Stable Carbon Isotopic Composition of the Wine and CO2 Bubbles of Sparkling Wines: Detecting C4 Sugar Additions

Sparkling wines have become a popular beverage in recent years, and the production of these wines is subject to adulteration during fermentation. This study investigated the stable carbon isotopic composition (expressed as δ13C) of the wine and of the CO2 bubbles produced during the second fermentation for a number of sparkling wines produced in different countries around the world. Carbon isotope ratio analyses were used to estimate the addition of sugar obtained from C4 plants (sugar cane or corn). The average δ13C values of the Brazilian brut, demi-sec, and doux sparkling wines were −20.5 ± 1.2‰ (n = 18), −18.1 ± 1.3‰ (n = 9), and −15.8‰ (n = 1), respectively. These values were statistically heavier (more positive carbon isotope ratio values) than the average δ13C of sparkling wines produced in other parts of South America (Argentina and Chile, −26.1 ± 1.6‰, n = 5) and Europe (France, Germany, Italy, Portugal, and Spain, −25.5 ± 1.2‰, n = 12), but not statistically different from sparkling wines produced in the United States or Australia. The most likely explanation for differences in the carbon isotope ratios of wines from these different regions is the addition of C4 sugar during the production of some sparkling wines from Australia, Brazil, and the United States. The isotopic composition of the CO2 bubbles (δ13C-CO2) followed similar trends. The average δ13C-CO2 of most of the Brazilian and Argentine sparkling wines was −10.8 ± 1.2‰ (n = 23), indicating that the likely source of carbon for the second fermentation was sugar cane. Conversely, the average δ13C-CO2 of most of the sparkling wines produced in Chile and Europe was −22.0 ± 1.2‰ (n = 13), suggesting that a different sugar (most likely sugar beet) was most used in the second fermentation. It was concluded that in many cases, the carbon isotope ratios of sparkling wine and CO2 bubbles can provide valuable information about the sugar sources.