Modelling the effect of the temperature and carbon dioxide on the growth of spoilage bacteria in packed fish products Begoña Alfaro a, * , Igor Hernández a , Yvan Le Marc b , Carmen Pin b a AZTI-Tecnalia, Parque Tecnológico de Bizkaia, Astondo Bidea, Edf. 609, 48160 Derio, Bizkaia, Spain b Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK article info Article history: Received 22 December 2011 Received in revised form 23 April 2012 Accepted 16 May 2012 Keywords: Kinetic modelling Spoilage bacteria Horse mackerel Software application abstract We have investigated the effect of storage temperature (0e20  C) and carbon dioxide concentration (0e100% v/v, balance nitrogen) on the growth of Carnobacterium maltaromaticum, Serratia proteamacu- lans, 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, CO 2 and O 2 were developed for each organism. C. maltaromaticum was the organism that showed the highest resistance to CO 2 and to the lack of O 2, 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. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Modified atmospheres (MA) packaging with carbon dioxide (CO 2 ) as active component is widely used, together with refriger- ation, to delay spoilage and extend the shelf life of fresh fishery products. The first report on the use of MA packaging to extend the shelf life of fish was published nearly a century ago (Killefer, 1930). Since then, many studies have reported that MA packaging extends shelf-life of fish without altering the organoleptic attributes char- acteristic of fresh products (Church & Parsons, 1995; Sivertsvik, Jeksrud, & Rosnes, 2002). Among of other factors (i.e. gas composition, initial microbial population and gas/product volume ratio), storage temperature is critical for the microbiological quality of MA packaged fish prod- ucts. The antimicrobial effect of CO 2 is enhanced when the storage temperature of the product is reduced (Gould, 2000) and therefore, temperature control is essential to ensure the quality and safety of these perishable foods. Those organisms with the highest spoilage potential in specific products/storage conditions are called Specific Spoilage Organism (SSO) and their identification is important for shelf-life determi- nation studies. Shewanella putrefaciens has been reported to be the SSO in marine-water fresh fish stored in ice (Gram & Huss, 1996; Koutsoumanis & Nychas, 2000). Lactic acid bacteria (LAB), such as Carnobacterium maltaromaticum, have been identified as the SSO in cooked and peeled MA packaged shrimps (Mejlholm, Bøknæs, & Dalgaard, 2005). Furthermore, Serratia liquefacines (now Serratia proteamaculans) was found to be associated to the spoilage of vacuum-packed cold-smoked salmon and trout (González- Rodríguez, Sanz, Santos, Otero, & García-López, 2002). Photo- bacterium phosphoreum has been identified as the SSO in MA packed cod fillets (Dalgaard, Gram, & Huss, 1993). In previous research, (Alfaro, Hernández, Pin, & Le Marc, 2011) isolates on non- selective medium from Atlantic horse mackerel fillets packed under MA obtained at the time of sensory rejection were genotypically characterized by 16S RNA sequencing. Carnobacterium, Serratia, Shewanella and Yersinia were the predominant bacteria, i.e. the SSO, at the time of sensory rejection. A high correlation between sensory quality and bacterial concentration in horse mackerel stored under * Corresponding author. Tel.: þ34 94 657 40 00; fax: þ34 94 657 25 55. E-mail address: balfaro@azti.es (B. Alfaro). Contents lists available at SciVerse ScienceDirect Food Control journal homepage: www.elsevier.com/locate/foodcont 0956-7135/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodcont.2012.05.046 Food Control 29 (2013) 429e437