Temperature Abuse Conditions Research Articles

Reuterin, lactoperoxidase, lactoferrin and high hydrostatic pressure on the inactivation of food-borne pathogens in cooked ham

The antimicrobial effect of high hydrostatic pressure (HHP) processing combined with reuterin, lactoperoxydase system (LPS) and lactoferrin (LF) on the survival of Listeria monocytogenes, Salmonella enterica subsp. enterica serovar Enteritidis and Escherichia coli O157:H7 in sliced cooked ham stored under strict refrigeration temperature (4 °C) and mild temperature abuse conditions (10 °C) was investigated. One day after treatment, L. monocytogenes counts in HHP at 450 MPa for 5 min were 0.8 log units lower, but a recovery was observed with counts not significantly different to those observed in control after 35 d. S. Enteritidis and E. coli O157:H7 levels were reduced around 5 log cfu/g by the pressure treatment (450 MPa/5 min) and the numbers of these pathogens did not increase significantly during the 35 d of storage at 4 °C. The individual application of reuterin and LPS influenced the survival of the three pathogens studied, extending the lag phase of L. monocytogenes and diminishing S. Enteritidis and E. coli levels throughout storage, whereas no effect was recorded when LF was added. When reuterin or LPS were applied in combination with HHP there was a synergistic antimicrobial effect against L. monocytogenes, avoiding at 4 °C the recovery observed with individual treatments. These combined treatments also kept the levels of S. Enteritidis and E. coli O157:H7 below the detection limit (<1 log unit) in cooked ham stored at 4 and 10 °C during 35 d. The results obtained in the present work suggest that HHP at 450 MPa for 5 min in combination with LPS or reuterin would be useful as a hurdle technology approach against L. monocytogenes, S. Enteritidis and E. coli O157:H7 in cooked ham.

Effect of higher temperature exposure on physicochemical properties of frozen buffalo meat

Aim: The aim was to study the changes in various physicochemical parameters of frozen buffalo meat undergone temperature abuse at two different isothermal storage temperatures (37±1°C, 25±1°C) using a simulated model. Materials and Methods: Frozen buffalo meat was evaluated after exposing to various temperature abuse conditions over selected durations for different meat quality parameters including pH, extract release volume (ERV), flourescein diacetate (FDA) hydrolysis, free amino acid (FAA), total volatile basic nitrogen (TVBN) and D-glucose value and compared against a control sample maintained at 4±1°C. Results: Of the various meat quality parameters evaluated pH, FDA hydrolysis, FAA content and TVBN content showed a significant (p<0.05) increase in temperature abused samples after temperature abuse and on subsequent refrigerated storage. However, ERV and D-glucose content decreased significantly (p<0.05) in temperature abused buffalo meat during the same period of study. Conclusions: The present study featured the influence of exposure temperature and duration in various physicochemical parameters and the rate of spoilage development in frozen buffalo meat after temperature abuse.

Quality Perceptions of Stakeholders in Beninese Export-Oriented Shrimp Chain

In recent years, the Beninese shrimp sector has faced a ban on export to the European Union due to lack of compliance with food safety standards. The present study aimed at obtaining insight into the factors that determine shrimp quality and safety in Benin. A survey was conducted to investigate the relationships between stakeholders, the conditions under which shrimps are handled at fishing areas and processed at shrimp plants, and the stakeholders' perceptions of quality. A total of 325 fishermen, 128 intermediate traders, 12 collectors, and 3 shrimp processing plant managers were interviewed face to face. The results showed that various specific relations existed between the stakeholders. For example, loyalty was ensured by family relationships, or incentives were provided to ensure a supply of shrimps between stakeholders. Shrimp handling practices during the steps prior to shrimp processing at the plants were not in agreement with the requirements of the European regulations. For example, shrimps were kept at ambient temperature (28 ± 1°C) by 94.1% of fishermen and 60.9% of intermediate traders. Shrimps were also stored in inappropriate holding containers and washed with nonpotable water. Fishermen, intermediate traders, and collectors considered shrimp size and texture their priority quality attributes, whereas plant managers considered shrimp appearance (freshness) and texture their priority quality attributes. This survey demonstrated that the steps prior to shrimp processing at the plants are the critical steps for shrimp quality and safety because of temperature abuse and inappropriate hygienic conditions. There is a need to communicate and provide incentives for the stakeholders in the first part of the chain to give priority to shrimp freshness. Moreover, training in Good Fishing Practices and safe food handling practices and evaluation of compliance with the practices through monitoring will contribute to better shrimp quality and safety management.

Shelf-life extension of vacuum-packaged meat from pheasant (Phasianus colchicus) by lactic acid treatment

We investigated the influence of lactic acid treatment of pheasant meat before vacuum-packaged storage of 3, 7, and 10 d at +6°C on microbiota and pH. Breast muscle samples were collected from carcasses of slaughtered as well as from hunted (shot) wild pheasants. Immersion of meat samples in 3% (wt/wt) lactic acid for 60 s effectuated a significant drop in pH of approximately 0.5 to 0.7 units, which remained during the entire storage period. In parallel, total aerobic counts of such treated and stored samples were on an average 1.5 to 1.7 log units lower than in non-acid-treated samples. Similar results were found for Enterobacteriaceae. A significant decrease in pH was measured at d 7 and 10 in the acid-treated samples in comparison with the untreated ones. In summary, the immersion of pheasant breast meat cuts in dilute lactic acid significantly reduced microbiota during vacuum-packed storage, even at slight temperature abuse conditions.

Effect of various decontamination treatments against Gram-positive bacteria on chicken stored under differing conditions of temperature abuse

The aim of this research was to compare the effectiveness of various chemical decontamination treatments against pathogenic and spoilage Gram-positive bacteria on poultry during storage under different simulated cold chain disruptions. The effect of dipping treatments (15 min; 20 °C) in aqueous solutions of 12% trisodium phosphate (TSP), 1200 ppm acidified sodium chlorite (ASC), 2% citric acid (CA), 220 ppm peroxyacids (PA) or 50 ppm chlorine dioxide (CD) was tested against Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus and Brochothrix thermosphacta artificially inoculated onto skinless chicken legs. Samples were stored for 120 h under three different simulated temperature abuse conditions: T1 (12 h at 1 ± 1 °C, followed by 6 h at 15 ± 1 °C and then 102 h at 4 ± 1 °C), T2 (18 h at 1 ± 1 °C, 6 h at 15 ± 1 °C and 96 h at 10 ± 1 °C) or T3 (18 h at 4 ± 1 °C, 6 h at 20 ± 1 °C and 96 h at 7 ± 1 °C). Microbiological analyses and pH determinations were carried out at 0, 24, 72 and 120 h of storage. TSP, ASC and CA reduced (P < 0.05) microbial populations, relative to control (untreated) samples, whereas PA and CD caused far less noteworthy reductions, independently of the temperature abuse condition selected. Under condition T1 (mild abuse) TSP exerted the highest antimicrobial effect among the decontaminants tested, while ASC showed the highest effectiveness under conditions T2 and T3 (moderate abuse). These findings extend knowledge about the behaviour of various chemical decontaminants under non-ideal storage situations, which very often occur in the poultry supply chain.

Antimicrobial activity of reuterin produced by Lactobacillus reuteri on Listeria monocytogenes in cold-smoked salmon

Lactobacillus reuteri INIA P579 was used for the production and purification of reuterin. The purity of reuterin was assessed by high resolution electrospray ionization mass spectrometry (HRESIMS) and nuclear magnetic resonance (NMR) spectroscopy. After purification, reuterin concentration obtained was 1.3 M. The inhibitory activity using Escherichia coli K12 as indicator strain was estimated to be 510 AU/ml. Survival curves in tryptic soy broth revealed that reuterin required to inhibit the growth of three Listeria monocytogenes strains was in the range of 2–4 AU/ml. Purified reuterin (10 AU/g) significantly reduced the growth of L. monocytogenes in cold-smoked salmon kept under moderate or strong temperature abuse conditions. After 15 d at 8 °C, cold-smoked salmon with added reuterin exhibited L. monocytogenes counts 2.0 log CFU/g lower than control smoked salmon with no reuterin added. At 30 °C, reuterin also controlled the growth of the pathogen, with counts 1.4 and 0.9 log CFU/g lower than those observed in control smoked salmon after 24 and 48 h, respectively. The addition of purified reuterin might be used as a hurdle technology to improve the safety and extend the shelf-life of lightly preserved seafood products such as cold-smoked salmon.

Postharvest transfer and survival of Salmonella enterica serotype enteritidis on living lettuce.

The potential for postharvest transfer of Salmonella to 'living lettuce' is not well understood. In this study, the transfer of Salmonella enterica Enteritidis (6 log CFU g(-1) ) from worker hands or contaminated roots to leaves of living lettuce was quantified. Transfer rates of Salmonella from contaminated gloves to sequentially handled lettuce heads ranged from 94% to head 1, 82% to head 2 and 69% to head 3. On average, 2.9 ± 0.1 log CFU g(-1) (64%) Salmonella was transferred from inoculated roots to leaves resulting from typical postharvest handling activities for living lettuce. Salmonella persisted on leaves stored at recommended storage temperatures (4°C) and increased 0.5 log CFU g(-1) when stored at temperature abuse conditions (12°C). Salmonella increased 1.6 log CFU g(-1) on roots after 18-day storage at 12°C, emphasizing the need to maintain temperature control to reduce the risk of human illness. Hydroponically grown lettuce packaged in plastic clamshells with intact roots, marketed as 'living lettuce', is increasing in popularity due to its extended shelf life. This study demonstrates the transfer of Salmonella from contaminated worker hands and contaminated roots to leaves where it persisted at 4°C for 18 day. Temperature abuse (12°C) increased Salmonella on roots and leaves. These findings suggest that failure to maintain temperatures below 12°C can pose a risk for consumers purchasing living lettuce at markets where recommended storage temperatures are not maintained.

Combined treatments of high-pressure with the lactoperoxidase system or lactoferrin on the inactivation of Listeria monocytogenes, Salmonella Enteritidis and Escherichia coli O157:H7 in beef carpaccio

The effect of high hydrostatic pressure (HHP) treatments in combination with the lactoperoxidase system (LPOS) or activated lactoferrin (ALF) on Listeria monocytogenes, Salmonella enterica subsp. enterica serovar Enteritidis and Escherichia coli O157:H7 was investigated in cured beef carpaccio stored at 8 °C or 22 °C during 7 d. HHP (450 MPa for 5 min) reduced pathogen levels by 1–3 log units and the antimicrobial effect remained during 7 d of storage under temperature abuse conditions at 8 °C and at 22 °C. The individual application of LPOS and ALF did not affect the survival of the three pathogens studied during storage. However, a synergistic bactericidal interaction between LPOS and HHP was observed against S. Enteritidis and E. coli O157:H7. Combined treatments of HHP with LPOS would be useful to reduce the intensity of pressurization treatments diminishing changes in the quality of meat products.

Investigación de Bacillus cereus y calidad sanitaria de muestras de arroz cocido recolectadas en diferentes establecimientos de la ciudad de Puebla

Bacillus cereus es reconocido como un agente patógeno causante de intoxicaciones alimentarias. Se han presentado brotes asociados al consumo de arroz contaminado con ésta bacteria. Es uno de los pocos patógenos con capacidad de deteriorar los alimentos. En un brote ocurrido en 1994, en el Estado de Puebla, las personas afectadas manifestaron haber consumido arroz ácido o agrio. Se determinó la calidad sanitaria de 50 muestras de arroz cocido recolectadas en diferentes establecimientos de la ciudad de Puebla (hogares, fondas, tortillerías y supermercados). El recuento de B. cereus se realizó en el agar MYP (manitol, yema de huevo polimixina), los recuentos de bacterias mesofílicas aerobias y bacterias coliformes totales, se realizaron siguiendo la metodología oficial vigente. Se obtuvieron recuentos elevados de bacterias mesofílicas aerobias (&gt; 106 UFC/g) en el 22 % de las muestras, y en el 44 % se demostró la presencia de bacterias coliformes totales. En el 10 % de la muestras se recuperó B. cereus. Aun en cifras muy por debajo de las consideradas como un riesgo para la salud, si se almacena enCondiciones de abuso de temperatura, como suele ocurrir en los sitios muestreados el arroz contaminado puede representar un riesgo a la salud del consumidor.

Effects of temperatures and storage time on resting populations of Escherichia coli O157:H7 and Pseudomonas fluorescens in vitro

Assessment of microbial interactions is crucial for documenting bacterial growth in pure and mixed cultures and their potential for biological applications. Pseudomonas fluorescens (non-plant pathogenic and non-pectinolytic) has been used as a biocontrol microbe for plant pathogens and food-borne bacteria. We determined the growth of Escherichia coli O157:H7 (Ec) and P. fluorescens(Pf) in monocultures and co-cultures in sterile distilled water (SDW), buffered peptone water (BPW) and trypticase soy broth (TSB). The effects of temperatures (5, 10, 15, 20, 25, 35, and 37 °C) and storage time (0, 2, 4, 6, 24, and 48 h) on bacteria populations were assessed. Bacteria counts in monocultures in SDW ranged from 2.14 to 3.03 and 2.54 to 3.31 Log CFU/ml for Ec and Pf; respectively. In BPW, mean bacteria counts (monocultures) ranged from 3.15 to 6.14 and 2.54 to 6.41 Log CFU/ml for Ec and Pf, respectively. Ec populations in co-culture varied with storage temperatures and time. After 48 h, Ec 43894 monocultures in TSB ranged from 2.17 to 8.75 and 2.31 to 8.85 Log CFU/ml at 20 and 35 °C; respectively. In co-cultures with Pf 2-79, Ec 43894 counts ranged from 1.71 to 5.83 (20 °C) and 1.90 to 9.03 Log CFU/ml (35 °C) in TSB. The reductions of Ec by Pf 2-79 varied among strains and generally ranged from 0.20 to 0.90, 0.63 to 1.18, and 0 to 0.56 Log CFU/ml in BPW (10 °C). Substrate availability, storage temperatures, and time significantly (P < 0.05) impacted Ec populations in co-culture. The liquid substrate experiments indicated suppressive conditions of Ec by Pf, however; the reduction of produce contamination by E. coli O157:H7 during transitory temperature abuse conditions such as the transportation of produce from fields needs further investigation.

Monitoring and modelling of headspace-gas concentration changes for shelf life control of a glass packaged perishable food

Gas concentrations in the headspace of hermetically sealed glass packages of seasoned soybean sprouts were monitored and related to their microbial quality, i.e., the change in aerobic bacterial count, in order to examine the potential for using package gas changes as a primary quality index for shelf life control. Aerobic bacterial count, CO2 and O2 concentrations were measured from packages stored at four different temperatures: 0, 5, 10 and 15 °C. The CO2 concentration increased and the O2 concentration decreased with microbial growth. The microbial growth and CO2 concentration change were described by a logistic function to yield kinetic parameters, and their temperature dependence was analysed by a square-root model. The kinetic parameters for microbial growth and CO2 production differed in their magnitude and temperature dependence. The lag time observed for the increase in CO2 concentration could be used as a shelf life index that corresponds to the time to reach a given microbial limit (here, 107 CFU/g) under different temperature conditions, particularly under conditions of temperature abuse.

Effectiveness of several chemical decontamination treatments against Gram-negative bacteria on poultry during storage under different simulated cold chain disruptions

Five chemical compounds – 12% trisodium phosphate (TSP), 1200 ppm acidified sodium chlorite (ASC), 2% citric acid (CA), 220 ppm peroxyacids (PA) and 50 ppm chlorine dioxide (CD) – were analyzed to determine their effectiveness against Gram-negative bacteria (Salmonella enterica serotype Enteritidis, Yersinia enterocolitica, Escherichia coli and Pseudomonas fluorescens) artificially inoculated on skinless chicken legs. Samples were stored for 120 h under three different simulated cold chain disruptions: T1 (12 h at 1 ± 1 °C, followed by 6 h at 15 ± 1 °C and then 102 h at 4 ± 1 °C), T2 (18 h at 1 ± 1 °C, 6 h at 15 ± 1 °C and 96 h at 10 ± 1 °C) or T3 (18 h at 4 ± 1 °C, 6 h at 20 ± 1 °C and 96 h at 7 ± 1 °C). Microbiological analyses and pH determinations were carried out at 0, 24, 72 and 120 h of storage. TSP, ASC and CA significantly (P < 0.05) reduced microbial populations, relative to control (untreated) samples. TSP and ASC caused higher (P < 0.05) reductions of S. enterica than CA under moderate temperature abuse conditions (T2 and T3). TSP and ASC (T2) or TSP and CA (T1 and T3) were the most effective compounds against E. coli. TSP and ASC showed the highest antimicrobial effect (P < 0.05) at mild temperature abuse conditions (T1) for Y. enterocolitica, while ASC was the most active compound against this pathogen under T2 and T3 conditions. TSP caused the largest average reductions of Ps. fluorescens at T1. PA and DC originated scant microbial reductions under all of the conditions proposed. These findings extend current knowledge about these chemical decontaminants, and may help the Regulatory Authorities in their decisions about the poultry decontamination authorization process within the European Union.

Inactivation of Escherichia coli O157:H7 in dry-cured ham by high-pressure treatments combined with biopreservatives

The effect of high-pressure (HP) treatments combined with biopreservatives such as a commercial nisin or pediocin on the survival of Escherichia coli O157:H7 and the physicochemical, rheological and color characteristics of sliced dry-cured ham stored under mild temperature abuse conditions (8 °C) was investigated. Immediately after treatments, a synergistic antimicrobial effect was registered when 400 MPa and 500 MPa for 10 min combined with nisin were applied. After 60 d, this synergistic effect was only maintained with the combined treatment of 500 MPa and nisin. Counts of E. coli in dry-cured ham were not affected by either nisin or pediocin applied individually, whereas counts in pressurized samples were 3 log units lower than in non-treated dry-cured ham after 60 d of refrigerated storage. Changes in textural parameters caused by pressurization and biopreservatives were minor. Lightness (L*) values were slightly affected, with lower values in samples pressurized at 500 MPa in combination with bacteriocins and a trend to decrease during storage. Redness (a*) and yellowness (b*) were less modified by HP and biopreservatives and tended to diminish during refrigeration. The results obtained in the present work demonstrate the effectiveness of pressurization of sliced dry-cured ham at 500 MPa for 10 min combined with nisin on the inactivation of E. coli O157:H7.

Prevalence and Levels of Bacillus cereus Emetic Toxin in Rice Dishes Randomly Collected from Restaurants and Comparison with the Levels Measured in a Recent Foodborne Outbreak

Whereas the prevalence of Bacillus cereus emetic strains in the environment has been shown to be very low, there is a lack of information on the prevalence of its toxin, cereulide, in food. Yet, the rice leftovers of a family outbreak which occurred after the consumption of dishes taken away from an Asian restaurant revealed significant amounts of cereulide, reaching up to 13,200 ng/g of food. The occurrence of cereulide in rice dishes collected from various restaurants was therefore evaluated using the liquid chromatography coupled with tandem mass spectrometry method, which allows for the direct quantification of the toxin in food. The cereulide prevalence was found to be 7.4% when samples were analyzed at the day of sampling, but reached 12.9% when exposed to temperature abuse conditions (25°C). The cereulide concentrations observed in cooked rice dishes were low (approximately 4 ng/g of food). However, since little is known yet about the potential chronic toxicity of cereulide, one needs to be very careful and vigilant.

High pressure treatments on the inactivation of Salmonella Enteritidis and the characteristics of beef carpaccio

The effect of high pressure (HP) on Salmonella enterica subsp. enterica serovar Enteritidis in beef carpaccio stored under temperature abuse conditions (8°C) during 30days was investigated. After treatment, reductions of S. Enteritidis were 3.68 and 5.94 log cfu/g in samples pressurized at 450MPa for 5 and 10min, respectively, whereas the pathogen was only detected after enrichment of samples treated at 450MPa for 15min. During storage, counts of S. Enteritidis decreased 0.26 log cfu/g in non-pressurized carpaccio, 1.33 log cfu/g in carpaccio treated at 450MPa for 5min and were only detected after enrichment in carpaccio pressurized at 450MPa for 10 or 15min. Color (L*, a* and b*) varied with pressurization and storage, with higher changes in carpaccio treated at longer pressurization times. Shear resistance was slightly lower in treated samples just after pressurization, but increased at the end of the storage period. Maximum force was less affected by treatment.

Survival and germination of Clostridium perfringens spores during heating and cooling of ground pork.

The effect of heating rate on the heat resistance, germination, and outgrowth of Clostridium perfringens spores during cooking of cured ground pork was investigated. Inoculated cured ground pork portions were heated from 20 to 75°C at a rate of 4, 8, or 12°C/h and then held at 75°C for 48 h. No significant differences (P > 0.05) in the heat resistance of C. perfringens spores were observed in cured ground pork heated at 4, 8, or 12°C/h. At heating rates of 8 and 12°C/h, no significant differences in the germination and outgrowth of spores were observed (P > 0.05). However, when pork was heated at 4°C/h, growth of C. perfringens occurred when the temperature of the product was between 44 and 56°C. In another set of experiments, the behavior of C. perfringens spores under temperature abuse conditions was studied in cured and noncured ground pork heated at 4°C/h and then cooled from 54.4 to 7.2°C within 20 h. Temperature abuse during cooling of noncured ground pork resulted in a 2.8-log CFU/g increase in C. perfringens. In cured ground pork, C. perfringens decreased by 1.1 log CFU/g during cooling from 54.4 to 36.3°C and then increased by 0.9 log CFU/g until the product reached 7.2°C. Even when the initial level of C. perfringens spores in cured ground pork was 5 log CFU/g, the final counts after abusive cooling did not exceed 3.4 log CFU/g. These results suggest that there is no risk associated with C. perfringens in cured pork products under the tested conditions.

DETERMINATION OF THE QUALITY AND SHELF LIFE OF SOUS VIDE PACKAGED WHITING (MERLANGIUS MERLANGUS EUXINUS, NORDMAN, 1840) STORED AT COLD (4C) AND TEMPERATURE ABUSE (12C)

ABSTRACT The effect of storage temperature on the shelf life of sous vide packaged (70C, 10 min) whiting was determined. Samples stored at 12 ± 1C spoiled according to sensory test on the 21st day, when mesophilic aerobic bacteria and trimethylamine nitrogen (TMA-N) exceeded the limits. However, their consumption is not advisable after 15 days because psychrophilic counts exceeded the recommended limits at that day. In cold storage (4 ± 1C) Total volatile basic nitrogen and TMA-N, values of the samples exceeded the limits on the 42nd day. However, because samples spoiled according to sensory test, and mesophilic and psychrophilic aerobic bacterial counts were above the limits, shelf life was considered as 35 days. Sous vide cooking at 70C for 10 min could extend significantly the shelf life of whiting both at 4C and temperature-abuse conditions (12C). PRACTICAL APPLICATIONS Sous vide is a long established but relatively little-known cooking process. The data regarding the effect of storage temperature on the shelf life and quality of sous vide fish are very limited. Therefore, this study aimed to determine the sensory, microbiological and chemical quality of sous vide packaged whiting during refrigerated storage (4 ± 1C) and temperature-abuse temperature conditions (12 ± 1C). The results of this study can be utilized by researchers in future studies as well as by manufacturers to determine the processing and storage conditions of sous vide fish.

Incidence, diversity and toxin gene characteristics of Bacillus cereus group strains isolated from food products marketed in Belgium

The major objectives of this study were to determine the incidence, diversity and characteristics of Bacillus cereus group spp. isolated from food products marketed in Belgium. The food products investigated in this study included cooked pasta, lasagna, béchamel sauce, bolognaise sauce, fresh minced beef, fresh-cut vegetables and raw basmati rice. B. cereus group spp. were detected in 56.3% (324 of 575) of the samples giving rise to 380 strains. The highest incidence (100%) occurred in the raw basmati rice. Although only 10 (2.6%) of the 380 isolates were determined to be psychrotolerant (able to grow at ≤7°C), 25 (6.2%), 189 (49.7%) and 334 (87.9%) isolates were able to grow at mild temperature abuse conditions of 8°C, 9°C and 10°C, respectively. The large diversity of the isolates obtained (overall and between isolates obtained from the same product type) was highlighted by the results of the (GTG)(5) PCR fingerprinting of 80 selected isolates. Sixty-one of these 80 isolates belonged to 15 distinct clusters (≥85% Pearson correlation) whereas the remaining 19 were each clustered separately. Further diversity was also found in the distribution of toxin genes as 16 different profiles were observed in the 80 selected isolates. Whilst none of 80 selected strains harboured the ces gene required for the production of the emetic toxin cereulide, 42 strains (52.5%) carried all seven genes required for the production of the diarrhoeal enterotoxins: haemolytic BL, non-haemolytic enterotoxin and cytotoxin K. The results of this study highlight not only the omnipresence but also the highly diverse ecology of B. cereus spp. within and across several food product types available on the retail market in Belgium. They should also provide the impetus for more studies to enable detailed risk assessment studies to be performed.

Combination of bioprotective cultures with EDTA to reduce Escherichia coli O157:H7 in frozen ground-beef patties

The effectiveness of bacteriocin-producing Lactobacillus curvatus CRL705 and Lactococcus lactis CRL1109 in combination with Na2EDTA on frozen ground-beef patties contaminated with Escherichia coli O157:H7, was investigated under temperature abuse conditions (5 °C during 9 days). The presence of the bioprotective cultures (ca. 107 CFU/g) and chelator (48 mM) resulted in one log CFU/g reduction for E. coli strain, compared to the control on day 0. Similarly, a significant decline for indigenous coliforms in ground-beef patties was also observed in the presence of bacteriocinogenic strains and chelator. However, in the absence of Na2EDTA, neither E. coli nor coliforms were inhibited by the bioprotective cultures, the pathogen reaching similar counts than control samples (5.22 and 3.60 log CFU/g, respectively) at 9 days. When the growth of bacteriocinogenic strains on patties was evaluated, they were able to increase their population producing bacteriocins after 48 h up to the end of incubation period while a near neutral pH in the presence of Na2EDTA was detected. Non substantial effect on of ground-beef patties color was produced in the presence of bioprotective cultures, while a darker color developed in those added with the chelator. The simultaneous treatment with bioprotective cultures and Na2EDTA may be of value for the control of E. coli O157:H7 in temperature abused ground-beef patties.

Growth characteristics of Listeria monocytogenes as affected by a native microflora in cooked ham under refrigerated and temperature abuse conditions

This study examined the growth characteristics of Listeria monocytogenes as affected by a native microflora in cooked ham at refrigerated and abuse temperatures. A five-strain mixture of L. monocytogenes and a native microflora, consisting of Brochothrix spp., isolated from cooked meat were inoculated alone (monocultured) or co-inoculated (co-cultured) onto cooked ham slices. The growth characteristics, lag phase duration (LPD, h), growth rate (GR, log 10 cfu/h), and maximum population density (MPD, log 10 cfu/g), of L. monocytogenes and the native microflora in vacuum-packed ham slices stored at 4, 6, 8, 10, and 12 °C for up to 5 weeks were determined. At 4–12 °C, the LPDs of co-cultured L. monocytogenes were not significantly different from those of monocultured L. monocytogenes in ham, indicating the LPDs of L. monocytogenes at 4–12 °C were not influenced by the presence of the native microflora. At 4–8 °C, the GRs of co-cultured L. monocytogenes (0.0114–0.0130 log 10 cfu/h) were statistically but marginally lower than those of monocultured L. monocytogenes (0.0132–0.0145 log 10 cfu/h), indicating the GRs of L. monocytogenes at 4–8 °C were reduced by the presence of the native microflora. The GRs of L. monocytogenes were reduced by 8–7% with the presence of the native microflora at 4–8 °C, whereas there was less influence of the native microflora on the GRs of L. monocytogenes at 10 and 12 °C. The MPDs of L. monocytogenes at 4–8 °C were also reduced by the presence of the native microflora. Data from this study provide additional information regarding the growth suppression of L. monocytogenes by the native microflora for assessing the survival and growth of L. monocytogenes in ready-to-eat meat products.