Differentiated application of oxygen levels for the preservation of high‑oxygen packaged beef based on initial microbial contamination

This study investigated the influence of various oxygen (O₂) levels on the storage quality of chilled beef steaks with different initial microbial loads (low initial microbial loads, LIML; high initial microbial loads, HIML). The steaks were stored under three modified atmosphere packaging (MAP) systems (MAP70 = 70 % O₂/30 % CO₂; MAP50 = 50 % O₂/30 % CO₂/20 % N₂; MAP30 = 30 % O₂/30 % CO₂/40 % N₂) for 20 days. Oxygen levels had no impact on bacterial counts and microbial diversity during storage, in which Serratia and Brochothrix became predominant bacteria. No differences in a*, b*, chroma, and sensorial traits were observed for LIML steaks under the three MAP systems, but MAP30 steaks showed the lowest (P < 0.05) lipid and protein oxidation. Compared to MAP70, MAP50 instead of MAP30 was sufficient to maintain a similar meat color and a better oxidative stability for HIML steaks. Overall, microbial proliferation was a significant determinant for the color stability of MAP beef, and therefore the O₂ optimization in high‑oxygen MAP should take initial microbial loads into account.