Growth Depth Effects of Bacteria in Ground Turkey Meat Patties Subjected to High Carbon Dioxide or High Oxygen Atmospheres

Modified atmosphere packaging (MAP) is used to extend the shelf life of ground meats by altering the gas atmosphere surrounding the meat. This study evaluated how deep MAP bactericidal effects penetrate into a ground meat patty. Patties made from freshly ground turkey breasts were subjected to 2 MAP treatments of high CO2 (97%) or high O2 (80% O2, 20% CO2). Total plate and lactic acid bacterial counts were determined for 3 patty depths (top, middle, bottom). Meat surface color and the package gas headspace composition were also measured. All analyses were performed on 0, 3, 6, 9, and 12 d. Changes in gas headspace and meat surface color were also measured at 0, 3, 6, 9, and 12 d. High CO2 atmosphere maintained a better meat surface color than high O2 atmosphere over the whole storage period. Overall counts were lower (P < or = 0.05) in a high-CO2 atmosphere compared with a high-O2 modified atmosphere. Patties stored under a high-CO2 atmosphere displayed slower bacterial growth in the top layer compared with the middle and bottom layers. Total plate count did not differ (P > or = 0.05) in layers for patties pack-aged in a high-O2 atmosphere Lactic acid bacterial counts increased in the high-O2 modified atmosphere by d 9 and 12 of storage; no increase was observed in CO2-packaged patties. Thus, high-CO2 MAP slowed the growth of total bacteria as well as lactic acid bacteria. Also, there was slower growth in the top meat layer exposed to CO2 compared with interior layers.