Listeria innocua and aerobic mesophiles during chill storage of inoculatedmechanically recovered poultry meat treated with high hydrostatic pressure

Mechanically recovered poultry meat (MRPM) was inoculated with Listeria inn ocua 910 CECT at a level of approximately 10(8) CFU g(-1). Vacuum-packaged samples were treated by combinations of pressure (350, 400, 450 and 500 MPa ), time (5, 10, 15 and 30 min) and temperature (2, 10 and 20 degrees C) and later stored at 2 degrees C for 2 months. Counts of L. innocua and aerobic mesophilic bacteria were determined 1, 4, 7, 15, 30 and 60 days after pres surisation, For mesophiles, in most treatments, pressurization at 2 degrees C gave the significantly best results. High pressure caused a marked bacte ricidal effect on L. innocua: reductions higher than 7.5 log units were ach ieved in several cases. Some cells were just sublethally injured by pressur e. Samples treated at 500 MPa for 30 min at 2 degrees C had counts of only 2.3 log units after 60 days of chill storage. Noninoculated pressurised MRP M did not show Listeria growth throughout storage. These results suggest th at high pressure processing can enhance the microbiological quality of MRPM . (C) 1999 Elsevier Science Ltd. All rights reserved.