Microbiological Studies on Aging of Intact and Excised Beef Muscle ¹

Beef cattle from the University herd were used for these studies; aging treatments after slaughter were as follows: (a) sides were held at room temperature (21-23 C), (b) sides were held at 2 C, (c) sides were kept for 6 hat room temperature and then the round was removed and placed at 2 C for 18 h (d) sides were held for 3 days at 2 C, then the excised round was kept for 4 days at 2 C for a total of 1 week of low temperature aging. After aging by procedures described, steaks were cut from the round, packaged and stored in a display case at about 5 C. Similar treatment was given to ground beef prepared from the same round muscles. Holding an entire side of beef at high temperature for 24 h promoted bacterial growth on the surface with subsequent proliferation on retail cuts. Shortening the aging treatment at high temperature resulted in reduced bacterial populations on packaged items. Highest bacterial loads and most rapid spoilage resulted from excising the muscle after low temperature holding and then continuing to hold the muscle in the cooler. This treatment was even more conducive to spoilage than was holding at room temperature for 24 h, and is not to be recommended.