Patrizia Cattaneo

Culture-Dependent and -Independent Methods To Investigate the Microbial Ecology of Italian Fermented Sausages

ABSTRACT In this study, the microbial ecology of three naturally fermented sausages produced in northeast Italy was studied by culture-dependent and -independent methods. By plating analysis, the predominance of lactic acid bacteria populations was pointed out, as well as the importance of coagulase-negative cocci. Also in the case of one fermentation, the fecal enterocci reached significant counts, highlighting their contribution to the particular transformation process. Yeast counts were higher than the detection limit (>100 CFU/g) in only one fermented sausage. Analysis of the denaturing gradient gel electrophoresis (DGGE) patterns and sequencing of the bands allowed profiling of the microbial populations present in the sausages during fermentation. The bacterial ecology was mainly characterized by the stable presence of Lactobacillus curvatus and Lactobacillus sakei, but Lactobacillus paracasei was also repeatedly detected. An important piece of evidence was the presence of Lactococcus garvieae, which clearly contributed in two fermentations. Several species of Staphylococcus were also detected. Regarding other bacterial groups, Bacillus sp., Ruminococcus sp., and Macrococcus caseolyticus were also identified at the beginning of the transformations. In addition, yeast species belonging to Debaryomyces hansenii, several Candida species, and Willopsis saturnus were observed in the DGGE gels. Finally, cluster analysis of the bacterial and yeast DGGE profiles highlighted the uniqueness of the fermentation processes studied.

Characterisation of naturally fermented sausages produced in the North East of Italy.

In the Friuli Venezia Giulia region, in the North East of Italy, a traditional fermented sausage is produced without the use of microbial starters. It is characterized at the end of the ripening period by accentuated acidity, slight sourness and elastic, semi-hard consistency. In this study, three fermentations, carried out in different seasons (winter, spring and summer) were followed analyzing the microbiological, physicochemical and sensory aspects of this product. The sausages were characterized by an important microbial activity of lactic acid bacteria and micro/staphylococci that resulted in a product with a final pH of about 5.6-5.7. An interesting aspect was the high number of fecal enterococci that can play an important role in the definition of the organoleptic profile of the final product. No Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus were ever isolated from the raw materials or the fermented sausages during the maturation, underlining the safety of this product. The final water activity of the product was 0.91-0.92. One hundred and fifty lactic acid bacteria were isolated and identified by molecular methods to understand which species were more predominant in the product. Lactobacillus curvatus and Lactobacillus sakei were the most numerous (54 and 64 strains isolated, respectively) and they were the only species common to all three fermentations. A cluster analysis of the profiles obtained from these strains after RAPD-PCR highlighted a population distribution that was fermentation-specific.

Prevalence and mean intensity of Anisakis simplex (sensu stricto) in European sea bass (Dicentrarchus labrax) from Northeast Atlantic Ocean

Viscera and muscle of a total of 40 wild 1-2kg European sea bass (Dicentrarchus labrax) from Northeast Atlantic (FAO area 27) were examined for Anisakidae larvae detection by digestion method. Extracted parasites were counted and mean intensity was calculated. Parasites were identified by genetic/molecular markers (allozymes and sequences analysis of the mtDNA cox2 gene) as belonging to the species Anisakis simplex (sensu stricto). In viscera, the main localisations of the larvae were under the gastric serosa, where several parasites alive and dead were found, and intestinal serosa. The visceral prevalence was 0.950 and the mean intensity was 96.39. The main localisation of A. simplex (s.s.) in edible parts was in belly muscles, with a prevalence of 0.425 and a mean intensity of 1.9. This is the first record on the prevalence and mean intensity of A. simplex (s.s.) in European sea bass muscle. This finding has an important consequence on epidemiology of anisakiasis and public health risk assessment.

Prevalence and Mean Intensity of Anisakidae Parasite in Seafood Caught in the Mediterranean Sea Focusing on Fish Species at Risk of Being Raw-consumed. A Meta Analysis and Systematic Review.

Objective: To assess the prevalence and mean intensity of anisakids in seafood caught in the Mediterranean Sea, focusing on fish species at risk of being raw-consumed. Design: Systematic review and meta-analysis of studies published from 1960–2012. Study selection: Main criteria for the inclusion of studies were as follows: Findings of anisakid larvae, in both muscles and viscera; fish species for human consumption caught in the Mediterranean Sea; prevalence and mean intensity data for each species; and sample size equal to or more than 40 fishes. Results: Twelve studies were identified. Among these, four studies considered the following three fish species that are often consumed raw or preserved lightly, or not cooked thoroughly: anchovy, pilchard, and Atlantic mackerel. Data synthesis: All pooled analyses were based on the random-effect model. Anisakids prevalence in fish muscle was 0.64% (P < 0.0001), in viscera it was 1.34% (P < 0.0001), and overall prevalence was 0.95% (P < 0.0001). Mean intensity in muscle was 2.31 (P = 0.0083), in viscera it was 1.55 (P = 0.0174), and overall it was 1.81 (P < 0.0005). Heterogeneity indices (I2) were significantly high with the exception of viscera mean intensity. Conclusions: Anchovy, pilchard, and Atlantic mackerel have a low prevalence and mean intensity of anisakidae larvae in both viscera and muscles. Mean Intensity was also low.

Selected results of DNA-based species identification on animal foods: DNA-based species identification on animal foods

BACKGROUND Animal food species identification by DNA sequencing has been increasing in recent years. During the last 10 years our species identification laboratory (LIS) produced nearly 1500 sequences from DNA of food species by means of polymerase chain reaction product sequencing. In this paper we desire to make public the LIS output of the last 10 years; that is, summarizing food species authentication projects that yielded good-quality (i.e. provided by Genbank accession number) DNA sequences. RESULTS Thirteen project clusters yielded n = 705 sequences with accession number. CONCLUSION The most relevant characteristics from the aforementioned project clusters were summarized.

Evaluation of a loop-mediated isothermal amplification method for the detection of Listeria monocytogenes in dairy food

Objective of the present study was to test the performances of a loop-mediated isothermal amplification (LAMP)-based method for the detection of Listeria monocytogenes, with particular focus on the dairy products. The specificity of the method was evaluated on 42 different Listeria spp. strains from collections, food and environmental samples. 100% (32 of 32) of the L. monocytogenes strains were correctly recognised, and none of other 10 Listeria spp. strains was misidentified. The sensitivity was evaluated on four L. monocytogenes strains from different sources. The instrument was able to detect 10-400 CFU/mL. The ability to detect low initial numbers of L. monocytogenes (0.3-0.7 Log CFU/g) was also evaluated, in duplicate, in pasteurised milk (whole and skimmed) and dairy samples (fresh ricotta, crescenza, mascarpone, mozzarella, cottage cheese, cream cheese, taleggio, gorgonzola). The analysis was performed after 18, 24 and 48 h of incubation, and was coupled with the count of L. monocytogenes in the broth. Microbial loads were insufficient to achieve a positive result after 18 and 24 h in most of the samples; after 48 h, all the products, except taleggio and one gorgonzola sample, were identified as positive; the sensitivity of the method when applied to contaminated dairy foods was about 5 Log CFU/g. The LAMP method tested can be considered a very useful tool, as it is a costeffective and easy-functioning method. The preliminary data obtained should be confirmed with a validation process taking into account different food typologies.

Microbiological and chemico-physical shelf-life and panel test to evaluate acceptability of liver mortadella

This study aimed to evaluate the shelf life of sliced cooked liver mortadella packaged in MAP (70-85% N2, 15-30% CO2) and stored in refrigeration (4°C) or slight thermal abuse (8°C) for up to 49 days (declared best before date 45 days). The proximate composition, aw nitrites and NaCl content were determined at T0. Weekly, samples were submitted to microbiological [total viable count (TVC), lactic acid bacteria (LAB), Enterobacteriaceae, Escherichia coli, Pseudomonas spp., coagulase positive staphylococci, sulphite reducing clostridia, yeasts and moulds, Listeria monocytogenes and Salmonella spp.] and physicalchemical analyses [pH, colorimetric parameters, total volatile basic nitrogen (TVBN), thiobarbituric acid reactive substances (TBARs)], in parallel with consumer acceptability tests. The product characteristics (low salt and nitrites concentration, high aw and pH close to 6.5) were not efficient hurdles for microbial growth. No pathogens were detected in the samples; the initial TVC [5.4 Log colony forming unit (CFU)/g] increased rapidly, reaching values around 8 Log CFU/g at T14 for both the series, and was almost totally composed by LAB, leading to the acidification of the product (pH at T49=5.05 at 4°C and 5.24 at 8°C). The other microbiological parameters were below 2 Log CFU/g. The product showed a good protein and lipid stability (TVBN <33 N/100 g and TBARs <8 nmol/g at T49). The sensorial quality of liver mortadella was more affected by the storage time than by the temperature. An evident colour modification was detected after T35, when the product was also frequently rejected by the panellists, mainly due to odour. Thus, the shelf life of sliced cooked liver mortadella should be shortened below 30 days.

A case study: shelf-life of smoked herring fillets by volatile compounds analysis.

Two different products of vacuum packed cold smoked herrings were analyzed at time intervals in order to evaluate the efficiency of the processing and product stability. Microbiological total counts, lactic acid bacteria, total coliforms, pH, water activity, water content, salt content (WPS) were determined. Differences in hygienic conditions and salt content were found. Principal components analysis (PCA) of volatile compounds determined by GC-MS analysis allowed the differentiation of the processing.

Molluschi bivalvi vivi ed echinodermi, tunicati e gasteropodi marini vivi

This issue contains: A short account of anatomy and physiology of bivalve molluscs, marine gastropods, echinoderms and tunicates. Economic importance of live bivalve molluscs . Bacterial and viral illness associated with consumption of live bivalve molluscs. Microbiological risk management. Marine biotoxins and chemical contaminants. Bivalve molluscs production. Harvesting of live bivalve molluscs and post harvest treatments. Packaging and labelling of live bivalve molluscs, echinoderms, tunicates and marine gastropods References. Enclosure: identification sheets of the main commercial species of bivalve molluscs and marine gastropods.