Elevated Carbon Dioxide Atmospheres for Packaging Poultry

Samples of microbiologically homogeneous ground chicken tissue were stored in glass jars containing 0, 20, 40, 60, 80, or 100% carbon dioxide (CO2) (balance air). Microbial analyses demonstrated that elevated CO2 levels reduced the numbers of aerobic colony forming units by a factor of as much as 102 to 103. This reduction in microbial load was accompanied by a change in the type of bacteria present; with CO2, Gram-positive organisms predominated, but in samples without elevated CO2, Gram-negative organisms predominated. Surface pH shifts were less than .10 pH unit for CO2 packaged samples, which is unlikely to be significant enough to have caused this inhibition. Samples lost redness when measured objectively at 28 days. The optimum concentration of CO2 for extending the shelf-life of ground poultry depends on how long an extension is desired. After one week of storage, 20% CO2 was as effective as higher levels (including 100%) in reducing spoilage organisms. However, after 28 days of storage, higher CO2 concentrations produced lower microbial counts.