Bubbles are fascinating entities that manifest in various forms and sizes, ranging from the large, ephemeral soap bubbles to tiny microbubbles and nanobubbles. Each type of bubble possesses unique properties and plays distinct roles in natural and industrial processes. This article delves into the science of bubbles with reference to beverages. There is a particular focus on microbubbles and nanobubbles, exploring their formation, stability, applications, and the underlying principles governing their behaviour. The sensory work on both nano- and microbubbles in beverages as opposed to other food structures such as foaming cream is less well defined but what has been explored so far reveals particular insights.
Basics of Bubble Formation
Bubbles form when a gas is trapped within a liquid, creating a gas-liquid interface. This process can occur through physical agitation, chemical reactions, or pressure changes. BY formal definition, a bubble consists of a small globule of gas separated from its liquid environment by either one of two interfaces. In carbonated beverages, the type of bubble consists of one interface.
The key driving force behind bubble formation is the reduction of surface tension, a phenomenon where the liquid molecules at the surface are attracted more strongly to each other than to the gas molecules, resulting in a minimization of the liquid’s surface area. Surface tension, is defined as the energy per unit area owing to the existence of the interface that is responsible for maintaining together the two halves of a bubble.
The Young-Laplace equation describes the pressure difference across the gas-liquid interface of a bubble:
ΔP=2γ/r
where ΔP is the pressure difference, γ is the surface tension, and r is the radius of the bubble. This equation highlights that smaller bubbles require higher internal pressure to balance the surface tension. Bubble growth is defined by the Scriven equation (Scriven, 1959). This is:-
d2=16β2Dt where d is the bubble diameter, D is the diffusion coefficient and β is the dimensionless growth parameter.
Scriven defined a dimensionless concentration driving force (φ) φ = RTP (Cb – Ci), where R is the gas constant, P is pressure, T is absolute temperature, Cb is bulk concentration and Ci the equilibrium.
Bubbles will form on vessel walls of cans and bottles at relatively low supersaturation levels of between 3 and 5. This depends on the presence of pre-existing gas-liquid interfaces (Wilt, 1986). The solubility is explained by Henry’s law, which states that
the concentration of dissolved CO2 in equilibrium (c) is proportional to the partial pressure of its gas phase (P).
Bubbles produce different states of less stability, such as disproportionation or coalescence, mainly caused by the bubble size distribution. Disproportionation is usually due to wide bubble size distribution, which leads the smaller bubbles that present high Laplace pressure to disperse into the larger bubbles with lower pressure, hence it provokes them to break more readily and to reduce foam stability. The De Vries equation defines this aspect.
Coalescence occurs when the lamellae are broken, leading two small bubbles to join and form a larger one and, therefore, decreasing its internal pressure.
From a sensory perspective, changing the size of bubbles affects the sensory experience too. We have written in the past about the perception of champagne through its bubbles. There is this interesting phenomenon where tingling on the tongue comes from mass transport of carbon dioxide in the bubbles which is converted to hydrocarbonic acid (H2CO3) catalysed by the enzyme carbonic anhydrase.
Methods For Measuring Bubble Stability
Bubble stability is highly important in food science, cosmetics, pharmaceuticals, and chemical engineering. Several methods are used to measure and analyse bubble stability.
1. Foam Height and Decay Measurement
- Method: Measure the initial foam height after generating foam in a liquid sample, then monitor the reduction in foam height over time.
- Equipment: Graduated cylinder, foam analyser, or similar setup.
- Applications: Widely used in food science for testing foams in beverages, whipped creams, and emulsions.
- Output: Foam stability index, which is the time it takes for the foam height to decrease by a certain percentage.
2. Bubble Lifetime Analysis
- Method: Observe individual bubbles and record their lifetime from formation to collapse.
- Equipment: High-speed cameras, microscopes, or bubble imaging systems.
- Applications: Used in research on surfactants, detergents, and stabilizing agents.
- Output: Average bubble lifetime or decay profile.
3. Draining Time Measurement
- Method: Measure the time it takes for liquid to drain out of the foam or bubble matrix.
- Equipment: Foam drainage apparatus or similar systems.
- Applications: Assess liquid retention properties in foams, often used in beverages or foamy formulations.
- Output: Drainage half-time, indicating how quickly liquid drains.
4. Surface Tension Measurement
- Method: Measure the dynamic surface tension of the liquid to understand its ability to stabilize bubbles.
- Equipment: Tensiometer (e.g., Wilhelmy plate, Du Noüy ring) or bubble pressure tensiometer.
- Applications: Evaluate surfactant performance in stabilizing bubbles.
- Output: Surface tension reduction efficiency.
5. Rheological Measurements
- Method: Study the viscoelastic properties of the foam or bubble interface.
- Equipment: Oscillatory rheometers, interfacial shear rheometers.
- Applications: Analyze the stability imparted by interfacial layers in foams stabilized by proteins, polymers, or particles.
- Output: Elastic modulus, viscous modulus, or other rheological properties.
6. Optical and Light Scattering Techniques
- Method: Use light scattering to measure bubble size distribution and monitor changes over time.
- Equipment: Laser diffraction systems, dynamic light scattering (DLS) devices.
- Applications: Characterizing foam stability in cosmetic formulations or surfactant research.
- Output: Changes in bubble size distribution over time.
7. Electrical Conductivity Measurement
- Method: Measure the change in electrical conductivity of the foam as liquid drains out.
- Equipment: Foam conductivity sensors.
- Applications: Useful in assessing the stability of liquid films in foams.
- Output: Conductivity profiles correlated with stability.
8. Microscopy and Imaging Techniques
- Method: Directly visualize the foam or bubble structure to study film thickness and coalescence.
- Equipment: Optical microscopes, confocal microscopes, or scanning electron microscopes (SEM).
- Applications: Understanding the mechanisms of instability, such as film rupture or coalescence.
- Output: Structural changes in bubbles over time.
With nano-bubbles to microbubbles, we have high-speed camera image analysis (Altuhafi et al., 2013) to try.
9. Acoustic Techniques
- Method: Use sound waves to monitor changes in foam or bubble layers.
- Equipment: Ultrasonic sensors or acoustic foam analysers.
- Applications: Studying foams in industrial processes like flotation or emulsification.
- Output: Acoustic attenuation or velocity changes indicating foam decay.
10. Spectroscopic Analysis
- Method: Use techniques like Raman or infrared spectroscopy to analyse molecular interactions at the bubble interface.
- Equipment: Raman or FTIR spectrometers.
- Applications: Evaluating chemical interactions that enhance or reduce bubble stability.
- Output: Spectral changes indicating interface composition and dynamics.
11. Film Drainage Techniques
- Method: Analyse the thinning behaviour of a liquid film between bubbles over time.
- Equipment: Thin-film balance apparatus.
- Applications: Investigate the effects of surfactants, polymers, or electrolytes on film stability.
- Output: Film thickness and thinning rate.
12. Bulk Foam Analyzer
- Method: Automated measurement of foam properties like volume, height, and lifetime using specialized instruments.
- Equipment: Foam analysers such as the Krüss DFA100.
- Applications: Quick assessment of foam stability in industries like detergents or brewing.
- Output: Quantitative foam stability data (e.g., foam volume half-life).
In more advanced systems, the bubble size distribution is measured using a laser diffraction particle size analyser. A particularly useful item is the Zetasizer Nano ZS-90 (Malvern Instruments Ltd. Warwick, UK). The particle size measurements can be analysed in the range of 0.02 to 2000 microns.
The two most common devices used for monitoring CO2 concentration are the Severinghaus electrode (Severinghaus & Bradley, 1958) or the infrared detector (Munkholm et al., 1988). The Severinghaus type CO2 electrode is a pH electrode in contact with a thin layer of bicarbonate buffer solution with the whole system encapsulated by a thin, gas-permeable membrane. CO2, in the sample under test, diffuses through the gas-permeable membrane and equilibrates with the internal aqueous solution, thus altering its pH (Descoins et al., 2006).
The change in pH is monitored by the pH electrode. The electrode has a long response
time, typically 5–15 min. The infrared absorption detector produces quick response times and the results are reliably quantitative, they are bulky and expensive, and only
applicable to gaseous CO2.
The other established method is the membrane covered dynamic thermal conductivity
(MDTC) sensor operating in a cyclic mode (Orbisphere Laboratories). It works by
measurement of the rate of diffusion of the gas through a semi-permeable membrane isolating the fluid from the receiving chamber which is periodically flushed with a
purge gas (N2).
Microbubbles
Microbubbles are bubbles with diameters typically ranging from 1 to 100 micrometers. Their small size endows them with unique physical and chemical properties compared to larger bubbles.
Formation and Stability:
-
- Formation: Microbubbles can be generated through various methods, including mechanical agitation, electrolysis, and ultrasonic cavitation. Ultrasonic cavitation, in particular, is effective, as high-frequency sound waves create intense pressure fluctuations, leading to the formation of microbubbles. The use of ultrasound has also been investigated for pasteurization of beverages but one of the consequences is the formation of tiny bubbles (Khan et al., 2021).
- Stability: Due to their high surface area-to-volume ratio, microbubbles are inherently unstable and tend to dissolve quickly. However, stability can be enhanced by coating them with surfactants or polymers, which reduce the surface tension and prevent coalescence.
- Current Applications:
- Medical Imaging: Microbubbles are used as contrast agents in ultrasound imaging. Their high reflectivity enhances the contrast of blood vessels and tissues, improving diagnostic accuracy.
- Drug Delivery: Encapsulated drugs within microbubbles can be targeted to specific sites in the body. Ultrasound can then be used to rupture the microbubbles, releasing the drug locally.
- Wastewater Treatment: Microbubbles enhance the efficiency of flotation processes used in wastewater treatment by promoting the aggregation and removal of fine particles and contaminants.
Nanobubbles (NBs)
Nanobubbles are even smaller than microbubbles, with diameters less than 1 micrometer, often in the range of tens to hundreds of nanometers, say, 10 to 200nm (Agarwal et al., 2011; Demangeat, 2015; Phan et al., 2020). They can also be described as ultrafine bubbles. Despite their diminutive size, nanobubbles exhibit remarkable stability and unique properties. Some consider them as ultrafine bubbles which have a greater range of 1 to 1000nm. Compare this with micro and macro bubbles which have diameters of 10 to 50 microns or above.
If we look at nanobubbles, they have excellent stability compared to ordinary bubbles and microbubbles because they have the largest surface to volume ratio, they have the highest mass transfer.
It is worth noting that the definition of an NB is developing constantly and no-one has yet agreed a consensus definition.
Formation and Stability
-
- Formation: Nanobubbles can be produced through methods such as pressure changes, electrochemical reactions, and ultrasonic cavitation. The exact mechanism of their formation is still an active area of research.
- Stability: Unlike microbubbles, nanobubbles can remain stable for extended periods (Alheshibri et al., 2016). This stability is attributed to several factors, including the high internal pressure predicted by the Young-Laplace equation, which slows down gas diffusion. Additionally, the presence of a charged or surfactant-coated surface can create a repulsive barrier that prevents bubble coalescence. From a thermodynamic perspective, nanobubbles are never stable. The high stagnation of NBs in the liquid phase can increase the dissolution of gas such as O2 or O3. above the super-saturation in water (Ushikubo et al., 2010).
Applications
-
- Water Treatment: Nanobubbles have shown great potential in water treatment applications. Their large surface area and high reactivity make them effective in removing contaminants, disinfecting water, and improving aeration.
- Agriculture: Nanobubbles can enhance the efficiency of nutrient delivery and oxygenation in hydroponic systems, promoting healthier and faster plant growth.
- Biomedical Applications: Like microbubbles, nanobubbles can be used in drug delivery and medical imaging. Their smaller size allows them to penetrate tissues and cells more effectively, providing targeted therapy and detailed imaging.
There are two types of NBs: surface and bulk. The measuring method needed for proving the existence of nanobubbles using dynamic light scattering (DLS), atomic force microscope (AFM) and transmission electron (TEM).
Nanobubbles in particular are seen as the next great arena for modifying texture, viscosity, food safety, improving freezing.
Mechanisms of Bubble Stability and Behaviour
Bubbles form in carbonated beverages when the concentration level of carbon dioxide is 3 to 5 times higher than the saturation equilibrium value. The value depends on the existing gas-liquid interface (Lubetkin & Blackwell, 1988). The maximum amount of carbon dioxide that can be dissolved is 9 g/litre at 4ºC.
The formation of bubbles is encapsulated in the term effervescence where the growth and generation of many bubbles rises through the liquid until reaching the surface and breaking up. The frequency depends on the growth time and nucleation lapse time of a bubble (Jones et al., 1998).
There is no correlation between the viscosity of a beverage and its ability to dissolve carbon dioxide save for the method employed.
The stability and behaviour of bubbles, particularly microbubbles and nanobubbles, are influenced by several factors:
- Surface Tension and Surfactants:
- Surfactants play a crucial role in stabilizing bubbles by reducing surface tension and preventing coalescence. These molecules have a hydrophilic head and a hydrophobic tail, allowing them to adsorb at the gas-liquid interface, creating a barrier that inhibits bubble merging.
- Ostwald Ripening:
- Ostwald ripening is a process where larger bubbles grow at the expense of smaller ones due to differences in internal pressure and gas solubility. This phenomenon is more pronounced in microbubbles than in nanobubbles, contributing to their instability.
- Electrostatic Stabilization:
- The presence of electrical charges on the surface of nanobubbles can create an electrostatic repulsion that prevents them from coalescing. This electrostatic stabilization is a key factor in the longevity of nanobubbles.
- Hydrodynamic and Acoustic Effects:
- In the case of ultrasound-mediated applications, the acoustic pressure can influence bubble dynamics. For instance, high-frequency sound waves can induce cavitation, leading to the formation of microbubbles and nanobubbles. These acoustic effects are harnessed in medical and industrial applications to control bubble formation and behaviour.
- Beverage Components
- Proteins and free amino-acids encourage carbon dioxide solubilization. It is reasoned that proteins, with their tertiary structure trap gaseous carbon dioxide and help solvate it. There is thought too be a weak interaction between amino-acids and CO2. Polar amino acids such as arginine and serine have a greater effect than arginine.
- Increasing the sugar concentration causes the solubility of carbon dioxide to decrease. This is slightly countered by the addition of amino acids.
Gushing
Gushing is a problem! It is particularly evident in packaged beer which usually contains between 4 and 5g CO2/litre and is roughly 2 volumes of gas. In such a situation, beer is actually supersaturated and thus overflowing and over-foaming is expected. If the package is opened more carefully, then excess pressure is released and CO2 comes out of solution more slowly with the formation of just bubbles. In the situation with gushing, the release of CO2 is uncontrolled because the release is so rapid. Often, beer is lost from the bottle as a result. Gushing is a consequence then of the formation of both small- and micro-bubbles along with excessive and uncontrolled release of CO2.
Advanced Applications and Future Directions
The unique properties of microbubbles and nanobubbles have spurred innovative applications across various fields:
- Environmental Engineering:
- Beyond wastewater treatment, microbubbles and nanobubbles are being explored for oil spill remediation, soil aeration, and enhancing microbial activity in bioremediation processes.
- Food and Beverage Industry:
- In the food industry, bubbles are critical in bread baking being produced by leavening agents. Nanobubbles are used to improve the texture and shelf life of products. For instance, nanobubble-infused beverages exhibit enhanced carbonation and flavour retention.
- Energy Sector:
- Nanobubbles can enhance the efficiency of fuel cells and batteries by improving mass transfer and reducing polarization losses. Additionally, they are being investigated for enhanced oil recovery techniques, where they aid in displacing trapped oil from reservoirs.
- Nanomedicine:
- The ability of nanobubbles to penetrate biological barriers opens new avenues for targeted drug delivery and gene therapy. Research is ongoing to develop nanobubble-based systems for precision medicine, where drugs can be delivered to specific cells or tissues with minimal side effects.
Suppliers Of Carbonation Equipment
Several prominent suppliers provide carbonation equipment to the beverage industry, offering a range of systems tailored to various production needs. Notable companies include:
- TechniBlend: Offers the ProCarb™ line of inline carbonation systems, designed for precision and efficiency in beverage carbonation. TechniBlend
- ProBrew: Provides the ProCarb™ series, including models like ProCarb™, ProCarb™ Mini, and ProCarb™ Plus, which help reduce carbonation times while maintaining product integrity. Probrew
- Alfa Laval: Supplies the Carboset™ beer carbonation systems, known for their reliability and efficiency in improving beverage quality. Alfa Laval
- QuantiPerm: Offers the MicroCarb system, an innovative commercial carbonation machine designed for small batch breweries or soda manufacturers. Quantiperm
- Beverage Craft: Provides McCann soda carbonators, including the Standard Flow and Big Mac Fast Flow models, suitable for various commercial applications. Beverage Craft
- Meritus Gas Partners: Supplies CO₂ beverage systems ideal for soda, beer, and wine, ensuring consistent carbonation quality. Meritus Gas
- Linde: Offers bulk liquid carbon dioxide that meets or exceeds industry specifications, supporting beverage carbonation needs.
Suppliers Of Gas For Carbonation
Several reputable suppliers provide carbon dioxide (CO₂), nitrogen (N₂), and nitrous oxide (N₂O) gases to the beverage industry in the United Kingdom. Notable companies include:
- Air Liquide: Offers a comprehensive range of pure gases, including carbon dioxide, nitrogen, and nitrous oxide, catering to various industrial applications. Air Liquide
- BOC: As the UK’s largest provider of industrial, welding, and specialist gases, BOC supplies carbon dioxide and nitrogen, along with gas mixtures suitable for beverage production. BOC Gases
- Air Products: Provides specialty gases, including ultra-high-purity nitrogen and nitrous oxide, suitable for various applications within the beverage industry. Air Products
- Pro Gases UK: Specializes in supplying beverage gases such as carbon dioxide and nitrogen to the hospitality industry, including pubs, bars, and restaurants. Progases UK
- IGC Engineering: Supplies carbon dioxide and other industrial gases, offering storage solutions tailored for the beverage sector, including soft drinks and brewing industries. IGC Pressure Vessels
- The CO2 Gas Company: Specializes in providing carbon dioxide gas and related equipment to the drinks industry, serving London and the South East. The CO2 Gas Company
These suppliers offer a range of gas products and services to meet the diverse needs of the beverage industry across the UK.
In the United States, several reputable suppliers provide carbon dioxide (CO₂), nitrogen (N₂), and nitrous oxide (N₂O) gases to the beverage industry. Notable providers include:
- EspriGas: Specializes in beverage-grade CO₂ and nitrogen, offering tailored solutions for restaurants, bars, and breweries. EspriGas
- Zephyr Solutions: Distributes 99.99% pure nitrogen gas and beverage-grade CO₂ across North America, catering to the food and beverage sector. Zephyr Solutions
- Geer Gas: Supplies food-grade CO₂, nitrogen, and oxygen for various beverage applications, providing both cylinder and bulk tank services. Geer Gas
- Helget Gas: Offers beverage-grade gases, including CO₂, nitrogen, and blended beer gases, to support diverse beverage production needs. Helget Gas
- Meritus Gas Partners: Provides bulk gases essential for the food and beverage industry, including CO₂ and nitrogen, ensuring quality and consistency. Meritus Gas
- nexAir: An industry leader in food and beverage gases, supplying CO₂, nitrogen, and specialty compressed gas cylinders for the restaurant and hospitality sectors. nexAir
- Central Welding Supply: Delivers quality beverage gases, such as nitrogen, CO₂, and mixed gas blends, with competitive pricing and prompt delivery services. Central Welding Supply
- Airgas: Provides premium food-grade gases, including CO₂ and nitrogen, critical in the food production process to ensure safety and preserve quality. Airgas
- MATHESON: Offers a comprehensive range of gases, including CO₂, nitrogen, and nitrous oxide, serving various industries with high-purity products.
Suppliers Of Equipment For Producing Microbubbles and Nanobubbles
Several companies specialize in manufacturing microbubble and nanobubble generation equipment across various industries. Notable suppliers include:
A global leader in nanobubble technology, Moleaer develops and delivers nanobubble-enabled solutions for industries such as agriculture, aquaculture, wastewater treatment, and more. Moleaer Inc. employs a patented gas-to-liquid injection technology to generate nanobubbles. This method involves introducing gases, such as oxygen, into water, producing nanobubbles approximately 100 nanometers in size. These nanobubbles are neutrally buoyant and remain suspended in water for extended periods, effectively increasing dissolved oxygen levels. The elevated oxygen concentration enhances water quality and promotes healthier plant growth. AvidWater
The company’s nanobubble generators, such as the Neo model, are designed for easy integration into existing irrigation or water treatment systems. The Neo features an integrated oxygen concentration system capable of producing oxygen with 93% purity, ensuring reliable on-site oxygen generation. It also includes a PLC controller for automation and control, as well as an integrated low-maintenance optical dissolved oxygen sensor for real-time monitoring.
By utilizing this technology, Moleaer’s nanobubble generators deliver high oxygen transfer efficiency, achieving over 85% transfer efficiency, which is higher than other aeration technologies on the market. This efficiency allows for the supersaturation of water with dissolved oxygen, benefiting various applications, including agriculture, aquaculture, and wastewater treatment. Moleaer
Manufactures micro and nano bubble generator pumps suitable for various applications, including dissolved air flotation, fuel production, and aquaculture cultivation aeration. Edonpump
The generator is designed for easy installation, featuring no moving parts and requiring neither maintenance nor additional electrical inputs. By integrating this system, facilities can achieve a cleaner and healthier hot water infrastructure, leading to improved operational efficiency and reduced equipment maintenance costs. Armstrong | Americas
Supplies nanobubble inline generators capable of delivering over 1 billion nanobubbles per milliliter of water, enhancing various aeration applications. Puroxi Water Treatment
All-Pumps (Australia)
All-Pumps is a leading dealer of microbubble generator pumps used to separate suspended solids and emulsified oils from industrial waste streams. All Pumps
OK Engineering Co., Ltd. (Japan)
OK Engineering manufactures microbubble and ultra-fine bubble generation nozzles, which are effective for various applications, including cleaning and water treatment. Microbubble Generator
These companies offer a range of microbubble and nanobubble generation equipment tailored to specific industry applications.
Perception of Carbonation And Nitrogenation In Drinks
Plenty of research has been conducted over well over a hundred years on the consumer perception of carbonation. It has been the main gas used in sodas, sparkling water, beer and ciders. Natural carbonation is produced by yeasts when fermented products such as beer and sparkling wine are consumed but the effects are enhanced by addition. Knowledge is based on personal preferences, cultural influences, and the context of consumption.
Generally speaking, flavour is a more important characteristic of a beverage than carbonation (Barker et al., 2021). Many of the points we make here are based on that research. There is not yet enough research concerning nitrogenation.
The main methods of generating bubbles in cans and bottles is to either infuse the liquid with gas above pressure or to use a widget. Cans in particular will usually have a widget in place. The other method is to inject the gas into the drink at the point of consumption. This is much more common with nitro brews such as nitro coffee. The foamability and foam stability of cold brew coffee affected by degree of bubble formation but it is most affected by coffee variety and a host of other parameters including composition such as low-molecular-weight nitrogen-containing compounds and high-molecular-weight polysaccharides present (Yu et al., 2022).
1. Enhances Sensory Experience
(a) Carbonation
- Fizziness and Texture: Consumers often associate carbonation with excitement and fun due to the fizzy, tingling sensation it creates on the palate. The perception is especially so on the tongue due to the release of CO₂ bubbles. Consumers also describe the sensation.
- Refreshing Quality: The bubbles are perceived as crisp and refreshing, making carbonated beverages particularly popular in hot weather or after physical activity.
- In the absence of flavours and aromas, the consumer is forced to focus on other properties such as beverage appearance and mouthfeel (Zampini & Spence, 2005; Rey-Salgueiro et al., 2013).
(b) Nitrogenation
- Creates a smooth, creamy, and velvety texture because nitrogen bubbles are much smaller than CO₂ bubbles.
- Lacks the sharp “bite” of carbonation, which some consumers find gentler and more sophisticated, especially in beverages like nitro coffee or stout beers.
2. Flavour Perception
(a) Carbonation
- Intensity: Carbonation can enhance the perception of flavours, particularly sweetness, acidity, and bitterness. It makes flavours seem more pronounced such as sweetness or brighter. It adds complexity and balance to drinks like soda, sparkling water, and champagne. It also makes beverages taste lighter and more invigorating because of a tangy sensation (FoodWrite, unpublished data).
- Bitterness Masking: Carbonation can suppress bitterness, making beverages like tonic water more palatable.
(b) Nitrogenation
- Tends to mute flavours slightly, giving beverages a more mellow, rounded taste.
- Often highlights earthy or rich notes (e.g., in coffee or stout beer) and reduces perceived bitterness or sharpness.
3. Cultural, Demographic and Social Associations
(a) Carbonation
- Premium Image: Drinks like sparkling water, champagne, and certain craft sodas are seen as sophisticated or premium products. Indeed, consumers associated carbonated beverages with special events which strongly tells us that designing high quality beverages or emphasizing the rich heritage of products like sparkling wines and champagne is sound marketing sense.
- Widely associated with mainstream soft drinks and energy beverages.
- Youthful Appeal: Fizzy drinks are often marketed as fun, energetic, and vibrant, resonating with younger demographics. There is of course a broader social appeal. It is associated with casual, entertainment and outdoor settings for example.
(b) Nitrogenation
- Conveys a sense of luxury, sophistication, and novelty. Nitro beverages are often marketed as premium or artisanal. Cold brew coffee especially seems to be a popular base for then creating nitro brews simply because it is not feasible to provide a carbonated or nitrogenated hot beverage. There are few studies on cold brew coffee and nitro coffee in particular other than what can be found in research reports but there has been a significant study by Claassen et al., (2021) which is worth exploring if further insights are required on cold brew coffee itself.
- Appeals to consumers who seek a unique sensory experience or a more relaxed, indulgent vibe (e.g., nitro coffee in cafes or stout beers in pubs). It is associated with those who are being more adventurous.
- Trendy nowadays amongst Millennials and Gen Z
4. Health-Related Perceptions
(a) Carbonation
- Positive Associations:
- Sparkling water is seen as a healthier alternative to sugary sodas, providing a similar sensory experience without added calories (Pelchat et al; 2014; Turkington et al., 2017; Barker et al., 2021).
- Carbonation is sometimes believed to aid digestion, though scientific evidence is limited.
- Negative Associations:
- Some consumers perceive carbonation as causing bloating or discomfort, especially when consumed in large quantities.
- A small segment of the population avoids carbonated drinks due to concerns about dental health or acid reflux.
(b) Nitrogenation
- Perceived as gentler on the stomach due to the absence of acidic CO₂.
- Attracts health-conscious consumers looking for lower-acid options, particularly in coffee or tea.
5. Preference Variations
(a) Carbonation
- Level of Carbonation: Preferences vary, with some consumers liking highly carbonated drinks for their “bite,” while others prefer milder fizz for a smoother experience.
- Artificial vs. Natural: Natural carbonation in mineral waters is often perceived as more authentic and appealing compared to artificially carbonated beverages.
(b) Nitrogenation
- Preferred by a consumer set looking for a less ‘aggressive’ bite to drinks. There are unusual associations with various organic acids that remain to be fully explored.
6. Novelty and Experimentation
(a) Carbonation
- Innovative carbonated drinks (e.g., sparkling teas, carbonated coffees, or functional beverages with vitamins) are attracting health-conscious and adventurous consumers looking for new taste experiences.
(b) Nitrogenation
- Still considered a niche or novel experience in many markets, which adds an element of curiosity and exclusivity. Nitro coffee is one of those brands that has been ripe for product development but whether nanobubbles or microbubbles change or enhance perception still remains to be explored.
As the size of bubbles in beverages becomes smaller, consumers consider the mouthfeel and texture of the beverage to improve. Apparently, 87% of tasters can recognise a more carbonated beverage whilst 73% consider a beverages with smaller bubbles but the same level of carbonation to be more carbonated (Barker et al., 2002). Carbonation can also influence the perception of texture of gels. Gas-filled gelatin gels containing nitrogen, air or helium have been created.
Bubbles including micro- and nanobubbles also significantly reduce the viscosity of liquid milk. Viscosity reduction in milk may also be influenced by the negative charge at the bubble/liquid interface having similar polarity with the charged particles such as casein in a dispersed solution. It is also understood that ionic particles including polyphenols, pectins and proteins are coating bubbles and altering their charge characteristics. Nitrogen gas can also alter the physical characteristics of liquid through gas infused NBs by raising the mobility of liquid molecules. This is an observation produced by the presence of negatively charged NBs due to the presence of an excess of OH ions. It is supposed to disrupt the entire hydrogen-bonding network of the aqueous system which in turn improves molecular mobility (Liu et al., 2013).
How Carbonation Affects Beer Quality
Carbonation, as perceived by the consumer affects beverage drinking in many ways, but none more so than beer. In the first case, when beer is poured, turbulence results in the production of bubbles which then causes foam formation. As it continues to be poured, the bubbles in the beer rise into the foam head alongside more bubbles. This is the process of effervescence. It is an important characteristic for the consumer as well as helping to keep the foam head forming. The impact is also felt on the tongue because bubbles form as a result of the tongue’s rough surface. The tongue is made up of numerous nucleation sites. These all impact the sensation of mouthfeel and on viscosity itself. There is a similar impact on perception of aroma and also even a pain stimulus through the sour-sensing cells on the tongue.
Microbubbles and Nanobubbles As Carriers Of Ingredients
Microbubbles and nanobubbles can be used as carriers of ingredients in beverages, and this application is gaining attention in food and beverage science. These bubbles have unique properties that make them suitable for delivering flavours, aromas, nutrients, or functional additives in liquid formulations.
1. How Microbubbles and Nanobubbles Act as Carriers
- High Surface Area:
- Nanobubbles, in particular, have an extremely high surface-area-to-volume ratio, allowing them to bind or encapsulate small amounts of ingredients like volatile compounds (aromas) or hydrophobic molecules.
- Microbubbles, while larger, also have sufficient surface area to interact with certain additives.
- Gas-Liquid Interface:
- The gas-liquid interface of bubbles provides an environment for the adsorption of compounds like flavour molecules, emulsifiers, or bioactive ingredients.
- This interface can stabilize volatile compounds, preventing them from dissipating too quickly during storage or consumption.
- Stabilization of Ingredients:
- Nanobubbles can stabilize sensitive compounds by protecting them from oxidation or degradation, extending the shelf life of functional ingredients like vitamins or antioxidants.
2. Potential Applications in Beverages
Flavour and Aroma Delivery
- Volatile Compounds: Nanobubbles can act as carriers for volatile aromatic molecules, enhancing the sensory perception of beverages such as sparkling water, juices, and alcoholic drinks. The slow release of these compounds during bubble dissolution can provide a more intense and lasting flavour experience.
- Flavoured Sparkling Water: Nanobubbles may improve the perception of delicate flavours (e.g., cucumber or elderflower) that tend to fade quickly in traditional carbonation.
Nutrient Enrichment
- Oxygenation: Oxygen nanobubbles are used in functional waters marketed for increased oxygen content, with claims of improved energy and focus (though scientific validation is limited).
- Hydrogen Enrichment: Hydrogen nanobubbles can be used to deliver molecular hydrogen for its potential antioxidant properties.
- Micronutrients: Microbubbles could serve as carriers for water-insoluble nutrients, such as fat-soluble vitamins (A, D, E, K), by encapsulating them with surfactants or emulsifiers.
Functional and Medicinal Additives
- Probiotics and Prebiotics: Microbubbles could encapsulate probiotics, protecting them during storage and release into the digestive system.
- Active Ingredients: Functional drinks containing caffeine, electrolytes, or herbal extracts could use nanobubbles to ensure even distribution and improve stability.
Alcoholic Beverages
- Microbubbles and nanobubbles may enhance mouthfeel and texture while also acting as carriers for flavours, hops extracts, or aging compounds in beer, wine, or spirits.
3. Advantages of Using Bubbles as Carriers
- Efficient Delivery
- Bubbles can release ingredients gradually during consumption, offering a sustained sensory or functional effect.
- Ingredients bound to bubbles may distribute more evenly within a liquid.
- Stabilization of Sensitive Ingredients
- Nanobubbles can protect delicate compounds, such as flavours or bioactives, from degradation due to light, heat, or oxygen.
- Enhanced Perception
- The interaction of bubbles with the tongue and palate enhances the perception of ingredients they carry, making flavours or functional benefits feel more pronounced.
- Improved palatability: Generating bubbles in high viscosity beverages and liquids could be a useful method of reducing viscosity of food to make it easier to consume. The viscosity of apple juice concentrate has been reduced by incorporating nanobubbles so it is easier to move without causing dilution. The viscosity increases disappears with time as NBs for example coalesce and the dissolved gas disperses (Phan et al., 2021). It might be feasible to treat food including gels to improve mastication. The theory behind this is to reduce fraction between food particles. The presence of particles increases viscosity.
4. Technical Considerations and Challenges
Stability
- Maintaining stable nanobubbles or microbubbles over time is a challenge, as bubbles can coalesce or dissolve depending on the beverage’s pH, temperature, or pressure.
- Functional coatings or surfactants may be needed to stabilize the bubbles and their cargo.
Compatibility with Ingredients
- Some ingredients may not bind effectively to bubbles or may destabilize the system.
- Bubbles’ effectiveness depends on the solubility and chemical properties of the ingredient being delivered.
Consumer Perception
- While bubbles enhance sensory appeal, consumers may be unfamiliar with the concept of bubbles as carriers, so education and marketing will play a role in acceptance.
Manufacturing Costs
- Equipment for generating stable nanobubbles and microbubbles is more complex and costly compared to traditional carbonation systems.
5. Current and Future Research Directions
Research is ongoing to:
- Optimize the stability and loading capacity of bubbles for various beverage applications.
- Explore new methods for encapsulating hydrophobic or volatile compounds using nanobubbles.
- Study the release kinetics of bubble-carried ingredients to maximize sensory and functional benefits.
Microbubbles and nanobubbles hold great potential as carriers of flavours, aromas, nutrients, and functional ingredients in beverages. While still an emerging technology, their ability to stabilize and deliver ingredients in unique ways offers exciting opportunities for innovation in the beverage industry. Overcoming challenges related to stability and cost will be key to unlocking their full potential.
Sensory Benefits Of Nanobubbles and Microbubbles
- Texture and Mouthfeel:
- Nanobubbles and microbubbles create a smoother, creamier mouthfeel compared to traditional carbonation. Their smaller size means they do not produce the same sharp tingling or bite.
- Microbubbles in particular have been noted for creating a “soft effervescence” that feels more velvety or luxurious, making them appealing for premium products.
- Nanobubbles may impart a silky texture that could influence the perception of body and richness in beverages.
- Flavour Perception:
- Nanobubbles have been reported to enhance the perception of certain flavours by increasing the surface area for gas-liquid interactions. This can affect the way volatile compounds (aromas) are released, potentially making beverages smell and taste fresher.
- Microbubbles may have a less pronounced impact on flavour release compared to traditional carbonation, as they release gas more gently and gradually.
- Visual Appeal:
- Microbubbles can create a fine, uniform bubble column that is visually striking, adding to the perception of quality or uniqueness in beverages.
- Nanobubbles are typically too small to be visible to the naked eye, but their effects on clarity and surface tension can enhance the drink’s appearance (e.g., maintaining head stability in beer).
Applications in Beverages
- Beer and Sparkling Wines:
- Microbubble technology has been tested in craft beer and sparkling wines to create a more refined effervescence, balancing the sensory impact while maintaining carbonation stability.
- Nanobubbles have shown potential to improve head retention and stabilize foam.
- Water and Functional Drinks:
- Nanobubble-infused water is marketed for its smooth mouthfeel and perceived health benefits (e.g., oxygen or hydrogen nanobubble water). Consumer perception studies suggest these bubbles can make the water feel more premium and refreshing.
- Coffee and Tea:
- Microbubbles have been explored in nitro coffee to enhance creaminess without additional milk or sugar. Nanobubbles, in contrast, may improve the perception of freshness and aroma.
- Juices and Smoothies:
- Microbubbles are being studied for their potential to improve the sensory qualities of juice products by enhancing the perception of natural flavours while reducing acidity or bitterness.
- One other unusual area of interest is to create dried juice droplets using plasma nanosecond spark discharges (Kozhayeva & Dubinov, 2017). These can be created from fruit and vegetable juice and from coffee. These are microbubbles which are hollow and very thin walled. It’s possible that a dried beverage could be generated to contain other substances including gas and various therapeutic drugs.
Health and Functional Perceptions
- Nanobubble and microbubble beverages are sometimes marketed with health claims, such as:
- Enhanced oxygenation of the body (in the case of oxygen nanobubbles).
- Improved hydration due to the bubbles’ unique surface properties.
- Better digestion or absorption of nutrients (though this is not yet supported by strong scientific evidence).
Consumer sensory work suggests that these claims, combined with the subtle textural changes nanobubbles and microbubbles impart, contribute to a perception of “clean,” “premium,” or “functional” beverages.
Challenges and Opportunities for Research
- Consumer Studies:
- Limited but growing: Some consumer panels have evaluated the sensory differences between nanobubble- and microbubble-infused beverages and traditionally carbonated beverages. Early results suggest positive reactions to the smoother mouthfeel and less aggressive effervescence.
- Perception may vary by demographic: Younger consumers and those seeking premium or functional products seem more open to these innovations.
- Technical Challenges:
- Stabilizing nanobubbles and microbubbles in beverages remains a technical hurdle. If the bubbles collapse or coalesce, the sensory benefits may be lost.
- More research is needed to quantify how these bubbles affect long-term flavour stability, texture, and product appearance.
- It would be worth exploring how microbubbles could be used with pressurized carbon dioxide as a strategy for pasteurization. These bubbles have been shown for example to inactivate enzymes amd kill microorganisms (Kobayashi et al., 2013; 2019).
Overall, carbonation in drinks is widely appreciated for its sensory, cultural, and emotional appeal, though preferences vary significantly depending on individual and demographic factors. Consumers perceive carbonation and nitrogenation as distinct experiences and that is helpful to anybody exploring product development within the beverage development sector. Carbonation is widely associated with energy, refreshment, and sharpness, while nitrogenation is linked to smoothness, luxury, and innovation. Beverage producers leverage these differences to target different consumer segments and create unique sensory experiences.
References
Alheshibri, M., Qian, J., Jehannin, M., Craig, V.S.J. (2016) A History of Nanobubbles. Langmuir 32(43) pp. 11086-11100 (Article).
Altuhafi, F., O’Sullivan, C., & Cavarretta, I. (2013). Analysis of an image-based method to quantify the size and shape of sand particles. Journal of Geotechnical and Geoenvironmental Engineering, 139(8), pp. 1290-1307 (Article). .
Amamcharla, J., Li, B. & Liu, Z. (2017). Use of micro- and nano-bubbles in liquid processing. United States Patent No. WO 2017/127636 A1
Babu, K. S., & Amamcharla, J. K. (2023). Generation methods, stability, detection techniques, and applications of bulk nanobubbles in agro-food industries: A review and future perspective. Critical Reviews in Food Science and Nutrition, 63(28), pp. 9262-9281
Barker, G.S., Jefferson, B., Judd, S.J. (2002a). The control of bubble size in carbonated beverages. Chemical Engineering Science 57 pp. 565−73
___________________________(2002b) Domestic carbonation process optimisation. Journal of Food Engineering, 52, pp. 405–412
Barker, S., Moss, R., & McSweeney, M. B. (2021). Carbonated emotions: Consumers’ sensory perception and emotional response to carbonated and still fruit juices. Food Research International, 147, 110534.
Claassen, L., Rinderknecht, M., Porth, T., Röhnisch, J., Seren, H. Y., Scharinger, A., … & Lachenmeier, D. W. (2021). Cold brew coffee—Pilot studies on definition, extraction, consumer preference, chemical characterization and microbiological hazards. Foods, 10(4), 865.
Čolić, M., Kraljević Pavelić, S., Peršurić, Ž., Agaj, A., Bulog, A., & Pavelić, K. (2024). Enhancing the bioavailability and activity of natural antioxidants with nanobubbles and nanoparticles. Redox Report, 29(1), 2333619.
Deotale, S. M., Dutta, S., Moses, J. A., & Anandharamakrishnan, C. (2020). Stability of instant coffee foam by nanobubbles using spray-freeze drying technique. Food and Bioprocess Technology, 13, pp.1866-1877.
Descoins, C., Mathlouthi, M., Le Moual, M., & Hennequin, J. (2006). Carbonation monitoring of beverage in a laboratory scale unit with on-line measurement of dissolved CO2. Food Chemistry, 95(4), pp. 541-553
Dessirier, J.-M., Simons, C., Carstens, M.-I., OMahony, M., & Carstens, E. (2000). Psychophysical and neurobiological evidence that the oral sensation elicited by carbonated water is of chemogenic origin. Chemical Senses, 25, pp. 277–284
Gonzalez Viejo, C., Torrico, D. D., Dunshea, F. R., & Fuentes, S. (2019). Bubbles, foam formation, stability and consumer perception of carbonated drinks: A review of current, new and emerging technologies for rapid assessment and control. Foods, 8(12), pp. 596.
Javed, M., Matloob, A., Ettoumi, F. E., Sheikh, A. R., Zhang, R., & Xu, Y. (2023). Novel nanobubble technology in food science: Application and mechanism. Food Innovation and Advances, 2(2), pp. 135-144
Jones, S.; Galvin, K.; Evans, G.; Jameson, G. (1998) Carbonated water: The physics of the cycle of bubble production. Chem. Eng. Sci., 53, pp. 169–173
Khan, M. K., Imran, M., Ahmad, M. H., Hassan, S., & Sattar, S. (2021). Ultrasound for beverage processing. In Design and Optimization of Innovative Food Processing Techniques Assisted by Ultrasound (pp. 189-215). Academic Press
Kobayashi, F., Ikeura, H., Odake, S., & Hayata, Y. (2013). Inactivation of enzymes and Lactobacillus fructivorans in unpasteurized sake by a two-stage method with low-pressure CO2 microbubbles and quality of the treated sake. Innovative Food Science & Emerging Technologies, 18, pp. 108-114.
Kobayashi, F., & Odake, S. (2019). Application of a two-stage system with pressurized carbon dioxide microbubbles for inactivating enzymes and microorganisms in unpasteurized sake and unfiltered beer. In Alcoholic Beverages (pp. 199-241). Woodhead Publishing.
Kozhayeva, J. P., & Dubinov, A. E. (2017). Producing of Microbubbles in Dried Juice Droplets Treated With Nanosecond Spark Discharges. IEEE Transactions on Plasma Science, 45(12), pp. 3089-3093.
Liu, S., Kawagoe, Y., Makino, Y. & Oshita, S. (2013). Effects of nanobubbles on the physicochemical properties of water: The basis for peculiar properties of water containing nanobubbles. Chemical Engineering Science, 93, pp. 250-256
Lubetkin, S., & Blackwell, M. (1988). The nucleation of bubbles in supersaturated solutions. Journal of Colloid and Interface Science, 26, pp. 610–615
Malahlela, H. K., Belay, Z. A., Mphahlele, R. R., & Caleb, O. J. (2024). Micro-nano bubble water technology: Sustainable solution for the postharvest quality and safety management of fresh fruits and vegetables–A review. Innovative Food Science & Emerging Technologies, 103665.
Mallesham, P., Parveen, S., & Naik, R. (2025). Nano-Bubbles: The Next Potential Drive to Advance Technologies in Food Industry─ A Review. ACS Food Science & Technology (Article).
Munkolm, C., Walt, D. R., & Milanovich, F. P. (1988). A fiber optic sensor for CO2 measurement. Analytical Chemistry, 35, pp. 109–112
Pelchat, M. L., Bryant, B., Cuomo, R., Di Salle, F., Fass, R., & Wise, P. (2014). Carbonation: A Review of Sensory Mechanisms and Health Effects. Nutrition Today, 49(6), pp. 308-312.
Phan, K. K. T., Truong, T., Wang, Y., & Bhandari, B. (2020). Nanobubbles: Fundamental characteristics and applications in food processing. Trends in Food Science & Technology, 95, pp. 118-130
Phan, K. K. T., Truong, T., Wang, Y., & Bhandari, B. (2021). Formation and stability of carbon dioxide nanobubbles for potential applications in food processing. Food Engineering Reviews, 13, pp. 3-14
Phan, K., Truong, T., Wang, Y., & Bhandari, B. (2021). Effect of CO2 nanobubbles incorporation on the viscosity reduction of fruit juice concentrate and vegetable oil. Int. J. of Food Science & Technology, 56(9), pp. 4278-4286
Rey-Salgueiro, L.; Gosálbez-García, A.; Pérez-Lamela, C.; Simal-Gándara, J.; Falqué-López, E. (2013) Training of panellists for the sensory control of bottled natural mineral water in connection with water chemical properties. Food Chem. 141, pp. 625–636
Severinghaus, J. W., & Bradley, A. F. (1958). Electrodes for blood pO2 and pCO2 determination. Journal of Physiology, 13, pp. 515–520
Turkington, L. G., Ward, E. C., & Farrell, A. M. (2017). Carbonation as a sensory enhancement strategy: a narrative synthesis of existing evidence. Disability and Rehabilitation, 39(19), pp. 1958-1967
Wang, Q., Zhao, H., Qi, N., Qin, Y., Zhang, X. & Li, Y. (2019). Generation and stability of size-adjustable bulk nanobubbles based on periodic pressure change. Scientific Reports, 9(1), 1118
Yu, D., Wang, X., & Lim, L. T. (2022). Investigation of the factors affecting foamability and foam stability of cold brew coffee. Journal of the Science of Food and Agriculture, 102(13), pp. 5875-5882
Zampini, M., Spence, C. (2005) Modifying the multisensory perception of a carbonated beverage using auditory
cues. Food Qual. Prefer. 16, pp. 632–641 .
Zhang, Z. H., Wang, S., Cheng, L., Ma, H., Gao, X., Brennan, C. S., & Yan, J. K. (2023). Micro-nano-bubble technology and its applications in food industry: A critical review. Food Reviews International, 39(7), pp. 4213-4235
Zúñiga, R.N., Aguilera, J.M. (2009). Structure–fracture relationships in gas-filled gelatin gels. Food Hydrocolloids 23 pp. 1351−57
Leave a Reply