Understanding Disgorgement and Dosage

pouring Franciacorta, photo by Becca Yeamans Irwin

Popping the Cork on Confusing Sparkling Winemaking Terminology

Most of us have enjoyed sparkling wine at one point or another. For some of us, it’s enjoyed at New Year’s or some other celebratory event, while for others it’s something we drink on the regular. Despite being a growing market (6.6% rise in sparkling wine consumption in the US in 2017, Beverage Information Group data), there is a lot of confusion about how sparkling wines are actually made. Two of the most confusing stages of sparkling winemaking are disgorgement and dosage.

Sparkling Wine Production, In the Tiniest of Nutshells

While there are several techniques for producing a sparkling wine, all of them have one common feature, and that the secondary fermentation. Some techniques, like the traditional method (a.k.a. Méthode Champenoise), complete this second fermentation within the bottle, while other techniques, such as the Charmat method (a.k.a. Tank method), complete the secondary fermentation inside of a tank and later transferred to the final packaging.

For those sparkling wines that undergo the secondary fermentation within the bottle, there becomes the issue of removing any dead yeasts/lees from the bottle prior to being consumed. Briefly, during the secondary fermentation, the wine is inoculated with a mixture of sugar, yeast, and wine (“liqueur de tirage”), which converts to a little more alcohol and CO2, giving the wine the characteristic bubbles that we all know and love. Once this is complete, however, the yeast doesn’t just disappear. Over time, the bottles rotated (“riddled”) so that these dead yeasts (“lees”) end up in the neck of the bottle near the cap.

Disgorgement: Explained

Disgorgement machine, photo by Becca Yeamans Irwin

After this lengthy riddling process, where the lees eventually collect in the bottle neck (picture an upside-down bottle with a little blob of “stuff” near the cap), it needs to be removed, the process of which is called “disgorgement”. First, the bottles are cooled down significantly, to help reduce the amount of wine lost to “gushing” after the cap is opened and the pressure immediately tries to equilibrate to the lower ambient room pressure. The necks of the bottles are then quickly frozen, which helps keep the lees into one solid piece for more efficient removal.

After the neck of the bottle is frozen, they must be quickly inverted (most producers do this by machine) and the cap is popped. The frozen lump of lees then subsequently shoots out. The bottle opening is then covered to prevent any wine from spraying out and to prevent excess ingress of oxygen into the bottle. Of course, during this disgorgement process, some wine is inevitably lost, which requires the winemaker to replace or “top off” what was lost to achieve the desired fill level in the bottle.

Dosage: Explained

As you can imagine, opening up a bottle of wine under great pressure is bound to result in a loss of some of the fluid inside, so that aforementioned “topping off” is necessary, and you’d see a lot of different fill levels in every bottle of sparkling wine that you purchase at the shop. This “topping off” process has a specific name, which is referred to as “dosage”.

Basically, the dosage is a solution of 60-70% sugar that is dissolved in wine, preferably the same base wine that was used in the beginning of the sparkling winemaking process. Sometimes, brandy or sulfur dioxide is added to the dosage, which functions to prevent spoilage and oxidation.

Topping off the bottle after disgorgement isn’t the only role of the dosage. It is also where winemakers can control the sugar level in the finished wine. For sparkling wines, there is a hierarchy of sugar levels, the end goal of which will influence how much of the dosage to add after disgorgement. Nature and Extra Brut wines are the driest, with <0.3% and <0.6% residual sugar, respectively. In these cases, the dosage often is dry (or has very little residual sugar). Brut wines receive enough dosage to bring the final residual sugar level to 1.5%, Extra-sec to 1.2-2%, Sec to 2-4%, Demi-sec to 3-5%, and Doux >5% residual sugar.

After the final volume and sugar levels are adjusted with the addition of the dosage, the bottles are finally corked.

Which sugar is the best sugar? And how much?

While it is common for winemakers to add a sweetened dosage solution to top off a sparkling wine and to adjust its final sugar level, there hasn’t been much study on what kind of sugar is preferred by consumers and how this might affect sales. Specifically, should a winemaker add a sucrose-based dosage solution? Or fructose? Glucose?

A 2017 study from a Washington State University group aimed to be the first study to evaluate the effect of sugar composition in dosage on the final wine’s sensory profile as well as consumer acceptance. To do this, they, along with a team from Chateau Ste Michelle Wine Estates, produced several different sparkling wines (using the traditional method) made with dosage solutions containing three different sugar types (sucrose, fructose, and glucose) and varying final sugar levels (no sugar added, brut, and demi-sec).

A team of trained panelists found the type of sugar used and the final residual sugar levels interacted to influence the final flavor profile of the wines. Specifically, they found that this interaction impacted the caramel, vanilla, and honey flavors, as well as sweet and sour taste characteristics the most. In terms of residual sugar levels, demi-sec wines had less green, yeasty, and sour tastes/flavors than wines with no added sugar.

Next, a group of 126 consumers were recruited from the university and surrounding community to evaluate the wines. For these consumers, general acceptance of the wines were correlated with the caramel, vanilla, and honey flavors, as well as sweet tastes and a creamy mouthfeel. Additionally, consumers preferred the wines made with fructose-based dosage compared to the other two sugar types evaluated. Cluster analysis found that within this group of consumers, there were 2 distinct sub-groups with different liking preferences. Specifically, while both groups preferred the wines made with fructose-based dosage, one group preferred the sweeter demi-sec wines while the second group preferred the brut wines.

The results that some consumers prefer sparkling wines sweeter while others like them drier is nothing new and unremarkable, but the finding that most of the study participants preferred the wines adjusted with fructose-based dosage could help winemakers decide what sugar to add to their dosage solution. Of course, it’s important to note the small sample size of participants, but the results are nonetheless interesting.

Conclusions

The path toward making a sparkling wine is much different than a still wine. While they both might start off the same, when you start to introduce the bubbles things take a more complicated turn. Just in case you need some inspiration for sparkling wines to pick up on your next trip to the wine shop, here are some examples of sparking wines with lower residual sugar (i.e. Brut or drier) that won medals at the 8th Annual New York International Wine Competition this past May, 2018.