The common collection of target strains has been characterised and six L. monocytogenes have been selected for further work. Listeria spp have been shown to survive during salt-curing and freezing, and recover and grow after rehydration and thawing. The stress caused by salt-curing leads to a significant lag phase in Listeria growth after rehydration. This represents a benefit for the food safety of rehydrated products. The lag period depend on temperature. Storage of rehydrated salt-cured cod at 4°C seems to be sufficient to avoid that Listeria contaminating the fish prior to salt-curing develop to infective dose within 11 days, provided that the initial level is below 20 cfu/g.
The effect of the three Carnobacterium, selected in the first year for their anti-listerial properties, has been tested on quality of CSS, both in sterile blocks and commercial slices. The results confirmed that C. divergens V41 is a potential anti-listeria agent that could be applied in CSS without modifying the quality. C. piscicola V1 gave also good results, although its anti-listerial effect is a little less effective.
Fifty-two presumptive psychrothrophic LAB strains with anti-bacterial properties have been isolated from various fish products. Seven strains were finally selected for an application in shrimp products and two of them did not show any sensory spoiling activity on good quality shrimp and prevent the spoilage of naturally contaminated shrimp.
Coatings with different concentrations of chitosan inhibit or retard growth of some spoiling and pathogenic microorganisms isolated from fishery products, on a fish model system based on smoked salmon (CSS broth). The higher chitosan concentration applied the higher antimicrobial effectiveness shown. Therefore, chitosan could be used as a hurdle to increase the shelf life of fishery products. A promising point is that chitosan does not inhibit (and even enhances) the growth of C. divergens V41.
