BACTERIAL-GROWTH DURING CHILLED STORAGE OF PRESSURE-TREATED MINCED MEAT

Freshly minced meat was pressure-processed for 20 min at 20°C and 200, 300, 400 or 450 MPa, then stored at 3°C in air or under vacuum. Its microbial population was monitored for 22 d. Gram-negative bacteria were more sensitive to pressure than Gram-positive bacteria. Processing at 200 and 300 MPa was moderately effective and delayed microbial growth by 2-6 d. Processing at 400 and 450 MPa appeared to completely inactivate all microorganisms tested, except for the total flora which was reduced by 3 to 5 log cycles. However, after a lag period that depended on the intensity of pressure processing, cells from Pseudomonas sp. were again detected and resumed growth. From a series of resuscitation experiments using minced meat inoculated with a Pseudomonas strain, it appeared that a certain proportion (0.01%) of cells were not inactivated but only stressed by high pressure processing and could resume growth after a repair phase of 3 to 9 d at 3°C. © 1994 Academic Press.