Catching cheaters: detecting artificial carbonation in “authentic” beverages

Artificial carbonation is illegal for a variety of traditionally produced sparkling wines and French appellation d’origine contrôllée-designated and organic cidre. But how, once it’s in the bottle, is anyone going to tell whether a producer has cheated? Subjective sensory judgments are one thing, but a group of French chemists who’ve made detecting counterfeit tipples a specialty have devised a strategy for discriminating between legitimate and illigitimate bubbles. 

Carbonated beverages become carbonated in two ways. The first, “natural” way is to capture the carbon dioxide that yeast produce during fermentation by keeping the beverage under pressure while (at least part) of fermentation is happening. Traditional methode champenoise sparkling wines are carbonated this way: an already-fermented base wine is bottled under a crown cap (think beer bottle) with extra sugar, which yeast ferment to produce a bit more alcohol and carbon dioxide that, under pressure, dissolves into the wine to reappear as bubbles when release the pressure by opening the bottle. Traditionally made ciders and beers are also carbonated this way, as are home-made fermented sodas (not your Soda Stream), kombucha, and water kefir.

The second, “artificial” or “forced” way is to inject the beverage with carbon dioxide. Again, the gas dissolves into the liquid under pressure to be released upon enjoyment, but the source of the gas is a tank instead of a microbe*. Commercial sodas are carbonated this way, along with some cheap sparkling wines and the majority of mass-produced commercial beers (something against which the fine folks at the Campaign for Real Ale are fighting).

Unsurprisingly, natural carbonation takes longer and requires more skill and finesse to get right, is consequently more expensive, and is generally regarded as superior. Which means that some less-than-upstanding folk might want to pass off an injected drink as natural. Enter forensics.

Carbon-14 dating is used to determine the age, origin, and authenticity of fossils, bones, and other organic (once-living) artifacts (other types of isotopes are used to date rocks.) Carbon comes in multiple isotopes, or molecular versions numbered by how many neutrons they hold; 12C is the major version, 14C a naturally occurring minority. 14C is unstable and decays over time. While a plant or animal is alive, it constantly takes up fresh 14C from the environment; after it dies, the 14C in its body continues to decay without being replenished, which (I’m simplifying here) allows scientists to determine how long ago the thing died.

Carbon dioxide produced industrially (from petroleum) doesn’t contain any 14C; grapes and apples do, and therefore so does the carbon dioxide yeast produces from grape and apple sugars. So, we can determine whether a beverage has been artificially carbonated by looking at how much 14C it contains. If 14C levels are lower than the expected norm, someone’s cheating.

This concept isn’t new, but working out a practical method for analyzing samples and figuring out benchmark expectations for how much 14C shows up in natural versus injected beverages has taken some doing. The recent journal article describing that method looks at French AOC and organic cidres, but attests that testing sparkling wine (and beer and sparkling water) will work the same way. And while “carbon authentication” hasn’t yet been tested as evidence in a legal case, the authors conclude that, by their evidence, four of ten cidres bearing the organic label can be “strongly suspected” of illicit bubbling.

One more tool in the growing arsenal of anti-wine fraud tactics. As with the others, the real question is whether anyone will use it. Will this technique — plus Rudy Kurniawan et al. — herald an era of French governmental crackdown on sly producers? Or will everyone keep on happily humming along, knowing that the rules and “the rules” are a bit different? The industries’ (because there’s not just one wine industry, right?) approach toward authentic wines made using technically illegal methods, in the context of it’s attitude toward altogether counterfeit wines, stands to say something interesting about governmental and corporate priorities.

*Or, in the case of natural sparkling waters, a chemical reaction between acidic water and limestone.