ß-hydroxyacyl-CoA-dehydrogenase activity differentiates unfrozen from frozen-thawed Yellowfin tuna (Thunnus albacares).

Changes in the ß-hydroxyacyl-CoAdehydrogenase (HADH) activity of fresh and frozen-thawed Yellowfin tuna were examined. A statistical approach to HADH activities determined in press juice allowed to set a critical value to differentiate fresh from frozen-thawed Yellowfin tuna: the threshold value was 3.7 U mL-1 at the probability level of 1%. The analysis of 37 tuna (not ready to eat) sampled on retail revealed the unconformity to labelling of 4 samples. A simple statistical algorithm was built to get probabilities from observed values on tuna of being or not frozen/thawed.

Non-thermal inactivation of Listeria spp. in a typical dry-fermented sausage: "Bergamasco" salami.

Aim of the present study was the evaluation of the growth potential of Listeria spp. inoculated in the typical North Italian dry fermented sausage "Bergamasco" salami during its production. As it was necessary to carry out the challenge test in the production line of the industry, according to the guidelines of the European Reference Laboratory for Listeria monocytogenes, a non-pathogenic "surrogate" microorganism was used: for the inoculum, two strains of Listeria innocua (1 ATCC, 1 strain isolated from a similar substrate) were used. The inoculation of the samples occurred during grinding and mixing of the sausage mass, before the filling. To avoid cross-contamination, the control samples were produced before the contaminated ones. After the dripping, salamis were subjected to the normal production process (drying and maturation in five steps at specific temperatures and humidity rates). The inoculated products were subjected to the enumeration of Listeria spp. at T0 (day of inoculation) and at T4 (post-drying), and every 10 days during curing (T10, T20, T30, T40, T50, T60, T70, T80 and T90), as this salami is generally sold as whole piece with varying levels of curing (from T20 to T90). Since the product may be cut in half and vacuumpacked, at each of the times starting from T20, half salami was vacuum-packed and stored for 30 days at 12°C, at the end of the which Listeria spp. enumeration was performed again. At all times and for each type of samples of each of the three batches, the enumeration of the natural microflora (Total Viable Count, lactic acid bacteria, Pseudomonas spp., Enterobacteriaceae) and the determination of water activity and pH were performed on control samples. The product was characterized by a high concentration of microflora (8-8.5 Log UFC/g), consisting mainly of lactic acid bacteria, added to the mixture at the beginning of the production process. The pH showed a decrease over time, expected for this type of products, due to the development of lactic acid bacteria (final pH: 5.42-5.55). The water activity reached values able to inhibit the development of Listeria spp. (final aw: 0.826-0.863). Listeria counts in the tested batches of "Bergamasco" salami showed the absence of significant growth in the product with a reduction of loads if compared to T0, between -0.59 and -1.04 Log CFU/g. Even in the samples subjected to vacuum packaging and storage at 12°C, the absence of significant increase of lactic acid bacteria in the product was highlighted with further decrease of bacterial loads (-0.70/-0.79 Log CFU/g if compared to T20). Considering the worst case scenario (thus the batch with the highest growth potential), in the products stored in the curing room at 14-16°C, at humidity of 80% and in the samples stored at 12°C and vacuum packaged, the threshold indicated by the EURL Lm guidelines (+0.5 Log CFU/g) for the growth of Listeria spp. was not reached, allowing to classify "Bergamasco" salami in the category 1.3 of the EC Reg. 2073/2005 as "Ready-to-eat food unable to support the growth of Listeria monocytogenes".

Histamine food poisonings: A systematic review and meta-analysis.

OBJECTIVE: The aim of this study was to assess the mean of histamine concentration in food poisoning. DESIGN: Systematic review and meta-analysis of reports published between 1959 and 2013. STUDY SELECTION: Main criteria for inclusion of studies were: all report types that present outbreaks of "histamine poisoning' or "scombroid syndrome" from food, including histamine content and type of food. Health status of people involved must be nonpathological. RESULTS: Fifty-five (55) reports were included, these studies reported 103 incidents. All pooled analyses were based on random effect model; histamine mean concentration in poisoning samples was 1107.21 mg/kg with confidence interval for the meta-mean of 422.62-2900.78 mg/kg; heterogeneity index (I2) was 100% (P < 0.0001); prediction interval was 24.12-50822.78 mg/kg. Fish involved in histamine poisoning was mainly tuna or Istiophoridae species. No clues of association between concomitant conditions (female sex, alcohol consumption, previous medication, and consumption of histamine releasing food) and histamine poisoning, were highlighted. CONCLUSIONS: This is the first systematic review and meta-analysis that analyzes all the available data on histamine poisoning outbreaks evaluating the histamine concentration in food involved. Histamine mean concentration in poisoning samples was fairly high. Our study suffers from some limitations, which are intrinsic of the studies included, for instance the lack of a complete anamnesis of each poisoning episode. Protocol registration: Methods were specified in advance and have been published as a protocol in PROSPERO database (18/07/2012 -CRD42012002566).

Selected results of 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. © 2017 Society of Chemical Industry.

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.

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 (I(2)) 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.

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.

Culture-dependent and -independent methods to investigate the microbial ecology of Italian fermented sausages.

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.