Not Surviving During Air Transport: Evaluation of Microbial Spoilage
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Italian Journal of Food Safety 2016; volume 5:5620 American lobsters economic resource of the coastal communities of North America, with more than 130,000 tons Correspondence: Cristian Bernardi, Department (Homarus americanus) of alive animals commercialised worldwide in of Health, Animal Science and Food Safety, not surviving during air 2006 and producing nearly 545 million of euros University of Milan, via G. Celoria 10, 20133 transport: evaluation of profits. Due to the decrease of the European Milan, Italy. lobster Homarus gammarus catching figures, Tel: +39.02.50317855 - Fax: +39.02.50317870. E-mail: [email protected] of microbial spoilage American lobsters are imported by several European countries, especially Mediterranean Erica Tirloni, Simone Stella, Acknowledgements: the authors would like to ones: in Italy about 4387 tons are annually thank METRO Italia SpA for providing the Mario Gennari, Fabio Colombo, introduced for an economic value of 44 million American lobsters. Professor Patrizia Cattaneo Cristian Bernardi of euros (Barrento et al., 2009; FAO, 2006). should also be acknowledged for her careful revi- Department of Health, Animal Science American lobsters are mainly commercialised sion of the manuscript. alive and cooked before consumption. After the and Food Safety, University of Milan, Key words: Dead American lobsters; Shipping; capture and during the air transport, they are Milan, Italy Food spoilage; Microbial population. submitted to several stresses like air exposure, changes of the natural environments in terms Contributions: ET and SS were involved in micro- of physical and chemical parameters such as biological analyses and writing of the paper. FC Abstract water salinity and temperature, hypoxia, fast- was involved in biomolecular analyses. MG was ing, interactions with other conspecifics and involved in phenotypical tests. CB was involved in human handling. These stressors can affect biomolecular analyses, reference search and planning of the trial. Eighteen American lobsters (Homarus their health, reducing their quality, and in americanus), dead during air transport, were some cases could be lethal. Opposite opinions analysed in order to evaluate the microbial Funding: the study was funded by the University are still existing about the edibility of lobsters of Milan, Piano di Sostegno alla Ricerca 2014, population of meat, gills and gut: no specific dead during air shipping: some sellers reject to Linea B. studies have ever been conducted so far on the sale the dead subjects, some others use these microbiological quality of American lobsters’ ones for cooked products, others sell these ani- Conflict of interest: the authors declare no poten- meats in terms of spoilage microbiota. The mals depreciated. At the moment there are no tial conflict of interest. meat samples showed very limited total viable available studies about the hygienic quality of Received for publication: 3 November 2015. counts, in almost all the cases below the level the living and dead animals, in terms of pres- of 6 Log CFU/g, while higher loads were found, Revision received: 25 January 2016. ence of potential pathogenic bacteria and of Accepted for publication: 26 January 2016. as expected, in gut and gills, the most probable microbial populations. However, we could sup- source of contamination. These data could jus- pose that the loads and the typology of micro- This work is licensed under a Creative Commons tify the possibility to commercialise these not- biota of lobsters reflect a combination of fac- Attribution-NonCommercial 4.0 International surviving subjects, without quality concerns tors including the environment where they are License (CC BY-NC 4.0). for the consumers. Most of the isolates result- captured, their feeding and living practices, ©Copyright E. Tirloni et al., 2016 ed to be clustered with type strains of the season of capture as well as the quality and Pseudoalteromonas spp. (43.1%) and Licensee PAGEPress, Italy temperature of the waters where they lived, as Italian Journal of Food Safety 2016; 5:5620 Photobacterium spp. (24.1%), and in particular already demonstrated for other crustaceans doi:10.4081/ijfs.2016.5620 to species related to the natural marine envi- and for finfish (Liston, 1980; Shewan, 1977). ronment. The distribution of the genera After death, once the immune response fails to showed a marked inhomogeneity among the function and the muscular structure declines tion of the meat of American lobsters not sur- samples. The majority of the isolates identified due to microbial activity, the alteration begins viving the air shipping from the harvest (USA) resulted to possess proteolytic (69.3%) and quickly: generally this situation does not to a seafood distribution platform of an inter- lipolytic ability (75.5%), suggesting their expose consumer to microbiological risks as potential spoilage ability. The maintanance of these animals are mainly consumed after national wholesaler, located in Northern Italy, good hygienical practices, especially during cooking. However, the increasing demand for and the identification of the most representa- the production of ready-to-eat lobsters-based ready-to-eat raw or cooked crustaceans and of tive bacterial populations in order to establish products, and a proper storage could limit the fresh lobster tails could enhance the risk posed the major genera/species involved with micro- possible replication of these microorganisms. by these products, if subjected to improper bial spoilage of these products. We also evalu- storage or poor hygienic practices during pro- ated the microbial loads of gut and gills as pos- duction and commercialisation. sible sources of contamination. Swartzentruber et al. (1980) found high total Introduction bacterial count values [more than 5 Log colony forming unit (CFU)/g] in 51.9% of frozen lob- The 90% of fish international market is ster tails samples, even if very low levels of col- Materials and Methods based on processed products, but live crus- iforms and E. coli were detected. Although, as taceans, especially clawed and spiny lobsters, already mentioned, no studies till now were Microbiological analyses crabs, marine and freshwater prawns and conducted on lobster meat bacterial popula- For this study, eighteen lobsters arrived freshwater crayfish, are really appreciated for tion, generally the microbiota of crustaceans dead after air transport lasted about 24 h from their high nutritional and commercial impor- captured in temperate waters includes harvest (USA) to the seafood distribution plat- tance (Fotedar and Evans, 2011). The Pseudomonas spp., Shewanella putrefaciens form, were collected. The subjects were trans- American lobster, Homarus americanus, is one and members of the group Acinetobacter- ported at refrigeration temperatures in card- of the most important commercial species Psychrobacter (Gram and Huss, 1996). board boxes containing ice gel packs where marketed internationally and one of the major Aim of our study was the microbial evalua- they were maintained separately thanks to [Italian Journal of Food Safety 2016; 5:5620] [page 75] Article cardboard dividers. The dead subjects were Lipolytic activity was assessed on Sierra’s transported under refrigerated conditions to agar containing Tween 80 (Sierra, 1957). The Results and Discussion the laboratory where they were analysed plates were incubated at 20°C for a week; pos- immediately. Aseptically, gills, meat and intes- itive strains showed a visible precipitation A total of 18 lobsters dead during shipping tine were withdrawn and submitted to microbi- around the colonies. were analysed: meat, gills (as the main access ological analyses: 5-10 g of each sample were All the isolates were screened for their abil- point for bacteria) and gut bacterial contami- diluted 1:10 in saline diluent (NaCl 10 g/L, ity to produce H2S. The medium used was Iron nations were screened. The Food and Drug MgSO4·7H2O 1.53 g/L, MgCl2·6H2O 1.28 g/L, KCl agar 1 (Gram et al., 1987); each plate was pre- Administration (FDA, 2013), which has issued 0.19 g/L, tryptone 1 g/L) and serial 10-fold dilu- pared with 40 mL of agar stab inoculated. H2S guidelines in order to define the microbiologi- tions were prepared. Total viable count (TVC) production was indicated by the formation of a cal quality of some food categories, indicates was enumerated onto modified Tryptose agar black precipitate of FeS. To enable the growth in 6 Log CFU/g the microbiological limit for as described by Bernardi et al. (2015), incubat- of halophilic microorganisms, the original crustaceans raw meat. There are no specific ed at 20°C for 72 h. The number of composition of some media (Iron Agar 1) were studies about the microbiological quality of Enterobacteriaceae was determined according added of the following final salt concentra- American lobsters’ meat; studies are available with ISO 21528-2:2004 method (ISO, 2004). tions: NaCl 10 g/L, MgSO4·7H2O 1.53 g/L, on frozen crabs meat (ICMSF, 1998), indicat- Colonies of fluorescent pseudomonads were MgCl2·6H2O 1.28 g/L, KCl 0.19 g/L. ing that counts below 5 Log CFU/g can be con- observed on plates of King’s B agar (King et al., The ability to growth at 5, 30, 37 and 42°C sidered satisfactory, while those comprised 1954) in ultraviolet light, after growth for 1-3 was tested isolating each of the strain onto between 5 and 6 Log CFU/g should be consid- days at 20°C. Bioluminescent bacteria were plates of modified Tryptose agar. Moreover the ered fairly satisfactory. Moreover, for fish prod- enumerated onto glycerol based marine agar ability to grow onto modified tryptose agar ucts, the threshold value used to identify the (GMA) (Makemson et al., 1992); plates were including different salt concentration (0 and end of the shelf-life is often 6 Log CFU/g 0.5%) was evaluated preparing the plates with incubated at 20°C for 72 h and observed daily (Olafsdottir et al., 2005), even if the total bac- the different percentages of salt included.