Tenderness and oxidative stability of Nellore bulls steaks packaged under vacuum or modified atmosphere during storage at 2 °C

• We evaluated the influence of MAP on the quality parameters of beef.
• A gradual tenderization of the meat was detected in the packaging systems.
• Tenderness was reduced by MAP with high O2 in comparison to vacuum and MAP with CO.
• Structural changes induced by the packaging type were observed in beef.

We have evaluated the influence of vacuum and modified atmosphere packaging (MAP) on protein oxidation, lipid oxidation, tenderness, and structural changes of fresh beef. Longissimus dorsi (LD) muscles from Nellore bulls (Bos indicus) were portioned into steaks and distributed into vacuum and three MAP systems: 75% O2/25% CO2, 60% CO2/0.2% CO/39.8% N2 and 40% CO2/0.4% CO/59.6% N2. The steaks were held at 2 °C for 28 days of storage. A gradual tenderization of the meat was observed in all the packaging systems. The anoxic packaging systems (vacuum and MAP with CO) were less susceptible to the oxidative process and contributed to major structural changes in the steaks that are associated with improvements in meat tenderness. Steaks under MAP with high O2 level showed tenderness reduced. High O2 level accelerated the protein oxidation process, which can affect the enzymes responsible for meat tenderization. These results were corroborated by the myofibril fragmentation index (MFI), the proteolytic process, and the structural changes of the steaks as evidenced by SDS-PAGE and transmission electron micrographs (TEM) analysis. The lipid oxidation was significantly increased in the MAP systems with O2 or CO when compared to vacuum.