Artisanal Italian salami and soppresse: Identification of control strategies to manage microbiological hazards

Variability in Physicochemical Parameters and Its Impact on Microbiological Quality and Occurrence of Foodborne Pathogens in Artisanal Italian Organic Salami

Artisanal salami is produced in small-scale production plants, where the lack of full automation might result in higher variability in food intrinsic properties. The aim of the present study was to evaluate the inter- and intra-batch variability in physicochemical parameters and its impact on microbial quality and occurrence of foodborne pathogens on 480 samples collected from six batches of an artisanal Italian production of organic salami. Relatively high total bacterial counts (TBC) were found on the surface of the table in the stuffing room (4.29 ± 0.40 log cfu/cm2). High loads of Enterobacteriaceae in the meat mixture of batch 2 and TBC in batch 5 were associated with a higher occurrence of bacterial pathogens. During ripening, water activity (aw) and pH failed to reach values lower than 0.86 and 5.3, respectively. Six Staphylococcus aureus and four Listeria monocytogenes isolates were collected from the salami meat mixture during ripening and the processing environment. A total of 126 isolates of Enterobacteriaceae were characterized at a species level, with Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Citrobacter freundii isolated from the final products. Results suggest the relevance of first steps of production in terms of the hygiene of raw materials and handling during stuffing procedures, especially when the physicochemical parameters of the final products do not reach values that represent hurdles for foodborne pathogens.

Microbiological profiling and knowledge of food preservation technology to support guidance on a neutropenic diet for immunocompromised patients

The current society consists of an increasing number of people vulnerable to infections. For certain people with severe immunodeficiency, a neutropenic or low-microbial diet is being prescribed, which substitutes high-risk foods that are more likely to contain human (opportunistic) pathogens with lower-risk alternatives. These neutropenic dietary guidelines are typically set up from a clinical and nutritional perspective, rather than from a food processing and food preservation perspective. In this study, the current guidelines in use by the Ghent University Hospital were evaluated based on the current knowledge of food processing and preservation technologies and the scientific evidence on microbiological quality, safety, and hygiene of processed foods. Three criteria are identified to be important: (1) the microbial contamination level and composition; (2) the potential presence of established foodborne pathogens such as Salmonella spp. (to which a zero-tolerance policy is recommended); and (3) an increased vigilance for L. monocytogenes as an opportunistic foodborne pathogen with a high mortality rate in immunocompromised individuals (to which a zero-tolerance policy should apply). A combination of these three criteria was used as a framework for the evaluation of the suitability of foodstuffs to be included in a low-microbial diet. Differences in processing technologies, initial contamination of products, etc., however, lead to a high degree of variability in microbial contamination and make it difficult to unambiguously accept or reject a certain type of foodstuff without prior knowledge of the ingredients and the processing and preservation technologies applied during manufacturing and subsequent storage conditions. A restricted screening on a selection of (minimally processed) plant-based foodstuffs on the retail market in Flanders, Belgium supported decision-making on the inclusion of these food types in a low-microbial diet. Still, when determining the suitability of a foodstuff to be included in a low-microbial diet, not only the microbiological status but also nutritional and sensorial properties should be assessed, which requires multidisciplinary communication and collaboration.

Investigation on the microbiological hazards in an artisanal salami produced in Northern Italy and its production environment in different seasonal periods

In the present study, the occurrence of Listeria monocytogenes, Staphylococcus aureus, Salmonella spp. and Escherichia coli VTEC was investigated in two batches of artisanal Italian salami tested in winter and summer. Moreover, enumerations of total bacterial count, lactic acid bacteria and Enterobacteriaceae were performed as well as monitoring of water activity and pH. Samples were taken from raw materials, production process environment, semi-finished product and finished products. The results revealed an overall increase of total bacterial count and lactic acid bacteria during the ripening period, along with a decrease of Enterobacteriaceae, pH and water activity. No significant difference was observed between the two batches. The enterobacterial load appeared to decrease during the maturation period mainly due to a decrease in pH and water activity below the limits that allow the growth of these bacteria. E. coli VTEC, Salmonella spp. or L. monocytogenes were not detected in both winter and summer batches. However, Klebsiella pneumoniae was detected in both summer and winter product. Except for one isolate, no biological hazards were detected in the finished salami, proving the efficacy of the ripening period in controlling the occurrence of microbiological hazard in ripened salami. Further studies are required to assess the virulence potential of the Klebsiella pneumoniae isolates.

Characterization of Lactic Acid Bacteria Isolated from Spontaneously Fermented Sausages: Bioprotective, Technological and Functional Properties

Fermentation is one of the most ancient strategies to improve safety and extend shelf-life of the products. Starter cultures are mainly represented by lactic acid bacteria (LAB), which may also be bioprotective agents controlling the fermentation process, the native microbiota and pathogen outgrowth. This work aimed to select new LAB strains from spontaneously fermented sausages produced in different areas of Italy, which can be effective as starter cultures and bioprotective agents in fermented salami. The strains, mainly belonging to the Latilactobacillus sakei species, were characterized for their ability to inhibit major meat pathogens, the presence of antibiotic resistances and amine production. Moreover, technological performances, such as growth and acidification kinetics at increasing NaCl concentrations, were studied. As a result, new autochthonous Lat. sakei strains were obtained, lacking antibiotic resistance, possessing antimicrobial activity against Clostridium sporogenes, Listeria monocytogenes, Salmonella and Escherichia coli and with high growth performance under osmotic pressure. These strains have the potential for future application to improve the safety of fermented meats, even under conditions in which chemical preservatives are reduced or eliminated. Moreover, studies on autochthonous cultures are pivotal for guaranteeing specific characteristics of traditional products that represent an important cultural heritage.

Control of Listeria monocytogenes in chicken dry-fermented sausages with bioprotective starter culture and high-pressure processing

Listeria monocytogenes is one of the most relevant pathogens for ready-to-eat food, being a challenge for the food industry to comply with microbiological criteria. The aim of the work was to assess the behavior of L. monocytogenes in two types of chicken-based dry-fermented sausages during the fermentation and ripening, with or without a bioprotective starter culture (Latilactobacillus sakei CTC494). To complement the challenge testing approach, simulations with different predictive models were performed to better understand the role of contributing factors. The impact of post-processing strategies, such as high-pressure processing and/or corrective storage was assessed. The chicken meat was inoculated with a cocktail of three L. monocytogenes strains, mixed with other ingredients/additives and stuffed into small (snack-type) or medium (fuet-type) casings. Snack-type was fermented (22°C/3 days) and ripened (14°C/7 days), while fuet-type was ripened (13°C/16 days). At the end of ripening, HPP (600 MPa/5 min) and/or corrective storage (4 or 15°C/7 days) were applied. The suitability of HPP after fermentation was evaluated in the snack-type sausages. Pathogen growth (>3 Log₁₀) was observed only during the fermentation of the snack type without a starter. The bioprotective starter prevented the growth of L. monocytogenes in the snack-type sausages and enhanced the inactivation (1.55 Log₁₀) in fuet-type sausages, which could be related to the higher lactic acid production and consequent decrease of pH, but also the production of the antilisterial bacteriocin sakacin k. The gamma concept model allowed us to identify the main factors controlling the L. monocytogenes’ growth, i.e., the temperature during the early stages and a_w at the end of the production process. The earlier acidification linked with the addition of starter culture made the interaction with the other factors (undissociated lactic acid, a_w and temperature) to be the growth-preventing determinants. High-pressure processing only caused a significant reduction of L. monocytogenes in snack-type, which showed higher a_w. The application of HPP after fermentation did not offer a relevant advantage in terms of efficacy. Corrective storage did not promote further pathogen inactivation. The findings of the work will guide the food industry to apply effective strategies (e.g., fermentation temperature and bioprotective starter cultures) to control L. monocytogenes in chicken dry-fermented sausages.

Mediterranean Spontaneously Fermented Sausages: Spotlight on Microbiological and Quality Features to Exploit Their Bacterial Biodiversity

The wide array of spontaneously fermented sausages of the Mediterranean area can represent a reservoir of microbial biodiversity and can be an important source of new technological and functional strains able to preserve product properties, counteracting the impoverishment of their organoleptic typical features due to the introduction of commercial starter cultures. We analysed 15 artisanal salamis from Italy, Spain, Croatia and Slovenia to evaluate the microbiota composition, through culture-dependent and culture-independent techniques (i.e., metagenomic analysis), chemical-physical features, biogenic amines and aroma profile. The final pH varied according to origin and procedures (e.g., higher pH in Italian samples due to long ripening and mold growth). Lactic acid bacteria (LAB) and coagulase-negative cocci (CNC) were the dominant population, with highest LAB counts in Croatian and Italian samples. Metagenomic analysis showed high variability in qualitative and quantitative microbial composition: among LAB, Latilactobacillus sakei was the dominant species, but Companilactobacillus spp. was present in high amounts (45-55% of the total ASVs) in some Spanish sausages. Among staphylococci, S. epidermidis, S. equorum, S. saprophyticus, S. succinus and S. xylosus were detected. As far as biogenic amines, tyramine was always present, while histamine was found only in two Spanish samples. These results can valorize the bacterial genetic heritage present in Mediterranean products, to find new candidates of autochthonous starter cultures or bioprotective agents.

Behaviour of Listeria monocytogenes and Natural Microflora during the Manufacture of Riojano Chorizo (Spanish Dry Cured Sausage)

Riojano chorizo is a dry cured sausage manufactured with traditional technologies without adding starter cultures at low temperatures. Its characteristics differ from other types of chorizo since sugars and nitrites are no added and processing temperatures are low- This work evaluates the behaviour of Listeria monocytogenes during the processing of inoculated Riojano chorizo as well as the natural microflora that can play a technological role or be of interest as indicators. The sausage mixture was inoculated with a cocktail of three selected strains of L. monocytogenes (CECT 932, CECT 934 and CECT 4032) (4 log10 CFU/g) and after processed following the traditional production method. Samples were taken before inoculation, after inoculation, after stuffing (day 0) and on days 6, 13, 21 and 28 of processing. L. monocytogenes, mesophiles, Micrococcaceae, lactic acid bacteria, Enterobacteriaceae, S. aureus, sulfite-reducing clostridia and molds and yeast counts were evaluated. Furthermore, pH, water activity and humidity were determined. No growth of L mocytogenes was observed during the first 6 days, when the temperature of processing was 4 °C. The low temperature in the initial stages was a relevant hurdle to control L. monocytoegenes growth. A significant decrease (p ≤ 0.05) in L. monocytogenes counts was observed on day 13 compared to the initial counts. During drying (days 6 to 21) a reduction in this pathogen of 1.28 log CFU/g was observed. The low water activity below 0.92 on day 13 and 0.86 on day 21 seems to be critical for the reduction of L. monocytogenes.

Behavior of Listeria monocytogenes and Other Microorganisms in Sliced Riojano Chorizo (Spanish Dry-Cured Sausage) during Storage under Modified Atmospheres

Sliced ready-to-eat meat products packaged under modified atmospheres are often marketed since they cover consumer demands. The slicing process could be a potential risk for consumers since contamination with Listeria monocytogenes could occur during this stage. The current study evaluated the behavior of L. monocytogenes and other microorganisms in commercial sliced Riojano chorizo. This meat product was sliced and inoculated with L. monocytogenes (3.5 log CFU/g) before packaging under different atmospheres (air, vacuum, 100% N2, 20% CO2/80% N2 and 40% CO2/60% N2) and stored at 4 °C for up to 60 days. Samples were taken on days 0, 7, 21, 28 and 60 of storage. L. monocytogenes, mesophiles, Enterobacteriaceae, lactic acid bacteria, Micrococcaceae, molds and yeast counts were evaluated. Additionally, water activity, humidity and pH were determined. L. monocytogenes counts decreased in inoculated sliced chorizo during storage. Packaging conditions and day of storage influenced microbial counts. After 60 days, a significant reduction (p ≤ 0.05) in the initial Listeria contamination levels (3.5. log CFU/g) between 1.1 and 1.46 logarithmic units was achieved in the sausages packaged in modified atmosphere. The highest reductions were observed in slices packaged in 40% CO2/60% N2 after 60 days of storage at 4 °C.

Modeling the behavior of Listeria innocua in Italian salami during the production and high-pressure validation of processes for exportation to the U.S

A model describing Listeria innocua evolution according to process parameters of 51 Italian salami processes and HPP in 31 companies was developed. A total of 51 challenge tests were performed. During processing a L. innocua reduction of 0.34-4.32 Log10 CFU/g was observed and HPP further reduced the count of 0.48-3.47 Log10 CFU/g; an overall reduction of 1.04-5.68 is reached. PH after acidification/drying process, a_w after seasoning, duration of the seasoning and caliber resulted associated (p < 0.05) with L. innocua decrease. HPP efficacy was associated (p < 0.05) with a_w and pH of the product: higher the pH and a_w after the acidification/drying and seasoning phases, higher resulted the L. innocua reduction after HPP. No significant association was observed between L.innocua and salt, nitrate and starter content and other characteristics of process. The model meets companies and Authorities needs and represents a useful tool to predict L. monocytogenes lethality, giving recommendations to food business operators interested in exportation to the U.S.

Effects of honeybush (Cyclopia subternata) extract on physico-chemical, oxidative and sensory traits of typical Italian salami

Honeybush (Cyclopia subternata Vogel) is an indigenous South African shrub enjoyed as hot brewed tea. "Unfermented" honeybush is also a potential antioxidant bioactive extract for foodstuffs due to its polyphenol content. The effect of "unfermented" honeybush extract (Hob; 0.5%) was evaluated in typical Italian salami and compared with nitrate (Nit; 100 mg/kg) and a control (Ctl; without nitrate or honeybush). After 35 days of ripening, Hob had a higher (p < .01) water activity (0.928), compared with Ctl (0.923) and Nit (0.924). Final pH (5.35-5.24) was not affected by treatments. Lower lipid oxidation was observed in Hob and Nit treatments (p < .001) compared with Ctl. Internal color and odor intensity were similar among treatments. Salami with honeybush extract had less spontaneous outer surface mold growth whereas the Ctl showed intermediate growth (p < .05). Honeybush extract seems a promising natural ingredient with antioxidant action.

Predictive Modeling of Microbial Behavior in Food

Microorganisms can contaminate food, thus causing food spoilage and health risks when the food is consumed. Foods are not sterile; they have a natural flora and a transient flora reflecting their environment. To ensure food is safe, we must destroy these microorganisms or prevent their growth. Recurring hazards due to lapses in the handling, processing, and distribution of foods cannot be solved by obsolete methods and inadequate proposals. They require positive approach and resolution through the pooling of accumulated knowledge. As the industrial domain evolves rapidly and we are faced with pressures to continually improve both products and processes, a considerable competitive advantage can be gained by the introduction of predictive modeling in the food industry. Research and development capital concerns of the industry have been preserved by investigating the plethora of factors able to react on the final product. The presence of microorganisms in foods is critical for the quality of the food. However, microbial behavior is closely related to the properties of food itself such as water activity, pH, storage conditions, temperature, and relative humidity. The effect of these factors together contributing to permitting growth of microorganisms in foods can be predicted by mathematical modeling issued from quantitative studies on microbial populations. The use of predictive models permits us to evaluate shifts in microbial numbers in foods from harvesting to production, thus having a permanent and objective evaluation of the involving parameters. In this vein, predictive microbiology is the study of the microbial behavior in relation to certain environmental conditions, which assure food quality and safety. Microbial responses are evaluated through developed mathematical models, which must be validated for the specific case. As a result, predictive microbiology modeling is a useful tool to be applied for quantitative risk assessment. Herein, we review the predictive models that have been adapted for improvement of the food industry chain through a built virtual prototype of the final product or a process reflecting real-world conditions. It is then expected that predictive models are, nowadays, a useful and valuable tool in research as well as in industrial food conservation processes.

Effect of Starter Culture and Low Concentrations of Sodium Nitrite on Fatty Acids, Color, and Escherichia coli Behavior during Salami Processing

The reduction of NaNO₂ and safety in meat products have been a concern to the meat industry for the last years. This research evaluated the changes in total fatty acids (TFAs) and myoglobin forms by adding starter culture (Lactobacillus sakei/Staphylococcus carnosus) and 50 ppm of NaNO₂ during salami processing. In the postripening stage, the starter culture influenced the concentration of the palmitic, oleic, vaccenic, and γ-linolenic TFAs, whereas the metmyoglobin concentration was lower (which could be related to the antioxidant effect of the starter culture). In this stage, an increase in enthalpy, specific heat, and onset temperature was found when adding starter culture and NaNO₂, which is directly related to polyunsaturated TFA. However, when adding just the starter culture without 50 ppm NaNO₂, the E. coli population was reduced in 4 log CFU/g. This study proposes the analysis of changes in meat product processing like salami in a holistic form, where the application of starter culture with low nitrite concentrations could be in the meat industry an upward trend for reducing this additive.

Listeria monocytogenes in Foods

Listeria monocytogenes causes listeriosis, a rare foodborne disease with a mortality rate of 20%-30%. The elderly and immunocompromised are particularly susceptible to listeriosis. L. monocytogenes is ubiquitous in nature and can contaminate food-processing environments, posing a threat to the food chain. This is particularly important for ready-to-eat foods as there is no heat treatment or other antimicrobial step between production and consumption. Thus, occurrence and control of L. monocytogenes are important for industry and public health. Advances in whole-genome sequence technology are facilitating the investigation of disease outbreaks, linking sporadic cases to outbreaks, and linking outbreaks internationally. Novel control methods, such as bacteriophage and bacteriocins, can contribute to a reduction in the occurrence of L. monocytogenes in the food-processing environment, thereby reducing the risk of food contamination and contributing to a reduction in public health issues.

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.