Storage-life and microflora of vacuum-packaged pork loin cuts in relation to beef from the same abattoir

Introduction:
Pork or beef in chilled, vacuum packaged (VP) form is widely traded domestically and internationally. In recent years, substantial increase in the storage life of beef has been reported for Canadian and Australian products. In contrast, recent reports on the storage life of vacuum-packaged pork cuts are largely lacking.

Purpose:
To determine the current shelf-life and microbiological conditions of chilled VP pork and beef.

Methods:
Beef and pork sub-primal cuts obtained from a federally inspected Canadian research abattoir were vacuum-packaged on the day of production and stored at 2 and -1.5°C. Organoleptic assessment and microbiological analysis were performed in triplicates at day 0 and at appropriate intervals for up to 190 days of storage. Selected bacterial isolates were identified to species level by 16S rRNA gene sequencing.

Results:
The odours of beef stored at 2oC for ≤ 110 days or -1.5oC for ≤ 190 days were mostly acceptable. Acid or dairy odours for VP pork stored at 2oC for ≤ 60 days or at -1.5oC ≤ 120 days were detected upon opening, but dissipated after a 2 h display. Before storage, the numbers of total aerobes were approximately 2 and 3 log CFU/cm2 for pork and beef, respectively, with the beef microflora being mainly strict aerobes and pork microflora including a substantial fraction of species of Enterobacteriaceae. At the end of storage life, lactic acid bacteria were predominant in the microflora of beef at either temperature and pork at 2°C, while Rahnella aquatilis accounted for >50% of the final microflora on pork stored at -1.5°C .

Significance:
The attainable storage life of Canadian VP pork and beef primal cuts is at least 120 and up to 190 days at -1.5°C. The microflora on beef and pork was different, indicating the animal sourced contamination.