Determination of the dissolved nitrogen (N2) content using heat conductivity in carbonated and non-carbonated beverages that have been nitrogenated
This analysis is suitable for determining the concentration of dissolved nitrogen (N2) in carbonated and non-carbonated beverages that have been nitrogenated.
Dissolved nitrogen in a liquid medium is measured using the same procedure as the CO2 determination, i.e., using heat conductivity.
CO2 is employed as a purge gas in the beverage industry. Therefore, in order to measure nitrogen, the change in thermal activity and CO2 and N2 is used. The thermal conductivity is determined in a small measurement chamber, which in turn is separated from the material being measured by a semipermeable membrane. Diffusion through the membrane changes the thermal conductivity in the measurement chamber.
The gas volume in the measurement chamber is fully replaced in cycles of 10–20 s. The changes in thermal conductivity over time are a measure of the diffusion of N2 through the membrane, which allows the concentration in the medium to be calculated, taking temperature into account.
The calculation for the concentration of N2 is achieved using the change in thermal conductivity in the measurement chamber, also taking the temperature into account.
Since the thermal conductivity of oxygen is similar to that of nitrogen, a second channel may need to be used to compensate for any oxygen in the medium [1].
Determination of the concentration of dissolved carbon dioxide in carbonated beverages in tanks, lines, bottles and cans by means of thermal conductivity
This analysis is suitable for dissolved carbon dioxide in carbonated beverages in concentrations ranging from 0–6.9 g/l.
The thermal conductivity is measured in a small chamber, which is in turn separated using a semi-permeable membrane from the medium being measured. The diffusion through the membrane alters the thermal conductivity in the measurement chamber. The gas volume in the measurement chamber is completely replaced in 10–20 s cycles. The changes in the thermal conductivity over time are a function of the quantity of CO2 diffusing across the membrane. Using this value and taking into account the temperature, the concentration in the medium being measured can be calculated. Other dissolved gases, such as nitrogen and oxygen, do not affect the result of the measurement, since either nitrogen or air is used to replace the gas in the measurement chamber [1].