Nutrients not the cause of minerality
Minerality in wine is most likely to stem from volatile thiols or esters and not directly from nutrients in the soil, according to this month’s edition of the drinks business.
Research shows that it’s impossible to get so-called “minerality” in a wine directly from the nutrients in the ground
In an article written by Sally Easton MW in db‘s April issue, she highlights research to show that it’s impossible to get minerality in a wine directly from the nutrients in the ground.
Having spoken to Professor Alex Maltman of the Institute of Geography and Earth Sciences at the University of Wales, she explains that mineral elements in a wine are not only minimal but also tasteless.
“Potassium rarely exceeds a few hundred parts per million (ppm) with a few tens of ppm for calcium and magnesium… these are tasteless anyway and their concentration in wine are below sensory thresholds measured in water,” says Maltman to Easton during a discussion on minerality.
However, Maltman is also quoted in the article as suggesting that minerality may stem from esters, which are created by the reaction of alcohol with an organic acid.
These he says can vaporize easily, and we can smell some of these aromatics in parts per trillion.
Meanwhile, Dr Wendy Parr, sensory scientist at Lincoln University in New Zealand suggests that tasters may be using the term “mineral” to describe characters produced by volatile thiols such as Benzenemethanethiol (BMT) in Sauvignon Blanc, which produces gunflint aromas.
Parr is studying descriptors of perceived minerality in Sauvignon Blancs, and although her research is yet to be published, she tells Easton that there’s a correlation between use of the term “mineral’ and screwcaps.
““The increased use of the term ‘mineral’ in relation to wine here in New Zealand parallels the increased use of screwcaps which some argue has produced many more wines exhibiting low levels of reductive notes,” she comments.
She also says, “The general pattern seems to be that wines judged lower in the fruity and green flavour notes are more likely to be judged mineral.”
Easton’s article also considers the use of the term “mineral” in tasting notes following research by Dr Jordi Ballester, who is oenology lecturer and researcher at the University of Bourgogne.
Although the descriptor is common today, Ballester points out that word minerality is absent from both Emile Peynaud’s The Taste of Wine (1983) and Ann Noble’s Wine Aroma Wheel (1984).
As Ballester concludes, “Wine has not changed that much; people have changed”.
For a full analysis of the term “minerality” over time and possible sources of aromas and flavours such as chalky, smoky and salty, see the April edition of the drinks business.
These assertions are incorrect. Potassium is a very important element in wine taste, as we demonstrated in sensory trials at Napa Valley College. This is why premium wineries hate to over-cold stabilize their wines. Potassium contributes to the perception of body and flavor persistence in the finish.
There’s a lot we don’t know about minerality, and much confusion about what the term means. It’s reasonable to suggest that esters or sulfur compounds are involved in the “wet stone” aroma, but in the case of soil minerals we are talking about an effect in the mouth, and it is certainly possible that potassium contributes to this. Wines are quite high in potassium, generally over 1,000 mg per liter, and wine is a significant source of dietary potassium.
Grapes by themselves lack the ability to take up complex nutrients. It is not impossible for grapes to import soil nutrients when they are grown in “living soil” conditions which foster the symbiosis of mycorrhizal fungi which have been shown to facilitate transport. In my view, this is why these wines taste different, and it certainly appears that wines grown on limestone, shist or decomposed granite exhibit similar effects.
For a fuller discussion, see my article Nov 2010 article in Wines and Vines.
Professor Maltman is mistaken about the concentrations of the major cations in wine. They are variable in the following ranges: Potassium, 400-1600 mg/L, Magnesium, 80-120, Calcium, 40-120, Sodium, 20-120. Although not a factor in the perception of ’minerality’, the inorganic cations and their salts do contribute to the taste of the wine. The presence of several g/L of salts changes the acidity qualitatively as well as quantitatively and is a significant factor in the difference between red and white wines, and between wines from different regions.
Inorganics cations, not only potassium, change the perception of sugar, of alcohol, and of tannins to…