title: Modeling and predicting the simultaneous growth of Listeria monocytogenes and natural flora in minced tuna.
abstract: The growth kinetics of Listeria monocytogenes and natural flora (NF) in minced tuna from 2 to 30 °C were examined, and a simultaneous growth model was developed. The inhibiting effect of the NF on the growth of L. monocytogenes was examined by inoculating different levels of NF isolated from the minced tuna. The kinetic data were fitted to the Baranyi model and estimated the growth parameters such as specific growth rate (μ(max)), maximum population density (N(max)), and lag time. The temperature and inoculated NF dependency on the μ(max) of L. monocytogenes and NF were described by modified Ratkowsky's square-root model. As the initial NF level increased, the slopes of the square-root models were decreased for both L. monocytogenes and NF. The N(max) of L. monocytogenes was described as a function of temperature and inoculated NF level. Simultaneous growth prediction of L. monocytogenes and NF under constant temperature conditions was examined by using the differential equations based on the Baranyi model with the effect of interspecies competition substituted into the developed μ(max) and N(max) models. The root mean square errors between the model prediction and the observation for L. monocytogenes and NF were 0.42 and 0.34, respectively. Predictive simulation under fluctuating temperature conditions also demonstrated a high accuracy of simultaneous prediction for both L. monocytogenes and NF, representing the root mean square errors of 0.19 and 0.34, respectively. These results illustrate that the developed model permits accurate estimation of the behavior of L. monocytogenes in minced tuna under real temperature history until consumption.
authors.affiliation: National Food Research Institute, 2-1-12, Kannondai, Tsukuba, Ibaraki 305-8642, Japan. koseki@affrc.go.jp
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Koseki
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Takizawa
authors.forename: Satoko
authors.initials: S
authors.lastname: Miya
authors.forename: Hajime
authors.initials: H
authors.lastname: Takahashi
authors.forename: Bon
authors.initials: B
authors.lastname: Kimura
mesh_terms: D000818:Animals; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D005396:Fish Products / Q000382:microbiology*; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006801:Humans; D007700:Kinetics; D008089:Listeria monocytogenes / Q000254:growth & development*; D008433:Mathematics; D008954:Models, Biological; D011237:Predictive Value of Tests; D013045:Species Specificity; D013696:Temperature; D014413:Tuna / Q000382:microbiology*