Effect of ozonation and γ-irradiation on post-harvest decontamination of mussels (Mytillus galloprovincialis) containing diarrhetic shellfish toxins.

Contamination of shellfish with diarrhetic shellfish poisoning (DSP) toxins readily occurs during algal blooms. Such phenomena raise important public health concerns and thus comprise a constant challenge to shellfish farmers, the seafood industry and health services, considering the increasing occurrence of toxic episodes around the world. To avoid the detrimental effects of such episodes, research has focused on the use of various detoxification methodologies that should be rapid, efficient, easy to apply, and will not alter the quality and sensory properties of shellfish. In the present study, both ozonation (15 mg kg(-1) for 6 h) and γ-irradiation (6 kGy) were utilised in order to reduce the toxin content of contaminated shucked mussels, collected during the DSP episodes of 2007 and 2009 in Greece. DSP toxicity was monitored using the mouse bioassay (MBA) whilst the determination of toxin content of the okadaic acid (OA) group (both free and esterified forms) was carried out by LC/MS/MS analysis. Toxin reduction using γ-irradiation was in the range of 12-36%, 8-53% and 10-41% for free OA, OA esters and total OA, respectively. The appearance and texture of irradiated mussels deteriorated, pointing to a low potential for commercial use of this method. Ozonation of mussels resulted in toxin reduction in the range of 6-100%, 25-83% and 21-66% for free OA, OA esters and total OA, respectively. Reduction of OA content was substantially higher in homogenised mussel tissue compared with that of whole shucked mussels. In addition, differences detected with regard to quality parameters (TBA, sensory attributes) between ozonated and control mussels were not considerable. Even though varying percentage reductions in OA and its derivatives were achieved using ozonation under specific experimental conditions tested, it is postulated that upon optimisation ozonation may have the potential for post-harvest commercial DSP detoxification of shucked mussels.

Effect of Lactobacillus-protective cultures with bacteriocin-like inhibitory substances' producing ability on microbiological, chemical and sensory changes during storage of refrigerated vacuum-packaged sliced beef.

AIMS: To investigate the effect of applying two different Lactobacillus-protective cultures, with bacteriocin-like inhibitory substances' (BLIS) producing ability, individually or in combination, on microbiological, chemical and sensory changes during storage of refrigerated vacuum-packaged sliced beef meat. METHODS AND RESULTS: Lactobacillus sakei CECT 4808 and Lactobacillus curvatus CECT 904(T), which were shown to be producers of BLIS, were inoculated individually or in combination on slices of beef M. semitendinosus. The samples were vacuum packaged and stored at 4 +/- 1 degrees C and were assessed during a 28-day storage period for microbiological [Enterobacteriaceae, Pseudomonas spp., lactic acid bacteria (LAB), Brochothrix thermosphacta and yeasts and moulds], chemical (pH, protein hydrolysis degree, lipid oxidation), sensory (abnormal odour) parameters and instrumental colour. Samples inoculated with the Lact. sakei strain and samples inoculated with the combination of the two strains had significantly (P < 0.05) lower spoilage microbial counts than those inoculated with the Lact. curvatus strain alone or the controls, while both chemical parameters (including lipid oxidation) and abnormal odour scores were also significantly (P < 0.05) improved by the former. Moreover, Lact. sakei alone showed a better preserving effect (P < 0.05) than the combination of both strains in the majority of the parameters tested. Instrumental colour measurements changed with storage time, but no treatment effects (P >or= 0.05) were observed during the whole 28-day storage period. CONCLUSIONS: The BLIS producer Lact. sakei CECT 4808 strain may be used for improving preservation of vacuum-packaged beef slices, as regards spoilage microbial counts and the chemical parameters tested in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: Inoculation with the BLIS producer Lact. sakei CECT 4808 strain would provide an additional hurdle to improve storage life of refrigerated vacuum-packaged sliced beef. Furthermore, this strain demonstrated limited antioxidative ability, which could make a contribution to the prevention of lipid oxidation in meat and meat products.