IMW seminar debunks minerality myths
An Institute of Masters of Wine (IMW) seminar on mineralogy has utterly debunked a persistent myth about minerality, saying it is not related directly to any sort of nutrient mineral uptake by vines – even though people do perceive minerality to exist in wine.
Alex Maltman, professor of earth sciences at Aberystwyth University outlined the disconnection between geological minerals and the mineral nutrients – elements – required by vines, of which there are 14, pointing out that “these 14 are not the same minerals as geological minerals”.
“Elements are not necessarily bio-available… weathering processes are too slow to keep pace releasing nutrients for vegetation year after year [and] the cycle is interrupted with agriculture. Nutrients are removed each year in crops, so we have to add compost, fertiliser… most of the nutrients are coming from humus [decayed plant and animal matter] not the geology,” he explained.
Added to which minerals do not vaporise – they are odourless, and their concentration in wine is far below the taste threshold.
Vinification upsets things further. Yeasts need their own nutrients. All in all, Maltman said “it is a distant, complex, tortuous and indirect relationship from what started in the soil.” But, he added, geology “may play a role indirectly. [While] minerality cannot be the taste of minerals, flavour relationships are indirect, and minerals could be important.”
Viticultural consultant Dr Richard Smart (whose words were read out as he was unable to take his place on the panel) agreed that viticulture “is not an issue” in wine minerality, saying of the 14 mineral elements/nutrients, “three of the most important are not derived from minerals being N, P and S; they are absorbed directly from soil organic matter (humus). Even those which are commonly found in minerals – being K, Ca, Mg, and Na – are not directly extracted, they are firstly cycled through organic matter.” He cited minerality as an “invented term as a wine descriptor.”
Looking at the human perception side of the debate, sensory scientist Dr Jordi Ballester of the University of Bourgogne in France discussed conceptualisation and between-person variability. The latter point was neatly illustrated during a tasting where attendees were asked to rate wines in a flight of Chardonnay and a flight of Sauvignon Blanc on perceived minerality, from low to high. The range of ratings was highly variable.
Previous work by Ballester highlighted the recent emergence of the term minerality into the lexicon. Minerality is utterly absent from Ann Noble’s 1984 ‘wine aroma wheel’ and Emile Peynaud and Jacques Blouin’s 1983 book ‘the taste of wine’.
Ballester’s work with Burgundian winemakers identified more than 30 definition-descriptors for minerality. Of these, he said more than half could be clustered into ‘stone/flint’, ‘acid/fresh’ and ‘sea/shellfish’ groups. This superficially suggests some sort of logical clustering of attributes by winemakers. But, he emphasised “experts have serious consensus issues when assessing minerality”. And, he added “for winemakers minerality is always good” but for consumers he found minerality was not even always a positive attribute. That’s a lot of between-person variability.
Research by Dr Wendy Parr, a sensory scientist from Lincoln University in New Zealand shows perceived minerality in Sauvignon Blanc is indeed a data-driven construct – i.e. coming from what’s in the glass, and that it has consistency and consensus across cultures. Her research worked with Sauvignon Blanc in France in New Zealand.
The other type of influence on perceived minerality, she said is “top-down perception, that is, what’s already in our heads – memory, experience. For example, you can see Chablis on the label and you already have expectations.”
Parr said a cross-cultural consensus showed “in an absence of passionfruit, and a positive for citrus, chalk, flint, smoke on the nose; in an absence of passionfruit, green and sweet on full taste [nose and palate], and a positive for fresh/zingy on palate only [tasters wearing nose-clips].”
She added: “for Sauvignon Blanc perceived minerality is not just what’s in our heads. Perceived minerality in our Sauvignon Blanc selection included fresh/zingy characters and an absence of passionfruit/green characters.”
But she also urged caution as to how the term is used because there was much between-judge variability.