On Minerality in Wine

A frequently cited, but just as frequently misunderstood characteristic in many wines, “minerality” belongs in every Napa Valley Wine Academy student’s sensory repertoire.

Minerality is an umbrella category encompassing such aroma and flavor descriptors as wet rock or stone, chalk, flint, crushed gravel and slate, among others.

Critics hold up minerality as a telltale sign of a wine expressing its terroir, but is it really the vineyard speaking? Could the winemaker be more responsible?

Those who favor the terroir link cite the white wines of Sancerre (Sauvignon Blanc) and Chablis (Chardonnay). Chalk dominates the soils of Sancerre, while the Kimmeridgean soils of Chablis contain large deposits of fossilized oyster shells. The latter soil is not found in any other viticulture area.

While research is ongoing, none currently exists indicating that the minerals present in such soils (calcium, zinc, magnesium) appear in sufficient concentration in wine to create a sensory response.

The research is arguably a bit more convincing on the winemaking side. Researchers from the University of Bordeaux have isolated a chemical compound in wine, benzyl mercaptan, which may be responsible for a mineral-like aroma.

Most mercaptans leave undesirable aromas in wine. They most commonly form when yeast lack access to sufficient quantities of nitrogen, a needed element for alcoholic fermentation to occur.

Desperate, the yeast will seek nitrogen bound up in amino acids in the wine. This process creates hydrogen sulfide, which in large amounts renders a wine undrinkable. Hydrogen sulfide can react with alcohol and amino acids to create mercaptans.

Regardless of its source, minerality remains a captivating attribute of certain wines, one that enhances enjoyment but also encourages further exploration into its origin.

Author- Peter Alig CSW, CWP

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