Use of Hydrostatic Pressure for Inactivation of Microbial Contaminants in Cheese

• DOI: 10.1128/aem.66.11.4890-4896.2000
• Publication Date: 2002-07-27T09:55:30Z
• Authors: Ciara E. O'Reilly; Paula M. O'Connor; Alan L. Kelly; Thomas P. Beresford; Patrick M. Murphy
• Keywords: Penicillium roqueforti; Hydrostatic pressure; Food microbiology; Pasteurization

ABSTRACT The objective of this study was to determine the effect high pressure (HP) on inactivation microbial contaminants in Cheddar cheese ( Escherichia coli K-12, Staphylococcus aureus ATCC 6538, and Penicillium roqueforti IMI 297987). Initially, slurries inoculated with E. , S. P. were used as a convenient means define effects range pressures temperatures viability these microorganisms. Cheese subjected 50 800 MPa for 20 min at 10, 20, 30°C. At 400 MPa, slurry decreased by >2-log-unit cycles 10°C 6-log-unit not detected after HP treatments >600 20°C >400 30°C, respectively. In addition cell death, presence sublethally injured cells HP-treated demonstrated differential plating using nonselective agar incorporating salt or glucose. Kinetic experiments that increasing from 300 resulted higher degree than pressurization time 0 60 min, indicating greater antimicrobial impact pressure. Selected conditions subsequently tested adding isolates milk treating resultant cheeses 100 500 20°C. relative sensitivities similar those observed slurry, i.e., more sensitive which . organisms especially On comparison microorganisms pH 5.3 phosphate buffer, cheese, greatest sensitivity shown buffer while exhibited cheese. Therefore, medium are treated is an important determinant level observed.