Understanding and Managing Carbonation in Beverages

Beverages that are carbonated involve a precise balance of pressure and carbon dioxide (CO2) to create the desired fizziness. While theoretically, an unlimited amount of CO2 can be dissolved in water under pressure, practical limits are set by the properties of CO2 and water. This article explores the phase diagrams of CO2 and the safe limits of carbonation in beverages.

Phase Diagrams and CO2 Dissolution

The Phase Diagram of CO2 is crucial in understanding how CO2 can be dissolved in liquid beverages. CO2 has specific points on its phase diagram, such as the triple point and the critical point, which determine its behavior under different pressures and temperatures.

The Triple Point

The triple point of CO2 is at 56.6°C and 5.11 atm. This means that liquid CO2 cannot exist at pressures lower than 5.11 atm. At a standard pressure of 1 atmosphere, CO2 sublimates directly from the solid phase to the gas phase at 78.5°C, bypassing the liquid phase.

The Critical Point

The critical point of CO2 is at 30.98°C and 72.79 atm. Above this point, CO2 exists as a supercritical fluid, where the properties of both gases and liquids merge. In the area labeled CO2 g, gaseous CO2 can be dissolved into a beverage if the temperature and pressure conditions are maintained.

Practical Carbonation Limits

While theoretically, the amount of CO2 that can be dissolved in water is not limited, practical limitations arise when considering the safety and stability of the beverage. The pressure applied to a carbonated beverage can be significantly increased, but this can lead to various issues.

The Safety Concerns of High Carbonation

For most beverages, a maximum carbonation level is recommended to ensure safety. For example, a beverage with a carbonation level of 4.5 volumes is considered safe. This means that 4.5 volumes of CO2 at the filling temperature have been forced into the drink. This level is considered a safe compromise compared to higher carbonations like those found in Champagne, which can be around 6.5 to 7 volumes.

Champagne is typically carbonated to these high levels due to its thick glass container, which can withstand the higher pressure. However, adding excess sugar to extend sealed-in-bottle fermentation can result in even higher pressures, but the risks are immense, even with robust packaging.

Practical Carbonation Levels

The practical carbonation level in a beverage is also affected by temperature. At temperatures close to 0°C, the solubility of CO2 in water decreases, leading to the formation of hydrates or clathrates of CO2 with water. This can cause the beverage to froth violently if the container fails, resulting in a significant safety hazard.

At higher temperatures, such as room temperature (20°C), the solubility of CO2 can increase up to 60 atmospheres. However, achieving this level of carbonation can be dangerous. Dropping a bottle containing a high-pressure carbonated beverage can lead to the release of a large amount of CO2 and liquid, potentially causing damage or injury.

Conclusion

Managing carbonation levels in beverages is critical for safety and quality. Understanding the phase diagram of CO2 and the practical limits of carbonation can help in maintaining a balance between the desired fizziness and safety.

For beverage manufacturers, it is essential to follow guidelines for safe carbonation levels. Whether it's a standard carbonated drink or a high-carbonation beverage like Champagne, proper packaging and handling are crucial to prevent accidents.