependent its vines, the higher its potential for mineralization. The mineralized juices carry the results of this initial richness, like archaeological excavations which bring to light old civilizations more or less advanced according to the degree of interdependence of their individual members. Vines communicate with each other through mycorrhizae and the meeting of their mycelial filaments, and exchange genetic material. This interaction is called the "Hartig network"; after a 19th century German agronomist.
R&B You’ve recently bought a vineyard. Please tell us about it.
In 2010 I bought a 20-acre acre parcel of riesling in Saint-Nabor, near Mont Sainte-Odile. 2013 was my first harvest
Next to the parcel are some wild, free-ranging Vitis vinifera vines which have scabs from phylloxera. It is very interesting to note that this wild vine is not affected by downy or powdery mildew. In other words, as soon as a vine is cultivated, it is becomes prone to diseases, and this is not the case when it remains attached to a living base. Philippe Chrétien Oberlin expounds on this in his book. When I got my parcel, it was fallow, and there were trees on it. I kept the trees on the vine rows. I found that vine does not cling to all trees: it does not climb birches - birch is water-oriented while vine is sun-oriented - nor to hazelnuts. On the other hand, it does well with cherry and apple trees. The soil is full of wild carrots, which, according to Gérard Ducerf, (see R & B N°113) , indicate decompaction and thus soil "verticalization” since carrots have pivoting roots.