Behaviour of Escherichia coli O157 (VTEC), Salmonella Typhimurium and Listeria monocytogenes during the manufacture, ripening and shelf life of low fat salami

Occurrence and genomic characterization of antimicrobial-resistant and potential pathogenic Escherichia coli from Italian artisanal food productions of animal origin

Escherichia coli can harbor a broad repertoire of virulence and antimicrobial resistance (AMR) genes, which can be exchanged across the human gastrointestinal microflora, thus posing a public health risk. In this study, 6 batches of artisanal soft cheese and a 6-month ripened fermented dried sausage were investigated to assess the occurrence, phylogeny, and genomic traits (AMR, virulence, and mobilome) of E. coli. 30 and 3 strains isolated from salami and cheese food chains, respectively, were confirmed as E. coli by whole genome sequencing. The accumulation of single nucleotide polymorphism differences within small clusters of strains encompassing batches or processing stages, combined with high serotype and phylogroup diversity, suggested the occurrence of different contamination phenomena among the facilities. A total of 8 isolates harbored plasmid-mediated resistance genes, including one cheese strain that carried an IncQ1 plasmid carrying AMR determinants to macrolides [mph(B)], sulfonamides (sul1, sul2), trimethoprim (dfrA1), and aminoglycosides [aph(3")-Ib and aph(6)-Id]. A pool of virulence-associated genes in the class of adhesion, colonization, iron uptake, and toxins, putative ColV-positive iron uptake systems sit, iro, or iuc (8 salami and 2 cheese), plasmid-encoded hemolysin operon hlyABCD (one salami), and potential atypical enteropathogenic E. coli (3 salami environment) were reported. Overall, our findings underscore the importance of routine surveillance of E. coli in the artisanal food chain to prevent the dissemination of AMR and virulence.

An Analysis of Changes in the Physicochemical and Mechanical Properties during the Storage of Smoked and Mould Salamis Made in Poland

The aim of the study was to analyse changes in the physicochemical, rheological, and textural properties occurring during the storage of industrially produced smoked salami and mould salami. Tests on these cold cuts were conducted on the 2nd, 15th, 30th, and 45th days of storage. There was a significant increase in the pH value of the mould salami from 5.16 on the 2nd day to 5.42 on the 45th day (p < 0.05). There was a downward trend in the A_w of the smoked salami sample from 0.892 on the 2nd day to 0.873 on the 45th day. The A_w in the mould salami sample decreased from 0.889 on the 2nd day to 0.847 on the 15th day and then increased to 0.871 on the 45th day (p < 0.05). In the first two test periods, the smoked salami was characterised by a higher modulus of elasticity value than the non-smoked salami but lower loss tangent and dynamic viscosity values. The hardness of the whole bars, as well as the hardness of the salami pieces, was affected by their storage time and the related water content. The texture test results showed that the smoked salami was more resistant to compressive force than the mould salami, which affected the sensory evaluation and ease of slicing of this type of salami.

Inactivation of Listeria monocytogenes and Salmonella spp. in Milano-Type Salami Made with Alternative Formulations to the Use of Synthetic Nitrates/Nitrites

During the manufacture of Italian salami, a traditional meat product, a sequence of hurdles like meat fermentation, air-drying, and long ripening processes are generally sufficient to inhibit the growth of most pathogens. Furthermore, Italian salami are traditionally produced by adding synthetic nitrates/nitrites to raw meat with safety and technological aims, even if controversial opinions about their use still remain, particularly in relation to the consumer demand for natural food products. In this context, the aim of the study was to investigate the inactivation of Listeria monocytogenes and Salmonella spp. during the manufacturing process of Milano-type salami made with different formulations to evaluate the contribution of the hurdles and the vegetable or synthetic additives on the inactivation of pathogens. Thus, a challenge study was performed dividing ca. 400 kg of Milano-type salami batter into three batches: Batch (A) without nitrates/nitrites; Batch (B) with vegetable nitrates, and Batch (C) with synthetic nitrates/nitrites. The batches were separately inoculated with L. monocytogenes and Salmonella spp. and the pathogens’ survival was evaluated during the fermentation, draining, and 70-day ripening of the Milano-type salami. The pathogen counts decreased in all tested conditions, even though the highest inactivation of L. monocytogenes and Salmonella spp. (p < 0.05) was observed when nitrates or nitrites were added to the batter. This study shows how the safety of these products cannot exclude the aspect of the hurdle technology during the process, which plays a major role in the reduction of pathogens, but additives like nitrates and nitrites allow for a greater margin of safety. Thus, further studies are needed to validate the use of natural compounds as alternatives to conventional preservatives in meat products. These results may provide new information to support food business operators in producing traditional foods with alternative preservatives and competent authorities in verifying the safety of the products made with natural compounds, and to control the process parameters responsible for the synergistic effect against pathogens such as L. monocytogenes and Salmonella spp.

One-Day Molecular Detection of Salmonella and Campylobacter in Chicken Meat: A Pilot Study

Salmonella and Campylobacter ssp. are bacterial pathogens responsible for most foodborne infections in EU countries. Poultry serves as a reservoir for these pathogens, and its important role in the meat industry makes it essential to develop a rapid detection assay able to provide results in one day. Indeed, the rapid identification of foodborne pathogens is an important instrument for the monitoring and prevention of epidemic outbreaks. To date, Salmonella and Campylobacter screening is mainly conducted through molecular methods (PCR or real-time PCR) performed after 18–24 h long enrichments. In this study, we evaluated short enrichments (0, 2, 4, and 6 h) combined with a colorimetric loop-mediated isothermal AMPlification (LAMP) or real-time PCR to detect Salmonella and Campylobacter in poultry meat contaminated at different concentration levels (10¹, 10³, and 10⁵ CFU/g). Our results show that real-time PCR allows the detection of Salmonella and Campylobacter, even after shorter enrichment times than prescribed by ISO references; particularly, it detected Salmonella down to 10¹ CFU/g since T0 and Campylobacter from 10³ CFU/g since T0. Detection with LAMP was comparable to real-time PCR without the requirement of a thermal cycler and with shorter execution times. These characteristics make colorimetric LAMP a valid alternative when one-day results are needed, improving the timely identification of positive meat batches, even in the absence of specialized instrumentation.

Sensory Changes and Listeria monocytogenes Behavior in Sliced Cured Pork Loins during Extended Storage

Cured pork loins are sausages with a production tradition in several regions worldwide. They are made from one of the noblest cuts of pork, and for this reason cured loins are one of the most expensive pork meat products. Establishing the correct shelf life allows products to be accepted by the consumer, and to avoid the costs associated with shorter shelf lives. The aim of this study is: (1) to establish proper shelf life by evaluating the willingness of participants to consume and the sensory modifications that occur during prolonged storage via Check All That Apply (CATA) questions; and (2) to study the behavior of Listeria monocytogenes through a microbial challenge test. Sliced cured pork loins can be stored at 6 ± 1 °C for 105 days while maintaining a consumer acceptance of more than 75%. The freshness loss was associated mainly with a decrease in aromatic notes (particularly the smoke and cured aroma), and with the appearance of spoiled characteristics, specifically a sour/vinegar aroma and acidic taste that were detected by a reduced proportion of participants. The freshness evaluation was positively influenced by the typical characteristics of cured products, such as color and a garlic and wine aroma. Sour/vinegar aroma and acidic taste were the attributes most associated with higher freshness penalization. During the period of the test, Listeria monocytogenes inoculated onto the cured loin slices did not grow.

Comparison of the fate of the top six non-O157 shiga-toxin producing Escherichia coli (STEC) and E. coli O157:H7 during the manufacture of dry fermented sausages

The study examined the relative fate of the top six non-O157 shiga-toxin producing Escherichia coli (STEC) and E. coli O157:H7 during the manufacture of dry fermented sausages (DFS). Three separate batches of sausages containing a five-strain cocktail for each serogroup and uninoculated control were manufactured and subjected to identical fermentation, maturation and dry curing conditions. Changes in physicochemical properties and inoculated STEC numbers were enumerated during the DFS production stages and log reduction and log reduction rates were calculated. Inoculation of very high concentrations (8logCFUg^-1) of STEC in the sausage batter did not significantly (P>0.05) affect the changes in the pH, a_w, moisture, protein, fat content compared to the uninoculated DFS. There was a significant (P<0.05) reduction in counts within the 48h fermentation for all STEC serogroups inoculated by about 0.97- to 1.42-log units. However, during the sausage maturation stage, all serogroups except O121 and O45 showed a significant reduction in numbers. During the extended 34day drying stage, all STEC serogroups showed a significant reduction in counts reaching a 5-log reduction within 20 to 27days of drying. ANOVA of the log reduction rates revealed significant differences in the reduction rates among the STEC serogroups examined. During the fermentation stage, serogroup O45 had the highest reduction rate at 0.98-logCFUg^-1day^-1 which was significantly higher compared to all other STEC serogroups (P<0.05), while O26 was the most tolerant to the conditions encountered during the fermentation stage with a reduction rate of 0.49-logCFUg^-1day^-1. However, during the extended 34days drying stage all STEC serogroups showed a steady reduction in population with a reduction rate ranging from 0.11- to 0.18-logCFUg^-1day^-1. The log reduction rate of E. coli O157:H7 was similar to that of serogroups O111 and O103, but was significantly lower (P<0.05) than all other STEC serogroups examined in the study. The log reduction rates of serogroups O121, O45, O145 and O26 during drying were not significantly different (P>0.05) from each other. These results indicate that the lethality of DFS production processes observed against E. coli O157:H7 would result in a similar inactivation of the top six non-O157 STEC.

Health and Safety Considerations of Fermented Sausages

Fermented sausages are highly treasured traditional foods. A large number of distinct sausages with different properties are produced using widely different recipes and manufacturing processes. Over the last years, eating fermented sausages has been associated with potential health hazards due to their high contents of saturated fats, high NaCl content, presence of nitrite and its degradation products such as nitrosamines, and use of smoking which can lead to formation of toxic compounds such as polycyclic aromatic hydrocarbons. Here we review the recent literature regarding possible health effects of the ingredients used in fermented sausages. We also go through attempts to improve the sausages by lowering the content of saturated fats by replacing them with unsaturated fats, reducing the NaCl concentration by partly replacing it with KCl, and the use of selected starter cultures with desirable properties. In addition, we review the food pathogenic microorganisms relevant for fermented sausages(Escherichia coli,Salmonella enterica,Staphylococcus aureus,Listeria monocytogenes,Clostridium botulinum, andToxoplasma gondii)and processing and postprocessing strategies to inhibit their growth and reduce their presence in the products.