The headspace CO concentration (Miyazaki et al., 1997) was measured using the Agilent Technologies 6890 N Network Gas Chromatograph System. Two 100 μL samples from each package (two packages per treatment) were collected and injected into the GC using a 100 μL Hamilton syringe (Cat. No. 14-815-80). One peak was obtained for each 100 μL sample that was injected into the GC. The two peaks per bag for the ground beef were then averaged and used in the following formulas to determine CO concentration in the headspace of the package: