Modeling time to inactivation of Listeria monocytogenes in response to high pressure, sodium chloride, and sodium lactate.
A mathematical model was developed to predict time to inactivation (TTI) by high pressure processing of Listeria monocytogenes in a broth system (pH 6.3) as a function of pressure (450 to 700 MPa), inoculum level (2 to 6 log CFU/ml), sodium chloride (1 or 2%), and sodium lactate (0 or 2.5%) from a 4°C initial temperature. Ten L. monocytogenes isolates from various sources, including processed meats, were evaluated for pressure resistance. The five most resistant strains were used as a cocktail to determine TTI and for model validation. Complete inactivation of L. monocytogenes in all treatments was demonstrated with an enrichment method. The TTI increased with increasing inoculum level and decreasing pressure magnitude, from 1.5 min at 700 MPa and 2 log CFU/ml, to 15 min at 450 MPa and 6 log CFU/ml. Neither NaCl nor sodium lactate significantly influenced TTI. The model was validated with ready-to-eat, uncured, Australian retail poultry products, and with product specially made at a U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS)-inspected pilot plant in the United States. Data from the 210 individual product samples used for validation indicate that the model gives "fail-safe" predictions (58% with response as expected, 39% with no survivors where survivors expected, and only 3% with survivors where none were expected). This model can help manufacturers of refrigerated ready-to-eat meats establish effective processing criteria for the use of high pressure processing as a postlethality treatment for L. monocytogenes in accordance with FSIS regulations.
Commonwealth Scientific and Industrial Research Organisation, Division of Food and Nutritional Sciences, P.O. Box 52, North Ryde 1670, New South Wales, Australia.
Alyssa M
AM
Youart
Yang
Y
Huang
Cynthia M
CM
Stewart
Robin M
RM
Kalinowski
J David
JD
Legan
D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D005519:Food Preservation / Q000379:methods*; D005520:Food Preservatives / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008089:Listeria monocytogenes / Q000187:drug effects / Q000254:growth & development*; D008433:Mathematics; D008954:Models, Biological; D011202:Poultry Products / Q000382:microbiology* / Q000592:standards; D011312:Pressure; D012965:Sodium Chloride / Q000494:pharmacology*; D019354:Sodium Lactate / Q000494:pharmacology*; D013696:Temperature; D013997:Time Factors
D005520:Food Preservatives; D012965:Sodium Chloride; D019354:Sodium Lactate