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Mataragas M.,University of Turin | Mataragas M.,National and Kapodistrian University of Athens | Bellio A.,Istituto Zooprofilattico Sperimentale del Pimonte | Rovetto F.,University of Turin | And 3 more authors.
Meat Science | Year: 2015

Fermentation is the most important killing step during production of fermented meats to eliminate food-borne pathogens. The objective was to evaluate whether the food-borne pathogens Listeria monocytogenes and Salmonella enterica may survive during the production of two Italian fermented sausages. Sausage batter was inoculated with five strains of L. monocytogenes or S. enterica (ca. 105-106cfu/g) and their kinetic behavior was monitored during production. Both pathogens survived relatively well (in Cacciatore L. monocytogenes and S. enterica inactivation was ca. 0.38±0.23 and 1.10±0.24logcfu/g, respectively; in Felino was ca. 0.39±0.25 and 1.62±0.38logcfu/g, respectively) due to the conditions prevailing during production (slow dehydration rate, small reduction of water activity and fermentation temperature mainly below 20°C during the first 48h of fermentation). Quantitative analysis of data originating from challenge tests provide critical information on which combinations of the process parameters would potentially lead to better control of the pathogens. © 2015 Elsevier Ltd. Source


Mataragas M.,University of Turin | Mataragas M.,National and Kapodistrian University of Athens | Bellio A.,Istituto Zooprofilattico Sperimentale del Pimonte | Rovetto F.,University of Turin | And 5 more authors.
Food Control | Year: 2015

The objective was to evaluate the survival capability and quantify the persistence of the food-borne pathogens Listeria monocytogenes and Salmonella enterica in the Cacciatore, Felino and Milano type salami preparation. The batter of each sausage was inoculated with a five-strain cocktail of L.monocytogenes or S.enterica (ca. 104-105CFU/g) and their progression was monitored at specific time intervals during preparation of the sausages. Four different batches were prepared at different times for each sausage/pathogen combination. Different models were used to fit the experimental data and to calculate the kinetic parameters. The best model was chosen based on statistical comparisons. S.enterica proved to be more sensitive susceptible to fermentation and ripening processes than L.monocytogenes. Both pathogens, however, survived relatively well as the result of the conditions (pH, aw and fermentation temperature) prevailing during fermentation and ripening of the sausages. Water activity proved to be a key factor in the survival of the microorganisms. The statistical analysis of quantitative data gathered from challenge tests is useful for the food business operators as it can provide practical information on the process parameters combinations that could lead to a better control of the pathogens. © 2014 Elsevier Ltd. Source


Mataragas M.,University of Turin | Mataragas M.,National and Kapodistrian University of Athens | Rovetto F.,University of Turin | Bellio A.,Istituto Zooprofilattico Sperimentale del Pimonte | And 4 more authors.
Food Microbiology | Year: 2015

The current study reports a) the in situ transcriptional profiles of Listeria monocytogenes in response to fermented sausage stress and b) an approach in which in situ RT-qPCR data have been combined with advanced statistical techniques to discover potential stress resistance or cell viability biomarkers. Gene expression profiling of the pathogen has been investigated using RT-qPCR to understand how L.monocytogenes responds to the conditions encountered during the fermentation and ripening of sausages. A cocktail of five L.monocytogenes strains was inoculated into the batter of Cacciatore and Felino sausages. The RT-qPCR data showed that the acidic and osmotic stress-related genes were up-regulated. The transcripts of the lmo0669 gene increased during the fermentation and ripening of Cacciatore, whereas gbuA and lmo1421 were up-regulated during the ripening of Felino and Cacciatore, respectively. sigB expression was induced in both sausages throughout the whole process. Finally, the virulence-related gene prfA was down-regulated during the fermentation of Cacciatore. The multivariate gene expression profiling analysis suggested that sigB and lmo1421 or sigB and gbuA could be used as different types of stress resistance biomarkers to track, for example, stress resistance or cell viability in fermented sausages with short (Cacciatore) or long (Felino) maturation times, respectively. © 2014 Elsevier Ltd. Source

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