A stochastic interspecific competition model to predict the behaviour of Listeria monocytogenes in the fermentation process of a traditional Sicilian salami

The present paper discusses the use of modified Lotka-Volterra equations in order to stochastically simulate the behaviour of Listeria monocytogenes and Lactic Acid Bacteria (LAB) during the fermentation period (168 h) of a typical Sicilian salami. For this purpose, the differential equation system is set considering T, pH and aw as stochastic variables. Each of them is governed by dynamics that involve a deterministic linear decrease as a function of the time t and an "additive noise" term which instantaneously mimics the fluctuations of T, pH and aw. The choice of a suitable parameter accounting for the interaction of LAB on L. monocytogenes as well as the introduction of appropriate noise levels allows to match the observed data, both for the mean growth curves and for the probability distribution of L. monocytogenes concentration at 168 h.Comment: 19 pages, 2 figures, 2 tables. To be published in Eur. Food Res. Techno

Application of an interspecific competition model to predict the growth of Aeromonas hydrophila on fish surfaces during the refrigerated storage

The growth of Aeromonas hydrophila and aerobic natural flora (APC) on gilthead seabream surfaces was evaluated during the refrigerated storage (21 days). The related growth curves were compared with those obtained by a conventional third order predictive model obtaining a low agreement between observed and predicted data (Root Mean Squared Error = 1.77 for Aeromonas hydrophila and 0.64 for APC). The Lotka-Volterra interspecific competition model was used in order to calculate the degree of interaction between the two bacterial populations (\beta_{Ah/APC} and \beta{APC/Ah}, respectively, the interspecific competition coefficients of APC on Aeromonas hydrophila and vice-versa). Afterwards, the Lotka-Volterra equations were applied as tertiary predictive model, taking into account, simultaneously, the environmental fluctuations and the bacterial interspecific competition. This approach allowed to obtain a best fitting to the observed mean growth curves with a Root Mean Squared Error of 0.09 for Aeromonas hydrophila and 0.28 for APC. Finally, authors carry out some considerations about the necessary use of competitive models in the context of the new trends in predictive microbiology.Comment: 16 pages, 1 table, 2 figure

Bacteriology of unshelled frozen blue swimming crab (Portunus pelagicus)

In this study, 45 (10 whole specimens and 35 frozen claws) frozen samples of Portunus pelagicus imported into Sicily (Italy) from the west coast of Africa were examined to assess their bacteriological characteristics and suitability for consumption. Bacteriological examination was performed on two subsamples for each whole crab. The first was the body and claw muscle; the second was a pool of viscera and gills. In the case of frozen claws, each muscle claw was a sample. An aerobic plate count at 30 degrees C (mesophilic aerobic plate count [MAPC]) and 18 degrees C (psychrotrophic aerobic plate count [PAPC]) for 3 days, sulfite-reducing anaerobes, total coliforms, Escherichia coli, enterococci, and Aeromonas spp. were enumerated. Detection of halophilic Vibrio spp. was also performed using salt polymixin broth as an enrichment medium and thiosulfate citrate bile salts sucrose agar as a selective medium; a further morphological and biochemical identification of suspected colonies was performed. The bacterial load of muscle and viscera and gills was low. The MAPC ranged from 0.78 to 3.26 log CFU/g, and the PAPC ranged from 0.48 to 2.41 log CFU/g. Vibrio spp., Aeromonas spp., sulfite-reducing anaerobes, and E. coli were never isolated from muscles or viscera and gills. In contrast to the findings of others, this study showed good bacteriological quality of crabs imported into Sicily from the west coast of Africa. This study also demonstrated the positive influence of the characteristics of environment of origin and postharvest handling hygiene; these parameters could be useful in the context of the application of the hazard analysis critical control point system to this production

Aida

De cada obra s'ha digitalitzat un programa sencer. De la resta s'han digitalitzat les parts que són diferents.Direcció: Ottavio ZiinoEmpresa: Juan A. PamiasÒpera en quatre actes de Giuseppe Verdi amb llibret d'Antonio Ghislanzon

Activity of Tagetes minuta Linnaeus (Asteraceae) essential oil against L3 Anisakis larvae type 1

Abstract Objective To evaluate in vitro effects of Tagetes minuta L. essential oil (TEO) on L3 Anisakis larvae type 1. Methods In order to evaluate the potential use of Tagetes minuta essential oil against L3 Anisakis larvae three different media were tested: 1) a saline solution (SS); 2) an industrial marinating solution (MS); 3) sunflower seeds oil (SO). For each media and concentrations of TEO (0.1%, 0.5%, 1.0% and 5.0% v/v), 20 parasites were introduced into plastic Petri dishes (diameter 90 mm) and maintained at room temperature. As controls, larvae were maintained without TEO under identical experimental conditions in SS, MS and SO. A total of 900 larvae were tested. The normalized mean viability, LT100, LT50 and the percentage of inactivation at 24 h were calculated. Results In vitro tests revealed a complete inactivation of parasites in saline solution after 2 h with 5% and 1% of TEO. In marinating solution, a complete inactivation of parasites was observed after 4 h at all concentrations used. A slower activity for all TEO concentration was reported in SO. Conclusions The results obtained, showing a strong activity against Anisakis larvae, confirm TEO as a larvicidal agent in the treatment of human anisakidosis and in the industrial marinating process

Study on microbial communities in domestic kitchen sponges: Evidence of Cronobacter sakazakii and Extended Spectrum Beta Lactamase (ESBL) producing bacteria

Domestic environment, in particular, kitchen setting is a well-established source of microbial contamination. Kitchen sponges represent an important vehicle of microbial transmission and maintenance of spoilage bacteria and pathogenic strains responsible for food borne diseases. The aim of this study was to evaluate the microbial communities of 100 ‘in-use’ kitchen sponges, improving the knowledge on their role in cross-contamination in domestic environment and transmission of ESBLproducing strains. Sponges were processed for: aerobic mesophilic bacteria (AMB), Enterobacteriaceae (EB), yeasts and molds (YM), coagulase-positive staphylococci (CPS), micrococci (MCC), anaerobic sulfite reducing bacteria (ASR), and for the detection of Listeria monocytogenes, Salmonella spp. and Yersinia enterocolitica. A total of 309 enterobacteria strains were identified and then processed for ESBL (Extended Spectrum Beta Lactamase) phenotypical expression. A high contamination level of kitchen sponges was observed (mean value AMB 8.25±1.1; EB 5.89±1.2; YM 5.57±1.1; MCC 4.82±0.1 log CFU/g). Identified enterobacteria strains revealed several opportunistic and pathogenic agents such as Enterobacter cloacae (28%), Citrobacter freundii (23.3%), Cronobacter sakazakii (14.6%) and other strains in lower percentage. Listeria monocytogenes was found in only one sponge (1%). A total of 69 (22.3%) enterobacteria resulted ESBL+, with the following prevalence: P. rettgeri (50%), L. adenocarboxilata (30%), K. pneumoniae (25%), K. oxytoca (25%), C. sakazakii (20%), E. cloacae (20.7%), C. freundii (20.1%). Results confirm the potential role of kitchen sponges as vehicle for food-borne pathogens such as, C. sakazakii for the first time, infectious agents and spoilage microorganisms. The observed high contamination level and the presence of several ESBLs opportunistic pathogens, stresses the necessity to improve a proper education of the consumers on the effective treatment to reduce their microbial loads

Quantitative Detection of Viable but Nonculturable <i>Vibrio parahaemolyticus</i> in Frozen Bivalve Molluscs

Vibrio parahaemolyticus is a foodborne pathogen diffusely distributed in the marine environment and often isolated from raw seafood belonging to different species, mostly shellfish. Ingestion of under- or uncooked seafood contaminated by V. parahaemolyticus can cause severe gastrointestinal symptoms in humans. Due to its ability to withstand low temperatures, Vibrio spp. could survive in frozen seafoods for long periods by entering the viable but nonculturable state (VBNC) and may constitute an unrecognized source of food contamination and infection. In the present study, seventy-seven frozen bivalve molluscs (35 mussels; 42 clams) were subjected to the detection and enumeration of viable V. parahaemolyticus using standard culture methods. VBNC forms were detected and quantified by applying an optimized protocol based on Propidium Monoazide (PMA) and Quantitative PCR (qPCR). All samples were negative for both the detection and enumeration of V. parahaemolyticus by the standard culture methods. VBNC forms were detected in 11.7% of the samples (9/77), with values ranging from 1.67 to 2.29 Log CFU/g. Only clam samples were positive for the detection of VBNC forms. The results of this study highlighted that VBNC V. parahaemolyticus may be present in frozen bivalve molluscs. Further data on the prevalence of VBNC V. parahaemolyticus in frozen seafood are needed in order to perform a robust risk assessment

Quality assessment of Zeus faber (Peter’s fish) ovaries regularly commercialized for human consumption

n the last few years, the consumption of fish eggs has increased rapidly, finding widespread use also in mass catering. This increase has involved also those of the Peter’s fish (Zeus faber). Females of this species, by their reproductive characteristics, have highly developed gonads in different periods of the year, making the raw material easy to find. The aim of the present study was to perform a quality assessment of Zeus faber ovaries regularly commercialized for human consumption. A total number of 34 samples, divided in fresh (11) and frozen (23), were processed for microbiological characterization, parasitological and histological evaluations. Fresh and frozen samples have significant (P<0.01) differences in total bacterial charge, with values of 4.75±0.5 Log CFU/g and 3.65±0.7 Log CFU/g respectively. The mean value of Enterobacteriaceae was 2.58±0.7 Log CFU/g in fresh products, while 52.17% (12) of frozen samples reported loads of <1 Log CFU/g. No Salmonella spp. and Listeria monocytogenes were found. Aeromonas spp. was detected in two frozen sample (with loads of 2.2 and <1 Log CFU/g) and in 5 fresh ovaries with value ranged from 1.70 to 3.48 Log CFU/g. Vibrio spp. was found in 4 (36.36%) and 3 (13.04%) of fresh and frozen samples respectively, with loads always <1 Log CFU/g. All 31 Vibrio strains isolated, were identified as Vibrio alginolyticus, and 61.29% (19) of them was positive for the ToxRS factor and 6.45% (2) for ToxR. The 47.06% (16) of total samples showed infestations by larvae of Anisakis Type 1 in the serous and inside the ovary. In this last case, histologically it was found to be free larvae. This study attested satisfactory hygiene conditions for Zeus faber ovaries currently marked for human consumption. The presence of potentially pathogenic strains of V. alginolyticus and Aeromonas spp., but above all the frequent infestation by Anisakis larvae, represent a potentially hazard for the consumer

Characterisation of yeasts isolated from ‘Nduja of Spilinga

The ‘Nduja of Spilinga protected geographical indication (PGI) is a spreadable italian salami, obtained by using fat (50%), lean of pork (25%), chili pepper (25%) and NaCl, stuffed into natural pork casing. Its predominant flora is represented by yeasts, reaching at the end of seasoning values of 6 log CFU/g. Considering the need to enhance and protect traditional local products, it seemed interesting to carry out a characterisation of yeasts of the ‘Nduja of Spilinga PGI. A total of 127 strains of yeast isolated from samples of ‘Nduja of Spilinga PGI (79 strains from samples at different days of curing and 48 from samples of commerce) was subjected to morphological identification, hydrolysis of urea, lipolytic activity and identification with API 20C AUX, ID 32C and simplified identification systems. One hundred twenty three (96.8%) strains were attributable to the phylum Ascomycetes (urease-negative), the remaining 4 strains (3.2%) were Basidiomycetes (urease-positive). <em>Debaryomyces hansenii</em> and its anamorph shape, <em>Candida famata</em>, represented the most prevalent species (61.42 and 17.32% respectively), followed by <em>Candida glabrata</em> (8.66%), <em>Pichia (Candida) guilliermondii</em> (5.17%), <em>Candida parapsilosis</em> and<em> Rhodotorula glutinis</em> (1.57%). <em>Candida catenulata</em>, <em>Criptococcus uniguttulatus</em>, <em>Rhodotorula minuta</em>, <em>Candida zeylanoides</em> and <em>Candida utilis</em> were observed with 0.79%. The lipolytic activity was observed only in 10 strains of <em>D. hansenii</em> and in one of <em>C. zeylanoides</em>. Further investigation will contribute to the selection of indigenous strains that could be used for the creation of specific starter, useful to improve the process of characterisation of the ‘Nduja of Spilinga and also to guarantee its safety

Hygienic-sanitary evaluation of sushi and sashimi sold in Messina and Catania, Italy

Sushi and sashimi are traditional Japanese food, mostly consisting of raw seafood alone or in combination with rice. Eating sushi and sashimi has become popular in many countries even outside Japan. This food is not free from health risks such as ingestion of pathogenic bacteria or parasite. The aim of this study was to investigate on hygienic-sanitary quality of sushi and sashimi sold in the cities of Messina and Catania, Southern Italy. Fifty samples (38 sushi and 12 sashimi) were analysed to determinate the aerobic mesophilic bacteria (AMB), psycrophilic bacteria (PB), <em>Enterobacteriaceae</em>, specific spoilage organisms (SSOs), <em>Pseudomonas</em> spp., coagulase-positive staphylococci, micrococci, <em>Vibrio</em> spp., <em>Bacillus cereus</em>, <em>Salmonella</em> spp. and <em>Listeria monocytogenes</em>. In sushi, AMB ranged from 5.00 to 8.18 log CFU/g, PB from 4.70 to 7.13 log CFU/g, <em>Enterobacteriaceae</em> from 1.41 to 6.67 log CFU/g, while SSOs and <em>Pseudomonas</em> spp. from 3.49 to 7.72 and from 3.36 to 8.00 log CFU/g, respectively. Micrococci ranged from 3.53 to 5.03 log CFU/g and coagulase positive staphylococci were found in 16 samples (2.00 to 3.60 log CFU/g). <em>Bacillus cereus</em> was found in 3 samples (1.70 to 4.00 log CFU/g), while <em>Vibrio</em> spp. was found in 15 of the sushi samples (1.70 to 3.70 log CFU/g). In sashimi, the AMB, PB and SSOs values were higher than 7.00 log CFU/g, <em>Pseudomonas</em> spp. and <em>Enterobacteriaceae</em> were from 6.00 to 8.00 log CFU/g, while <em>Vibrio</em> spp. were found in six samples with means of 2.00 log CFU/g. No <em>Salmonella</em> spp. and <em>Listeria monocytogenes</em> were detected in all sushi and sashimi samples