CARBON MONOXIDE EFFECTS ON COLOR AND MICROBIAL COUNTS OF VACUUM-PACKAGED FRESH BEEF STEAKS IN REFRIGERATED STORAGE

Ribeye, top round, and eye of round steaks were treated for 30 min with 100% carbon monoxide (CO), vacuum packaged, and held in refrigerated storage. Instrumental color determinations (L*, a*, and b* values) were made on uncooked ribeye and round steaks every 7 days. Aerobic plate counts (APC), psychrotrophs, and lactic acid bacteria (LAB) were determined on eye of round samples after 1, 4, and 8 weeks. Initially, CO-treated steaks were more red (higher a* values) than untreated steaks. The a* values of treated steaks decreased during storage; at 6 weeks no differences existed due to CO treatment. CO-treated steaks were more yellow (higher b* values) at all storage times than untreated steaks. APC of CO-treated samples were 1 log cycle lower than control after 8 weeks in storage; LAB counts were nearly 1 log cycle lower for CO-treated samples after 8 weeks. Psychrotrophic counts were similar for control and CO-treated samples during the first 4 weeks of refrigerated storage but were nearly 2 log cycles lower for CO-treated samples after 8 weeks. These data suggest that CO-treated steaks are more red and that they have extended shelf-lives compared with untreated, vacuum-packaged steaks.