Nutritional Regime, Post-Slaughter Conditioning Temperature, and Vacuum Packaging Effects on Bacteriology of Beef...

Thirty-eight crossbred steers were used to evaluate effects of nutritional regime (grass-, short-, long-, and forage-fed) and post-slaughter chilling (3 C) and conditioning temperature (13 C) on carcass psychrotrophic and mesophilic bacterial counts. Inside chucks from right halves of carcasses chilled at 3 C for 48 h were used to evaluate effects of nutritional regime and vacuum packaging on total aerobic and anaerobic bacterial counts. Psychrotrophic and mesophilic mean bacterial counts tended to decrease from 1 to 46 h postmortem regardless of temperature treatment. At 46 h postmortem, the forage-fed group mean psychrotrophic count was significantly lower (P < 0.05) than that for any of the other feeding regimes. Mesophilic mean counts were significantly different (P < 0.05) at 46 h postmortem (grass-fed >short-fed >long-fed > forage-fed). Carcass halves chilled at 3 C for 46 h had lower total psychrotrophic and mesophilic mean bacterial counts than did corresponding halves conditioned at 13 C for 8 h then chilled at 3 C for 38 h. Total aerobic and anaerobic counts tended to remain constant or decrease slightly during vacuum storage for 21 days at 0 to 1 C. Both aerobic and anaerobic counts on vacuum-stored cuts from carcasses of grass-fed steers were significantly higher (P < 0.05) than other feeding-regime means. Aerobic and anaerobic counts on vacuum-stored cuts from carcasses of short-, long-, and forage-fed steers were statistically similar. All carcass and inside-chuck bacterial counts were well within acceptable limits. Scalpel-template sampling was considered to be a significant improvement over previously used methods.