1 National Food Institute, Technical University of Denmark2 Division of Industrial Food Research, National Food Institute, Technical University of Denmark3 Institut de Recerca i Tecnologia Agroalimentàries
Various predictive models are available for high pressure inactivation of Listeria monocytogenes in food, but currently available models do not consider the growth kinetics of surviving cells during the subsequent storage of products. Therefore, we characterised the growth of L. monocytogenes in sliced cooked meat products after a pressurization treatment Two inoculum levels (10(7) or 10(4) CFU/g) and two physiological states before pressurization (freeze-stressed or cold-adapted) were evaluated. Samples of cooked ham and mortadella were inoculated, high pressure processed (400 MPa, 5 mm) and subsequently stored at 4,8 and 12 degrees C. The Logistic model with delay was used to estimate lag phase (lambda) and maximum specific growth rate (mu(max)) values from the obtained growth curves. The effect of storage temperature on mu(max) and lambda was modelled using the Ratkowsky square root model and the relative lag time (RLT) concept. Compared with cold-adapted cells the freeze-stressed cells were more pressure-resistant and showed a much longer lag phase during growth after the pressure treatment Interestingly, for high-pressure inactivation and subsequent growth, the time to achieve a concentration of L. monocytogenes 100-fold (2-log) higher than the cell concentration prior to the pressure treatment was similar for the two studied physiological states of the inoculum. Two secondary models were necessary to describe the different growth behaviour of L. monocytogenes on ready-to-eat cooked ham (lean product) and mortadella (fatty product). This supported the need of a product-oriented approach to assess growth after high pressure processing. The performance of the developed predictive models for the growth of L. monocytogenes in high-pressure processed cooked ham and mortadella was evaluated by comparison with available data from the literature and by using the Acceptable Simulation Zone approach. Overall, 91% of the relative errors fell into the Acceptable Simulation Zone. (C) 2014 Elsevier B.V. All rights reserved.
International Journal of Food Microbiology, 2014, Vol 186, p. 84-94
cooked meat product meat product; relative lag time; Eubacteria Bacteria Microorganisms (Bacteria, Eubacteria, Microorganisms) - Regular Nonsporing Gram-Positive Rods  Listeria monocytogenes species strain-CTC1034; 04500, Mathematical biology and statistical methods; 10515, Biophysics - Biocybernetics; 13502, Food technology - General and methods; 13516, Food technology - Meats and meat by-products; 25502, Development and Embryology - General and descriptive; 31000, Physiology and biochemistry of bacteria; Computational Biology; logistic model mathematical and computer techniques; mathematical model mathematical and computer techniques; predictive model mathematical and computer techniques; pressurization treatment laboratory techniques; quantitative modeling mathematical and computer techniques; simulation model mathematical and computer techniques; Development; Foods; Models and Simulations; FOOD; MICROBIOLOGY; HIGH HYDROSTATIC-PRESSURE; COLD-SHOCK PROTEINS; DRY-CURED HAM; BACTERIAL-GROWTH; NATURAL ANTIMICROBIALS; INACTIVATION KINETICS; LACTOCOCCUS-LACTIS; SLICED HAM; LAG TIME; TEMPERATURE; High pressure processing; Physiological state; Survival; Growth kinetics; Mathematical modelling