CO2 packaging increases shelf life through reduction of off-odor production by CO2 tolerant bacteria in addition to growth inhibition of the spoilage bacteriota

Summary

Optimized packaging conditions to improve the shelf life of chicken fillets is important to prevent food spoilage and food waste. Anaerobic packaging with CO2 or by vacuum packaging is commonly used to increase the shelf life of skinless chicken fillets, but the literature is inconsistent about the spoilage bacteriota. The aim of this work was to determine which bacterial genera that spoil raw chicken fillets packaged under two common packaging conditions and how the packaging gas itself affects the production of off odors for these genera. The spoilage potential of Pseudomonas, Carnobacterium, Hafnia, Serratia, Brochothrix and Shewanella isolated from spoiled chicken fillets was evaluated. Fresh chicken fillets were inoculated with mono- and multi genera strain cocktails (4 log CFU/cm2) and packaged with 100% N2 or 60% CO2/40% N2, stored at 4 °C, and bacterial numbers, bacteriota, gas in headspace and sensory profiles assessed. Additionally, the effect of CO2 on the production of off-odors from fillets inoculated with similar levels of Shewanella spp. or Brochothrix spp. was determined by both sensory profiling and measuring volatile organic components. All bacterial cocktails grew relatively well in chicken meat packed with 100% N2, while 60% CO2/40% N2 resulted in growth inhibition of all isolates compared to 100% N2. All genera except Serratia and Pseudomonas gave rise to off-odors after 11 days of storage in 100% N2. During storage in 60% CO2/40% N2, only fillets with Carnobacterium spp. and Brochothrix spp. showed significantly higher intensities of off-odors compared to the reference fillets. Shewanella spp. and Brochothrix spp. also exhibited significantly higher intensities of negative odor attributes during storage in 100% N2 compared to 60% CO2/40% N2, at a similar total bacterial count. Thus, CO2 improves shelf life not only by reduction of the growth of CO2 tolerant and sensitive bacteria, but also through inhibition of the production of off-odors.