Return to Minerality: Acidity
In this little series on minerality – from which I have had an enforced break, partly down to my trip to the Loire to see the 2013 harvest in action and my Bordeaux 2013 reports – I have looked at many different explanations for the mysterious ‘minerality’ that now seems so commonplace in wine. Some explanations that have been offered – such as the presence of minerals, chemical or geological, in the wine, just don’t ring true. Others, however, have more promise; of these, the most enticing is related to what is commonly termed ‘reduction’, which is actually the presence of mercaptans in the wine, mercaptans commonly being produced during fermentation of nutrient-poor (especially nitrogen-poor) musts. Their presence is enhanced by protecting the embryonic wine from oxygen, hence they have become associated with ‘reductive’ winemaking techniques, and in a leap of faith have since been ascribed by many to reduction itself, which of course isn’t quite true. See my previous posts, starting with my examination of minerality and soil minerals, for more information.
Throughout all my previous posts, however, there has been an elephant in the room, and this particular elephant’s name is acidity. Acidity, and its relationship with minerality, has been there in the back of my mind all along, and it has eventually come to the fore. Now it’s time to take a look at acidity in a little more detail.
It seems to me that there is a strong correlation between the presence of minerality and acidity in wine. Draw up a short-list of wines that show minerality – Riesling from the Mosel and Rhine Valleys in Germany and Alsace in France, Chablis, Loire whites including both Sauvignon Blanc and Chenin Blanc and so on, and you clearly have a list of northern cool-climate wines that also tend towards higher levels of acidity. The correlation is far from solid, however, as there are many white wines rich in acidity that do not necessarily show minerally characters. This shouldn’t dissuade us from pursuing acidity as a potential part of the minerality ‘story’ though, as it may be that some other process in the winery influences whether or not acidic wines hold onto their ‘minerality’ (rather akin to how the presence of mercaptans can be preserved, or disrupted, by winery practices). Alternatively, it might be some aspect of the vineyard that is associated with minerality which also enhances the acidity. More on this in a minute.
The commonly proposed theory is that minerality in wine is not due to minerals at all (we know that much already), but is in fact down to the presence of acidity, perhaps accentuated by a lack of fruit ripeness which would otherwise disguise the chalky/stony/slatey minerality of the acids. This might explain why only more cool-climate northern regions tend to show minerality as although all wines have acidity it is only these regions that would produce wines with the lower levels of ripe-fruit character necessary to induce the ‘minerally’ sensation. Terroir may also be important; this is a vital consideration if we are to somehow link the apparent relationship between minerally wines, and minerally terroirs. It is plausible that some soils may influence acidity (and thus minerality) levels through their ability to radiate heat back to the vines and fruit, or by their propensity (or lack of it) to hold onto water. In addition it seems accepted that more alkaline soils – such as limestone, as found in Chablis, Sancerre and Vouvray, for example – tend to produce wines with higher acidity (regardless of how incongruous this birth of acidity from alkalinity may seem!). Variety must also play a role, as some varieties seem to express minerality much better than than others; Riesling in Alsace, for example, might be regarded as more minerally than Gewurztraminer. Riesling is also the more acidic of the two varieties, wines made from Gewurztraminer tending more towards a softer, low-acid style.
It all seems very tempting. Surely soil, acidity and minerality are intertwined? I see a couple of minor problems with the concept of low-fruit-ripeness plus acidity as the cause of minerality, and these are as follows;
First, the term ‘minerality’ has really only entered the wine tasting lexicon in the past 10 or 15 years. And yet the features that have been discussed here – soil, stones, climate, variety – all of which may have some effect on the eventual acidity level in the wine in question, seem to me to be long-standing constants. Sancerre has been as we know it today really since the immediate post-phylloxera era, when Sauvignon Blanc came to dominate the appellation (in place of Pinot Noir, which had been the mainstay until that time) during the replanting. The variety, the limestone soils, these are unchanged, so why weren’t tasters reporting this minerally sensation in the 1960s and 1970s?
Secondly, it seems very unlikely that we should suddenly begin detecting acidity as minerality, when acidity itself gives such a clear message to the palate. I’m not really prepared to accept that minerality and acidity are one and the same. Nevertheless it seems clear that minerality and higher acidity are related in some way; many observers – writers, critics, sommeliers, winemakers – have reported a correlation between the two. This has been confirmed in sensory studies, such as that by Wendy Parr of the University of Lincoln which was published in New Zealand Winegrower this year. In her study, Parr recorded the tasting opinions of groups of French and New Zealand tasters (all wine industry professionals), all of whom sat down to blind-taste 16 French and New Zealand Sauvignon Blancs. Looking at their assessments, it was clear that there was a correlation between perceived sourness/acidity and the perception of minerality in a wine. This still doesn’t tell us what is causing the sensation of minerality though, although again the combination of high acidity and low fruit-ripeness is put forward by Parr and colleagues. Of note though, other perceived aromas felt to be a description of minerality demonstrated a correlation with ‘reductive’ sulphide characteristics. Acidity seems to be part of the story, even if it is perhaps nothing more than a constant spectator, or perhaps a catalyst, but here again we have ‘reduction’ – as I discussed in Mineralty – A Reductive Phenomenon? – raising its head. I can’t help feeling – especially with changes in winemaking practises pushing many wines towards a more reductive character in recent years – that ‘reduction’, or rather mercaptans, play a somewhat more significant role than acidity.
Further reading: Parr W, Ballester J, Valentin D, Peyron D, Sherlock R, Robinson B, Breitmeyer J, Darriet P, and Grose C. 2013 The nature of perceived minerality in white wine: preliminary sensory data. New Zealand Winegrower, 78, 71-75. Link (forward to page 71)