Unusual Compositions of Microflora of Vacuum-Packaged Beef Primal Cuts of Very Long Storage Life

Abstract

Vacuum-packaged top butt cuts from a beef packing plant that does not use any carcass decontaminating interventions were assessed for their organoleptic and microbiological properties during storage at 2 or −1.5°C. Cuts stored at 2°C were acceptable after storage for 140 days but were unacceptable after 160 days because of persistent sour, acid odors. Odors of cuts stored at −1.5°C for 160 days were acceptable. The numbers of aerobes on cuts increased from <1 log CFU/cm2 to 7 or 6 log CFU/cm2 for cuts stored at 2 or −1.5°C, respectively. The numbers of Enterobacteriaceae increased from < −1 log CFU/cm2 to 5 or 3 log CFU/cm2 for cuts stored at 2 or −1.5°C, respectively. Bacteria recovered from initial microflora were, mainly, strictly aerobic organisms. Bacteria recovered from cuts stored for 160 days were mainly Carnobacterium spp. that grew on an acetate-containing agar generally selective for lactic acid bacteria other than Carnobacterium. C. divergens and C. maltaromaticum were recovered from cuts stored at 2°C, but C. maltaromaticum was the only species of Carnobacterium recovered from cuts stored at −1.5°C. No lactic acid bacteria of genera that usually predominate in the spoilage microflora of vacuum-packaged beef at late storage times were recovered from the spoilage microflora. The findings indicate that carnobacteria, initially present at very small numbers, grew exponentially to persistently dominate the spoilage microflora of vacuum-packaged beef cuts of unusually long storage life.