Modelling the effect of the temperature and carbon dioxide on the growth of spoilage bacteria in packed fish products
Begoña Alfaro, Igor Hernández, Yvan Le Marc, Carmen Pin
AZTI-Tecnalia, Parque Tecnológico de Bizkaia, Astondo Bidea, Edf. 609, 48160 Derio, Bizkaia, Spain.
We have investigated the effect of storage temperature (0–20 °C) and carbon dioxide concentration (0–100% v/v, balance nitrogen) on the growth of Carnobacterium maltaromaticum, Serratia proteamaculans, Yersinia intermedia and Shewanella baltica, as well as on the growth of a mixed culture of the four species. These species were identified as the organisms responsible for spoilage in mackerel fillets packed under modified atmospheres in preliminary studies. The growth rates of all those groups were measured at several temperatures between 0 and 20 °C in cultures stored under air. Models describing the dependence of the maximum specific growth rate on temperature, CO2 and O2 were developed for each organism. C. maltaromaticum was the organism that showed the highest resistance to CO2 and to the lack of O2, while under aerobic condition at 0 °C. S. baltica showed the fastest growth rate. Model predictions were compared with observations on naturally contaminated horse mackerel fillets packed under modified atmospheres as well as inoculated with the bacteria strains used to generate the data for model development. These validation studies showed a good performance of models under constant and fluctuating temperature conditions. Models were implemented in a user-friendly computing tool called “Fishmap” (freely available at http://www.azti.es/en/fish-map-software.html). This program predicts the growth of spoilage bacteria in horse mackerel fillets stored at constant and fluctuating temperature conditions under modified atmospheres and under air.