T9-02 Microflora on Vacuum Packaged Beef from Decontaminated Carcasses Stored at 2 or -1.5°C

Wednesday, August 6, 2014: 8:45 AM
Room 201-202 (Indiana Convention Center)
Mohamed Youssef, Agriculture and Agri-Food Canada, Lacombe, Canada
Colin Gill, Agriculture and Agri-Food Canada, Lacombe, Canada
Xianqin Yang, Agriculture and Agri-Food Canada, Lacombe, Canada
Introduction: The microbiological condition of beef produced at North American plants has been improved as a result of the use of effective carcass decontaminating treatments. The effect of these treatments on the storage life of beef has not been established.

Purpose: The objective was to determine the shelf life and the microbial flora on vacuum packaged beef from decontaminated carcasses.

Methods: Vacuum packaged bone-in and boneless cuts from decontaminated beef carcasses were assessed for their organoleptic and microbiological properties when stored at 2°C or -1.5°C for up to 160 days. Total aerobic counts (TAC) in rinse fluid from each cut were determined by plating on tryptone soya agar. Colonies recovered from fluids obtained from cuts before storage and at appropriate times during storage were randomly selected for identification of isolates by 16S rRNA gene sequencing.

Results: A storage life of 120-140 days was attained for vacuum packaged cuts of both types stored at -1.5 °C. The bone-in cuts stored at 2 °C were spoiled at earlier times. The TAC increased by 4 log units during storage to about 7.5 and 7.0 log CFU/cm2 on cuts of either type stored at 2°C or -1.5°C, respectively. More than 20 microbial species that were mostly obligate aerobes found in soil and water were present on both types of cuts before storage. After storage for ≥ 30 days, the microflora of both cut types stored at either temperature was dominated by carnobacteria; but other lactic acid bacteria, Lactobacillus and Leuconostoc were substantial fractions of the spoilage flora at later storage times. Enterobacteriaceaewere recovered from both types of cut at early storage times, but from only bone-in cuts at later storage times.

Significance: The findings show the longer storage life of vacuum packaged beef is likely a result of the difference in the composition of the initial microflora on beef.