‘Minerality’ is used by wine professionals to describe the character of certain wines, with vague references made to wet stones, crushed rock and soil. Regarded variously as a taste, a smell, a trigeminal (mouth-feel) sensation, or all three, until now there’s been little agreement on what is actually meant by this common but enigmatic term, or whether it even exists.

Intrigued by the lack of scientific knowledge and the plethora of anecdotal evidence around minerality, Dr Parr collaborated with scientists in France and at Plant and Food Research in New Zealand to investigate what the concept means in Sauvignon Blanc wines, and whether there are cultural differences in perceptions of minerality.

Wine professionals from France and New Zealand experienced in the production and tasting of Sauvignon Blanc participated in two sensory studies carried out over two sessions, with wine samples served blind in opaque, standardised glasses in unique order for each participant. Participants evaluated the wines by palate (taste and mouth-feel) alone, smell alone and both palate and smell together.

Minerality was perceived by both groups in all cases, and was consistently associated with several wine characteristics, for example citrus. There were more similarities in perception between the groups than differences, implying that wine professionals in France and New Zealand share a mental construct of the concept ‘mineral’, as experienced in Sauvignon Blanc wines.

“The concept of minerality in wine is undoubtedly real,” Dr Parr says, “but the source of the perception is still unclear.” It has been variously attributed to acidity, sulphide reduction, and relative absence of perceived flavour. So what are people smelling, sensing and tasting that they describe as mineral?

“Only one of our specific hyphotheses was supported by the current data, namely a positive association between perceived minerality and lack of perceived flavour,” says Dr Parr. “In the absence of other flavours, it appears that wine is more likely to be referred to as mineral.”

Associating wine’s perceived minerality with a wine’s source of origin has been a powerful marketing tool for producers of many of the world’s more expensive wines, with wine producers linking perceptions such as ‘flinty acidity’ with vineyard minerals such as calcium in the soil. Geologist Alex Maltman however has argued that there is no evidence for a direct link between the smell and taste of a wine and the geology of the vineyard.

Dr Parr’s sensory study didn’t find evidence for a link either. “For example, there was no evidence that perceived acidity, in the form of sour taste, predicted increased minerality.” Her team will continue to investigate this by looking at aspects of wine chemical composition including the relationship of ions such as calcium and compounds associated with sulphide reduction to perceptions of minerality in French and New Zealand wines.

Sulphide reduction as a result of inert bottle closures has been another popular hypothesis behind the recent increase in use of the wine descriptor `mineral’. Some wine professionals believe screwcaps used to seal wine can cause low-level reductive notes in the wine that tasters call mineral, but Dr Parr has not found any clear connection between the two in her data to date. “There was no evidence that reductive notes in the wines predicted enhanced mineral character.”

Dr Parr says that while there were shared mental representations of ‘minerality’ across the two cultures, the boundaries of the concept remain fuzzy. “This is not surprising in fact, as we know that when more abstract aspects of a wine such as ‘minerality’ or ‘quality’ are described, people’s responses are more idiosyncratic, reflecting their personal experiences, than they are when a more concrete aspect of a wine such as intensity of passionfruit flavour is judged.”