Effects of carbon dioxide injection and modified atmosphere packaging on surface pigments and shelf life of ground beef.

A modified atmosphere meat grinder was developed to allow gas to be pumped into the grinding chamber during operation. Using this modified grinder, four treatments were employed to determine their effect on ground beef surface color, total aerobic bacterial populations and meat surface pigments during 9 days of refrigerated storage (2 days in the dark followed by 7 days in lighted display). The four treatments were: 1) ground in air, vacuum-packaged (AV), 2) ground in air, packaged in 100% CO2 (AC), 3) ground in 100% CO2, vacuum-packaged (CV), and 4) ground in 100% CO2, packaged in 100% CO2 (CC). CO2 packaging maintained redder color and inhibited bacterial growth longer than vacuum-packaging regardless of the grinding treatment; however, when meat was ground in CO2, packages either did not collapse, or collapse of packages was reduced during storage, suggesting that CO₂ grinding altered CO₂ absorption and improved headspace stability. Vacuum-packaged meat had lower levels of oxymyoglobin after day 0, while CO₂-packaged meat maintained high levels of oxymyoglobin during storage resulting in a redder appearance throughout display.