Survival of Enterococcus hirae in ripened cheese subjected to ultra high pressure.
The samples of a sliced, hard cheese were placed in commercially used polyamide-polyethylene bags, inoculated with E. hirae and sealed under vacuum. The samples were exposed to high hydrostatic pressure of 300, 400 and 500 MPa for 5, 10 and 15 min. The number of surviving E. hirae and Aerobic Plate Counts (APC) were determined. The bacterial counts were transformed to logarithms and D-values (time required for decimal reduction of E. hirae at given pressure) were calculated using linear regression method. It was found that numbers of E. hirae decreased with the increase of pressure and prolongation of treatment time. D-values amounted to: D300MPa - 33.67 min, D400MPa - 17.83 min and D500MPa - 16.03 min. The obtained results indicate that E. hirae is one of the most resistant vegetative bacteria to ultra high pressure treatment.
Szczawiński
J
J
Department of Food Hygiene and Public Health, Faculty of Veterinary Medicine, Warsaw Agricultural University, Nowoursynowska 159, 02-776 Warszawa, Poland. szczawinski@alpha.sggw.waw.pl
Stańczak
B
B
Peconek
J
J
D000818:Animals; D002611:Cheese / Q000382:microbiology*; D016983:Enterococcus / Q000502:physiology*; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D011312:Pressure