Determination of the concentration of dissolved carbon dioxide in carbonated beverages in bottles and cans
The total gas pressure in beer is measured after the beer has been forcefully shaken. The carbon dioxide is then bound through the addition of potassium hydroxide. The amount of air in the beer contributes the remaining volume of gas. Once the value for the total pressure has been corrected by subtracting the quantity of air present in the beer, the carbon dioxide can be measured [1].
Determination of dissolved carbon dioxide concentration in carbonated beverages in bottles and cans by means of pressure and temperature measurement
The carbon dioxide concentration is calculated from the pressure and temperature after piercing the container and shaking it vigorously [1, 2].
Since the air present in the container is not taken into account, the results are somewhat too high. In the case of beer, however, the influence of the headspace gas can be reduced by measurements immediately after bottling by means of so-called snifting (see procedure). The advantage of this method is that it can be carried out very quickly.
For precise measurements, the partial pressures of the dissolved foreign gases (O2, N2) must be taken into account if necessary.
For carbonated beverages with a sugar content of more than 10 g/l, the lower solubility of the carbonic acid due to the dissolved sugar must be taken into account.
Determination of the concentration of dissolved carbon dioxide in carbonated beverages by means of volumetric expansion
This analysis is suitable for determining the concentration of dissolved carbon dioxide in carbonated beverages by means of volumetric expansion at concentrations between 2.5 and 6.2 g/l.
This device makes use of a method patented and entitled by Anton Paar "Multiple Volume Expansion". Here, the volume in the measuring chamber is increased in two separate steps, and at the end of each step the equilibrium pressure and temperature are recorded for use in the calculation. The true carbon dioxide content is determined independently of any other gases which may be dissolved in the beverage [1, 2, 3].
The figure below depicts the calibration correcting for air in the sample and shows how the effect of any dissolved gases other than CO2 (air or nitrogen) on the result of the analysis is eliminated using the volumetric expansion employed in this method. The CO2 content is determined after two separate volumetric expansions in the measuring chamber. If no dissolved other gases are present in the sample, the two results are identical, and no correction is necessary. If gases other than CO2 are dissolved in the sample, this causes the result to be lower after the larger volumetric expansion (the second measurement) than the result at smaller volumetric expansion (the first measurement). A correction value is calculated based upon the difference between the two results, which completely eliminates the influence of the dissolved foreign gases (air or nitrogen) on the ultimate result of the analysis.