Influence of residual pressure on color stability of vacuum packaged beef

The influence of incomplete evacuation in vacuum packages on the color stability of beef was investigated. Silverside ( M. semitendinosus , M. gluteobiceps, and M. gastrocnemius ) slices were vacuum packaged with 15, 60, 125, 250, 500, and 750 mbar residual pressure and stored at 2 °C for 14 days. L*a*b* -values, myoglobin redox states, and oxygen concentration were measured non-invasively over the storage period of 14 days. After 14 days of storage, the α -tocopherol, β -carotene, and retinol contents were measured. An increase in residual pressure resulted in an increase in oxygen concentration in the packages. The increased oxygen concentration led to oxidative processes in the form of metmyoglobin (MMb) formation, a decrease of the contents of α -tocopherol and β -carotene, and visible discolorations after 14 days of storage, that increased in severity with the residual pressure. E.g. on day 14, the oxygen concentrations were 0.02% (15 mbar) and 12.49% (750 mbar), the MMb levels 0.71 (15 mbar) and 1.11 (750 mbar), the α -tocopherol content 4.34 μg/g (15 mbar) and 3.36 μg/g (750 mbar), and the β -carotene content 0.66 μg/g (15 mbar) and 0.14 μg/g (750 mbar). The results showed that an incomplete evacuation of the vacuum packages led to air pockets which resulted in discoloration. Non-invasive measurements of the packaging during the storage period, combined with measurements of antioxidants, provided detailed insights into the discoloration mechanisms of the beef samples and the development of oxygen concentration in the air pockets.