Lactic fermentation of cooked, comminuted mussel, Perna canaliculus.

The endogenous microflora of mussels, filter feeders, can include pathogens with resulting food safety concerns. The aim was to develop a cook-then-ferment technology to extend shelf life and safety of a ready-to-eat mussels. Only after cooking to destroy the mussel's endogenous microflora could an edible product be made as determined by pH decline after fermentation and the fate of common pathogens. Perna canaliculus was bought live at retail on many dates. Fermentation was with commercial lactic cultures incubated under vacuum at 30 °C for four days. Using one culture containing Pediococcus pentosaceus and Staphylococcus carnosus as a model, pH typically declined to 4.5 to 4.7, and common pathogens, Staphylococcus aureus, Salmonella and Vibrio parahaemolyticus were absent or reduced to acceptable levels. The fate of Listeria monocytogenes was studied with five cultures. These were variably effective at inhibition with one clear success, Chr Hansen's T-SC-150 containing a specific strain of Lactobacillus sakei, and flavour-generating Staphylococcus carnosus. This culture's efficacy was confirmed with sterile extracts of LAB challenging L. monocytogenes in vitro. This culture was also the most rapid fermenter by pH fall. Cook-then-ferment technology may be applied to other novel foods to minimise a disruptive endogenous microflora.

Post-process treatments are effective strategies to reduce Listeria monocytogenes on the surface of leafy greens: A pilot study.

Growth of L. monocytogenes is among the most important factors affecting the risk of human listeriosis. In ready to eat leafy greens, the use of anti-Listeria treatments represents a good alternative to inhibit growth during storage. Several commercially available antimicrobial agents have been suggested as effective intervention strategies. Among them, phage preparations and bacteriocin-producing strains have shown promising results against L. monocytogenes. In this study, we investigate the efficacy of two commercially available surface treatments, the bacteriophage formulation PhageGuard Listex (Micreos Food Safety B.V., NL) and the bacteriocin-producing culture SafePro® (CHR Hansen, DK) to inactivate L. monocytogenes in fresh-cut curly endive after processing and during storage. Fresh-cut endive was inoculated with a cold-adapted L. monocytogenes cocktail of 6 strains (4.4 ±â€¯0.0 log cfu/g) and treated with the anti-Listeria treatments. The treatments were applied using a spray system at two different places within the processing line, on the conveyor belt and in the centrifuge. A total of 5 different treatments were applied: i) Untreated (CT); ii) PhageGuard Listex on the conveyor belt (Listex_Conveyor); iii) PhageGuard Listex during centrifugation (Listex_Centrifuge); iv) SafePro on the conveyor belt (SafePro_Conveyor); and v) SafePro during centrifugation (SafePro_Centrifuge). Samples were stored 3 days at 5 °C plus 5 days at 8 °C. PhageGuard Listex treatment reduced L. monocytogenes in fresh-cut endive by 2.5 logs, regardless of the place of treatment application (conveyor belt or centrifuge). On the other hand, SafePro only reduced L. monocytogenes by 0.2 and 0.4 logs, at the conveyor belt and centrifuge, respectively. Maximum L. monocytogenes reductions of about 3.5 log units were observed in fresh-cut endive treated with PhageGuard Listex after 3 days of storage. At the end of the shelf life (8 days), the initial trends were maintained and the fresh-cut curly endive treated with PhageGuard Listex showed the lowest L. monocytogenes concentration. However, by the end of the shelf-life, L. monocytogenes showed higher levels (1.3-fold) than immediately after the application of the treatment. One hypothesis could be that L. monocytogenes cells, which were able to survive the anti-Listeria treatments, were also able to proliferate under the specific storage conditions. Based on the obtained results, PhageGuard Listex seems to be a promising decontamination agent for leafy greens aiming to reduce growth of the bacteria but further work is needed.

Evaluation of the microbiological safety and sensory quality of a sliced cured-smoked pork product with protective cultures addition and modified atmosphere packaging.

The aim of this study was to evaluate the effect of two protective lactic acid bacteria cultures combined with modified atmosphere packaging on the survival/growth of Listeria innocua 2030c (as a surrogate for Listeria monocytogenes) and on sensory attributes of ready-to-eat 'lombo' over storage time. Sliced 'lombo', a traditional cured-smoked pork loin, was inoculated with L. innocua 2030c, Lactobacillus sakei ST153 (isolated from 'salpicão') and BLC35 culture (with Lactobacillus curvatus, Staphylococcus xylosus and Pediococcus acidilactici; CHR Hansen) as protective cultures. Samples were packed in two modified atmosphere packaging conditions (20% CO2/80% N2 and 40% CO2/60% N2) and stored at 5 ℃ for 124 days. Both cultures led to a reduction of 1-2 log CFU/g of L. innocua 2030c after 12 h; however, at the end of storage only Lb. sakei ST153 maintained this antilisterial effect, which was more evident at 40% CO2/60% N2. The influence of cultures addition and modified atmosphere packaging conditions on the sensory characteristics of the product were not significant. Thus, Lb. sakei ST153 combined with modified atmosphere packaging is a strong candidate to be used in a biopreservation strategy maintaining the traditional sensory quality of cured-smoked pork products and increasing their safety with respect to Listeria spp.

Diversity of culturable microorganisms and occurrence of Listeria monocytogenes and Salmonella spp. in Tuber aestivum and Tuber melanosporum ascocarps.

The aim of this study was to investigate the total mesophilic microorganisms, Pseudomonas genus, Enterobacteriaceae family, mold and yeast counts and the presence of Listeria monocytogenes and Salmonella spp on Tuber aestivum and Tuber melanosporum ascocarps. The results confirmed that the major percentage of the microorganisms, approximately 9.0 log ufc/g, were present in the peridium, the glebas of healthy truffles being practically free of microorganisms. The predominant microbial group was the Pseudomonas averaging 8.3 and 8.4 log cfu/g on T. aestivum and T. melanosporum whole ascocarps, respectively. The Enterobacteriaceae also achieved high populations, especially in T. aestivum truffles, with 6.3 log cfu/g. Molds and yeasts never exceeded 5.0 log cfu/g. The characterization of the isolates revealed that the fluorescens pseudomonads were the most prevalent. Raoultella terrigena and Enterobacter intermedius were the dominant Enterobacteriaceae. The identification of the yeast isolates revealed five species: Debaryomyces hansenii, Issatchenkia scutulata, Rhodotorula aurantiaca, Saccharomyces dairensis and Trichosporon beigelii subspecies A and B. The mold genera detected in both species of truffles were Aspergillus, Cladosporium, Penicillium and Fusarium, Trichoderma being present only in T. aestivum. L. monocytogenes was found in 10% of the samples of T. aestivum analysed but Salmonella spp. was not detected. Knowledge of the microbial population in terms of possible food borne and pathogen microorganisms is very useful for establishing successful disinfection and storage methods to prolong the shelf-life of ascocarps of T. aestivum and T. melanosporum.