Effect of oxygen concentration in modified atmosphere packaging on color changes of the M. longissimus thoraces et lumborum from dark cutting beef carcasses.

The objective of this study was to investigate the effect of modified atmosphere packaging (MAP) with different oxygen concentrations on color changes of dark-cutting beef steaks from M. longissimus thoraces et lumborum. Four normal-pH (mean pH = 5.52) and four dark-cutting beef carcasses (mean pH = 6.36) were obtained from a commercial abattoir at 48 h post-mortem. The gas compositions in MAP were as follows: (i) 20% O/20% CO/60% N, (ii) 40% O/20% CO/40% N, (iii) 60% O/20% CO/20% N and (iv) 80% O/20% CO. Steaks were stored in the dark at 2 °C for 14 days. Surface color of dark-cutting beef steaks was improved (P < .05) by 60%O-MAP and 80%O-MAP after 4 days storage, to a level similar to the initial normal-pH steaks. Steaks in 60%O-MAP and 80%O-MAP had lower metmyoglobin reducing activity and higher TBARS values (P < .05), but deeper oxygen penetration depth (P < .05) that may have masked discoloration resulting from metmyoglobin formation under the surface. While both 60%O-MAP and 80%O-MAP improved the appearance of dark-cutting beef, 60%O-MAP may be preferred owing to the lower level of lipid oxidation.