Effect of Time and Method of Aging on the Microbiological Quality of Beef Loins and Corresponding Steaks ¹

Twenty-four cattle were slaughtered at a commercial packing plant. Carcasses were chilled for 72 h at 4°C, and then fabricated into wholesale cuts. Right loins were vacuum packaged and aged for 1, 3 and 5 weeks at 4°C while the left loins were aged conventionally for 1, 2 and 3 weeks at the same temperature. Core samples were removed from both ends of the loins and were analyzed using standard microbiological procedures. Loins were cut into 2.54-cm thick steaks, wrapped in oxygen-permeable fresh meat wrap and placed at 4°C in a simulated meat case. On days 1, 3, 6 and 7 steaks were evaluated using the same microbial technique used for loins. Counts generally were similar for conventionally and vacuum-aged loins after aging 1 week. After 3 weeks of aging, the vacuum-aged loins had higher (P<.05) coliform, anaerobic, streptococcus and lactobacillus counts. In addition to these counts, the aerobic (20°C and 35°C) of vacuum-aged loins increased (P<.05) after an additional 2 weeks of aging. Counts of steaks from 1-week old loins generally were not different as a result of method of loin aging. Lactobacillus counts of steaks from 3-week old loins differed as a result of method of aging. Except for higher lactobacillus counts, counts of steaks from 5-week old vacuum aged loins were similar to the counts of steaks from loins which were vacuum-aged for 3 weeks.