David Lefebvre and MINERALITY

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 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 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 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 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 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 ‘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 19^th century German agronomist.