Microbiology of Beef, Pork and Lamb Stored in Vacuum or Modified Gas Atmospheres

Abstract

Beef, pork and lamb loins were vacuum-packaged as subprimal cuts (controls), reformed subprimal cuts and as retail cuts (steaks or chops). Subprimal cuts, reformed subprimal cuts and one group of retail cuts remained vacuum-packaged. Other groups of retail cuts were injected with atmospheres of either 20% CO₂ + 80% N₂ or 40% CO₂ + 60% N₂. Cuts were randomly assigned to storage periods of 0–21 days at 2 ± 1 C. At weekly intervals, steaks or chops were removed from each treatment and examined after storage for 5 days under retail display conditions. Psychrotrophic bacterial counts and lactobacilli counts of steaks and chops stored in CO₂-N₂ atmospheres usually were lower, though not often statistically significant, than those of comparable vacuum-packaged steaks, chops or loins. Psychrotrophic counts of steaks and pork chops, initially held in CO₂,-N₂ atmospheres and then subjected to retail display, usually were lower than those of comparable steaks and chops that had been vacuum-packaged (without added CO₂-N₂) or prepared from vacuum-packaged loins.