What Is a CO2 Analyzer? A Guide to Measuring Carbonation in Beverages
A CO2 analyzer measures the amount of carbon dioxide dissolved in a carbonated drink, such as beer, a soft drink or sparkling water. CO2 content is a critical quality parameter: it shapes the taste and the mouthfeel of the product, and it must stay within specification from filling to consumption. Breweries and beverage producers measure it frequently during production.
How does a CO2 analyzer work?
Most CO2 analyzers use the pressure and temperature method, based on Henry's law: at equilibrium, the amount of gas dissolved in a liquid is proportional to the pressure of that gas above the liquid, and the solubility of the gas depends on the temperature.
The closed bottle or can is pierced without letting gas escape, and connected to a pressure indicator and a temperature probe. The container is then shaken until the gas in the headspace and the gas dissolved in the liquid reach equilibrium, which means the pressure stops rising. The equilibrium pressure and the temperature give the CO2 content, read from a table or calculated automatically.
Shaking is the critical step. If the sample is not shaken enough, equilibrium is not reached and the measured CO2 content is too low.
Main applications
Breweries: checking the carbonation of beer in bottles and cans.
Soft drinks and sparkling water: verifying that each batch meets its CO2 specification after filling.
CO2 gas purity: checking purchased CO2, or CO2 recovered for reuse, before it goes into the product.
Sample preparation: drawing a sample from a closed container for other analyses, or degassing a drink for tests that require a flat sample.
Key concepts: volumes, g/L and temperature
CO2 content is expressed in grams per liter (g/L) or in volumes. One volume means that the drink contains its own volume of CO2 gas, measured at 0 °C (32 °F) and standard atmospheric pressure (1 atm). One volume corresponds to about 1.96 g/L, so a drink at 3 volumes contains about 5.9 g/L of CO2. Some producers also use % by weight or P20 (kg/cm²).
Temperature: CO2 is less soluble in a warm liquid. For the same CO2 content, a warm bottle shows a higher pressure than a cold one. This is why the temperature must be measured together with the pressure, and why many laboratories bring their samples to a stable temperature before testing.
Accuracy depends on the pressure indicator. On the AT2E CO2EASY (0 to 6 bar, or 0 to 87 psi), the analog indicator has an accuracy of ±2.5 % F.S., while the digital indicator of the CO2EASY-D reaches ±0.5 % F.S.
Why shaking must be repeatable
Everyone has seen a shaken soda bottle foam when it is opened: shaking speeds up the release of dissolved CO2 into the headspace. A CO2 analyzer uses the same effect, in a controlled way.
With manual shaking, the result depends on the operator: how strongly, how long and how often the container is shaken. Two operators can obtain two different values from the same batch. Motorized shaking applies the same speed and the same time to every sample. On the AT2E CO2DA, the shaking speed and time are set on the touch screen, which gives highly reproducible results.
Calibration of a CO2 analyzer
A CO2 analyzer has two sensors, pressure and temperature, which are checked separately:
Compare the pressure indicator with a certified reference indicator at several points of its range, for example with a pressure calibration device such as the CDP-1.
Check the temperature probe against a reference thermometer.
Record the deviations, and adjust or recalibrate the instrument if they exceed the acceptable limit.
Keep the piercing needle and the lines clean: drink residues can disturb subsequent measurements.
AT2E CO2 analyzers
AT2E covers every step of CO2 control, from a simple manual device to a fully automatic system:
CO2EASY / CO2EASY-D: CO2 measuring device with analog or digital pressure indicator, 0 to 6 bar (0 to 87 psi), for bottles up to 105 mm (4.1 in) in diameter.
CO2EASY-DA: automatic CO2 calculator, 0.00 to 9.99 g/L, with results in g/L, volumes, % by weight or P20.
CO2DA: automatic shaker and CO2 calculator for glass bottles, PET bottles and cans.
CO2-CS: fully automatic CO2 calculating system: piercing, sealing, shaking, display and venting in one cycle.
CO2-P: CO2 purity tester, 99.0 to 99.999 % v/v CO2.
ABSD-1 and BSD-1: sampling devices that transfer the drink from a closed bottle or can to other analysis instruments.
AD-1 / AD-2: automated degassers for carbonated drinks.
Conclusion
With the pressure and temperature method, the CO2 content of a drink is not measured directly: it is calculated from a pressure and a temperature, after an equilibrium that depends on shaking. Each of these three steps can introduce an error. Accurate sensors, a stable sample temperature and repeatable shaking are what make CO2 results reliable from one sample, one operator and one day to the next.
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AT2E is an ISO 9001 certified company (AFNOR Certification).
Request a quote: info@at2e.com
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