In London earlier this month, Olivier Humbrecht, of Alsatian Domaine Zind-Humbrecht, discussed minerality in wine.
His presentation was part of a tasting of biodynamic wines from members of Biodyvin Syndicat International des Vignerons en Culture Biodynamique, the organisation of which Humbrecht is president, though his discussion was not uniquely about minerality in biodynamic wines.
He kicked off by dispelling some commonly held mis-perceptions: “for most people minerality is reductive, or a certain green flavour, it doesn’t taste fruity or floral, and you end up calling the wine ‘mineral’. Minerals don’t smell. If stones, or water, or salt smell of something, it’s because it’s associated with an organic compound that is volatile.”
The compound commonly associated with minerality is sulphur, about which he said “sulphur is a very broad component in nature, it’s found in very many organic molecules. It smells a lot. At worst, think of wet dog, mercaptan, H2S.
“These sulphur compounds can be linked into more complex molecules, not smelling obviously like sulphur, and these elements might be associated with some kind of minerality. And the most common mistake is to associate reductive character with minerality. [Another mistake] is to associate certain forms of organic acidity with minerality, if the wine is tight, with green acidity. All these are not minerality.”
Minerals are present in soil, coming from the degradation of rock by erosion, weathering, frost action, as well as the activity of microorganisms, all of which break down larger particles to smaller particles. When the size of these particles is smaller than two microns, it is called clay.
Humbrecht said “the finer the structure, the more it can trap minerals in the soil. And minerals are necessary to the plant. But will the minerals in the soil give a taste in the wine, that is questionable” though he did say “the mineral fraction in the soil will be represented in the wine as a mineral fraction.” And it is this that is interesting to analyse in a wine.
“Often people analyse minerality of a wine by analysing dry extract, or reduced dry extract” he said. “This consists of evaporating all the liquids, then burning all the organic elements. Or by calculating the reduced dry extract. It’s good to have a high reduced dry extract as it shows wine is more concentrated.
“But the organic fraction of a wine is expendable, according to physiology of the plant – you can easily have more sugar, more organic acids, as the vine continues to function. [Dry extract] is something the vine is continuously producing, so it can change with time. It can also be altered if you acidify a wine or add sugar to a wine.
“So when we talk about minerality we should talk about the ashes. Take a wine and burn it till you have only dust left. You end up with few milligrams of dust which directly comes from the earth. It’s the only solid fraction in a wine that you can directly link to the earth, everything else comes from photosynthesis – 99.9% of wine is made from heat, air and light.
“The fraction of minerals is a very, very small quantity. Whether the wine is very acid, or high or low alcohol, it doesn’t really change the mineral fraction.”
And, he added “we don’t analyse the mineral fraction in a wine very often because it’s very expensive. But it’s the best way to see if a wine has been produced from a high or low yield. The reduced dry extract could be the same for a wine made from 25 or 100hl/ha, but the mineral fraction will be divided by 4.”
Digging deeper into the issue to understand the soil, Humbrecht said “a soil should be able to feed a plant without doing anything. For us having a living soil means having a soil that is able to supply all that the plant needs at different moments in the year. And this is something modern agriculture has forgotten.” He spoke of forests that have survived centuries in a sustainable fashion without man’s interference in the form of soil additions, be they fertilisers or chemicals.
But even biodynamic producers add composts to their soils. Humbrecht said “it’s not really to bring fertilisers to the soil, but to bring something alive, microorganisms, and the elements of humus to stabilise the mineral fraction in the soil and bring energies to bring back harmony into our wines.
“We want our soil to be alive, with worms, fungus, micro-organisms, everything it takes to allow the mineral fraction to combine with organic fraction in the soil. If you don’t have this link the soil will fall apart” for example being eroded after rain, or compacted from repeated machinery passes.
This is so important, he said “because the very small mineral fraction is absolutely necessary for the vines to grow properly.”
Will this mineral fraction give a taste to the wine? Find out what Humbrecht said in part two.
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