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High-pressure destruction kinetics of Listeria monocytogenes on pork
D M Mussa1, H S Ramaswamy, J P Smith
1Department of Food Science and Agricultural Chemistry, McGill University, Ste. Anne-de-Bellevue, Quebec, Canada.
Abstract:
Packaged fresh pork chops (30-g samples) containing an indigenous bacterial population of approximately 10(7) CFU/g were inoculated with 10(7) CFU of Listeria monocytogenes Scott A per g, heat sealed, and subjected to high-pressure processing at 200 to 400 MPa for up to 90 min. Total counts and the number of surviving L. monocytogenes cells were determined by a spread plate technique on tryptic soy agar and modified Oxford medium, respectively. The pressure destruction was characterized by a dual-behavior, consisting of a step change in the number of survivors (Pk0) with the application of a pressure pulse and a first-order rate drop in the number of survivors during the pressure hold period. Higher pressures resulted in higher rates of microbial inactivation, as indicated by their associated lower D values (and higher k values). The pressure sensitivities of the kinetic parameters were evaluated on the basis of Arrhenius and pressure death time (PDT)-type models. The results suggested that L. monocytogenes was more resistant to pressure inactivation than the indigenous microflora (the volume change of activation, deltaV* [Arrhenius model]), and Zp values (PDT model) were -4.17 x 10(-5) m3 mole(-1) and 134 MPa for indigenous microflora and -3.43 x 10(-5) m3 mole(-1) and 163 MPa for L. monocytogenes respectively.
Insights
High-pressure processing effectively inactivates Listeria monocytogenes in pork chops. This study details the inactivation kinetics, finding L. monocytogenes more resistant than indigenous microflora.
Area of Science:
- Food Science
- Microbiology
- Food Engineering
Background:
- Listeria monocytogenes is a significant foodborne pathogen.
- High-pressure processing (HPP) is a non-thermal method for microbial inactivation in foods.
- Understanding HPP inactivation kinetics is crucial for food safety.
Purpose of the Study:
- To investigate the inactivation kinetics of Listeria monocytogenes Scott A in packaged fresh pork chops using high-pressure processing.
- To compare the pressure resistance of L. monocytogenes with the indigenous microflora of pork.
Main Methods:
- Inoculation of pork chops with L. monocytogenes and indigenous bacteria.
- Application of high-pressure processing (200-400 MPa for up to 90 min).
- Microbial enumeration using spread plate techniques on selective media.
Main Results:
- Pressure inactivation exhibited dual behavior: an initial step change and a first-order rate drop.
- Higher pressures led to increased microbial inactivation rates (lower D-values, higher k-values).
- L. monocytogenes demonstrated greater resistance to pressure inactivation than the indigenous microflora.
Conclusions:
- High-pressure processing is effective in reducing L. monocytogenes in pork.
- Kinetic models (Arrhenius and PDT) quantify pressure inactivation and microbial resistance.
- Specific kinetic parameters (deltaV* and Zp values) highlight differential resistance between L. monocytogenes and indigenous microflora.