Number crunching

Looking behind the numbers on Alcohol and Acidity in sparkling wine

Welcome, bubbleheads.

I’m trawling through my enormous spreadsheet of Blanc de Blancs for the Decanter report on the go at the moment. There’s a column for ABV - alcohol by volume - and it’s causing me much more of a headache than the stuff itself normally does.

Why?

Because, short of having the bottle in front of you, it can be almost impossible to nail down. Unlike for still wines, Champagne producers seem to think we're not that interested; try finding it on a technical sheet or website and you'll likely come up empty-handed.

With that in mind, I’ve put something together on the oh-so-simple-looking topic of two numbers you might come across if you look at the vital stats on a bottle of sparkling wine:

1. Alcohol By Volume.

EU labelling law is changing - soon we will have access to ‘ingredients’ in wine, beyond sulphites.

Ah, it used to be so simple. Champagne was or 12%, perhaps 11.5%, perhaps 12.5%….but essentially alcoholic content was by design. Sugar additions, often required at harvest (chaptalisation), ensured that base wine was of a targeted alcoholic content, onto which was added a known quantity of alcohol produced by the second fermentation in bottle (between 1% and 1.5% by volume). Grapes, at least in the 1970s, 1980s and most of the 1990s, were never so high in potential alcohol in the first place as to threaten to send finished alcohol levels any higher.

Today, things are different. 2019 has produced a number of what taste, at least to me, as fairly boozy champagnes. It’s a great vintage, but the question of integration of alcohol has occasionally nibbled away….Didier Gimonnet’s (excellent) 2019 vintage Fleuron is 13.4% A.B.V., a number that turns out to be far from uncommon (and far from the highest, either - yes, there will be some champagnes over 13.5% in 2019 and 2020). Champagne, before the enormous fertiliser/clonal-selection/herbicide-driven yields of the 1970s and 1980s, did occasionally see harvests with such ripenesses, but they look like becoming much, much more mainstream.

So, what’s on the bottle? Here’s where labelling law pulls a blinder: EU law allows a 0.8% ‘tolerance’ for sparkling wine A.B.V. on the labels, meaning that a 13.3% Champagne could be labelled as 12.5% (still wine only has a 0.5% tolerance, presumably because the second fermentation for sparkling wines can be a little unpredictable). At this point, if we had all day, we could look at the UK’s daft post-Brexit Duty reforms, and what that might mean for Champagne….but that’s a can of worms you may want to pre-open here.

There are three ways to keep alcohol low in Champagne; to pick early, to reduce the sugar (and hence the pressure) added at second fermentation or to practise tirage à moût. Each has its drawbacks, although the taste of aggressively early-picked Champagne is one not to relish (Chardonnay picked before true ripeness seems to smell of slightly soapy-green flavours, a bit like Fairy liquid, an English washing-up liquid brand, whereas Pinot Noir goes stalky-green-vegetal - two different shades of under-ripeness, for me at least). Best, it seems, to pick when the flavours are there and deal with the juice chemistry.

Which leads us on to…

2. Total Acidity

Total Acidity, the number that ‘TA” refers to in wine technical data sheets, is different to pH; pH is a measure of the strength of the acidity in the wine (between 2.8 and 3.2 for most sparkling wines) whereas total acidity is a measure of the quantity of acid (given that different forms of acid have different strengths). TA is more about the acidic force of what you actually taste, whereas pH has a more wide-ranging impact on a wine’s style and stability.

In France, a wine’s total acidity is measured “as Sulphuric equivalent”, meaning the quantity in g/l it would be if it were assumed that all the acid present was sulphuric. Elsewhere it is given “as Tartaric equivalent”, which is roughly 1/3rd higher. This is why French TA levels sometimes look low: an English Sparkling wine that claims a TA of 10 g/l actually has the similar TA as a French sparkling wine that says it’s 6.4 g/l.

Tartrate crystals - precipitated potassium bitartrate - recovered from a carboy of (dark pink) wine I made in Kent.

A topic that seems entirely sidestepped in discussions about acidity is acidification - the addition of tartaric acid to must or wine to bring up acid levels - and de-acidification, the practice of using carbonates to remove acid (usually only tartaric, but, with a little trickery, malic too) from must and, occasionally, wines.

We’re into frightening-the-horses territory here; nobody really likes the idea that the acidity of their wines has been mucked around with, although some Champenois certainly acidify; in 2023, thanks to unusually low acidity and high pHs, producers were allowed to add 1.5 g/l to both must and wine (it is usually just permitted once, to must). It’s a fairly open secret that high quality houses such as Louis Roederer are not averse to acidification; it’s better to have ripe grapes and acidify than unripe grapes with the right acidity in my book. EU labelling laws are changing, though, to require that additions of tartaric acid are declared (even if tartaric acid can be declared online, on a page trackable via a code, rather than on the label itself). When this works its way through to Champagne, we will be able to check.

De-acidification is more invasive, and difficult. English producers have certainly used it in years, for example. where Chardonnay TA has been as high as 15g/l or above. There are a number of technical drawbacks, however, that mean it is not often conducive to balanced wines.

Sometimes, rainfall and huge yields can dilute both sugars and acidities; 2023, for example, showed unusually low levels of both.

Getting tecchie with it

Checking bottles from 2019 and 2020 for whether they say 12.5%, or 13% is going to be a new habit, it seems. Hopefully it will be a non-issue, although I think we’re going to see more and more people think about tirage å moût if the high alcohol levels persist.

The issue of tartaric acid is potentially a little more controversial - on the one hand it’s hard to buy into the idea that boosting the level of the most prevalent organic acid already in the wine is somehow erasing Terroir. You could argue that it actually magnifies it, by allowing producers to pick later and achieve full flavour ripeness, although if the pH of the wine shifts significantly downwards that does start to look like that bogeyman-word of wine; an intervention.

The bigger issue, perhaps, is that it muddies a sense of Vintage. I love getting to know vintages, and I'm not sure how I feel about the possibility that a wine that is strikingly bright, energetic and brisk for a hot vintage is partly so just because of an acid adjustment, rather than wizardly viticulture or special vineyards.