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The quality of ground beef stored in high-oxygen modified atmosphere packaging (MAP) (80% O 2 and 20% CO 2 ) was evaluated and compared to controls stored in oxygen-impermeable chubs. Patties were formed from the stored ground meat at d 1, 6, and 10. Color, microbial load, thiobarbituric acid (TBA) number, and sensory acceptability were measured. Patties from both treatments bloomed to red with a* values > 16. Aerobic plate counts increased to 9 × 10 5 CFU/g by 10 d storage, but were not different (p < 0.05) between treatments. TBA number of highoxygen samples increased to 2.1 after 10 d, compared to 0.8 for controls. The flavor of samples in high-oxygen were rated less desirable after 6 or 10 d.

Cooked meat color is an important quality attribute for consumers. This study compared color and thiobarbituric acid (TBA) values of cooked ground beef (internal temperatures of 49 to 79°C), after storage of raw product in atmospheres of 0.4% carbon monoxide (CO), 80% oxygen, or vacuum at 2°C for 7 to 21 d. Premature browning, observed as a brown cooked color at internal temperatures as low as 49°C, was found in patties made from meat stored in 80% oxygen. At all cooking temperatures, samples stored in high oxygen had less internal red color, higher myoglobin denaturation values, and were more rancid with higher TBA values than CO or vacuum-packaged ground beef. Raw ground beef held in 0.4% CO modified-atmosphere packaging (MAP) remained bright red throughout the 21-d storage period. Premature browning and high TBA values in cooked patties were avoided by use of this packaging system. However, internal patty color remained somewhat red even at the highest internal cooking temperature of 79°C. The persistent pink color observed in CO-treated patties cooked to 79°C internal temperature was likely due to development of heat-denatured CO-hemochrome, rather than the presence of undenatured CO myoglobin. The problems of PMB and high TBA values of cooked patties were also avoided by vacuum packaging. However, the development of dark purple color associated with vacuum packaging of raw beef limits the use of this packaging method for products in retail display.