Validation of a traditional Italian-style salami manufacturing process for control of Salmonella and Listeria monocytogenes

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.

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.

The COM-Poisson Process for Stochastic Modeling of Osmotic Inactivation Dynamics of Listeria monocytogenes

Controlling harmful microorganisms, such as Listeria monocytogenes, can require reliable inactivation steps, including those providing conditions (e.g., using high salt content) in which the pathogen could be progressively inactivated. Exposure to osmotic stress could result, however, in variation in the number of survivors, which needs to be carefully considered through appropriate dispersion measures for its impact on intervention practices. Variation in the experimental observations is due to uncertainty and biological variability in the microbial response. The Poisson distribution is suitable for modeling the variation of equi-dispersed count data when the naturally occurring randomness in bacterial numbers it is assumed. However, violation of equi-dispersion is quite often evident, leading to over-dispersion, i.e., non-randomness. This article proposes a statistical modeling approach for describing variation in osmotic inactivation of L. monocytogenes Scott A at different initial cell levels. The change of survivors over inactivation time was described as an exponential function in both the Poisson and in the Conway-Maxwell Poisson (COM-Poisson) processes, with the latter dealing with over-dispersion through a dispersion parameter. This parameter was modeled to describe the occurrence of non-randomness in the population distribution, even the one emerging with the osmotic treatment. The results revealed that the contribution of randomness to the total variance was dominant only on the lower-count survivors, while at higher counts the non-randomness contribution to the variance was shown to increase the total variance above the Poisson distribution. When the inactivation model was compared with random numbers generated in computer simulation, a good concordance between the experimental and the modeled data was obtained in the COM-Poisson process.

Effect of the Dry-Cured Fermented Sausage "Salchichón" Processing with a Selected Lactobacillus sakei in Listeria monocytogenes and Microbial Population

In the present work, the effect of processing of dry-cured fermented sausage “salchichón” spiked with the selected Lactobacillus sakei 205 was challenge-tested with low and high levels of L. monocytogenes. The evolution of the natural microbial population throughout the “salchichón” ripening was also evaluated. For this, a total of 150 “salchichón” were elaborated and divided into six equal cases which were inoculated with different levels of L. monocytogenes, and L. sakei 205. Afterwards, sausages were ripened for 90 days according to a typical industrial process. Moisture content (%) and water activity (a_w) decreased throughout the ripening up to values around 26% and 0.78, respectively. No differences for moisture content, a_w, pH, NaCl and nitrite concentration were observed between the analyzed cases. Lactic acid bacteria counts in the L. sakei 205 inoculated cases were always higher than 6 log CFU g⁻¹ during ripening. Enterobacteriaceae counts were reduced during ripening until non-detectable levels at the end of processing. Reductions in L. monocytogenes counts ranged from 1.6 to 2.2 log CFU g⁻¹; therefore, the processing of “salchichón” itself did not allow the growth of this pathogen. Reduction in L. monocytogenes was significantly higher in the cases inoculated with L. sakei 205.

Use of Starter Cultures in Foods from Animal Origin to Improve Their Safety

Starter cultures can be defined as preparations with a large number of cells that include a single type or a mixture of two or more microorganisms that are added to foods in order to take advantage of the compounds or products derived from their metabolism or enzymatic activity. In foods from animal origin, starter cultures are widely used in the dairy industry for cheese, yogurt and other fermented dairy products, in the meat industry, mainly for sausage manufacture, and in the fishery industry for fermented fish products. Usually, microorganisms selected as starter culture are isolated from the native microbiota of traditional products since they are well adapted to the environmental conditions of food processing and are responsible to confer specific appearance, texture, aroma and flavour characteristics. The main function of starter cultures used in food from animal origin, mainly represented by lactic acid bacteria, consists in the rapid production of lactic acid, which causes a reduction in pH, inhibiting the growth of pathogenic and spoilage microorganisms, increasing the shelf-life of fermented foods. Also, production of other metabolites (e.g., lactic acid, acetic acid, propionic acid, benzoic acid, hydrogen peroxide or bacteriocins) improves the safety of foods. Since starter cultures have become the predominant microbiota, it allows food processors to control the fermentation processes, excluding the undesirable flora and decreasing hygienic and manufacturing risks due to deficiencies of microbial origin. Also, stater cultures play an important role in the chemical safety of fermented foods by reduction of biogenic amine and polycyclic aromatic hydrocarbons contents. The present review discusses how starter cultures contribute to improve the microbiological and chemical safety in products of animal origin, namely meat, dairy and fishery products.

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.

Effect of production process and high-pressure processing on viability of Listeria innocua in traditional Italian dry-cured coppa

In this study the effect of the application of High Pressure Treatment (HPP) combined with four different manufacturing processes on the inactivation of Listeria innocua, used as a surrogate for L. monocytogenes, in artificially contaminated coppa samples was evaluated in order to verify the most suitable strategy to meet the Listeria inactivation requirements needed for the exportation of dry-cured meat in the U.S. Fresh anatomical cuts intended for coppa production were supplied by four different delicatessen factories located in Northern Italy. Raw meat underwent experimental contamination with Listeria innocua using a mixture of 5 strains. Surface contamination of the fresh anatomical cuts was carried out by immersion into inoculum containing Listeria spp. The conditions of the HPP treatment were: pressure 593 MPa, time 290 seconds, water treatment temperature 14°C. Listeria innocua was enumerated on surface and deep samples post contamination, resting, ripening and HPP treatment. The results of this study show how the reduction of the microbial load on coppa during the production process did not vary among three companies (P>0.05) ranging from 3.73 to 4.30 log CFU/g, while it was significantly different (P<0.01) for the fourth company (0.92 log CFU/g). HPP treatment resulted in a significant (P<0.01) deep decrease of L.innocua count with values ranging between 1.63-3.54 log CFU/g with no significant differences between companies. Regarding superficial contamination, HPP treatment resulted significant (P<0.01) only in Coppa produced by two companies. The results highlight that there were processes less effective to inhibit the pathogen; in particular for company D an increase of L. innocua count was shown during processing and HPP alone cannot be able to in reaching the Listeria inactivation requirements needed for exportation of dry-cured meat in the U.S. According to the data reported in this paper, HPP treatment increases the ability of the manufacturing process of coppa in reducing Listeria count with the objective of a lethality treatment.

Isolation of Salmonella Typhimurium, Listeria monocytogenes and coagulase-positive Staphylococcus from salami sold at street fairs in Porto Alegre, Brazil

ABSTRACT: Salami is a ready-to-eat (RTE) product frequently purchased at street fairs in Porto Alegre. Salmonella enterica, Listeria monocytogenes, and coagulase-positive Staphylococcus (CPS) are important causes of foodborne disease and can be transmitted through the consumption of RTE foods. The aim of this study was to evaluate the presence of these pathogens in salami sold at street fairs. Ninety salami samples from three commercial brands available at street fairs were analyzed by routine bacteriological methods for Salmonella spp. and Listeria spp., as well as enumeration of CPS. In addition, two samples from each commercial brand were analyzed for water activity (aw). Samples of brand A showed aw values (0.938 and 0.942) above those set by the legislation, while brand B (0.849 and 0.860) and brand C (0.826 and 0.854) were compliant. Microbiological analyses showed that 67.7% were negative to all investigated bacteria. Salmonella Typhimurium was isolated from 4.4% (4/90) of salami samples, all from commercial brand A. Listeria monocytogenes was detected in 3.3% (3/90) of samples, from commercial brands B and C. Moreover, 7.7% (7/90) of samples contained CPS populations non-compliant with legislation. Although the great majority of salami sold at street fairs of Porto Alegre was compliant with standards, S. enterica, L. monocytogenes, and CPS ≥ 5 × 103 cfu.g-1 could be found in this RTE product. Therefore, control measures in the processing industry and consumer’s education about foodborne illness prevention should be maintained.

Analysis of Process Factors of Dry Fermented Salami to Control Listeria Monocytogenes

Challenge tests are a clear opportunity for manufacturers interested in the evaluation of their management system with the aim to reduce the spread of foodborne pathogens. This is a main concern especially in ready-to-eat food in relation to the risk associated with Listeria monocytogenes. For small and medium-scale food industry the manufacturing practices and products formulation are characterised by a wider variability and poor repeatability. The use of ad hoc challenge test and the comparison among different processing systems are strongly required. This paper reports a preliminary comparison among different challenge tests (n=12) commissioned by three manufacturers of raw-fermented salami during a period of three years (2013-2016). The challenge tests were designed to evaluate the growth potential (δ) of L. monocytogenes during the whole processing period of the salami. The doughs were prepared according to different formulations: the simplest formulation was represented by the use of salt, potassium nitrate, black pepper and starter cultures, while the most composited formulations also included the use of sugars and ascorbic acid in addition to nitrite salt. All the processing steps were conducted within an experimental laboratory dedicated for the processing of meat. After stuffing, the salami were dried and ripened under temperature and relative humidity control. The sugar inclusion can be considered as a protective factor, while the drying step at high temperature (above 20°C) was associated with higher δ values (δ>0.5 log₁₀ cfu/g). The addition of starter cultures, and the subsequent acidification highlighted the importance of pH as the parameter able to affect the L. monocytogenes growth.

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.

Growth potential of exponential- and stationary-phase Salmonella Typhimurium during sausage fermentation

Raw meat for sausage production can be contaminated with Salmonella. For technical reasons, meat is often frozen prior to mincing but it is unknown how growth of Salmonella in meat prior to freezing affects its growth potential during sausage fermentation. We investigated survival of exponential- and stationary-phase Salmonella Typhimurium (DT12 and DTU292) during freezing at -18°C and their subsequent growth potential during 72h sausage fermentation at 25°C. After 0, 7 and >35d of frozen storage, sausage batters were prepared with NaCl (3%) and NaNO2 (0, 100ppm) and fermented with and without starter culture. With no starter culture, both strains grew in both growth phases. In general, a functional starter culture abolished S. Typhimurium growth independent of growth phase and we concluded that ensuring correct fermentation is important for sausage safety. However, despite efficient fermentation, sporadic growth of exponential-phase cells of S. Typhimurium was observed drawing attention to the handling and storage of sausage meat.

Behavior of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium in teewurst, a raw spreadable sausage

The fate of Listeria monocytogenes, Salmonella Typhimurium, or Escherichia coli O157:H7 were separately monitored both in and on teewurst, a traditional raw and spreadable sausage of Germanic origin. Multi-strain cocktails of each pathogen (ca. 5.0 log CFU/g) were used to separately inoculate teewurst that was subsequently stored at 1.5, 4, 10, and 21 degrees C. When inoculated into commercially-prepared batter just prior to stuffing, in general, the higher the storage temperature, the greater the lethality. Depending on the storage temperature, pathogen levels in the batter decreased by 2.3 to 3.4, ca. 3.8, and 2.2 to 3.6 log CFU/g for E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, during storage for 30 days. When inoculated onto both the top and bottom faces of sliced commercially-prepared finished product, the results for all four temperatures showed a decrease of 0.9 to 1.4, 1.4 to 1.8, and 2.2 to 3.0 log CFU/g for E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, over the course of 21 days. With the possible exceptions for salt and carbohydrate levels, chemical analyses of teewurst purchased from five commercial manufacturers revealed only subtle differences in proximate composition for this product type. Our data establish that teewurst does not provide a favourable environment for the survival of E. coli O157:H7, S. Typhimurium, or L. monocytogenes inoculated either into or onto the product.

Fate of surface-inoculated Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella typhimurium on kippered beef during extended storage at refrigeration and abusive temperatures

The behavior of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium on kippered beef was evaluated. Individual pieces of the product were separately inoculated on the top and bottom surfaces with each three- to six-strain pathogen cocktail at ca. 6.0 log CFU per piece and stored at 4, 10, 21, or 30 degrees C for up to 28 days in each of two trials. When kippered beef was inoculated with E. coli O157:H7, Salmonella Typhimurium, or L. monocytogenes and stored at 4, 10, 21, or 30 degrees C for up to 28 days, pathogen numbers decreased ca. 0.4 to 0.9, 1.0 to 1.8, 3.0 to > or = 5.25, and > or = 5.0 to 5.25 log CFU per piece, respectively. Average D-values for E. coli O157:H7, Salmonella Typhimurium, and L. monocytogenes stored at 4 to 30 degrees C for 28 days were ca. 41 to 4.6, 40.8 to 5.3, and 29.5 to 4.3 days, respectively. As expected, the higher the storage temperature, the greater the level and rate of inactivation for all three pathogens. These data establish that kippered beef does not provide an environment conducive to proliferation of these pathogens.

Application of high pressure processing to kill Escherichia coli O157 in ready-to-eat meats

Uncooked ready-to-eat (RTE) meats have previously been identified as vehicles for the transmission of the foodborne pathogen Escherichia coli O157. In this study, the potential for high pressure processing (HPP) to kill E. coli O157 in two RTE meats (Hungarian salami and All Beef salami) was investigated. The RTE meats were inoculated with a five-strain cocktail of E. coli O157, vacuum packed, and then pressure treated at 600 MPa with a hold time of 3 min. Samples were stored at 15 degrees C for 28 days. HPP initially reduced E. coli numbers on both RTE meats by greater than 4 log CFU/g. However, with enrichment and immunomagnetic separation we were able to recover E. coli O157 from the samples. During storage, the numbers of E. coli O157 increased on the All Beef samples but remained static on the Hungarian salami, which had a restrictive pH and water activity. Increasing the hold time to 6 or 9 min did not result in additional reduction of E. coli O157. The sensory appeal of the two products was not significantly changed by HPP as determined by a sensory panel (n = 50). Analysis of the reflected light parameters of luminance, green-red, and blue-yellow revealed no significant changes. The results of these experiments indicate that HPP has potential as a lethal treatment for E. coli O157 on RTE meats with minimal changes in consumer appeal.

Effect of packaging and storage temperature on the survival of Listeria monocytogenes inoculated postprocessing on sliced salami

The survival of postprocess Listeria monocytogenes contamination on sliced salami, stored under the temperatures associated with retail and domestic storage, was investigated. Sliced salami was inoculated with low and high concentrations of L. monocytogenes before being packaged under vacuum or air. Survival of L. monocytogenes was determined after storage of sausages for 45 or 90 days for low or high sample inocula, respectively, at 5, 15, and 25 degrees C. All survival curves of L. monocytogenes were characterized by an initial rapid inactivation within the first days of storage, followed by a second, slower inactivation phase or "tailing." Greater reduction of L. monocytogenes was observed at the high storage temperature (25 degrees C), followed by ambient (15 degrees C) and chill (5 degrees C) storage conditions. Moreover, vacuum packaging resulted in a slower destruction of L. monocytogenes than air packaging, and this effect increased as storage temperature decreased. Although L. monocytogenes numbers decreased to undetectable levels by the end of the storage period, the time (in days) needed for this reduction and for the total elimination of the pathogen decreased with high temperature, aerobic storage, and high inoculum. Results of this study clearly indicated that the kinetics of L. monocytogenes were highly dependent on the interaction of factors such as storage temperature, packaging conditions, and initial level of contamination (inoculum). These results may contribute to the exposure assessment of quantitative microbial risk assessment and to the establishment of storage-packaging recommendations of fermented sausages.