Divers discovered bottles in a shipwreck off the Finnish Aland archipelago in the Baltic Sea in 2010. After tasting the bottles on site, the divers realized they were likely drinking century-old champagne. Soon after, 168 unlabeled bottles were retrieved and were identified as champagnes from the Veuve Clicquot Ponsardin (VCP), Heidsieck, and Juglar (known as Jacquesson since 1832) champagne houses. A few of the recovered bottles had been lying horizontal in close-to-perfect slow aging conditions.

Discovery of these wines, likely the oldest ever tasted, unleashed a flood of questions. When were these wines produced? What winemaking processes were in use at the time? Where was the wine going when the shipwreck occurred?

An analytic approach

A team of scientists gathered to search for the answers through the application of current analytical techniques, an approach called archaeochemistry. Using a combination of targeted and nontargeted modern chemical analytic approaches, the researchers aimed to uncover aspects of the winemaking practices.

The team tasted and analyzed three of the “Baltic Champagne” samples and compared them to three modern champagne samples from VCP. Elemental analyses alongside metabolomics and aroma analyses yielded a significant amount of data that, once analyzed, shed light on the champagne making process used in the 19th century.

These Baltic champagne samples contained unusually high concentrations of iron and copper cations. Iron levels reached up to 13-118 mg/L compared with 1-4.6 mg/L in modern samples, and copper levels were as high as 100-1,400 µg/L compared to 27-78 µg/L in modern samples. The scientists proposed a variety of reasons for the elevated metal cation levels.

At the estimated time of production of the champagne (~170 years ago), proper picking and pressing methods ensured high quality of the extracted grape juice (musts) that would allow for the delicate white wines needed for champagne. Fractionation of the musts was performed by gently pressing the grapes, resulting in two portions with differing qualities. In champagne, the first 2,050 liters of grape juice (out of 4,000 kg grapes) are typically considered the finest wine, called the cuvée. The final 500 liters of grape juice pressed are generally of a coarser quality, called the taille.

The taille is characterized by lower total acidity and increased pH, mineral, and phenolic concentrations compared to the cuvée. The researchers speculate that the high concentrations of iron and copper in the Baltic champagne samples could be the result of a higher proportion of taille incorporated into the blend.

An alternative rationale could be increased metal iron extraction from the grapes, combined with use of metal-containing vessels used during the winemaking process. Our current knowledge of the practices used during that time period indicates that smaller berries were harvested, which would have meant more grape skin per volume. This would have resulted in a greater concentration of metals extracted from the skin. Barrels were also assembled with iron nails, and iron rods held sulfur wicks during the sulfurization; these would have been oxidized during winemaking, which could lead to the increased iron levels.

Fermentation processes

The must then would have undergone its first alcoholic fermentation. Analytical techniques identified wood markers such as 5-carboxyvanillic acid and castalin, which suggest that alcoholic fermentation took place in barrels. The Baltic champagne samples exhibited lower alcohol levels (9.34-9.84 percent alcohol by volume) compared to modern ones (12.33 percent alcohol by volume).

Records indicate that at this time period the first alcoholic fermentation step occurred during colder months of the year with native yeasts, which would be less efficient than modern selected yeasts. As a result, the researchers think it may have been common for incomplete alcoholic fermentation to occur, contributing to the lowered alcohol content. The colder weather could have also led to lowered sugar levels due to retardation of the grape maturation, which could also have contributed to the lower alcohol content.

Baltic champagne samples also exhibited significantly higher concentrations of Na+, Cl-, and Br-. The team quickly ruled out contamination by seawater as a source of the elevated levels; they suspect that they're more likely to be related to winemaking practices such as wine clarification, which is used to control aggregates that make the wine cloudy. The team found that historical records indicate that gelatin was used for clarification, which would require sodium chloride to facilitate protein dissolution.

Another process that is used to avoid precipitation of acid salts is tartaric stabilization, which is performed after blending. Historical records indicate that the blending of wines predates the 19th century. Similarities between the Baltic and modern champagne samples regarding the average concentrations of the two ions central to tartaric acid salt precipitation suggest that this process was indeed performed to produce these champagnes.

Next, the second alcoholic fermentation would take place in capped bottles using indigenous yeast after the addition of sugar. It is at this time that carbon dioxide would be produced, resulting in the effervescence characteristic of champagne. In that time period, the characteristic amount of CO 2 dissolved in a champagne was about 10g per liter of wine. However, in the Baltic champagne bottles, a large amount of the CO 2 had diffused through the porous corks over time.

The final touch: sugar

Finally, the Baltic champagne samples contained extraordinarily high levels of sugar (over 140 g/L). The typical amount of sugar added to modern champagnes before corking is 0-50 g/L. The presence of ribose suggested that grape syrup was at least one component used. The presence of difructose dianhydrides, which are key markers of caramelization, point toward the use of grape juice concentrated by heating to produce grape syrup with over 700g of sugar per liter.

Surprisingly, it appears that good hygiene practices were followed during the production of the Baltic champagnes. This wine exhibited very low concentrations of acetic acid, which is a sign of wine spoilage. Though we often equate good hygiene practices with modern civilization, these findings suggest otherwise.

Once oxygenated in a glass the wine was described as “empyreumatic, grilled, spicy smoky, and leathery, together with fruity and floral notes.” Thus, this rare champagne has served as both a delicious beverage and a complex clue providing insight on the historical winemaking processes.

PNAS, 2015. DOI: 10.1073/pnas.1500783112 (About DOIs).