(An excerpt from the book “WINE”, p66)
The word “minerality” often crops up in tasting notes, especially when describing white wine. This often implies that there should be a direct link between the minerality of soil and wine. The generally accepted notion assumes the higher the mineral content of the soil, the more intense the mineral flavour in wine. This is nonsense. Most minerals do not have a flavour and at most a slightly salty taste. Their presence in wine is minute and they go organoleptically unnoticed amongst fruit flavour, tannin, acidity and alcohol. Scientific trials have shown that there is no direct relationship between soil composition and the flavour of wine. Minerals are essential plant nutrients necessary for growth, photosynthesis, etc. The most important minerals are nitrogen, phosphorus, potassium, calcium, magnesium, sulphur and iron. A surplus of minerals in the soil causes vigorous growth of the vine and excessive yields that result in a thin and flat wine. Therefore the theory that more soil minerals make a more complex wine is obsolete. “Mineralic” wines are mostly grown on stony soils which tend to be poor because they contain little nutrient-rich humus. Vines on stony soils have to fight for survival and the grapes, just like the vines, accumulate few minerals, especially very little nitrogen. This can cause problems during fermentation as yeasts require nitrogen to convert sugar into alcohol. If there is insufficient nitrogen in the grapes, yeasts will split sulphur-containing amino acids to access nitrogen. This can cause the formation of volatile sulphur compounds which can come across as “mineralic” in wine. This does not point to a sulphur-rich soil but explains the indirect link between soil and wine flavour.
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