Cristian Bernardi

Vacuum-packaged pasta products may undergo package swelling during refrigerated storage, although the microbial mechanisms responsible for this spoilage remain poorly understood. This study investigated the cause of blown pack spoilage in vacuum-packaged spinach lasagna stored at 4 °C. Three production batches were examined by microbiological, physicochemical, phenotypic, and molecular analyses. A total of 200 bacterial isolates were characterized using conventional tests and automated ribotyping. Nitrate and nitrite concentrations, gas composition, and spoilage-associated physicochemical parameters were also determined.,Only Bacillus circulans (currently classified within the genus Niallia circulans according to recent genome-based taxonomy) strains were recovered from all samples, revealing marked intraspecies heterogeneity. Ten phenotypic subgroups were identified, but package swelling occurred exclusively in one production batch contaminated with strains belonging to two specific phenotypic subgroups (H and K), able to These strains were able to grow at refrigeration temperature, to reduce nitrate to nitrite, and to produce CO₂ under anaerobic conditions. During storage, nitrate concentrations decreased while nitrite accumulated only in swollen packages, supporting the involvement of nitrate reduction in gas formation. These findings demonstrate that blown pack spoilage of vacuum-packaged spinach lasagna is associated with specific nitrate-reducing B. circulans strains rather than with the species as a whole.

This study investigated the growth of Bacillus cereus and the production of cereulide toxin in powdered infant formula (PIF) reconstituted according to two different protocols. B. cereus NCTC 11143 spores were inoculated in infant formula samples (approximately 1.5-2 log CFU/ml of final product), that were alternatively reconstituted following the WHO (using water pre-heated to 70°C) or the FDA method (using room-temperature water). Following reconstitution, samples were stored under ideal refrigeration (4°C), thermal abuse (10°C) and strong thermal abuse (20°C) until 72 hours to simulate different storage conditions of leftover formula. B. cereus total count, spore count and cereulide quantification were performed at settled times. Results demonstrated that B. cereus did not grow at 4 and 10°C. At 20°C, spores rapidly germinated and B. cereus grew to very high counts (over 8 Log CFU/ml) in both sample series. Formula prepared according to WHO protocol exhibited earlier growth, exceeding 7 Log CFU/g within 24 hours, whereas such level was reached in 36 h with the FDA protocol. In parallel, cereulide toxin was only detectable after 48 hours of storage at 20°C, when bacterial count exceeded 8 log CFU/g, with lower concentration in the FDA series. These findings suggest the particular nature of the risk posed by B. cereus in PIF if compared to other pathogens, and underscore the critical importance of adhering to proper hygiene, immediate feeding practices, and avoiding the storage of reconstituted formula at abuse temperatures to protect vulnerable infant populations from severe foodborne risks.

Shrimp are among the most valuable seafood commodities worldwide, but are also highly perishable, making their quality preservation a critical issue for both food safety and supply chain sustainability. The rapid deterioration of fresh shrimp contributes to significant post-harvest losses, highlighting the need for reliable freshness indicators capable of supporting shelf-life assessment under commercial conditions. This study evaluated the evolution of microbiological, physicochemical, and sensory parameters in two commercially important Mediterranean shrimp species, Parapenaeus longirostris and Melicertus kerathurus, stored on ice for up to 15 days under retail-like conditions. Microbial load, pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), formaldehyde, formic acid, and sensory attributes were monitored during storage. Microbial populations increased progressively over time but remained below commonly accepted spoilage thresholds, while physicochemical indicators showed significant changes associated with post-mortem biochemical processes. In particular, TVB-N, pH, and formic acid increased during storage, whereas formaldehyde levels decreased, suggesting the progressive transformation of trimethylamine-N-oxide degradation products. Sensory analysis indicated that shrimp maintained high quality up to approximately 12 days of iced storage, whereas samples stored for 15 days approached the limit of consumer acceptability. The combined behaviour of microbial, chemical, and sensory indicators highlights the importance of a multidimensional approach for evaluating shrimp freshness under commercial storage conditions. Based on the experimental dataset, practical reference ranges for key quality parameters are proposed (pH < 7.4; TVB-N ≤ 30 mg N/100 g; formaldehyde < 10 mg/kg; formic acid < 18 mg/kg). These results may support improved freshness evaluation, contribute to more accurate shelf-life estimation, and help reduce unnecessary seafood waste within the supply chain.

This study aimed to evaluate the microbiological quality and safety of powdered formulae intended for infant consumption on the Italian market. A total of 83 samples, including 23 infant formulae (PIF), 42 follow-on formulae (FOF), and 18 formulae for special medical purposes (SMPs), were taken between 2023 and 2024. Low total viable counts were highlighted with all SMP samples, 87.0% of PIF samples and 97.6% of FOF samples being compliant with the threshold set by the Code of Hygienic Practice for Powdered Formulae for Infants and Young Children (2.70 Log CFU/g). High contamination levels (>4 Log CFU/g) were found exclusively in PIF (8.7%) and FOF samples (2.4%). Considering potential pathogenic bacteria, the presence of Listeria monocytogenes, Yersinia enterocolitica, Salmonella spp., Bacillus cereus, and Cronobacter sakazakii was investigated. Enumeration of Bacillus cereus, Staphylococcus aureus, and Clostridia was also performed. Only presumptive B. cereus was detected (37 samples, and in 3 samples was enumerated with counts equal to 1 Log CFU/g). A total of 42 presumptive B. cereus isolates were tested for the production of hemolysin BL, phosphatidylcholine-specific phospholipase C, proteases, and for the presence of chromosomal toxin-encoding genes, showing a relevant prevalence of virulence factors and highlighting a potential concern for infants. The antimicrobial resistance pattern of the isolates showed high resistance rates to β-lactams and a moderate resistance to erythromycin. A chemical–physical characterization of the formulae was also performed showing high heterogeneity in terms of pH, Aw, and concentration of organic acids. The results obtained provide useful information for monitoring the potential exposition of infants to microbial populations and to evaluate the safety of the products available on the market.

This study evaluated the diffusion of Listeria monocytogenes (LM) in a beef steak tartare production chain, aiming to (1) evaluate Listeria spp. diffusion in finishing farms supplying beef cattle, (2) evaluate LM prevalence in carcasses, and (3) map LM diffusion in the production plant. A detection rate of 6/76 was observed in the farm, while carcasses after skinning and before refrigeration tested positive in 19/30 and 11/30, respectively. During tartare production, 57/154 meat and 35/191 environmental samples tested positive. A total of 114 LM isolates were characterized via a whole-genome sequencing approach. Five clonal complexes (CCs) and seven sequence types (STs) were identified, with CC9-ST580 being the most prevalent. Four clusters were identified from both the slaughtering and production phases. Genes related to resistance to fosfomycin, quinolones, sulfonamides, lincosamide, and tetracycline were detected. Two hypervirulent strains (CC6-ST6 and CC2-ST145), harboring a full-length inlA, several virulence genes, and stress islands, were detected. Stress Survival Islet 1 was found in almost all the isolates. The wide diffusion of LM in steak tartare requires the management of some critical phases of the production chain (mainly slaughtering); genomic methodologies could be useful in describing the circulation and virulence of LM strains.

Döner kebab, a meat product of Middle-Eastern origin, has gained significant popularity and is now widely consumed across Europe. The recipe varies depending on the area, with beef, turkey, lamb, or chicken being used as main ingredients. The aim of this work was to assess the hygienic-sanitary quality of raw and cooked döner kebabs stored at 4 ± 2 °C for 10 days and at 8 ± 2 °C for the next 20 days or frozen (−18 °C) for one month. One additional aim was to determine the potential growth of Listeria monocytogenes intentionally inoculated in cooked döner kebab during storage at 4 ± 2 °C or freezing. The concentration of Total Viable Count (TVC) and the Enterobacteriaceae of the 100 samples of raw döner kebab were less than 7 log CFU/g and 4 log CFU/g, respectively. Consequently, the samples can be considered acceptable and similar to traditional raw meat. The cooked döner kebab can be considered safe for a period of 30 days, especially from a microbiological point of view, when stored under refrigerated conditions, also taking into account possible thermal abuse. Coagulase Positive Cocci (CPC), Clostridium H₂S⁺, Salmonella spp., and Listeria monocytogenes were never found in any of the samples. After 30 days, the TVC was at the level of 6 log CFU/g and Enterobacteriaceae at less than 4 log CFU/g. The main concern was related to microbial or tissue activity, resulting in an increase in total volatile basic nitrogen (TVB-N) content. However, in the cooked samples, the TVB-N content remained below 40 mg N/100 g at the end of the shelf-life period (32.5 mg N/100 g), which is still considered an acceptable value. In addition, the level of Malondialdehyde (MDA) was found to be within acceptable limits, with a reading of 1.4 nmol/g attained after 30 days. The same product, when frozen and stored at −18 °C, can be considered stable for a minimum of 6 months, both from a microbiological and a physico-chemical point of view. No microbial growth was observed. The TVB-N and the MDA levels increased, but after 6 months, their levels were still acceptable, with values of 19.1 mg N/100 g and 1.2 nmol/g, respectively. These observations demonstrate low protein degradation and lipid oxidation during the shelf-life period. The challenge test showed that Listeria monocytogenes did not grow in döner kebab either when stored at 4 ± 2 °C for 10 days and 8 ± 2 °C for 20 days or when stored at −18 °C for 6 months. The concentration of L. monocytogenes was found to be 5.4 log CFU/g in the refrigerated products and 4.9 log CFU/g in the frozen products. At the end of the shelf-life period, the L. monocytogenes load in both products was lower than the initial concentration that had been added. Finally, the use of air-packaging has been proven to be beneficial to the preservation of the product and maintained its microbiological and physico-chemical properties intact. Despite these good results, future directions could be to investigate different plastic films and packaging such as Modified Atmosphere (MAP), Vacuum (VP), and Sous Vide packaging (SVP).

This study tested 32 carcasses of control-culled wild boars in a subalpine area of Northern Italy between May and November 2021, delivered to three approved game meat establishments. Carcasses and organs were submitted to the detection of Salmonella spp., Campylobacter spp., Listeria spp., and Listeria monocytogenes; carcass surfaces were also sampled for microbial counts [total viable count (TVC), Enterobacteriaceae, Escherichia coli, coagulase-positive Staphylococci]. Campylobacter spp. was detected with high prevalence (90.9%) in the caecum as well as Listeria spp. and L. monocytogenes (37.5% and 25%, respectively), whereas only one animal harbored Salmonella spp. (3.8%). A low contamination rate was detected on the carcasses for Campylobacter spp. and Listeria spp. High TVC, Enterobacteriaceae, and E. coli counts were detected on the carcasses (5.90, 4.83 and 2.54 Log CFU/cm2, respectively). Animal sex and weight exerted a weak effect on bacterial counts; the same was observed for the culling/sampling interval. Moderately higher counts were detected in animals culled with high (>15°C) environmental temperatures. Animals shot in the abdomen showed higher counts for all the parameters except for Staphylococci, and an increasing count of enteric bacteria was observed when considering head/neck, shoulder, chest, and abdomen locations. A significant difference among the plants was observed, independently from the other factors, thus stressing the importance of the application of hygiene procedures in approved game meat establishments to limit carcass contamination.

Cooked sausages packaged in a modified atmosphere (MAP: 20% CO_2, 70% N₂, 2) with evident yellow stains were analyzed. The aims of this work were to study the microbial cause of the spoilage and to evaluate different antimicrobial compounds to prevent it. Leuconostoc gelidum was identified as the primary cause of the yellow coating in spoiled cooked sausage, as confirmed by its intentional inoculation on slices of unspoiled sausage. Leuconostoc gelidum was the main bacteria responsible for the yellow coating in spoiled cooked sausage, as confirmed by its intentional inoculation on slices of unspoiled sausage. The yellow color was also evident during growth in the model system containing cooked sausage extract, but the colonies on MRS agar appeared white, demonstrating that the food substrate stimulated the production of the yellow pigment. The spoilage was also characterized by different volatile compounds, including ketones, ethanol, acetic acid, and ethyl acetate, found in the spoiled cooked sausage packages. These compounds explained the activity of Leuc. gelidum because they are typical of heterofermentative LAB, cultivated either on food substrates or in artificial broths. Leuc. gelidum also produced slight swelling in the spoiled packages. The efficacy of different antimicrobials was assessed in model systems composed of cooked sausage extract with the antimicrobials added at food product concentrations. The data showed that sodium lactate, sodium acetate, and a combination of sodium lactate and sodium diacetate could only slow the growth of the spoiler—they could not stop it from occurring. Conversely, hop extract inhibited Leuc. gelidum, showing a minimal inhibitory concentration (MIC) of approximately 0.008 mg CAE/mL in synthetic broth and 4 mg CAE/kg in cooked sausage slices. Adding hop extract at the MIC did not allow Leuc. gelidum growth and did not change the sensorial characteristics of the cooked sausages. To our knowledge, this is the first report of the antimicrobial activities of hop extracts against Leuc. gelidum either in vitro or in vivo.

Recently, during the ripening of goose sausage, a defect consisting of ammonia and vinegar smell was noticed. The producer of the craft facility, located in Lombardia, a Northern region of Italy, asked us to identify the cause of that defect. Therefore, this study aimed to identify the potential responsible agents for the spoilage of this lot of goose sausages. Spoilage was first detected by sensory analysis using the “needle probing” technique; however, the spoiled sausages were not marketable due to the high ammonia and vinegar smell. The added starter culture did not limit or inhibit the spoilage microorganisms, which were represented by Levilactobacillus brevis, the predominant species, and by Enterococcus faecalis and E. faecium. These microorganisms grew during ripening and produced a large amount of biogenic amines, which could represent a risk for consumers. Furthermore, Lev. brevis, being a heterofermentative lactic acid bacteria (LAB), also produced ethanol, acetic acid, and a variation in the sausage colour. The production of biogenic amines was confirmed in vitro. Furthermore, as observed in a previous study, the second cause of spoilage can be attributed to moulds which grew during ripening; both the isolated strains, Penicillium nalgiovense, added as a starter culture, and P. lanosocoeruleum, present as an environmental contaminant, grew between the meat and casing, producing a large amount of total volatile nitrogen, responsible for the ammonia smell perceived in the ripening area and in the sausages. This is the first description of Levilactobacillus brevis predominance in spoiled goose sausage.

The aim of this study was to investigate the microbial and physico-chemical characteristics of cold smoked sea bass (CSSB), a novel italian fish product. The microbiological analyses showed the presence of bacterial contamination from the raw material, the environment, and the production process. The microbial spoilage population was dominated by lactic acid bacteria (LAB) associated with Gram-negative fermenting bacteria, including Photobacterium phosphoreum and psychrotrophic Enterobacteriaceae. Brochotrix thermospacta and Aeromonas spp. were also present; in contrast, mould and yeast were not detected (Salmonella spp. and Listeria monocytogenes were not detected. Currently, there is a growing demand for seafood due to its high quality and nutritional value. Cold smoked sea bass offers a source of macro- and micronutrients essential for the proper functioning of the human body. It is also rich in protein and omega-3 fatty acids. The WHO and FAO evaluated the benefits and risks and concluded that there is convincing evidence of health benefits from fish consumption, such as a reduction in the risk of heart failure and improved neurodevelopment in infants and young children when fish is consumed by the mother before and during pregnancy. The CSSB analysed in this study demonstrated to have health benefits due to long-chain omega-3 PUFAs and other nutrients, such as proteins, minerals, and vitamin D, which are sometimes difficult to obtain from other sources. The results show that CSSB has a high nutritional value and excellent microbial quality.