New discovery explains what makes Champagne bubbles so special

Scientists from Brown University and the University of Toulouse in France have discovered the secret behind the unique bubble behavior in Champagne, explaining why its bubbles rise in a straight line compared to other carbonated beverages like beer or soda. 

This research not only sheds light on the science behind the formation of bubbles in Champagne but also offers valuable insights into fluid mechanics, with potential applications in other bubbly flows.

The findings, recently published in the journal Physical Review Fluids, are the culmination of a series of numerical and physical experiments that involved pouring glasses of Champagne, beer, sparkling water, and sparkling wine. 

The researchers aimed to investigate the stability of bubble chains in carbonated drinks and understand the fluid mechanics that give each beverage its distinct characteristics.

Study senior author Roberto Zenit, an engineering professor at Brown, explained the significance of the research: “This is the type of research that I’ve been working out for years. Most people have never seen an ocean seep or an aeration tank but most of them have had a soda, a beer or a glass of Champagne. By talking about Champagne and beer, our master plan is to make people understand that fluid mechanics is important in their daily lives.”

When enjoying carbonated beverages, the formation of bubbles and fizz is a key part of the overall experience. In Champagne and sparkling wine, gas bubbles continuously rise to the top in a single-file line and persist for some time, forming what is known as a stable bubble chain. 

In contrast, bubble chains in other carbonated drinks like beer tend to be unstable, with many bubbles veering off to the side and appearing as if multiple bubbles are emerging simultaneously.

Why study bubbles?

The researchers sought to understand the mechanics behind stable bubble chains and explore if they could recreate them, making unstable chains as stable as those in Champagne or prosecco.

The experiments revealed that the stable bubble chains in Champagne and other sparkling wines are due to the presence of ingredients that act as soap-like compounds called surfactants. These surfactant-like molecules help reduce the tension between the liquid and gas bubbles, enabling a smooth rise to the top.

“The theory is that in Champagne, these contaminants that act as surfactants are the good stuff,” said Zenit. “These protein molecules that give flavor and uniqueness to the liquid are what makes the bubble chains they produce stable.”

The stability of bubbles in carbonated beverages is influenced by the size of the bubbles themselves and the presence of surfactant-like molecules. 

The research, which involved pouring glasses of various carbonated beverages such as Pellegrino sparkling water, Tecate beer, Charles de Cazanove Champagne, and a Spanish-style brut, sheds light on the fluid mechanics behind bubble formation and has potential applications in bubbly flows.

What the researchers learned

The experiments revealed that chains with large bubbles have a wake similar to those with contaminants, resulting in a smooth rise and stable chains. However, bubbles in beverages are generally small, making surfactants crucial for producing straight and stable chains. 

While beer also contains surfactant-like molecules, the stability of its bubbles varies depending on the type of beer. In contrast, bubbles in carbonated water are always unstable due to the absence of contaminants that help them move smoothly through the wake flows left behind by other bubbles in the chain.

“This wake, this velocity disturbance, causes the bubbles to be knocked out. Instead of having one line, the bubbles end up going up in more of a cone,” explained Professor Zenit.

Implications of the study

The findings have implications beyond understanding the science behind celebratory toasts. They provide a general framework for understanding the formation of clusters in bubbly flows, which has both economic and societal value. 

Technologies that utilize bubble-induced mixing, such as aeration tanks at water treatment facilities, would benefit from a clearer understanding of bubble clustering, origins, and predictability. Additionally, understanding these flows could help explain ocean seeps, where methane and carbon dioxide emerge from the ocean floor.

How to study bubble chains

To study bubble chains and their stability, the researchers used a small rectangular plexiglass container filled with liquid and inserted a needle at the bottom to pump in gas, creating different types of bubble chains. 

They gradually added surfactants or increased bubble size and discovered that making bubbles larger could stabilize unstable bubble chains even without surfactants. Similarly, adding surfactants to fixed bubble sizes also resulted in the transition from unstable to stable chains.

The team performed numerical simulations on a computer to answer questions that physical experiments could not address, such as calculating the amount of surfactants in the gas bubbles, the weight of the bubbles, and their precise velocity.

The researchers plan to continue exploring the mechanics of stable bubble chains and apply their findings to various aspects of fluid mechanics, particularly in bubbly flows. Zenit emphasized their ongoing interest: “We’re interested in how these bubbles move and their relationship to industrial applications and in nature.”

This research not only offers valuable insights into the science behind the behavior of bubbles in carbonated beverages but also opens the door to new applications in fluid mechanics and bubbly flows, potentially benefiting a range of industries and natural processes.

More about carbonation

Carbonation is the process of dissolving carbon dioxide (CO2) gas in a liquid, typically water or a beverage. This process creates the fizzy sensation and bubbly appearance associated with carbonated drinks such as soda, sparkling water, beer, and Champagne. The carbonation process can occur naturally through fermentation, as in beer and some sparkling wines, or artificially by injecting pressurized carbon dioxide into the liquid.

When a carbonated drink is poured or opened, the pressure inside the container decreases, causing the carbon dioxide dissolved in the liquid to come out of solution and form gas bubbles.

The bubbles are attracted to imperfections or rough spots on the container or glass, known as nucleation sites, where they begin to grow. The bubbles in carbonated drinks can also form around tiny particles or impurities in the liquid.

The size, stability, and behavior of the bubbles in carbonated beverages can vary depending on several factors:

Concentration of dissolved CO2

The more CO2 dissolved in the liquid, the more bubbles will be produced, and the fizzier the drink will be.

Temperature

Cold liquids can hold more dissolved CO2 than warm liquids. As a result, carbonated beverages are usually served cold to maintain their fizziness.

Presence of surfactants

Surfactant-like molecules, which can be naturally occurring or added to the beverage, can influence bubble formation and behavior. They reduce surface tension between the liquid and gas bubbles, helping create more stable bubble chains, as seen in Champagne and some sparkling wines.

Bubble size

The size of the bubbles can impact their stability and movement. Larger bubbles tend to rise more quickly and create more stable chains than smaller bubbles.

Beverage composition

The ingredients and composition of a drink can affect the carbonation process. For example, beer contains proteins and other compounds that may influence bubble behavior, while sugar in soda can make the liquid more viscous, which affects the size and rise of the bubbles.

Understanding the science behind carbonation and bubbles in drinks has various applications beyond the beverage industry, including fluid mechanics, water treatment, and environmental research. 

By studying the behavior of bubbles in carbonated beverages, researchers can gain insights into bubbly flows and improve technologies and processes that rely on the movement and interaction of gas bubbles in liquids.

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