Minerality of the soil

by Augusto Oriani

This topic is very important, we will discuss it in the company of Dr. Luigi Demartino.

-University degree Forestry and Environmental Sciences

-Master`s Degree ,Forestry and environmental sciences

-Master in Energy and Bioproducts from Biomass, Sustainable management of

process supply chains

Minerality: sensory reality, marketing cunning or convenient neologism? The two-volume treatise on enology by “Ribéreau-Gayon” which has become the bible of winemakers around the world in 3000 pages dedicates only 3 pages to minerals and minerality.

Could it be thought that it is a bit insufficient, considering that minerals have great importance?

Not only the soil but also environmental factors (such as the altitude or the level of rainfall) can affect the mineral expression in a wine; longer ripening and later harvests – also conditioned by cultivation techniques – often correspond to higher feelings of minerality, while short cycles will not lead to the development of these notes. The mineral scents are therefore more evident in complex and mature wines, rather than structured and soft, and it is above all the acidic picture and its relationship with sugars to exercise a decisive role on minerality.

Is minerality a taste or a smell?

Geologist Alex Maltman, in his recent publication in The Journal of Wine Research, argues that there is no evidence of a direct link between the taste and smell of wine and the composition of the soil. The minerals in wine, in fact, are nutritional elements – typically metal cations – far from being linked to the geology of the vineyard, where the minerals are instead complex crystalline compounds. The mineral nutrients in wine are normally present in minimal concentrations and in any case insufficient to confer aromas. Experiments were carried out in France and New Zealand, which consisted of the tasting test of 16 Sauvignon Blancs. The wine was mainly evaluated only through orthonasal smell, smell, taste and trigeminal stimulation (global perception), therefore only with non-olfactory sensations on the palate (therefore taste and consistency or trigeminal sensations). the nerve that presides over the entire oropharyngeal tract and that carries a lot of information on irritating and tactile stimuli is the real responsible for the perception of the wine flavour (trigeminal sensitivity).

The discovery was made by a group of scientists from the Ruhr-University Bochum (Germany), led by Hanns Hatt and published in the journal Chemical Senses.

Wine professionals in France and New Zealand have shared a common mental construct of the concept of minerality, at least in wines with which they have direct experience, such as Sauvignon Blanc. “The concept of minerality in wine is undoubtedly real” explains Dr. Parr “but the source of the perception is still unclear. It has been vaguely attributed to acidity, hints of reduced and the absence of perceived flavour “.

The minerality of the soil

The concept of minerality is not clear to me so I shift my attention to the soils. The soils are divided into clayey, alluvial and loamy, marly or calcareous soils. The soil is the most superficial layer with a thickness ranging from a few to tens of centimetres, formed as a result of the alteration of the rocky substrate due to subsequent physical, chemical, biological actions by exogenous agents and organisms that are implanted there. In it, all three main states of aggregation of matter coexist solid, liquid and gaseous, water and its solutions as well as atmospheric air and more.

It consists of an inorganic part and an organic part. The fertility of the soil depends on 50% of the organic portion and 50% on the inorganic one but there are no certainties that the soil brings these elements into the wine. There are many minerals in the soil and not all are absorbed by the roots and used by the vines. Only a percentage of them is used for metabolic processes and this percentage is called bioavailability.

The bioavailability of the mineral elements in the soil depends on the degree of acidity of the soil itself. The degree of acidity is known as pH and has values between 0 and 14. The pH regulates, through the cationic exchange of ions, the solubility of the various salts of the soil and therefore the availability of nutrients for the plants.

The results of the scientific studies made by Antonio Palacios Garcia on “Minerality in wines” indicate that the relationship between the chemical composition of wines and their perception described in the tastings as “mineral” have no direct link with the minerals that make up the soil of the vineyard. On the same line is Maltman in 2013 and Attilio Scienza: “The perception of minerality is not the imperfect reflection of a soil but a mental representation that designates with a noun, a strong evocative power”. Vanessa Proti in 2016 states “Since no concrete scientific evidence and evidence has yet been found on the relationship between the components of wine and the perception of this perfume and if the odorous sensations indicated above (chalk, flint, graphite) prove to be the closest to the idea of minerality associated with wine, it is perhaps plausible to think that the direct link with the soil is rather questionable “.

The minerality in the vines

Since wine is not made with mineral water, how do minerals get into wine? Obviously through the roots of the vine which absorb them from the ground to have a perfect ripening of the fruit which then the man will transform into must, which no one I say no one has ever dreamed of defining mineral. Because?

Lymph is the blood of the plant: the lymphatic flow represents the main aspect of plant physiology since it depends on the distribution of water, nutrients, organic compounds, hormones that control the rhythm and speed of growth and the reactions to both positive and external interference. than negative. Its composition, density and flow rate are decisive indicators for assessing the health and growth rate of the plant. If we could analyze the lymph in the various periods of the year based on the phenological phase of the moment, we would always find it different.

The vine needs minerals like a human being. They serve for its metabolism and have a double function: the plastic function of building tissue cells and the catalytic function necessary for chemical reactions within the cells. When there is a defect or an excess of bioavailability, even serious problems can arise that affect the life of the vine or the production of grapes.

The minerals present in the soil naturally or brought with fertilizers so that the vine can absorb them must be disintegrated and transformed into chelates which, being soluble, split into ions and cations; these yes, absorbable by the roots and transported with the sap in the leaves and bunches. As for the nutritional elements, each plant must absorb a considerable volume of water from the soil, to meet its needs in macro and microelements, in case of drought this absorption becomes difficult and there are problems.

The main minerals useful to the vine are about 15: 7 semimetals (macrolements) H, O, C, N, P, S, B, Ca and 8 metals (microelements-hologelements) K, Mg, Fe, Mn, Cu, Zn, Mo.

The elements in greater proportion are: nitrogen, potassium, phosphorus and calcium; sulphur, on the other hand, is not necessary for its growth. Nitrogen is very important not only for nutrition but also for the development of secondary wine aromas.

The ions are transferred into the must and then into the wine by the intake of mineral substances by the vine, or by the voluntary addition of compounds having various functions to the must and raw wine or even brought by the machines used in the cellar.

Mineral aromas in wine

The minerality in wine exists but it is not what tasters talk about. In it as already described there are the minerals brought by the sap and the others added voluntarily or involuntarily by the producers. However, no one has dreamed or dreams of giving a tasting value to zinc, copper, lead, cadmium, which instead was done for iron, flint, calcium and sulphur.

The minerals in wine are important because they also regulate the chemical reactions within yeast cells, others serve as antiseptics, others added as clarifiers and which in any case are always in smaller quantities than those present in the soil.

What we can taste are their salts: sodium chloride, iron sulphate or smell like sulphur compounds in the form of sulphur dioxide or hydrogen sulphide. But in wine, there are organic molecules that have trace elements in their structure such as sulphur in mercaptans, nitrogen in pyrazines and carbon in hydrocarbons, as well as hydrogen and oxygen and which give rise to the whole range of aromas.

Having ascertained that there are minerals in wine, these contribute to its flavour but given their infinitesimal concentrations, they would be barely noticeable as in mineral waters. But, there is a but and it is that their flavour would be masked by the other components such as alcohols, sugar alcohols, acids, polyphenols and residual sugars which are in much higher concentrations. Therefore, finding a wine that tastes like flint, shell chalk, iron filings, and other insoluble products is inaccurate for two reasons. The first is that for those who had the courage to taste these minerals, as they are not soluble, they would not give taste sensations but only somatic sensations and general chemistry. And the second is that it would be impossible to separate the taste of silicon from that of iron, copper, potassium …

I think that there are no mineral scents in wine, and those we are talking about are organic and not inorganic scents. The second is that flint, granite, slate, shell, iron filings, etc. as they are not volatile they cannot give rise to typical odours.

There would still be a lot of notions, but I have a conviction, that these gustatory sensations are more in people’s heads than in wine. And in any case, they belong more to marketing than to the sensory analysis mode. In conclusion, I would like to know what Dr. Luigi Demartino thinks.

Dr.Luigi Demartino :the concept of minerality is linked to the vine, cultivation and ripening conditions, but not to the geological nature of the soil. The soil is an integral and essential part of the concept of minerality, combined with all the other characteristics of the environment and climate, it allows to obtain unique and unrepeatable wines elsewhere. Finally, human intervention often manages to alter these balances. The soil can in fact be altered by changing its composition and, with this, the wine it can produce.

I thank Dr. Luigi Demartino for his availability.

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