Ready-to-eat Meat Research Articles

Safety and quality assessment of ready-to-eat pork products in the cold chain

It is of crucial importance for Ready-To-Eat (RTE) foodstuffs producers to guarantee the quality and safety of their products under the cold chain variations related to different time–temperature profiles. Experimental designs were used to investigate and model the effects of temperature on safety and quality attributes of selected RTE meat products. Three types of RTE sliced pork products (cooked ham, cooked paté and smoked ham) were stored at different temperatures (5, 8, 12 and 15°C) up to 6weeks. Microbiological and physico-chemical attributes were followed. Growth parameters of Listeria monocytogenes were investigated by challenge testing for the three RTE products at the four temperatures. Two lactic acid bacteria (Lactobacillus sakei and Leuconostoc mesenteroïdes) were also investigated by challenge testing but only for cooked ham and cooked paté at 8°C. Changes in quality indicators including colour, texture and water content, water activity and water dripping were evaluated over storage time for the three RTE products. Spoilage experiments were conducted (at 2, 8, 12, 15°C for 48days) on cooked ham and the production of ethanol, as a representative volatile deriving from bacterial metabolism, was correlated to bacterial outgrowth. Growth parameters of the three strains for the given food were mathematically modelled and validation tests were performed for L. monocytogenes in cooked ham and cooked paté. Physico-chemical attributes were not significantly affected by time–temperature storage. The production of ethanol on spoiled cooked ham was related to growth of lactic acid bacteria, especially Leuconostoc. A threshold value of ethanol concentration was defined in relation with a threshold count numbers of LAB under the conditions studied.

Characterization of virulent Listeria monocytogenes isolates recovered from ready-to-eat meat products and consumers in Cairo, Egypt

Aim: This study aimed to investigate the occurrence of some virulence genes distributed in Listeria monocytogenes isolated from ready-to-eat (RTE) meat products and consumers in Cairo province, Egypt. Materials and Methods: A total of 120 beef luncheon, chicken luncheon and frankfurter beef (40 samples, each) were collected from 10 different local shops situated in Al-salam city, Cairo province, Egypt. Stool samples were collected from 40 people who had the habit of consuming RTE meat. The suspected L. monocytogenes isolates were subjected to a multiplex polymerase chain reaction (PCR) for rapid speciation and virulence determination using primers specific for inIA, inIC, and inIJ genes. Results: Culture examination of all samples on Oxford media revealed presence of colonies characteristic to L. monocytogenes in 6 beef luncheon (15%), 4 chicken luncheon (10%), 1 frankfurter beef (2.5%) and 1 human stool (2.5%) samples. Species identity of L. monocytogenes was verified through the amplification of a 800 bp fragment with inIA primers in 2 out of 6 culture isolates from beef luncheon (5%), and 1 out 4 culture isolates from chicken luncheon (2.5%) samples. Statistical analysis revealed no significant difference between the occurrence of L. monocytogenes in different food samples examined (p>0.05). The virulence of these strains was ascertained by the presence of 517 bp and 238 bp fragments of inIC and inIJ genes, respectively in the isolates that contained the 800 bp fragment. The culture isolates obtained from one frankfurter beef sample, and one human stool sample were found negative by multiplex PCR for the presence of L. monocytogenes and its virulence specific genes. Conclusion: It could be concluded that L. monocytogenes are circulating in beef and chicken luncheon sold in Cairo, Egypt. Multiplex PCR is reliable for confirmation of L. monocytogenes. This study suggests the implementation of hygienic measures at all levels from production to consumption in order to improve food safety. Furthermore, authors recommended consumption of beef frankfurter or any RTE meat sold in their original intact packing due to low level of contamination.

Enhanced Inactivation of Food-Borne Pathogens in Ready-To-Eat Sliced Ham by Near-Infrared Heating Combined with UV-C Irradiation and Mechanism of the Synergistic Bactericidal Action

The objective of the study described in this article was, first, to investigate the effect of the simultaneous application of near-infrared (NIR) heating and UV irradiation on inactivation of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in ready-to-eat (RTE) sliced ham and as well as its effect on product quality and, second, to elucidate the underlying mechanisms of the synergistic bactericidal action of NIR heating and UV irradiation. With the inoculation amounts used, simultaneous NIR-UV combined treatment for 70 s achieved 3.62, 4.17, and 3.43 log CFU reductions of E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively. For all three pathogens, the simultaneous application of both technologies resulted in an additional log unit reduction as a result of their synergism compared to the sum of the reductions obtained after the individual treatments. To investigate the mechanisms of NIR-UV synergistic injury for a particular microorganism in a food base, we evaluated the effect of four types of metabolic inhibitors using the overlay method and confirmed that damage to cellular membranes and the inability of cells to repair these structures due to ribosomal damage were the primary factors related to the synergistic lethal effect. Additionally, NIR-UV combined treatment for a maximum of 70 s did not alter the color values or texture parameters of ham slices significantly (P > 0.05). These results suggest that a NIR-UV combined process could be an innovative antimicrobial intervention for RTE meat products.

Effect of E-beam treatment on the bioaccessibility of folic acid incorporated to ready to eat meat products

Meat products are a potential matrix to fortify with folic acid (FA). In previous studies the effect of E-beam treatment on the stability of FA in ready to eat (RTE) meat products has been described. However, the FA bioaccessibility in both traditional and treated (3 kGy) RTE meat products has not yet been studied. We investigated the availability for intestinal absorption (bioaccessibility) of FA using a dynamic gastrointestinal model (TIM system). Three different types of meat products, hamburgers, cooked sausages and dry fermented sausages, initially fortified with 24 μg/g FA were tested as freshly prepared products and as RTE products. The bioaccessibility of FA during the passage through the TIM system was high for all three products, irrespective the E-beam treatment. From hamburgers the bioaccessibility was 82% and 100%, from cooked sausages, 61 and 79% and from dry fermented sausages 81 and 82%, with or without e-beam treatment, respectively.

Antimicrobial Polylactic Acid Packaging Films against Listeria and Salmonella in Culture Medium and on Ready-to-Eat Meat

The contamination of Listeria monocytogenes and Salmonella spp. in ready-to-eat (RTE) meat products has been a concern for the meat industry. In this study, edible chitosan-acid solutions incorporating lauric arginate ester (LAE), sodium lactate (NaL), and sorbic acid (SA) alone or in combinations were developed and coated on polylactic acid (PLA) packaging films. Antimicrobial effects of coated PLA films on the growth of Listeria innocua, L. monocytogenes, and Salmonella Typhimurium in a culture medium (tryptic soy broth, TSB) and on the surface of meat samples were investigated. Antimicrobial PLA films containing 1.94 mg/cm2 of chitosan and 1.94 μg/cm2 of LAE were the most effective against both Listeria and Salmonella in TSB and reduced them to undetectable level (<0.69 log CFU/ml). The same PLA films with LAE significantly (p < 0.05) reduced the growth of L. innocua, L. monocytogenes, and S. Typhimurium on RTE meat during 3 and 5 weeks’ storage at 10 °C, achieving 2–3 log reduction of Listeria and 1–1.5 log reduction of Salmonella as compared with controls. PLA films coated with 1.94 mg/cm2 of chitosan, 0.78 mg/cm2 of NaL, and 0.12 mg/cm2 of SA significantly reduced the growth of L. innocua but were less effective against Salmonella. The combination of NaL (0.78 mg/cm2) and SA (0.12 mg/cm2) with LAE (1.94 μg/cm2) did not generate additional or synergetic antimicrobial effect against Listeria or Salmonella on the meat surface. L. innocua had a similar sensitivity to the film treatments as L. monocytogenes, suggesting that L. innocua may be used as a surrogate of L. monocytogenes for further scaleup and validation studies. The film treatments were more effective against the microorganisms in TSB culture medium than in RTE meat, which suggests that in vivo studies are a necessary step to develop antimicrobial packaging for applications in foods.

Antimicrobial resistance of Listeria monocytogenes and Listeria innocua from meat products and meat-processing environment

A total of 336 Listeria isolates from ready-to-eat (RTE) meat products and meat-processing environments, consisting of 206 Listeria monocytogenes, and 130 Listeria innocua isolates, were characterized by disc diffusion assay and minimum inhibitory concentration (MIC) values for antimicrobial susceptibility against twenty antimicrobials. Resistance to one or two antimicrobials was observed in 71 L. monocytogenes isolates (34.5%), and 56 L. innocua isolates (43.1%). Multidrug resistance was identified in 24 Listeria isolates, 18 belonging to L. innocua (13.9%) and 6 to L. monocytogenes (2.9%). Oxacillin resistance was the most common resistance phenotype and was identified in 100% Listeria isolates. A medium prevalence of resistance to clindamycin (39.3% isolates) and low incidence of resistance to tetracycline (3.9% isolates) were also detected. Listeria isolates from RTE meat products displayed higher overall antimicrobial resistance (31.3%) than those from the environment (13.4%). All the strains assayed were sensitive to the preferred antibiotics used to treat listeriosis. Results showed that although antimicrobial resistance in L. monocytogenes still occurs at a low prevalence, L. innocua can form a reservoir of resistance genes which may transfer between bacterial species, including transference to organisms capable of causing disease in humans.

Antimicrobial films and coatings for inactivation of Listeria innocua on ready-to-eat deli turkey meat

Edible antimicrobial coating solutions incorporating chitosan, lauric arginate ester (LAE) and nisin were developed to reduce foodborne pathogen contamination on ready-to-eat (RTE) meats. RTE deli meat samples were directly coated with the solutions, or treated with solution-coated polylactic acid (PLA) films. The antimicrobial efficacy of the coatings and films against Listeria innocua inoculated onto the surface of RTE meat samples was investigated. Antimicrobial coatings with 1.94 mg/cm2 of chitosan and 0.388 mg/cm2 of LAE reduced L. innocua by ca. 4.5 log CFU/cm2. Nisin (486 IU/cm2) showed less effectiveness than LAE (0.388 mg/cm2) and addition of nisin to the antimicrobial coatings or films containing LAE (0.388 mg/cm2) did not enhance the total antimicrobial effectiveness. Combining antimicrobial coatings or films with flash pasteurization (FP), which uses short burst of steam under pressure, further reduced L. innocua, achieving over a 5 log reduction. There was no significant difference in the effectiveness of antimicrobial films versus the coatings (p > 0.05). These data show the potential use of antimicrobial packaging alone, or in combination with FP, in preventing foodborne illness due to post-processing contamination of RTE meat products.

Quantification of viable Escherichia coli O157:H7 in meat products by duplex real-time PCR assays

Rapid and specific detection of viable Escherichia coli O157:H7 cells in ready-to-eat (RTE) meat products, by duplex quantitative PCR (qPCR) procedures with mRNA and SYBR Green and TaqMan methodologies were developed. Specific primers and probes were designed based on the serotype of E. coli O157:H7, fliCh7 and rfbE genes. No cross-reactivity with other microorganisms was observed. The detection limit of the assays was 101 or 102CFU/g for artificially contaminated meat products, and after a 4h enrichment period at 37°C, the detection limit decreased to about 1CFU/g. Time-to completion of the assay was approximately 8h. Thus, these qPCR methods offer a useful, rapid and efficient tool for screening viable E. coli O157:H7 in RTE meat products. This tool could also be proposed for monitoring these foodborne pathogens in HACCP programs.

Efficacy of bacteriophage LISTEX™P100 combined with chemical antimicrobials in reducing Listeria monocytogenes in cooked turkey and roast beef

The aim of this study was to verify the effectiveness of the commercially available anti-Listeria phage preparation LISTEX™P100 in reducing Listeria monocytogenes on ready-to-eat (RTE) roast beef and cooked turkey in the presence or absence of the chemical antimicrobials potassium lactate (PL) and sodium diacetate (SD). Sliced RTE meat cores at 4 and 10°C were inoculated with cold-adapted L. monocytogenes to result in a surface contamination level of 103CFU/cm2. LISTEXTMP100 was applied at 107 PFU/cm2 and samples taken at regular time intervals during the RTE product's shelf life to enumerate viable L. monocytogenes. LISTEX™P100 was effective during incubation at 4°C with initial reductions of L. monocytogenes of 2.1 log10 CFU/cm2 and 1.7 log10 CFU/cm2, respectively, for cooked turkey and roast beef without chemical antimicrobials (there was no significant difference to the initial L. monocytogenes reductions in the presence of LISTEXTMP100 for cooked turkey containing PL and roast beef containing SD-PL). In the samples containing no chemical antimicrobials, the presence of phage resulted in lower L. monocytogenes numbers, relative to the untreated control, of about 2 log CFU/cm2 over a 28-day storage period at 4°C. An initial L. monocytogenes cell reduction of 1.5 log10 CFU/cm2 and 1.7 log10 CFU/cm2, respectively, for cooked turkey and roast beef containing no chemical antimicrobials was achieved by the phage at 10°C (abusive temperature). At this temperature, the L. monocytogenes cell numbers of samples treated with LISTEX™ P100 remained below those of the untreated control only during the first 14days of the experiment for roast beef samples with and without antimicrobials. On day 28, the L. monocytogenes numbers on samples containing chemical antimicrobials and treated with LISTEXTMP100 stored at 4 and 10°C were 4.5 log10 CFU/cm2 and 7.5 log10 CFU/cm2, respectively, for cooked turkey, and 1.2 log10 CFU/cm2 and 7.2 log10 CFU/cm2, respectively, for roast beef. In both cooked turkey samples with and without chemical antimicrobials stored at 10°C, the phage-treated samples had significantly lower numbers of L. monocytogenes when compared to the untreated controls throughout the 28-day storage period (P<0.0001). For roast beef and cooked turkey containing chemical antimicrobials treated with LISTEXTMP100 and stored at 4°C, no more than a 2 log CFU/cm2 increase of L. monocytogenes was observed throughout the stated shelf life of the product. This study shows that LISTEX™P100 causes an initial reduction of L. monocytogenes numbers and can serve as an additional hurdle to enhance the safety of RTE meats when used in combination with chemical antimicrobials.

A simplified modelling approach established to determine the Listeria monocytogenes behaviour during processing and storage of a traditional (Italian) ready-to-eat food in accordance with the European Commission Regulation N° 2073/2005

This paper considers the applications of the European Commission (EC) Regulation N° 2073/2005 concerning Listeria monocytogenes in ready-to-eat (RTE) food products. A simplified modelling approach (SMA), which is intended for a practical evaluation of the behaviour of the pathogen during processing and storage of an RTE meat product (Pitina) from traditional producers, was presented. This approach included a growth/no-growth model, which was developed by using the limits adopted as safety criteria by the EU, a model based on the gamma concept (GM) and a kinetic three-phase model (TPL). Based on the findings of the present study, Pitina was incapable of supporting the growth of L. monocytogenes and the no-growth conditions assessed through the shelf life by the model were confirmed by challenge testing. When the simplified approach was used to estimate the total pathogen growth relative to the Pitina multistage process, taking into account the effects of various hurdles, it provided predictions of L. monocytogenes growth corresponding to the observed data in the inoculation studies. Therefore, this simplified approach is expected to enable the food producers to identify appropriate processing conditions. The successfully validated SMA was found sufficiently complex to predict growth responses of L. monocytogenes in RTE foods, but at the same time easy-to-use for practical processing situations.

The Effects of Sodium Chloride on the Physiological Characteristics of Listeria monocytogenes

Sodium chloride is used to improve various properties of processed meat products, e.g., taste, preservation, water binding capacity, texture, meat batter viscosity, safety, and flavor; however, many studies have shown that sodium chloride increases the resistance of many foodborne pathogens to heat and acid. Listeria monocytogenes has been isolated from various readyto- eat (RTE) meat and dairy products formulated with sodium chloride; therefore, the objective of this paper was to review the effects of sodium chloride on the physiological characteristics of L. monocytogenes. The exposure of L. monocytogenes to sodium chloride may increase biofilm formation on foods or food contact surfaces, virulence gene transcription, invasion of Caco-2 cells, and bacteriocin production, depending on L. monocytogenes strain and serotype as well as sodium chloride concentration. When L. monocytogenes cells were exposed to sodium chloride, their resistance to UV-C irradiation and freezing temperatures increased, but sodium chloride had no effect on their resistance to gamma irradiation. The morphological properties of L. monocytogenes, especially cell elongation and filament formation, also change in response to sodium chloride. These findings indicate that sodium chloride affects various physiological responses of L. monocytogenes and thus, the effect of sodium chloride on L. monocytogenes in RTE meat and dairy products needs to be considered with respect to food safety. Moreover, further studies of microbial risk assessment should be conducted to suggest an appropriate sodium chloride concentration in animal origin foods.

MicroSEQ®Listeria spp. Detection Kit

Abstract The Applied Biosystems Performance Tested MethodSM for detecting Listeria species in food and environmental samples was compared to the Health Canada reference method (MFHPB-30) for the analysis of five ready-to-eat (RTE) meats (deli turkey, hot dogs, liver paté, deli ham, and raw fermented sausage) and a stainless steel surface. The MicroSEQ method includes the MicroSEQ®Listeria spp. Detection Kit and the option of two different sample preparation kits, either the automated high-throughput PrepSEQ™ Nucleic Acid Extraction Kit or the manual low- to mid-throughput PrepSEQ™ Rapid Spin Sample Preparation Kit. For each sample matrix, 20 replicates were analyzed at two inoculum levels: for RTE meats a low-level inoculum at 0.2–2 CFU/25 g and a high-level inoculum at 2–5 CFU/25 g; and for environmental surfaces, a low-level inoculum at 0.2–2 CFU/5 cm2 sampling area and a high-level inoculum at 2–5 CFU/5 cm2 sampling area. Five control replicates were also analyzed at 0 CFU/25 g (uninoculated) for food or 0 CFU/5 cm2 sampling area for environmental surface. Both sample preparation methods returned identical results. There was no statistically significant difference in the number of positive samples detected by the MicroSEQ Listeria species method and the MFHPB-30 reference method for three RTE meats and for the one stainless steel environmental surface tested. For deli turkey, there was a statistically significant difference in the number of positive results detected by the MicroSEQ method and the Health Canada MFHPB-30 reference method for the low inoculation level, with the MicroSEQ method detecting more positives. For hot dogs, statistical equivalence was not applicable since hot dogs were spiked with 10x Listeria innocua as competitive background, and the MicroSEQ method detects all known Listeria. Because the MicroSEQ method uses real-time PCR to detect pathogens, it provides faster time-to-results with equivalent detection compared to culture methods. The MicroSEQ method detects Listeria species within 2 to 3 h following 24 to 28 h enrichment compared to culture methods that take at least 5 days for presumptive positive results.

MicroSEQ®Listeria monocytogenes Detection Kit

Abstract The Applied Biosystems Performance Tested MethodSM for detecting Listeria monocytogenes in food and environmental samples was compared to the Health Canada reference method (MFHPB-30) for the analysis of five ready-to-eat (RTE) meats (deli turkey, hot dogs, liver paté, deli ham, and raw fermented sausage) and a stainless steel environmental surface. The MicroSEQ® method includes the MicroSEQListeria monocytogenes Detection Kit and the option of two different sample preparation kits, either the automated high-throughput PrepSEQ™ Nucleic Acid Extraction Kit or the manual low- to mid-throughput PrepSEQ Rapid Spin Sample Preparation Kit. For each sample matrix, 20 replicates were analyzed at two inoculum levels: for RTE meats, a low-level inoculum at 0.2–2 CFU/25 g and a high-level inoculum at 2–5 CFU/25 g; and for environmental surfaces, a low-level inoculum at 0.2–2 CFU/5 cm2 sampling area and a high-level inoculum at 2–5 CFU/5 cm2 sampling area. Five control replicates were also analyzed at 0 CFU/25 g (uninoculated) for food or 0 CFU/5 cm2 sampling area for environmental surface. Both sample preparation methods returned identical results. There was no statistically significant difference in the number of positive samples detected by the MicroSEQ Listeria monocytogenes method and the MFHPB-30 reference method for four of the five RTE meats and the one stainless steel surface tested. For deli turkey, there was a statistically significant difference in the number of positive results detected by the MicroSEQ method and the Health Canada MFHPB-30 reference method for the low inoculation level, with the MicroSEQ method detecting more positives. Because the MicroSEQ method uses real-time PCR to detect pathogens, it provides faster time-to-results compared to culture methods while at the same time demonstrating equivalent detection. The MicroSEQ method detects L. monocytogenes within 2 to 3 h following 24 to 28 h enrichment compared to culture methods that take at least 5 days for presumptive positive results.

VIDAS®Listeria monocytogenes II (LMO2)

This AOAC GovVal study compared the VIDAS Listeria monocytogenes II (LMO2) to the Health Products and Food Branch MFHPB-30 reference method for detection of L. monocytogenes in ready-to-eat (RTE) meats. The VIDAS LMO2 test is an automated enzyme-linked fluorescent immunoassay for the detection of L. monocytogenes in foods. The LMO2 test, following the enrichment procedure from the MFLP-33 method, also included use of the chromogenic media, chromID Ottaviani Agosti Agar (OAA) and chromID Lmono for confirmation of LMO2 presumptive results. In previous AOAC validation studies comparing the VIDAS LMO2 method to the U.S. Food and Drug Administration Bacteriological Analytical Manual and U.S. Department of Agriculture-Food Safety and Inspection Service reference methods, LMO2 was approved as AOAC Official Method 2004.02 for the detection of L. monocytogenes in dairy products, vegetables, seafood, raw meats and poultry, and processed meats and poultry. The GovVal comparative study included 20 replicate test portions, each at two contamination levels for each matrix, where fractionally positive results (5-15 positive results/20 replicate portions tested) were obtained by at least one method at one level. Five uncontaminated controls were included. Chi-square analysis of the comparative data in this study indicates no statistical differences between the VIDAS LMO2 and the MFHPB-30 standard methods at the 5% level of significance. Confirmation of presumptive LMO2 results with the chromogenic OAA and Lmono media was shown to be equivalent to the appropriate reference method agars. The data demonstrate that the VIDAS LMO2 method is an acceptable alternative method to the MFHPB-30 standard culture method for the detection of L. monocytogenes in RTE meats, including liver paté, hot dogs, raw fermented sausage, sliced deli turkey, and sliced deli ham.

Comparative Evaluation of the VIDAS®Listeria monocytogenes Xpress (LMX) for the Detection of Listeria monocytogenes in a Variety of Foods

The VIDAS Listeria monocytogenes Xpress (LMX) test is an enzyme-linked fluorescent immunoassay designed for use with the automated VIDAS or mini-VIDAS instruments for the specific detection of L. monocytogenes using a 26 h proprietary enrichment broth. The VIDAS LMX method was validated according to harmonized AOAC Research Institute (RI) and Official Methods of Analysis guidelines in both the AOAC Performance Tested Method (PTM) and GovVal programs. In the PTM comparison studies, the VIDAS LMX method was compared to the U.S. Department of Agriculture-Food Safety and Inspection Service Microbiology Laboratory Guidebook, the U.S. Food and Drug Administration Bacteriological Analytical Manual, and AOAC Official Methods. The comparative food studies consisted of two main parts: internal testing and AOAC independent laboratory testing, which included seven food matrixes (deli ham, processed cheese, vanilla ice cream, cooked shrimp, smoked white fish, frozen spinach, and peanut butter). As part of the AOAC R1 GovVal program, the VIDAS LMX method was compared to the Health Canada MFHPB-30 method for the detection of L. monocytogenes in five ready-to-eat (RTE) meats (hot dogs, deli turkey, deli ham, fermented sausage, and liver paté). Twenty replicates of each inoculation level and five uninoculated controls were evaluated in each study. The LMX method also included the use ofchromogenic media, chromID Ottaviani Agosti agar and chromID L. mono. agar, for confirmation of LMX presumptive results. In both the PTM and GovVal evaluations, there were no significant differences in the Chi-square values for the LMX method when compared to reference methods. The additional parameters tested in the PTM evaluation (inclusivity, exclusivity, ruggedness, stability, and lot-to-lot) satisfied the AOAC RI performance requirements. In both the PTM and GovVal validation studies, the VIDAS LMX method demonstrated reliability as a rapid qualitative method for next-day detection of L. monocytogenes in a variety of foods, including RTE meats.

3M™ Tecra™ Listeria Visual Immunoassay: AOAC Official MethodsSM 995.22 and 2002.09

A validation study of the 3M Tecra Listeria Visual Immunoassay (VIA; 3M Food Safety, St. Paul, MN) was conducted at Q Laboratories, Inc., Cincinnati, OH. The 3M Tecra Listeria VIA method was compared to the Health Canada MFHPB-30 reference method for the analysis of five ready-to-eat (RTE) meats: deli turkey, hot dogs, liver pate, raw fermented sausage, and deli ham, and on a stainless steel environmental surface. Twenty replicates of each of the five food matrixes were analyzed at a low and a high inoculum level. The low-level test portions were inoculated with 0.2-2 CFU/25 g, and the high-level test portions with 2-5 CFU/25 g. In addition, 20 replicates of one environmental surface were analyzed at a low and a high inoculum level. The low-level sampling area was inoculated with 0.2-2 CFU/5 cm2, and the high-level area with 2-5 CFU/5 cm2. Five control replicates were also analyzed at 0 CFU/25 g (uninoculated) for the foods and at 0 CFU/5 cm2 for the environmental sampling area. There was no significant difference in the number of positives detected by the 3M Tecra Listeria VIA and the Health Canada MFHPB-30 reference method for four of the RTE meats and the stainless steel environmental surface analyzed in this study. For the raw, fermented sausage, there was a significant difference in the number of positives detected for the high inoculum level by the 3M Tecra Listeria VIA and the Health Canada MFHPB-30 reference method, with the 3M Tecra Listeria VIA method detecting more positives.

Microbiological hazard analysis of ready-to-eat meats processed at a food plant in Trinidad, West Indies

BackgroundA bacteriological assessment of the environment and food products at different stages of processing was conducted during the manufacture of ready-to-eat (RTE) chicken franks, chicken bologna and bacon at a large meat processing plant in Trinidad, West Indies.MethodsSamples of air, surfaces (swabs), raw materials, and in-process and finished food products were collected during two separate visits for each product type and subjected to qualitative or quantitative analysis for bacterial zoonotic pathogens and fecal indicator organisms.ResultsStaphylococcus aureus was the most common pathogen detected in pre-cooked products (mean counts = 0.66, 1.98, and 1.95 log10CFU/g for franks, bologna, and bacon, respectively). This pathogen was also found in unacceptable levels in 4 (16.7%) of 24 post-cooked samples. Fifty percent (10 of 20) of pre-cooked mixtures of bacon and bologna were contaminated with Listeria spp., including four with L. monocytogenes. Pre-cooked mixtures of franks and bologna also contained E. coli (35 and 0.72 log10 CFU/g, respectively) while 5 (12.5%) of 40 pre-cooked mixtures of chicken franks had Salmonella spp. Aerobic bacteria exceeded acceptable international standards in 46 (82.1%) of 56 pre-cooked and 6 (16.7%) of 36 post-cooked samples. Both pre-and post-cooking air and surfaces had relatively high levels of aerobic bacteria, Staphylococcus aureus and coliforms, including equipment and gloves of employees. A drastic decrease in aerobic counts and Staphylococcus aureus levels following heat treatment and subsequent increase in counts of these bacteria are suggestive of post-cooking contamination.ConclusionA relatively high level of risk exists for microbial contamination of RTE meats at the food plant investigated and there is a need for enhancing the quality assurance programs to ensure the safety of consumers of products manufactured at this plant.

Evaluation of a novel Listeria enrichment broth combined with a real‐time PCR diagnostics assay for the specific detection of Listeria monocytogenes in RTE pork products

Foodborne outbreaks of listeriosis, human infection with Listeria monocytogenes, are relatively uncommon with approximately 0.1–1.1 cases /100 000 population globally, but high mortality rates of 20–30% are associated with infection (Siegman-Igra et al., 2002; Anonymous, 2012). Those at particular risk of infection include the immunocomprised, the elderly, neonates and pregnant women (Anonymous, 2011; Rocourt et al., 2003). Since the 1990s, over 40% of foodborne listeriosis outbreaks have been associated with ready to eat (RTE) meat products (Warriner & Namvar, 2009). The most significant outbreak of recent times took place in Canada in 2008, with a total of 57 listeriosis cases associated with RTE deli meats which resulted in 23 deaths (Anonymous, 2010; Gilmour et al., 2010). Other significant outbreaks were related with meat frankfurters [USA, 108 cases and 14 deaths in 1998–99] (Anonymous, 1998, 1999; Mead et al., 2006); pât e [Australia, 11 cases and 6 deaths in 1990] (Kittson, 1992; Watson & Ott, 1990); turkey deli meats [USA, 54 cases and 8 deaths in 2002] (Anonymous, 2002; Gottlieb et al., 2006); ‘Quargel’, a brand of acid ripened curd cheese [Austria, Germany and Czech Republic, 34 cases and 8 fatalities in 2009/2010] (Fretz et al., 2010a,b). Listeriosis outbreaks such as these highlight the importance of surveillance in RTE foods. In spite of high salt content and low water activity (Aw), cured and ripened RTE meat products such as those examined in this study can also harbour L. monocytogenes. The organism is capable of growing in 10% NaCl with a water activity (Aw) of 0.90 which is typical of production conditions (AFSSA, 2000; Ryser & Donnelly, 2001). Traditional methods for the specific detection of L. monocytogenes in food are both time consuming and laborious. Recently, a new culture-based method for the identification of L. monocytogenes from foods has been developed, namely the Listeria Precis method. This method uses a single enrichment in Oxoid Novel Enrichment Broth Listeria (ONE Broth-Listeria) followed by selective plating on chromogenic agar [ALOA (Agar Listeria selon Ottaviani & Agosti) One Day] and can provide presumptive results 48 h earlier than ISO 11290-1 (Anonymous, 2004a), a current standard method (Oxoid, 2010). This initial study was performed to determine the feasibility of reducing turnaround time of the Listeria Precis method (considered the reference method used in this study) by incorporating a rapid molecular test after culture enrichment in the ONE Broth-Listeria. A previously described qPCR assay for the specific detection of L. monocytogenes in food (O’Grady et al., 2008, 2009) was combined with the ONE Broth-Listeria culture enrichment step (24 h) of the Listeria Precis method (considered the alternative method used in this study). *Correspondent: Fax: +35391494598; e-mail: thomas.barry@nuigalway.ie Present address: Centre for Clinical Microbiology, University College London (Royal Free Hospital campus), London NW3 2PF

Use of active packaging structures to control the microbial quality of a ready-to-eat meat product

Antimicrobial packaging appears to be a promising application of active food packaging technology. This project was undertaken to evaluate the effectiveness of selected antimicrobial packaging structures in improving the microbial quality of a ready-to-eat (RTE) meat product. Cooked ham samples (25 g) inoculated with a five-strain mixture of Listeria monocytogenes (2 or 4 log CFU g−1) were packaged into three different antimicrobial packaging structures, respectively, and samples in the non-antimicrobial packaging structure served as controls. The samples were stored at 4, 10, or 22 °C, and populations of total aerobic bacteria, Enterobacteriaceae, and inoculated L. monocytogenes were determined twice a week over a 4 w storage period. Packaging structures with an O2 scavenger or a CO2 generator were more effective than the structure with an allyl isothiocyanate (AIT) generator. Listeria populations in the packaging structure with the O2 scavenger were 1.80–2.65, 3.69–4.76, and 4.62–4.67 log CFU g−1 lower than the controls at 4, 10, or 22 °C. Samples in the packaging structure with the CO2 generator were 1.11–1.63, 4.30–4.45, and 4.01–4.44 log CFU g−1 lower than the controls at 4, 10, or 22 °C. Significant inhibitions on total aerobic bacteria and Enterobacteriaceae counts were also observed in packaging structures with the CO2 generator and O2 scavenger. However, packaging structures with the AIT generator only significantly inhibited L. monocytogenes, total aerobic bacteria, and Enterobacteriaceae in some samples, mainly those stored at 22 °C. These results suggest that some of the evaluated packaging structures can effectively control bacterial populations, particularly Listeria populations on RTE meat products.

IMPROVING FOOD THERMAL PROCESSING: A DEATH-TIME STUDY ON PROCESSED MEAT PRODUCTS

ABSTRACT Ready-to-eat (RTE) meat products, consumed directly or after warming, are a source for the transmission of Listeria monocytogenes. With the growing demand and the increasing variety of RTE meat products, the food industries face serious challenges with regard to their safety. The appropriate application of heat treatments becomes an essential issue for food processors. However, quantitative data on thermal inactivation of pathogenic and spoilage microorganisms in different meat products cannot be extrapolated directly because of the particularities of the formulations, the variability of heat resistance among bacterial strains, and the heating procedures. Therefore, the heat resistance parameters (D and z values) of L. monocytogenes, Lactobacillus delbrueckii and accompanying microflora in meat slurry were established in order to provide more accurate F values and improve operation conditions. Results showed overprocessing. L. delbrueckii had the largest z value (9.3C) and adjusted F values of 2.4 and 3.8 min would render hot dogs and cured coarse sausages safe. PRACTICAL APPLICATIONS Thermal processing is still the dominant technology to assure food safety. However, consumer demands for more convenient, easy-to-prepare food with whole nutritional content drive to reevaluate and improve commercial processes. In this study, the heat resistance of target microorganisms in a meat product was calculated and modeling was used to assess and document process lethality. This study may assist the meat industry in the quantification of bacterial lethalities and the proper design of thermal processes.