Tag Archives: sparkling wine

In celebration of the New Year, we’ll once again focus our blog posts on current research related to Champagne/sparkling wine!

Briefly, the bubbles in Champagne and other sparkling wine beverages are created by trapped CO2 molecules during the secondary fermentation process.  The vessel in which these bubbles are trapped varies depending upon the method used; however, they all effectively function the same way:  sugar and yeasts are added to a still base wine in a closed system.  The yeast consume the sugars producing alcohol and carbon dioxide, and since the fermentation is taking place inside a closed system, there is nowhere for the bubbles to escape, thus remaining trapped within the wine itself, creating the characteristic bubbly.  In the traditional method (or méthode champenoise in Champagne, France), secondary fermentation is completed in the bottle itself, while with other methods (i.e. Charmat method), fermentation is completed in a sealed tank.

How many bubbles are actually in that bottle of Champagne or Sparkling Wine?

According to Henry’s Law, “the concentration of a dissolved gas is proportional to its partial pressure in the vapor phase” (Liger-Belair 2012).  Taking it a step further, the dissolved carbon dioxide portion in Champagne or sparkling wine is proportional to the amount of sugar added to the base wine to start secondary fermentation.  The amount of sugar added dictates how much alcohol and CO₂

By Waldo Jaquith (Flickr) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

The CO2 bubbles in the Champagne or sparkling wine are known to affect sensory perception during Champagne or sparkling wine tasting.  Some studies have found that the bubble “pops” intensify the aromatics of the wine, therefore the levels of dissolved CO₂ within the wine would effectively alter the sensory and quality perception by the taster.  It should therefore be the goal of the winemakers and those serving the beverage to maintain higher levels of dissolved CO₂ in the wine for as long as possible.

After a bottle of Champagne or sparkling wine is uncorked, CO₂ loss is already taking place.  CO₂ escapes a few different ways, with effervescence being the one most visually obvious.  Cracks or tiny imperfections within the bottle act to entrap the bubbles and produce a steady stream of bubbles that travel up through the wine and are released when they break the surface tension at the top of the liquid.

One less obvious mechanism for CO₂ loss in Champagne or sparkling wine that actually results in the greatest levels of CO₂ loss is what is known as “invisible diffusion”.  This takes place at the air/liquid barrier at the top of the bottle (or glass) and is a mechanism that one does not actually see.  Studies have shown that for every one CO₂ molecule that escapes via bubble that one can see, 4 more molecules escape via “invisible diffusion” at the air/liquid barrier.

There has been a lot of research done on CO₂ loss in Champagne or sparkling wine; however most of these studies have only focused on “bubble physics”.  According to the authors of the study presented today, there has been very little research done on the pouring step of the serving process and the CO₂ losses associated with the physical pouring of the wine into the glass.

Imagine how a bottle of Champagne or sparkling wine is served:  the standard practice is that the bottle is moved from a vertical to a horizontal position while the liquid is being poured directly into the center/bottom of the glass.  The air-

By ori2uru (originally posted to Flickr as champagne tower) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

The study presented today aimed to explore this concept of CO₂ loss during the pouring step during whole bottle Champagne or sparkling wine service, which has been not been properly studied or included as a source of CO₂ loss in this type of research in past studies.

Methods

The wine used in this study was a “standard commercial Champagne wine” (Liger-Belair 2012) using 100% Chardonnay grapes from the 2009 vintage from the Cooperative Nogent l’Abbesse in Marne, France.  Prior to use, the wines were stored in a cellar at 12^oC.

Bottle types used during this study were Champagne/sparkling wine shaped and were: 1) standard 750mL; 2) magnum 1500mL; and 3) half bottle 375mL.  The authors noted that while the bottle volumes were different, the headspace volumes were the same. Similar corks were used to seal all wines.

24g/L of sugar were added to the base wine for all bottle sizes.

Temperature dependence of the Champagne was measured and it was found that the smaller the bottle, the lower the starting dissolved CO₂ concentration.

Glasses used in this study were identical “long-stemmed glasses with a deep tapered bowl and a narrow aperture” (Liger-Belair 2012).  All flutes were etched at the bottle in an attempt to avoid the randomness of CO₂ loss via visual effervescence.  After each use, glasses were washed with a dilute aqueous formic acid solution, rinsed with distilled water, then dried using compressed air.  When not in use, flutes were stored at room temperature.

After uncorking a bottle, 100mL of Champagne was poured successively into flutes.  The magnum bottle required 14 flutes, the standard bottle required 7 flutes, and the half bottle required 3 flutes to finish the bottle.  Flutes were lined up horizontally on a table and close to each other so that each pour of Champagne was vertical and hitting the bottom of each glass.

Experiments were performed at three different temperatures: 4^oC, 12^oC, and 20^oC.

Dissolved CO₂ was measured in each flute immediately after pouring.  5 pourings were completed for each bottle size and each temperature, in order to create an average dissolved CO₂ value per bottle size and temperature for statistical analysis.

Complex mathematical models were created to try and simulate the results found during this study, the gory details of which I will spare you for this post.

Results

• Dissolved CO₂ levels in the flutes were lower than what they were in the bottle.
  • This indicates there is a loss of dissolved CO₂ during the pouring process.
  • Loss of dissolved CO₂ during the pouring process was roughly between 3 and 4g/L.
• The levels of dissolved CO₂ within the flute decreases as bottle volume decreased.
  • Example given: The amount of dissolved CO₂ in the flute from a magnum bottle was higher than the amount of dissolved CO₂ in the flute from a standard bottle, with the amount of dissolved CO₂ in the flute from a half bottle containing the lowest levels of dissolved CO₂.
• The levels of dissolved CO₂ within successive flutes in general decreased with each flute further down the line.
  • In other words, the last flute in pouring succession had lower levels of CO₂ than the 3^rd flute in pouring succession.
• Despite the general trend of CO₂ decreasing with each subsequent pour, the first pour actually saw an increase in dissolved CO₂ levels.
  • The authors attribute this to the “glug glug” effect.  When the bottle is full of liquid, it comes out quickly and more “wild”, introducing more air bubbles into the liquid.  Once the liquid level inside the bottle decreases, the flow becomes more uniform and gentle, and we see the aforementioned decrease in dissolved CO₂ levels with each subsequent pour.  The “glug glug” name comes from the sound we attribute to the quickness of the liquid frantically coming out of the bottle when it’s full.
    • The “glug glug” effect was seen in the first 4 flutes poured from the magnum bottle, the first 2 flutes poured from the standard bottle, and the first flute poured from the half bottle.
• Levels of dissolved CO₂ within the flutes decreases as serving temperature increased.
  • In other words, the higher the serving temperature, the fewer the bubbles present in the flutes (i.e. the greater the CO₂ loss to the atmosphere).
  • The higher the serving temperature, the greater the dissolved CO₂ loss for each successive pour.
• The levels of dissolved CO₂ within successive flutes decreased with each flute further down the line and were highly affected by temperature increases.
  • In other words, the difference in dissolved CO₂ levels between the first and last flute was greater with higher serving temperatures (i.e. greater dissolved CO₂ loss between the last and first flutes at 20^oC than at 4^oC).
• The mathematical model confirmed much of the experimental data described above.
  • The model accurately described the phenomena that dissolved CO₂ decreases with each subsequent pour.
  • The model confirmed that dissolved CO₂ concentrations are higher in larger sized bottles than smaller bottles.

Conclusions

Overall, the results of this study found that there is a decreasing trend of dissolved CO2 as one moves from the first flute to the last flute of the succession.  In other words, the pouring process has an effect on the “bubbliness” of the wine with each subsequent pour.  In order to maintain a higher level of dissolved CO2 (i.e. more bubbles) when pouring for tasting or other serving purposes, the results indicate that a larger bottle may be the best choice.

Figure 4 from Liger-Belair et al, 2012

The authors speculate from these results that the magnum bottle is able to better retain dissolved CO₂ within the bottle and therefore the flutes poured from the bottle, thus may be important for those tasting and drinking the beverage.  In general, the larger the volume, the greater the ability of the wine to retain dissolved CO₂ bubbles and maintain Champagne/sparkling wine quality.  Armed with this knowledge, one may want to grab one of the first flutes poured rather than the one of the last in order to be certain the levels of dissolved CO₂ are high enough to experience the full glory of the Champagne or sparkling wine.

The authors also noted that serving temperature also has a significant effect on dissolved CO₂ loss in Champagne/sparkling wine.  The results indicated that higher temperatures resulted in a faster loss of dissolved CO₂, therefore resulting in “flat” wine a lot faster at a higher temperature after being poured than if the wine were served at a colder temperature.  It is important to keep the Champagne or sparkling wine at a cooler temperature in order to maintain the levels and quality of the bubbles therein.

One thing I would like to have seen is the relative contribution of the pouring step in regards to overall dissolved CO₂ loss in Champagne/sparkling wine.  We can clearly see from the results that the pouring step does elicit dissolved CO₂ loss, but just how much loss is this compared with losses via the other studied mechanisms.  Is the pouring process the most significant mechanism for dissolved CO₂ loss?  Or is there something else that’s more important?

I would have also liked to have seen the same experiments run with different types of sparkling wine.  How does Champagne compare with sparkling wine, Prosecco, Cava, etc?  How does the winemaking method affect the rate of dissolved CO₂ loss in the wines?  Is dissolved CO₂ loss greater in the traditional method, the Charmat method, or any other method?  Or is dissolved CO₂ loss independent of winemaking methods?

Finally, I would have liked to have seen the authors go one step further and examine which pouring method results in the smallest loss of dissolved CO₂.  We can see that the traditional pouring method results in a certain loss of dissolved CO₂, but how does this compare with other pouring methods?  If you hold the glass at a 45^o angle, does this result in less dissolved CO₂ loss?  What if both the glass and the bottle are held at an angle?  Surely this takes longer and isn’t as “pretty” as the traditional pouring method, but if maintaining the integrity of the dissolved CO₂ bubbles and maintaining Champagne/sparkling wine quality is the ultimate goal, it may be of interest to determine which pouring method minimizes dissolved CO₂ losses.

I’d love to hear what you all think of this study! Please feel free to leave your comments!

HAPPY NEW YEAR from The Academic Wino!  Cheers!

Photo by The Academic Wino: November 2008.

Source: Liger-Belair, G., Parmentier, M., Cilindre, C. 2012. More on the Losses of Dissolved CO₂ during Champagne Serving: Toward a Multiparameter Modeling. Journal of Agricultural and Food Chemistry 60: 11777-11786.