Pathogens In Meat Products Research Articles

Emulsified and Nanoemulsified Essential Oils in the Control of Clostridium botulinum and Clostridium sporogenes in Mortadella.

Clostridium botulinum is a foodborne pathogen responsible for severe neuroparalytic disease associated with the ingestion of pre-formed toxin in food, with processed meats and canned foods being the most affected. Control of this pathogen in meat products is carried out using the preservative sodium nitrite (NaNO2), which in food, under certain conditions, such as thermal processing and storage, can form carcinogenic compounds. Therefore, the objective was to use nanoemulsified essential oils (EOs) as natural antimicrobial agents, with the aim of reducing the dose of NaNO2 applied in mortadella. The antimicrobial activity of nanoemulsions prepared with mixtures of EOs of garlic, clove, pink pepper, and black pepper was evaluated on endospores and vegetative cells of C. botulinum and Clostridium sporogenes (surrogate model) inoculated in mortadella prepared with 50 parts per million NaNO2. The effects on the technological (pH, water activity, and color) and sensory characteristics of the product were also evaluated. The combinations of EOs and their nanoemulsions showed sporicidal effects on the endospores of both tested microorganisms, with no counts observed from the 10th day of analysis. Furthermore, bacteriostatic effects on the studied microorganisms were observed. Regarding the technological and sensorial characteristics of the product, the addition of the combined EOs had a negative impact on the color of the mortadella and on the flavor/aroma. Despite the strong commercial appeal of adding natural preservatives to foods, the effects on flavor and color must be considered. Given the importance of controlling C. botulinum in this type of product, as well as the reduction in the amount of NaNO2 used, this combination of EOs represents a promising antimicrobial alternative to this preservative, encouraging further research in this direction.

Numerical simulation of heat transfer during meat ball cooking and microbial food safety enhancement.

This study was conducted to apply the finite volume method (FVM) to solve the partial differential equation (PDE) governing the heat transfer process during meat cooking with convective surface conditions. For a one-dimensional, round-shaped food, such as meat balls, the domain may be divided into shells of equal thickness, with energy balance established for each adjacent shell using in the finite difference scheme (FDS) to construct a set of finite difference equations, which were then solved simultaneously using the FORTRAN language and the IVPAG subroutine of the International Mathematics and Statistics Library. The FDS is flexible for temperature-dependent physical properties of foods, such as thermal conductivity (k), specific heat (Cp ), thermal diffusivity (α), and boundary conditions, for example, surface heat transfer coefficient (h), to predict the dynamic temperature profiles in beef and chicken meat balls cooked in an oven. Once the FVM model was established and validated, it was used to simulate the dynamic temperature profiles during cooking, which were then used in combination with the general method to evaluate the thermal lethality of Shiga toxin-producing Escherichia coli and Salmonella spp. using D and z values in ground meats during cooking. The method can be applied to design cooking processes that effectively inactivate foodborne pathogens while maintaining the quality of cooked meats and evaluate the adequacy of a cooking process. PRACTICAL APPLICATION: The temperature dependences of thermal conductivity (k) and thermal diffusivity (α) of raw ground beef and ground chicken meats were measured. These thermal properties were then used in numerical simulation to predict the dynamic heating temperature profile and thermal lethality of ground beef and chicken meat balls. The numerical simulation method may be used to optimize and evaluate thermal processes and ensure the inactivation of pathogens in meat products during cooking.

Antimicrobial effect of garlic against foodborne pathogens in ground mutton

The antimicrobial effect of fresh garlic (20, 30, and 50 g/kg) and the equivalent concentrations of garlic oil (80, 120, and 200 mg/kg) was investigated in ground mutton during storage at 4 °C. By day 6 and thereafter, mutton meatballs treated with 50 g/kg of fresh garlic and 200 mg/kg garlic oil exhibited a significant decline in psychrotrophic and Pseudomonas counts in comparison with control. Fresh garlic added at a concentration of 50 g/kg exhibited the highest antimicrobial effect, followed by garlic oil at 200 mg/kg, fresh garlic at 30 g/kg, and garlic oil at 120 mg/kg. By the 15th day of storage, the fresh garlic added at concentrations of 50 and 30 g/kg and garlic oil added at concentrations of 120, and 200 mg/kg inactivated the populations of foodborne pathogens artificially inoculated into ground mutton and exhibited significant (P < 0.01) lower counts in Salmonella Typhimurium, Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus by more than 3 logs CFU/g, in comparison to control. Therefore, fresh garlic and garlic oil can be used as natural antimicrobial food additives to extend the shelf life and inactivate the populations of foodborne pathogens in meat products.

Synergistic Activity of Essential Oils from Herbs and Spices Used on Meat Products against Food Borne Pathogens

Essential oils (EOs) could be utilized as natural agents to improve the safety of meat products. However, the high concentration required to achieve an antimicrobial effect in foods might be incompatible with their sensory acceptance. To avoid this problem, combinations of EOs provide an effective approach reducing the odds of sensory rejection. In our study, 13 EOs of herbs and spices commonly used in the seasoning of meat products were assessed for their antimicrobial activity against Salmonella spp., Listeria monocytogenes, Escherichia coli and Staphylococcus aureus. However, only 7 of them were selected to study their synergistic effect based on their antimicrobial activity and minimum inhibitory concentration (MIC) against foodborne pathogens. EOs of thyme and cinnamon presented the largest antibacterial activity against foodborne pathogens. Combinations of selected EOs displayed a synergic effect against foodborne pathogens and also an important decrease in their individual MIC. Thyme EO presented the lowest individual MIC, but its utilization in combination decreased the MIC of the other EOs. Utilization of cinnamon EO also improved the reduction of the individual MICs of the EOs of cumin and parsley. Our results suggest the potential use of EO mixtures to control foodborne pathogens in meat products. Although the individual MIC values of selected EOs decreased, the sensory impact on meat products needs to be assessed.

Prevalence of pathogenic microorganisms in raw meat products from retail outlets in Alexandria Province

Contamination of raw meat products is very common and the presence of enteric pathogens in meat products will render the meat unsafe to the consumer as they are encountered in causing food poisoning and also they reflect the hygienic standard of the vendors' shop. In the current study, a total of 100 random samples of raw meat products including; minced meat, sausage, pasterma and beef burger (25 samples of each) were collected from different super markets at Alexandria province. The collected samples were examined bacteriologically for detection of some pathogenic bacteria. The obtained results revealed that the incidence of Enteropathogenic E. coli in the examined samples of minced meat, sausage, and pasterma and beef burger was 44, 40, 32and 36%, respectively. The incidence of Salmonella in the examined samples of minced meat, sausage, and pasterma and beef burger was 8, 12, 4 and 8%, respectively. Serotyping of Salmonella revealed the detection of S. Enteritidis, S. Typhi and S. Paratyphi. The incidence of Shigella in the examined samples of minced meat, sausage, and pasterma and beef burger was 20, 24, 12and 24%, respectively. The incidence of Y. enterocolitica in the examined samples of minced meat, sausage, and pasterma and beef burger was 16, 20, 8 and 24%, respectively. The hygienic significance as well as public health hazard of each isolated microorganism, as well as the recommended measures to lower these microorganisms in meat products and improve the quality of meat products was discussed.

Detection of some foodborne pathogens in meat products by Polymerase Chain Reaction

Detection of some foodborne pathogens in meat products by Polymerase Chain Reaction

Antimicrobial nanocomposite films made of poly(lactic acid)-cellulose nanocrystals (PLA-CNC) in food applications: part A—effect of nisin release on the inactivation of Listeria monocytogenes in ham

New bioactive nanocomposite films were prepared by compression molding method for food applications. Film matrix was composed of poly(lactic acid) containing cellulose nanocrystals (PLA-CNC). Nanocomposite films were converted to bioactive films using nisin as an antimicrobial agent by an adsorption coating method. Resulting antimicrobial films were then introduced in packages containing sliced cooked ham as a food model and stored for 14 days at 4 °C to determine their inhibiting capacity against Listeria monocytogenes and their physicochemical and structural properties. The study also focused on the nisin release from the films by using an agar diffusion bioassay. It was observed that mechanical properties such as tensile strength, tensile modulus, elongation at break and water vapor permeability values of the bioactive films were stable after 14 days of storage. Fourier transform infrared spectroscopy analysis allowed characterizing the adsorption of nisin onto PLA-CNC surface. Microbiological analysis of sliced cooked ham inoculated with L. monocytogenes (3 log CFU/g) allowed determining the potentiality of nisin as a strong antimicrobial agent in PLA-CNC-based films. Bioactive PLA-CNC-nisin films showed a significant reduction of L. monocytogenes in ham from day 1 and a total inhibition from day 3. The percentage of nisin release increased continuously from day 0 to day 14, up to 21 % at day 14. These results demonstrated the potential application of PLA-CNC-nisin films on controlling the growth of food pathogens in meat products.

Incidence of Shiga toxin–producing Escherichia coli strains in beef, pork, chicken, deer, boar, bison, and rabbit retail meat

The objective of the current study was to determine the incidence of contamination by the top 7 Shiga toxin-producing Escherichia coli (STEC) O-groups, responsible for the majority of E. coli infections in human beings, in retail meat from different animal species. Samples from ground beef (n = 51), ground pork (n = 16), ground chicken (n = 16), and game meat (deer, wild boar, bison, and rabbit; n = 55) were collected from retail vendors for the detection of 7 STEC O-groups (O26, O45, O103, O111, O121, O145, and O157). Meat samples were tested by using a multiplex polymerase chain reaction assay targeting the wzx gene of O antigen gene clusters of the 7 STEC O-groups. The positive samples were further tested for Shiga toxin genes (stx1 and stx2). Out of a total of 83 ground beef, pork, and chicken samples, 17 (20%) carried O121, 9 (10%) carried O45, 8 (9%) carried O157, 3 (3%) carried O103, and 1 (1%) carried O145. None of the samples were positive for O26, O111, or the stx gene. All 3 white-tailed deer samples (100%) were positive for O45, O103, or both, 2 (10%) out of 20 red deer samples exhibited the presence of O103, and all 3 bison samples were contaminated with either O121, O145, or O157. One sample from ground deer, contaminated with E. coli O45, carried the stx1 gene. This preliminary investigation illustrates the importance of microbiological testing of pathogens in meat products, as well as the recognized need for increased surveillance and research on foodborne pathogens.

A Multiplex PCR Assay for the Detection of Food-borne Pathogens in Meat Products

Meat and meat products are a potential source of food-borne pathogens, including Staphylococcus aureus, Salmonella spp., Escherichia coli O157:H7, and Bacillus cereus. A sensitive and specific PCR assay for the detection of these pathogens in meat and meat products was developed in this study, as part of a broader effort to reduce the potential health hazards posed by these pathogens. Initially, PCR conditions were standardized with purified DNA. Under standard conditions, the detection level for PCR was as low as 10 pg of purified bacterial DNA. After overnight growth of bacteria in a broth medium, as few as <TEX>$10^2$</TEX> CFU of bacteria were detected by PCR assay. The primers employed in the PCR assay were found to be highly specific for individual organisms, and evidenced no cross-reactivity with heterologous organisms. Additionally, the multiplex PCR assays also amplified some target genes from the four pathogens, and multiplex amplification was obtained from as little as 10 pg of DNA, thus illustrating the excellent specificity and high sensitivity of the assay. In conclusion, this PCR-based technique provides a sensitive and specific method for the detection of S. aureus, Salmonella spp., E. coli O157:H7, and B. cereus in meat and meat products.

The effect of the pediocin PA-1 produced by Pediococcus acidilactici against Listeria monocytogenes and Clostridium perfringens in Spanish dry-fermented sausages and frankfurters

The inhibitory effects of the pediocin PA-1 in frankfurters and the Pediococcus acidilactici MCH14 pediocin-producing strain itself in Spanish dry-fermented sausages were evaluated. The experiments were carried out by in situ assays using Listeria monocytogenes and Clostridium perfringens as target bacteria strains. The inhibition of L. monocytogenes by the P. acidilactici MCH14 pediocin-producing strain was effective in Spanish dry-fermented sausages, being the counts of this pathogen reduced by 2 log cycles compared to the control. In frankfurters, the counts of L. monocytogenes, using 5000 bacteriocin units/ml (BU/ml) of the pediocin PA-1 produced by P. acidilactici MCH14, decreased by 2 and 0.6 log cycles after storage at 4 °C for 60 days and at 15 °C for 30 days, respectively, with respect to the control. Similar results were obtained for C. perfringens, with 5000 BU/ml the counts of this strain were reduced by 2 and 0.8 log cycles after storage at 10 °C for 60 days and at 15 °C for 30 days, respectively, with respect to the control. Both the pediocin PA-1 and the P. acidilactici MCH14 pediocin-producing strain could be a useful alternative for protection against these food-borne pathogens in meat products.

Sodium lactate, sodium diacetate and pediocin: Effects and interactions on the thermal inactivation of Listeria monocytogenes on bologna

The effects and interactions of temperature (56.3–60 °C), sodium lactate (SL; 0–4.8%), sodium diacetate (SD; 0–0.25%) and pediocin (0–10,000 AU) on Listeria monocytogenes on bologna were studied and a predictive inactivation model was developed. Bologna was manufactured with different SL/SD concentrations in the formulation, dipped in pediocin solution and treated at different temperatures using combinations of parameters determined by central composite design. D-values were calculated and analyzed using second order response regression. Predicted D-values were also calculated. The observed D-values for L. monocytogenes on bologna ranged from 2.10 to 35.59 min. Temperature alone decreased predicted D-values from 99.02 min at 56.3 °C to 44.71 min at 60.0 °C. Adding SL decreased D-values (85.43–22.71 min) further; however, heat and SD combined was the most effective for reducing L. monocytogenes on bologna. An SD level of 0.25% at 58.2 °C had the overall lowest predicted D-value (15.95 min). Combination treatments increased or decreased D-values, depending on the temperature. Pediocin (2500 and 5000 AU) and heat decreased D-values, but exhibited a protective effect at higher concentrations (≥7500 AU). The results showed that interactions between additives in formulations can vary at different temperatures/concentrations, thereby affecting thermal inactivation of foodborne pathogens in meat products. Hence, food processors should modify food formulations carefully, and verify with adequate testing so that product safety is not compromised.

Effect of Water Activity on Thermal Inactivation of Salmonella in Ground Turkey

ABSTRACTMany factors, such as fat content and pH, are known to affect thermal inactivation of pathogens in meat products, and a few studies have suggested that the humidity of the cooking environment also affects thermal inactivation. However, the effect of process humidity has not been previously isolated from the effect of water activity on Salmonella inactivation. Therefore, the objective of this study was to directly test the effect of meat water activity on thermal inactivation of Salmonella. Ground turkey was dried to achieve water activities of 0.95 to 0.99, inoculated with an 8‐strain Salmonella cocktail, and heated isothermally (60 °C) in a water bath. The rate of thermal inactivation of Salmonella decreased 64% (P &lt; 0.01) when decreasing meat water activity from 0.99 to 0.95. Inclusion of water activity improved the accuracy of a 1st‐order/Arrhenius‐type inactivation model from 1.94 log10 to 0.8 log10 (colony‐forming units [CFU]/g).

Clostridium perfringens: hazards in new generation foods

The retail increase in refrigerated ready-to-eat foods provides an exploitable environment suitable for an opportunistic pathogen such as Clostridium perfringens. The microorganism, in spite of a requirement for 13 essential amino acids, an optimal growth range of 43–45 °C, pH range 5–8, and a substrate water activity range of 0.93–0.97, can be found to be ubiquitously viable in food, water and air. Survival under extreme conditions is largely a factor of differentiation from metabolically active vegetative cells to highly resistant (100 °C for 60 min), dormant spores. It is the sporulation of large numbers of vegetative cells (10 6/g of food) and the associated release of enterotoxin in the human intestine that results in typical gastrointestinal symptoms of acute abdominal pain and diarrhea in conjunction with a loss of membrane ionic balance. As a consequence of the inevitable presence of C. perfringens in foods, the Food Safety Inspection Service (FSIS) of the US Department of Agriculture (USDA) has established performance standards for the pathogen in meat products. This review examines the current knowledge base of specific characteristics and attributes that make this microorganism a food safety concern. In addition, suggestions are made to reduce the likelihood of food-borne infection and transmission.

Occurrence of Bacillus cereus and Yersinia enterocolitica in South African retail meats

Ground beef, chicken broilers and processed meats (Vienna sausages, ham, salami) obtained from supermarkets in the Pretoria area (South Africa) were tested for the presence of Bacillus cereus and Yersinia enterocolitica. B. cereus counts were carried out on Bacillus cereus -selective agar and confirmed by the rapid confirmation procedure. Y. enerocolitica was isolated on Y. enterocolitica -selective agar. Total aerobic counts were performed on all the samples. Out of 51 samples, B. cereus was recovered from one broiler, three salami and five Vienna sausage samples, but not from gound beef or ham samples. The levels of detection ranged from log101·0 to log103·1 g−1sample. Y. enterocolitica occurred in eight ground beef, eight broiler, one Vienna sausage and two ham samples. Our results emphasize the potential hazard of the presence of B. cereus and Y. enterolitica in meat and poultry products in South Africa. This necessitates the implementation of methods to prevent the entry or proliferation of these pathogens in meat products.

Rambach agar as a new plate differential medium for the identification of some enteric pathogens in meat products

An investigation of the efficacy of both Rambach agar and xylose-lysine-desoxycholate (XLD) agar as media for isolation of some enteric pathogenic bacteria from raw meat and ready-to-eat meat products was conducted. For this purpose, 50 samples representing 20 and 30 samples of raw and ready-to-eat meat products respectively were examined and the growth characteristics of various Gram-negative bacteria on XLD and Rambach agars were compared. In the case of raw meat products 33.3% of suspected salmonella colonies showing growth on XLD agar and not on Rambach agar gave false results in biochemical and serological examinations. In contrast, all suspected salmonella colonies on Rambach agar were positive biochemically and serologically. Furthermore, suspected salmonella colonies isolated from ready-to-eat meat products on XLD agar showed 83.3% false positive cases while in case of Rambach agar no false positive cases were detected. Therefore, Rambach agar excelled XLD agar in the isolation of salmonella from both raw and ready-to-eat products.