Influence of temperature variations during processing and storage on the microbial profile of ground beef
Duysen, Katie Elise
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The effects of dark storage and retail display temperatures on the microbial profile of ground beef of three different compositions were evaluated. Ground beef loaves of three compositions (lean: fat; 73:27, 81:19 and 91:9) packed in high oxygen MAP (80% O2/ 20% CO2) were evenly and randomly assigned to two storage temperatures (-1.1° to 0°C or 3.3° to 4.4°C) for 5 or 9 d. After storage, packages from each storage temperature and length were assigned to one of two retail display temperatures (-0.5° to 0.5°C or 2.2° to 3.3°C) and displayed for up to 5 d. During each d of retail display (0, 1, 2, 3, 4 and 5) packages were removed from retail display and analyzed for populations of anaerobic bacteria (ANA), aerobic bacteria (APC), coliforms, Enterobacteriaceae, lactic acid bacteria (LAB), and psychrophillic aerobic bacteria (pAPC) using direct-plating on selective media under appropriate atmospheres and temperatures for each bacteria. Storage length, storage temperature and display temperature had variable, yet measurable influences on microbial proliferation among lean compositions of ground beef. Warmer storage temperature (3.3° to 4.4°C) and warmer display temperature (2.2° to 3.3°C) generally resulted in greater proliferation in ANA, APC, coliforms, Enterobacteriaceae, and LAB. Psychrophilic aerobic bacteria counts remained below 1.3 log CFU/g across lean compositions, with the exception of 81:19 aged trim ground beef that reached 1.9 log CFU/g on d 1 of display when stored at -1.1° to 0°C.