Application Note: ORBISPHERE 510 Air Calculation Used To Minimize Can Corrosion

Aluminum can manufactures require bottlers to limit the "Air" content in beverages in order to minimize corrosion. Pinholes in the polymer can-lining will cause products with acidic or isotonic properties to leak due to oxidation of the raw metal. The specification from various can manufactures is for the "Air" content to be less than 2.0 mL.

Work is ongoing to persuade the International Society of Beverage Technologists to adopt Total Package Oxygen determination as the industry standard.

The most widely used method to determine "Air" content is the Zahm & Nagel caustic shakeout. In this procedure, the headspace gas in the package is released into a caustic solution that chemically combines with CO2 leaving a bubble that is deemed as "Air". In facilities where N2 is used instead of CO2 as the seamer cover-gas, a direct dissolved oxygen measurement must be used to quantify the corrosion potential of the package.

The common assumption is that the "Air" is an 80/20 ratio of N2/O2. Some soft drink manufacturers assume that the dissolved oxygen measurement is like O2 in air and that the total gas concentration will be five times the O2 content. Others have devised their own models, upon study of the partitioning between O2/N2 during the filling process, and have derived their own scalier not based on the 80/20 relationship between the gas volumes.

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