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The Canadian Food Inspection Agency is developing an Establishment-based Risk Assessment (ERA) model for commercial and on-farm mills involved in the manufacture, storage, packaging, labeling, or distribution of livestock feed (ERA-Feed Mill model). This model will help inform the allocation of inspection resources on the basis of feed safety risk, including animal health and food safety risk. In a previous study, 34 risk factors, grouped into inherent, mitigation, and compliance clusters, along with assessment criteria were selected. The objective of this current study was to estimate the relative risk (RR) of the 203 assessment criteria on the basis of the impact on feed safety to design an ERA-Feed Mill model algorithm. Furthermore, the intent of this study was to assess the maximum increase or decrease of risk obtained when multiple criteria belonging to a same cluster were identified in a specific feed mill. To do so, a two-round face-to-face expert elicitation was conducted with 28 Canadian feed experts. Results showed no significant association between respondent profiles (years of experience and work sector) and estimated RR. Uniformity of answers between experts improved between rounds. Criteria having the highest increase in risk (median RR ≥ 4) included the presence of materials prohibited to be fed to ruminants in a facility that produces ruminant feed, the presence of multiple livestock species on-site, and historical noncompliances related to the inspection of the feed mill's process control and end-product control programs. Risk mitigation criteria having the highest impact on decreasing the risk were the implementation of feed safety certifications, the use of dedicated manufacturing lines (prohibited materials or medications), and having a hazard sampling plan in place for finished feed. The median RR assigned to each criterion and cluster will be used to build an algorithm of the Canadian Food Inspection Agency's ERA-Feed Mill model. HIGHLIGHTS

The Canadian Food Inspection Agency (CFIA) is developing a risk assessment model aimed at quantifying the food safety risk associated with food establishments under its jurisdiction. To support the development of this model, the current study was undertaken to quantify the relative importance of selected criteria considered for inclusion in the model. This process also aimed at estimating the risk associated with specific clusters of criteria. Overall, 173 criteria were presented to experts during a two-round face-to-face expert elicitation to estimate their relative risk to human health. Twenty-nine Canadian experts participated in the expert elicitation including members from academia (31%), industry (31%), and government (38%). A good consensus on the relative risks given to most criteria and clusters of criteria was achieved, and experts assessed them as significantly affecting the risk related to a food establishment. None of the experts expressed opposition to the inclusion of any criterion or to the way they were clustered. Experts assigned a relative risk of ≤4, of 4–8, and of ≥8–67% (116), 29.5% (51), and 3.5% (6) of the 173 criteria identified, respectively. Those having the highest impact on establishment food safety risk were: historical food safety recalls and lack of compliance for the sanitation program, the control of critical control points, followed by the equipment maintenance and calibration program, and the general food hygiene program. Having a sampling plan with trend analysis and follow-up actions was considered as an important mitigation factor. As a result, the median values calculated for each criterion and cluster will be used in the new Canadian Food Inspection Agency Establishment-based risk assessment model to support the allocation of inspection resources based on risk.

Biofilms are known to play important roles in bacterial survival and persistence in food-processing environments. This study aimed to determine the ability of the top 7 STEC serotypes to form biofilms on polystyrene (POL) and stainless steel (SS) plates and to quantify their survival and transfer from dry-surface biofilms to lettuce pieces. The ability of 14 STEC strains to form biofilms on these two materials at different exposure times and temperatures was assessed using crystal violet, Congo red and SEM. At 10 °C all serotypes were weak biofilm producers on both surfaces. In contrast, serotypes O45-040, O45-445, O103-102, O103-670 and O157-R508 were strong biofilm producers at 25 °C. Strains O103-102, O103-670, O111-CFS, O111–053 and O157:H7-R508 were expressers of curli. Under scanning electron microscopy, strains O103-670, O111-CFS, O157-R508, and O121-083 formed more discernible multilayer, mature biofilms on SS coupons. Regardless of the surface (POL/SS), all STEC strains were able to transfer viable cells onto fresh lettuce within a short contact time (2 min) to varying degrees (up to 6.35 log cfu/g). On POL, viable cell of almost all serotypes exhibited decreased detachment (p = 0.001) over 6 days; while after 30 days on SS, serotypes O45-040, O103-102, O103-670, O111-053, O111-CFS, O121-083, O145-231 O157:H7-R508 and O157:H7-122 were transferred to lettuce. After enrichment, all 14 STEC strains were recovered from dry-surface biofilms on POL and SS plates after 30 days. Results demonstrated that the top 7 STEC remained viable within dry-surface biofilms for at least 30 days, transferring to lettuce within 2 min of exposure and acting as a source of adulteration.

Health claims for barley β-glucan (BG) have prompted the development of food products containing barley; however, some new products (such as milled grain used without a cook step, as in a smoothie) do not use any form of heat treatment during processing or prior to consumption, which could affect microbial safety and potential health benefits. The aims of this research were to evaluate current commercial barley products for microbial counts and BG characteristics and to determine the effects of different heat treatments on these attributes in whole grain barley samples. Three heat treatments (micronization, roasting, and conditioning) were performed on three cultivars of barley (CDC Rattan, CDC McGwire, and CDC Fibar). The microbial quality was measured with standard plate count (SPC), mold and yeast count (MYC), and coliforms or Escherichia coli. Only four of the 17 commercial barley products tested met acceptable microbial limits used in this study. All three heat treatments applied to the barley sample...

Fresh pork loin slices were packaged under three different anoxic atmospheres (100% N 2 , 100% CO 2 and 50% N 2 +50% CO 2 ) and kept at two storage temperatures (-1 o C and 4 o C) and two pressures (1.0 and 1.2 atm.) in reusable, gas impermeable metal boxes. A gas headspace to meat weight ratio of >31 per kg was maintained. Carbon dioxide concentrations were unchanged (controlled) during storage. Microbiological, biochemical and physical measurements were made during the 3-week storage period. While atmospheric pressure did not have a significant impact on shelf-life, samples stored at -1 o C were satisfactory at 21 days in both CO 2 treatments. Samples under N 2 did not fare so well, showing higher levels of psychrotrophic bacteria after 18 days at -1 o C and 14 days at 4 o C. Samples kept in N 2 at 4 o C were spoiled within 2 weeks. Bacterial growth was slowest under 100% CO 2 , but samples stored under 50%-50% N 2 -CO 2 at 4 o C were also observed to be in good microbiological condition at 21 days of storage. Use of CO 2 -containing atmospheres provided more than 7 extra days of shelf-life at 4 o C over that attainable under 100% N 2 . Shelf-life at -1 o C was improved by 3 to 4 days over that at 4°C. Except for the length of time in storage, treatments had only a minor effect on pH, color, water holding capacity and shear force. These physicochemical characteristics were not factors which limited shelf-life

The safety of livestock feed is recognized worldwide as a prerequisite for the protection of animal and human health. In this context, the Canadian Food Inspection Agency is developing an Establishment-based Risk Assessment model for livestock feed mills (ERA-Feed Mill) to assist in the allocation of inspection resources based on feed safety risk. The objectives of the present study were to identify and select animal health and food safety-related risk factors along with their assessment criteria, pertaining to Canadian feed mill practices, to be included in the ERA-Feed Mill model. To do so, a review of the scientific literature and consultations with feed experts were conducted. A final list of 34 risk factors was generated, 21 identified from the scientific literature and 13 from feed expert advice. Risk factors were grouped into three clusters: inherent risk factors, mitigation factors and compliance factors for which 4, 10 and 20 factors were identified, respectively. Criteria for quantitatively assessing each risk factor were defined based on common practices found in the Canadian feed industry. These findings contributed to the initial steps of the CFIA's ERA-Feed Mill model development. By assessing the feed safety risk factors related to feed mills in Canada, this tool will help inform the CFIA on the level of oversight required to manage these risks, and will contribute to the production and maintenance of healthy livestock and the production of safe food.

UNLABELLED Listeria monocytogenes is an important foodborne pathogen that can cause infection in children, pregnant women, the immunocompromised and the elderly. Antibiotic resistance in this species would represent a significant public health problem since the organism has a high fatality/case ratio and resistance may contribute to failure of therapeutic treatment. This study was designed to explore whether the in vitro transferability of antibiotic resistance from enterococci to Listeria spp. could occur. It was found that 2/8 Listeria strains were able to acquire tetracycline resistance from Enterococcus faecium. Listeria monocytogenes GLM-2 acquired the resistance determinant tet(M) and additional streptomycin resistance through in vitro mating with Ent. faecium S27 isolated from commercial fermented dry sausage. Similarly, Listeria innocua became more resistant to tetracycline, but the genetic basis for this change was not confirmed. It has been suggested that enterococci may transfer antibiotic resistance genes via transposons to Listeria spp., and this may explain, in part, the origin of their antibiotic resistance. Thus, the presence of enterococci in food should not be ignored since they may actively contribute to enhanced antibiotic resistance of L. monocytogenes and other pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY Acquisition of antibiotic resistance by pathogenic bacteria in the absence of antibiotic pressure represents an unquantified threat to human health. In the present work resistance to tetracycline and streptomycin were transferred by nonplasmid-based conjugation from Enterococcus faecium isolated from fermented sausage to Listeria monocytogenes and Listeria innocua. Thus, natural transfer of antibiotic resistance to Listeria strains may occur in the future which reinforces the concern about the safety of enterococcal strains present in foods.

The purpose of this study was to determine the effectiveness of a commercial Salmonella bacteriophage mixture (SalmoFresh™ 6-phage strains) and to compare its effectiveness with a chlorinated water treatment to reduce Salmonella on produce and seeds at different temperatures and storage times. Two sets of experiments were designed to test phage and chlorinated water effectiveness on produce at 2, 10 and 25 °C at different storage times (1, 24, 48 and 72 h). First, SalmoFresh™ was applied to the surface of lettuce, mung bean sprouts and mung bean seeds that were spot-inoculated with a five Salmonella strain mixture (Newport, Braenderup, Typhimurium, Kentucky, and Heidelberg, 105 CFU/mL) by spraying phages onto lettuce (n = 48 pieces, 3×3 cm2 per treatment) and sprouts (n = 48 pieces per treatment). A second set of experiments (scaled-up) consisted in the application of phages by immersion to Salmonella adulterated lettuce (600 g), 300 g sprouts (300 g) or mung bean seeds (30 g) in a phage cocktail (108 PFU/mL) for 15 min (lettuce and sprouts) or 1 h (seeds). Another group of samples was washed with chlorinated water and yet another group was treated with a combination of chlorinated water followed by phage cocktail. Each experiment was repeated three times by quadruplicates. After the treatments for spot-inoculated and scaled-up experiments, lettuce and sprouts were separated into different lots (10 g/lot) and stored at 2, 10 and 25 °C; Salmonella was enumerated after 1, 24, 48 and 72 h. Adulterated phage-treated seeds were packaged and stored dry at 25 °C. Salmonella was enumerated after 72 h of storage. Groups of phage treated mung bean seeds (720 g) were germinated, and the reduction in Salmonella determined. Results of microplate virulence assays indicated that SalmoFresh™ reduced (P = 0.007) Salmonella by an average of 5.34 logs CFU/mL after 5 h at 25 °C. Spraying SalmoFresh™ onto lettuce and sprouts reduced Salmonella by 0.76 and 0.83 log10 CFU/g, respectively (P

UNLABELLED Nanocomposite carboxymethyl cellulose films containing sinigrin (SNG) were prepared by stirring 2% (w/v) carboxymethyl cellulose (CMC) and 2% (w/v) glycerol (as a plasticizer) in distilled water with or without SNG (an antimicrobial precursor) as a 99% pure reagent (pSNG) or as a crude extract (cSNG). These films plus normal CMC film with or without SNG were tested on Escherichia coli O157:H7- inoculated beef for antimicrobial activity. Beef pieces measuring 6 × 5 × 2 cm(3) (L × W × H) were dipped in an E. coli O157:H7 broth suspension containing >8 log10 CFU ml(-1) and were drained for 3 min over a sterile cloth. They were wrapped in CMC or NCMC films, placed in a high oxygen barrier film (Deli *1), vacuum-packaged and stored at 8°C for 5, 8, 12 and 18 days. The CMC and NCMC films without SNG were not antimicrobial against E. coli O157:H7; however, NCMC and CMC films with SNG were highly antimicrobial. After 5 days at 8°C, E. coli O157:H7 was reduced more than 4 log10 by the NCMC•pSNG film and this reduction remained almost the same until 18 days at 8°C when E. coli O157:H7 was reduced >5 log10 CFU g(-1) meat. SIGNIFICANCE AND IMPACT OF THE STUDY Transparent nanoparticulate carboxymethyl cellulose (CMC) films containing sinigrin (SNG), an antimicrobial precursor, controlled surface contamination of packaged fresh beef by the pathogen Escherichia coli O157:H7 when stored at 8°C. Films with nanoparticulation that carried pure SNG or the naturally occurring SNG in Oriental mustard were significantly more antimicrobial than similar films without nanoparticulation. As films without sinigrin were not antimicrobial, the combinations studied showed that nanoparticulation of the packaging film enhanced delivery of the antimicrobial incorporated within the film.

The Canadian Food Inspection Agency (CFIA) is developing a risk assessment model for food establishments. Previous research on the significance of food safety risk factors determined by literature review and expert advice served as the bases for the current study, to further refine, discriminate and select the most important criteria to be included in the model. This process considered the availability of data sources, the clarity and measurability of the selected factors, undertook the elimination of lower-rated risk factors and grouped those with similar focus of attention, enabling the selection of a final list of risk factors for the model. A method of assessment for the remaining factors was then proposed to allow the quantification of individual risk factors within the model. From the 155 risk factors initially identified, 17 consolidated factors were kept and will be considered for the development of the risk assessment model.

Decreasing the health burden caused by foodborne pathogens is challenging and it depends on the identification of the most significant hazards and food sources causing illnesses, so adequate mitigation strategies can be implemented. In this regard, the Canadian Food Inspection Agency (CFIA) has developed the Establishment-based Risk Assessment (ERA) model, so that a more effective and efficient allocation of resources can be assigned to the highest food safety risk areas. To assess risk, the model considers the type of food sub-products being manufactured by establishments and its scope is limited to the 17 most important foodborne pathogens representing the highest level of food safety risk. However, the information on source attribution at the sub-product level based on a structured approach is limited. To overcome this challenge, an expert elicitation was conducted in 2016 to estimate the relative contribution and associated certainty of each sub-product for 31 pathogen-commodity combinations to the total Canadian health burden associated with foodborne illnesses (expressed in DALYs). These DALYs represent 78% of the total Canadian health burden associated with federally-regulated food commodities considered within the model. A total of 49 Canadian experts recruited using a “snow ball” sampling strategy participated in the study by completing an electronic survey. Results of the elicitation displayed variable levels of health burden allocation between the pathogens and the different commodity sub-products. Assessment of the certainty levels showed some combinations being evaluated with more confidence (e.g., Campylobacter and eggs/poultry sub-products) than others, where a bimodal distribution of certainty was observed (e.g., Toxoplasma in pork sub-products). Furthermore, no participant raised concerns on the food classification scheme, suggesting their agreement with the proposed sub-products categorization of the elicitation. Relative contribution estimates will be included in the CFIA ERA model and used to enhance its applicability for risk prioritization and effective resource allocation during food establishment inspections. While substantial uncertainty around the central tendency estimates was found, these estimates provide a good basis for regulatory oversight and public health policy.

The antimicrobial activity of different essential oils was screened against five Salmonella serotypes using disk diffusion. Cinnamon (Cinnamomum zeylanicum) and thyme (Thymus vulgaris) essential oils exhibited the highest activity with inhibition zones of 22.5–38.5 mm in diameter. These oils were also investigated for their ability to control Salmonella and mesophilic aerobic bacteria (MAB) in hummus stored at 4 or 10°C. Salmonella cells were not detected in hummus with 0.5%–1.0% cinnamon essential oil by 7 or 1 d, respectively, at both 4 and 10°C. Cinnamon oil at 0.5%–1.5% reduced the MAB in hummus by 1.3–4.6 log CFU/g at 4 or 10°C. However, addition of 0.5%–1.5% thyme essential oil to hummus reduced Salmonella by 1.0–2.9 log CFU/g, at 4°C by 10 d. Thyme oil also inhibited growth of MAB in hummus and the count remained constant until the end of storage at 4°C, but at 10°C, thyme oil was less inhibitory. PRACTICAL APPLICATIONS: Consumption of hummus has been linked to several salmonellosis outbreaks. Addition of cinnamon and thyme essential oils at concentrations of 0.5% may improve the safety and extend the shelf‐life of hummus with acceptable organoleptic properties.

The glucosinolate sinigrin (SNG) is converted by endogenous plant myrosinase or by bacterial myrosinase-like activity to form the potent antimicrobial allyl isothiocyanate. In order to use SNG as a natural antimicrobial precursor in food, it became important to better understand the ability of bacteria to synthesize the enzyme(s) and understand factors influencing this synthesis at a constant SNG concentration. Eight spoilage, pathogenic, or starter culture bacteria were grown separately in medium containing individual or combined salts with SNG. SNG degradation by the bacteria and the formation of its major degradation product, allyl isothiocyanate, were followed for 12 days at 30 or 35°C. The bacterial strains varied in their ability to metabolize SNG, and this was enhanced by NaCl and/or NaNO(3). SNG hydrolysis took place after 4 days, and the greatest amount occurred by day 12. At 12 days, Escherichia coli O157:H7 showed the greatest capacity to hydrolyze SNG (45.3% degradation), followed by Staphylococcus carnosus (44.57%), while Pseudomonas fluorescens was not active against SNG. The ability of tested strains to metabolize SNG, in decreasing order, was as follows: Escherichia coli O157:H7Staphylococcus carnosusStaphylococcus aureusPediococcus pentosaceusSalmonella TyphimuriumListeria monocytogenesEnterococcus faecalisPseudomonas fluorescens.

The effect of Bifidobacterium breve on the survival and growth of Enterobacter sakazakii in rehydrated infant milk formula stored at 4–45C was studied. A commercial culture of B. breve and a five-strain cocktail E. sakazakii were mixed with rehydrated formula and stored up to 8 h. The populations of B. breve and E. sakazakii at each storage time/temperature were determined. There was a two-way interactive effect between B. breve numbers and temperature on the number of E. sakazakii in the rehydrated formula at 3–8 h of storage. E. sakazakii did not grow in the rehydrated formula at 4C. At 12 and 20C, the numbers of E. sakazakii in the presence of B. breve were lower than those in the formula without B. breve at 8 h of storage, and at 45C, when the bacteria were combined, a similar result was obtained at 6- and 8-h storage. The presence of B. breve in the formula appeared to enhance the growth of E. sakazakii at 37C in the rehydrated formula stored at 2–8 h. Other more competitive inhibitory probiotic cultures would be more appropriate to control E. sakazakii growth in unrefrigerated rehydrated milk-based formula. PRACTICAL APPLICATIONS Results obtained showed that the probiotic organisms Bifidobacterium breve did not reduce Enterobacter sakazakii levels in rehydrated infant formula if held >2 h at >30C. At 37C, B. breve stimulated the growth of the pathogen after 2 h. Choice of probiotic bacteria for inclusion in these products to improve infant gut microflora should be based on their neutral or negative influence on E. sakazakii survival/growth to reduce the risk to health associated with the contamination of these products during manufacture.

Increasing the growth performance of broiler chickens by supplementing their diets with exogenous enzymes can also contribute to positive changes in gut health. In this respect the growth of various bacteria normally associated with the gastrointestinal tract of poultry was assessed in vitro using a medium containing arabinoxylan, β-glucan, guar gum and raffinose and their corresponding enzymes. Overall, enzymes releasing the largest amounts of free sugars yielded the largest increase in bacterial numbers. Accordingly, β-glucan and raffinose treated with their respective enzymes promoted the largest number of bacterial types, reaching a minimum of 1.0 log10 population within 6 h at 40 °C. A broiler chicken growth trial was also conducted using wheat-, barley- and corn-based diets with and without enzyme and probiotic addition. Escherichia coli, coliforms, enterococci and aerobic and anaerobic sporeformers were monitored for growth in both the caecum and ileum. Enzyme supplementation reduced E. coli levels in the caecum of broilers fed wheat- or corn-based diets. A further reduction in E. coli numbers was observed in broilers fed the same diets supplemented with a combination of enzyme and probiotic. Enzyme supplementation had much less of an effect on microbial populations in the ileum. Inclusion of probiotics reduced E. coli levels in the caecum and ileum but only in broilers fed wheat- and corn-based diets. Anaerobic spore levels in the ileum increased in all diets containing probiotic. Overall, inclusion of enzymes or probiotics exhibited mixed effects on gut bacteria, depending on the nature of the carbohydrate source and enzyme. Copyright © 2007 Society of Chemical Industry

Previous studies have reported that the mechanism of bactericidal action of the plant oil aromatics, eugenol, carvacrol and cinnamaldehyde involves inhibition of adenosine triphosphate generation and membrane disruption. In this study the capacity of the aromatics to inhibit the membrane bound ATPase activity of Escherichia coli and Listeria monocytogenes was investigated by experiments on isolated membranes. Inhibition of the ATPase activity of E. coli membranes was observed with 5 mM or 10 mM eugenol or carvacrol. Progressively greater inhibition by cinnamaldehyde was observed as concentration increased from 0.1 to 10 mM. L. monocytogenes ATPase activity was significantly inhibited by eugenol (5 or 10 mM), carvacrol (10 mM) and cinnamaldehyde (10 mM). Lactobacillus sakei is highly resistant to cinnamaldehyde compared to E. coli and L. monocytogenes. To determine whether this resistance was related to the relative hydrophobicity of the cell surface and hence the ability of the cell to take up the aromatics, the percentage of the three organisms partitioning in dodecane was compared. No significant difference was found between the partitioning percentage of L. monocytogenes (17.2%) and L. sakei (13.8%), indicating that surface hydrophobicity does not explain the differing sensitivity to cinnamaldehyde of these two organism. The percent partitioning of E. coli was significantly greater than both other organisms (23.3%) and may explain the greater sensitivity of E. coli to all three aromatics.

The role of membrane disruption in the bactericidal activity of the plant oil aromatic compounds eugenol, carvacrol and cinnamaldehyde was investigated using confocal laser scanning microscopy, changes in ATP levels and cell viability. In 25 mM HEPES buffer pH 7 at 20 degrees C, 10 mM eugenol or carvacrol increased uptake of propidium iodide by Escherichia coli, Listeria monocytogenes and Lactobacillus sakei over a 10-min period. The same treatments resulted in lowered viability, rapid depletion of cellular ATP and release of ATP, with the exception of Lb. sakei treated with carvacrol. Eugenol or carvacrol at 5 mM to 10 mM inhibited E. coli and L. monocytogenes motility. Lb. sakei was resistant to cinnamaldehyde. Thus, its effects were only studied on E. coli and L. monocytogenes. At 10 mM, cinnamaldehyde caused a slight but statistically significant increase in propidium iodide staining of E. coli, but had no effect on L. monocytogenes. Cinnamaldehyde treatment of E. coli at 10 mM and L. monocytogenes at 40 mM resulted in decreased cellular ATP, but there was no concomitant release of ATP. Cinnamaldehyde at 5 and 10 mM inhibited E. coli and L. monocytogenes motility. Results for eugenol and carvacrol are consistent with non-specific permeabilization of the cytoplasmic membrane. Evidence for increased membrane permeability by cinnamaldehyde is less conclusive. The release of ATP from eugenol and carvacrol-treated cells and absence of release from cinnamaldehyde-treated cells could indicate that eugenol and carvacrol possess ATPase inhibiting activity. Secondary effects would also be consistent with membrane disruption.

Aim: To evaluate the effect of NaCl, growth medium and temperature on the antimicrobial activity of bovine lactoferrin (LF) against Escherichia coli O157:H7 in the presence of different chelating agents. Methods and Results: LF (32 mg ml−1) was tested against E. coli O157:H7 strain 3081 in Luria broth (LB) and All Purpose Tween (APT) broth with metal ion chelators sodium bicarbonate (SB), sodium lactate (SL), sodium hexametaphosphate (SHMP), ethylene diamine tetraacetic acid (EDTA) or quercetin at 0·5 and 2·5% NaCl at 10 and 37°C. LF and the chelators were tested against four other E. coli O157:H7 strains in LB at 2·5% NaCl and 10°C. LF alone was bacteriostatic against strains 3081 and LCDC 7283 but other strains grew. Antimicrobial effectiveness of LF was reduced in APT broth but enhanced by SB at 2·5% NaCl and 10°C where 4·0 log10 CFU ml−1 inoculated cells were killed. EDTA enhanced antimicrobial action of the LF–SB combination. SL alone was effective against E. coli O157:H7 but a reduction in its activity at 2·5% NaCl and 10°C was reversed by LF. The combinations LF–SHMP and LF-quercetin were more effective at 37°C and NaCl effects varied. Conclusions: LF plus SB or SL were bactericidal toward the same 3/5 E. coli O157:H7 strains and inhibited growth of the others at 2·5% NaCl and 10°C. Significance and Impact of the Study: The combination of LF with either SL or SB shows potential for reducing viability of E. coli O157:H7 in food systems containing NaCl at reduced, but growth permissive temperature.

Commercial allyl isothiocyanate (AIT) was examined for its ability to reduce numbers of Escherichia coli O157:H7 inoculated in fresh ground beef packaged under nitrogen and stored refrigerated or frozen. A five-strain cocktail of E. coli O157:H7 containing 3 or 6 log10 cfu/g was inoculated into 100 g ground beef and formed into 10x1-cm patties. A 10-cm diameter filter paper disk treated with AIT suspended in sterile corn oil was placed on top of a single patty. One patty and paper disk were placed in a bag of Nylon/EVOH/PE with O2 permeability of 2.3 cm3 m(-2) 24 h atm at 23 degrees C. The bags were back-flushed with 100% nitrogen, heat-sealed and stored at 10, 4 and -18 degrees C for 8, 21 or 35 days, respectively. During storage, the AIT levels in the package headspaces were determined by gas liquid chromatography, and mesophilic bacteria and E. coli O157:H7 were counted. The mesophilic aerobic bacteria in ground beef patties were largely unaffected by the addition of AIT. At an initial population of 3 log10 cfu/g, E. coli O157:H7 was reduced by AIT to undetectable levels after 18 days at 4 degrees C or 10 days at -18 degrees C. In samples inoculated with 6 log10 cfu/g, a3 log10 reduction of E. coli O157:H7 was observed after 21 days at 4 degrees C, while a 1 log10 reduction was observed after 8 and 35 days at 10 and -18 degrees C, respectively. The final AIT concentrations in the headspaces after storage at 10, 4, and -18 degrees C were 444, 456, and 112 microg/ml at 8, 21, and 35 days, respectively. Results showed that AIT can substantially reduce numbers of E. coli O157:H7 in fresh ground beef during refrigerated or frozen storage.

This study was undertaken to determine whether the glucosinolates naturally present in non-deheated mustard flour could serve as a source of allyl and other isothiocyanates in sufficient quantity to kill Escherichia coli O157:H7 inoculated in ground beef at three different levels, during refrigerated storage of the meat under nitrogen. Mustard flour was mixed at 5%, 10% or 20% (w/w) with freshly ground beef, then the beef was inoculated with a cocktail of five strains of E. coli O157:H7 at either 3, 6 oror =1.6 log10 cfu/g. The ground beef was formed into 100 g patties and each was placed in a bag of Nylon/EVOH/PE, which was back-flushed with 100% N2, heat-sealed and stored at 4 degrees C foror =21 days. During storage, the allyl isothiocyanate (AIT) levels in package headspaces were determined by gas liquid chromatography. By 21 days, the levels present in treatments were not significantly different. After 21 days storage, there were 0.5, 3 and 5.4 log10 decreases in numbers of E. coli O157:H7 from the initial levels of 6 log10 cfu/g in meat containing 5%, 10% and 20% mustard flour, respectively. When inoculated at 3 log10 cfu/g, E. coli O157:H7 was reduced to undetectable levels after 18, 12 and 3 days with 5%, 10% and 20% mustard flour, respectively. When immunomagnetic separation (IMS) was used for E. coli recovery following its inoculation ator =1.6 log10 cfu/g, 5% mustard did not completely eliminate the pathogen from ground beef stored for 6 days. The natural microflora of the ground beef which developed in vacuum packages was unaffected by the addition of 5% mustard flour but some inhibition was found at higher concentrations. Sensory evaluation of the cooked ground beef showed that there were no significant differences in the acceptability of meat treated with 5 or 10% mustard flour. However, panelists could distinguish untreated controls from mustard treatments, but considered the mustard-treated meat to be acceptable. These results showed that it is possible to use mustard flour at levels of5-10% to eliminate E. coli O157:H7 from fresh ground beef.

The temperatures and ages of 5389 packs of beef in 10 multiple shelf display cabinets were determined. The median temperature of the packs in each cabinet was 7 °C. All packs in three cabinets were ⩽2 days old. The percentages of packs older than 2 days were

Effet du bacteriophage DC22 sur Escherichia coli O157:H7 dans un systeme de rumen artificiel (Rusitec) et de moutons infectes. L'effet du bacteriophage DC22, sur la survie d'Escherichia coli O157: H7 dans un systeme de rumen artificiel (Rusitec) et chez des moutons experimentalement infectes a ete evalue. Le test de detection des plages de lyse des souches E. Coli au DC22 a montre que 23 des 23 souches E. Coli O157:H7 etaient sensibles au DC22, tandis que 12 souches E. Coli enterohemorragique non-O157 n'etaient pas sensibles au bacteriophage. Sur les etudes utilisant le fluide ruminal clarifie, la multiplicite d'infection (MI) du DC22 sur E. coli O157:H7 a ete superieure a 10 4 unites formant des plages (UFP)/unite formant des colonies (UFC). Dans le rumen artificiel (Rusitec), 10 4 UFC.mL -1 de la souche E. coli Q157:H7 3081 ont ete eliminees des fermenteurs (n = 4), 4 hapres l'administration du DC22 (MI = 10 5 UFP/UFC, P 0,05) n'a ete observee en ce qui concerne les concentrations d'E. coli O157:H7 dans les feces, entre le groupe DC22 et le groupe temoin, sur une periode de 30 jours. Les taux de DC22 retrouves dans les feces du groupe DC22 ont diminue de 5,98 log 1o UFP.g -1 le 3 e jour a un niveau indetectable le 13 e jour chez tous les agneaux. L'adsorption non specifique du DC22 ou son inactivation avant d'atteindre le tractus digestif inferieur a probablement diminue son efficacite a eliminer E. coli O157:H7 de la portion intestinale du tube digestif des agneaux.

A feed supplement, SCB, containing Saccharomyces cerevisiae subsp. boulardii, produced substances which were successful in inhibiting strains of E. coli O157:H7 in a spot agar assay. Growth and/or survival of E. coli O157:H7 in ruminal fluid in the presence of SCB was investigated in a batch culture incubation and in continuous culture using a Rumen Simulation Technique (Rusitec). In the batch culture incubation, E. coli O157:H7 (EC) was inoculated (104 CFU/ml final concentration) into 100 ml of clarified ruminal fluid amended with SCB at 0 (control), 5 (SCB5), 10 (SCB10), 15 (SCB15) or 20 (SCB20) mg/ml (n=3). Treatments were incubated at 39 °C, and EC was enumerated after 0, 12, 24 and 48 h by plating onto selective medium. Treatments SCB15 and SCB20 completely eradicated 104 CFU EC/ml within 48 h (P 0.05). In the Rusitec incubation, fermentations were established in 12 Rusitec vessels using ruminal inoculum confirmed negative for E. coli O157. Each vessel was inoculated with EC (104 CFU/ml), then 8 h later, with stock solutions of SCB yielding initial concentrations of 0 (control), 5 (SCB5) or 20 (SCB20) mg/ml (n=4). Enumerations of EC were conducted 0, 4, 8, 12 and 24 h after EC inoculation, and daily thereafter for 6 days. Counts of EC did not differ (P>0.05) from the control with either level of SCB, at any of the time points assessed. The inhibitory effect of SCB on E. coli O157:H7 observed in batch culture at 48 h was not observed in continuous culture (Rusitec). Lack of an effect of SCB on E. coli O157:H7 in the Rusitec suggests that the production of inhibitory substances by S. cerevisiae may not occur in the mixed microflora of the rumen. Also, diffusion of inhibitory substances in the rumen or degradation of inhibitory substance by rumen microorganisms may have reduced their effectiveness against E. coli O157:H7.

Cilantro oil is an essential oil preparation extracted from the plant Coriandrum sativium. A series of experiments were conducted to evaluate the ability of cilantro oil to control the growth of Listeria monocytogenes on vacuum-packed ham. The in vitro minimal inhibitory concentration for five strains of L. monocytogenes was found to vary from 0.074% to 0.018% depending on strain. Cilantro oil treatments were then tested on ham disks inoculated with a cocktail of the five L. monocytogenes strains. The treatments studied were 0.1%, 0.5%, and 6% cilantro oil diluted in sterile canola oil or incorporated into a gelatin gel in which lecithin was used to enhance incorporation of the cilantro oil. Gelatin gel treatments were also conducted with 1.4% monolaurin with or without 6% cilantro oil to determine if an interaction between the antimicrobials could increase inhibition of L. monocytogenes. Treated ham was then vacuum-packed and stored at 10 °C for up to 4 weeks. The only cilantro oil treatment which inhibited growth of L. monocytogenes on the ham samples was 6% cilantro oil gel. Samples receiving this treatment had populations of L. monocytogenes 1.3 log CFU/ml lower than controls at week 1 of storage, though there was no difference between treatments from week 2 onward. It appears that immobilization of the antimicrobial in a gel enhanced the effect of treatments. Cilantro oil does not appear to be a suitable agent for the control of L. monocytogenes on ham. The possible reasons for reduced effectiveness of cilantro oil against L. monocytogenes on ham are discussed.

There is a growing interest in modelling microbial growth as an alternative to time-consuming, traditional, microbiological enumeration techniques. Several statistical models have been reported to describe the growth of different microorganisms, but there are accuracy problems. An alternate technique 'artificial neural networks' (ANN) for modelling microbial growth is explained and evaluated. Published data were used to build separate general regression neural network (GRNN) structures for modelling growth of Aeromonas hydrophila, Shigella flexneri, and Brochothrix thermosphacta. Both GRNN and published statistical model predictions were compared against the experimental data using six statistical indices. For training data sets, the GRNN predictions were far superior than the statistical model predictions, whereas the GRNN predictions were similar or slightly worse than statistical model predictions for test data sets for all the three data sets. GRNN predictions can be considered good, considering its performance for unseen data. Graphical plots, mean relative percentage residual, mean absolute relative residual, and root mean squared residual were identified as suitable indices for comparing competing models. ANN can now become a vehicle whereby predictive microbiology can be applied in food product development and food safety risk assessment.

Biogenic amines are formed in foods as a result of amino acid decarboxylation catalyzed by bacterial enzymes. When consumed in sufficient quantities, these compounds will cause headache, hypertension, fever, and heart failure. Technologies such as vacuum packaging and carbon dioxide-modified atmosphere packaging (CO2-MAP), when combined with low-temperature storage (-1.5 degrees C), allow fresh pork to have a storage life long enough for export to overseas markets. During low-temperature storage of pork in these packaging systems, the lactic acid bacteria (LAB), which possess the enzymes for biogenic amine formation, dominate the microflora. The objectives of this study were to determine the quantities of biogenic amines in packaged fresh pork, to monitor LAB growth, and to determine the storage life by sensory evaluation. Vacuum-packaged and CO2-MAP pork were stored at -1.5+/-0.5 degrees C for 9 and 13 weeks, respectively. Phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermidine, and spermine concentrations were determined weekly by high-performance liquid chromatography and capillary gel electrophoresis. LAB and carnobacteria were enumerated weekly. Samples were evaluated for odor and appearance. The CO2-MAP was successful in delaying bacterial growth and the development of unacceptable off-odors compared with the vacuum packaging. The storage lives of the vacuum-packaged and CO2-MAP pork were 5 and 13 weeks, respectively. High-performance liquid chromatography was the superior method for biogenic amine quantification. Tyramine and phenylethylamine in pork of both packaging treatments approached levels considered to be potentially toxic. Given Canada's increasing role in the export of fresh meat to foreign markets, it is recommended that the formation of biogenic amines in vacuum-packaged and CO2-MAP pork be further investigated.

A previously-designed insulated container was modified to improve the hold period (variable) nitrogen (N 2 ) use of the cryogenic system used to cool the container. Although fresh meat storage life is longest at −1.5±0.5°C, the target temperature range for the system was changed to −1.0±0.5°C to eliminate any economic loss caused by the freezing of meat. A centrifugal fan, with its motor mounted outside the container, provided a uniform temperature within the container and lowered the hold period N 2 use of the system. Chilling of the product from an initial temperature of 7.0°C to −1.0°C required on average 33.7, 31.7, 34.7, and 30.6 kg of N 2 at outside temperatures of 30, 15, 0, and −15°C, respectively. Average hold period N 2 use for maintaining the required temperature was 4.8, 2.8, 1.2, and 0.1 kg/h at outside temperatures of 30, 15, 0, and −15°C, respectively, and these were an improvement over the previous design. The overall maximum temperature of the container during the trials was −0.3°C, while the overall minimum was −1.4°C. A vacuum insulated transfer line decreased hold period N 2 use by 51% in comparison with a steel braided transfer line. A simulated N 2 failure of the system resulted in an average temperature increase of 0.5 o C/h within the container.

Pre-cooked roast beef slices were stored 28 days at 4 +/- 2 degrees C in air or 100% N2 with and without vaporized horseradish essential oil (HEO). Addition of 20 microliter HEO/L restricted growth of most spoilage bacteria. Pseudomonas spp. and Enterobacteriaceae were strongly inhibited by HEO. Lactic acid bacteria were more resistant to the antimicrobial effect and dominated spoilage flora. Sensory evaluation and headspace analysis by gas chromatography/mass spectrometry revealed that development of off-flavors and odors derived from fat oxidation products was delayed by HEO. Cooked meat color was also preserved in samples stored under HEO.

Centralized packaging of retail meat cuts is growing more popular because of its economies and potential to maintain quality, enhance safety, and extend the shelf life of fresh meat. Requirements for optimizing shelf life of centrally prepared retail cuts for periods up to 15 weeks are slightly different from those needed to extend the shelf life of fresh, chilled meat. Chilled meat primarily deteriorate at the cut or uncut muscle surface. In long-term storage, primal cuts are placed in an atmosphere saturated with carbon dioxide and containing very low residual oxygen. These cuts are held at -1.5+/-0.5 degrees C. When the meat is removed, it is fabricated into retail or food service cuts. New fresh surfaces are created in the process, revitalizing the meat's appearance. After being prepared for retail display, the meat normally has four more days of shelf life. Depending on the meat species, shelf life is usually limited by development of undesirable organoleptic changes, usually defects in color, which are independent of microbial presence. The microbes consist of a lactic acid bacterial population that maximizes under storage conditions at about 10(8) CFU/cm2 well before shelf life ends. Circumstances are different with centralized distribution of retail-ready fresh meat. The wholesale storage period following initial packaging of the retail cuts is about 20 to 30 days. Prepared products must withstand retail display for up to 2 days without further manipulation of package contents. Retail packages are simply moved from their storage container (usually a unit or overwrap containing a modified atmosphere) to retail display, where desirable meat color develops upon exposure to air. Three gas atmospheres have some potential to satisfy storage needs for centralized distribution of retail-ready packages: 100% CO2, 100% N2, or 70% N2 + 30% CO2. Shelf life is limited by undesirable changes in surfaces exposed at initial packaging, caused by growth of psychrotrophic bacteria. If 100% CO2 is used, these are all lactic acid bacteria (LAB). Therefore, initial bacterial numbers on the meat and storage temperature become critical to success. The most attractive storage option is 100% CO2 used at - 1.5 +/-0.5 degrees C. This review presents the reason for that recommendation, along with basic concepts of meat chemistry, a discussion of modified atmosphere packaging, meat microbiology, and current results with simulated centralized packaging of retail-ready meats.

Heat resistance, germination and sensitivity to selected antimicrobials was investigated using Penicillium roqueforti , Penicillium aurantiogriseum and Penicillium viridicatum spores, produced on potato dextrose agar (PDA) adjusted to 0.88 a W using either glycerol or NaCl. Results indicated that spores produced on media without a W adjustment (0.99 a W ; control) appeared more heat resistant (55°C, 10 min) compared to those produced at 0.88 a W (treatment). For treatment spores only, heat resistance was observed to decrease further when initially incubated (25°C, 48 h) in sterile, distilled water. All treatment spores were more sensitive to benzoate and sorbate but more resistant to cycloheximide. The time taken for germination, especially for P. roqueforti spores appeared to vary depending on the a W and solute used during spore production. ©

Thermophillic Campylobacter and Camp. jejuni were detected from samples of chicken liver, gall bladder, muscle and contaminated milk and chicken meat after an enrichment step by using immunomagnetic capture of cells with monoclonal antibody against a specific outer membrane protein of thermophilic Campylobacter. The detection of captured cells was achieved using two different hybridization methods. In one of the methods, the captured cells were lysed by guanidine isothiocyanate and the 23S rRNA was reacted with a microtitre plate-immobilized rDNA probe specific for thermophilic Campylobacter. In the other method, the captured cells were subjected to lysis by ultrasonication and the genomic DNA reacted with a microtitre plate-immobilized RNA probe specific for Camp. jejuni. Detection of the RNA-DNA hybrids formed in the wells was carried out using a monoclonal anti-RNA-DNA hybrid antibody.

A model for studying spoilage in sliced cooked delicatessen meats using conventional plating procedures was characterized by following the transfer of adventitious lactic acid bacteria (LAB), thermotolerant LAB and pediococci from a dry fermented sausage to cooked ham and bologna during a simultaneous slicing procedure. The major group of organisms present in these products was LAB. Each of the three groups of organisms was transferred to the cooked meats, but during storage under vacuum at 7°C, only the adventitious lactobacilli from the sausage appeared to contribute to cooked meat spoilage. Pediococci declined within 28 days of co-slicing, thermotolerant LAB grew slowly and never reached levels of >5 log 10 cfu cm −2 , but transferred adventitious LAB from the sausage grew and reached peak populations 4 weeks earlier in the co-sliced cooked meats than in controls. During storage at 7°C co-sliced cooked meats spoiled, as assessed by purge (liquid) and ropy slime formation, 2–4 weeks faster than the separately-sliced and vacuum-packaged products. The distribution of organisms on package slices differed. In control cooked products numbers of bacteria present on center package slices were lower than on outside slices. Bacterial numbers were greatest at the meat surface–packaging film interface. In co-sliced cooked products organisms were evenly distributed throughout slices in the packages. Based on findings from use of the co-slice model, in vacuum packages of sliced cured meats where >10 5 cfu bacteria cm −2 are equally distributed throughout package slices, poor slicing hygiene is the cause. Commercially-sliced bologna was repackaged with allyl isothiocyanate (AIT) to test its ability to delay bacterial growth at the meat surface. The preservative effects of AIT were tested under vacuum or when backflushed with CO 2 . CO 2 alone was more effective than AIT in delaying LAB growth but neither treatment was particularly effective.

Microtitre plate nucleic acid probe hybridization systems were developed for the detection of thermophilic Campylobacter and Campylobacter jejuni. Specific RNA probes obtained by in vitro transcription of DNA templates synthesized by polymerase chain reaction using two sets of specific primers incorporating bacteriophage T7 promoter sequences were immobilized on a microtitre plate. The hybridizations were carried out on samples of genomic DNA sheared by ultrasonication. Optimum conditions for the ultrasonic treatment were determined in order to obtain the highest degree of hybridization with immobilized RNA probe. Finally, detection of RNA-DNA hybrids in the wells was accomplished by an immunoenzymatic assay using a monoclonal anti-RNA-DNA hybrid antibody. This rapid, simple hybridization and immunoenzymatic assay system will facilitate the detection of Campylobacter in foods and clinical samples.

Aims Effects of sublethal levels of cinnamaldehyde (CIN) on the viability and morphology of Escherichia coli O157:H7 and E. coli 8 WT were investigated at 6 and 37°C. Methods and Results The minimum inhibitory concentration of CIN against E. coli O157:H7 and E. coli 8WT was 400 mg l−1. At 37°C and ≤300 mg l−1, CIN delayed the multiplication of both strains, causing a ≤5 and ≤13 h lag, respectively. Delayed multiplication at ≤300 mg l−1 was partly due to cell elongation and injury as determined by LIVE/DEAD viability, CTC vitality and bis-(1,3-dibutylbarbituric acid) trimethine oxonol staining. The greatest extent of cell elongation (87%) and greatest mean length (6·4 μm) occurred with E. coli O157:H7 at 2-h exposure to 200 mg l−1 CIN. After initial delays in multiplication, both E. coli O157:H7 and E. coli 8WT returned to exponential growth and normal morphology before reaching the stationary phase. In contrast at 6°C, CIN at ≥100 mg l−1 prevented cell elongation which occurred in untreated control cells. Treatment with 200 or 300 mg l−1 CIN at 6°C was lethal to both E. coli strains. At 300 mg l−1, CIN caused a ≥5 log CFU ml−1 reduction at ≤3 days and completely inactivated both of these organisms, causing ≥7 log CFU ml−1 reduction at 7 days. Conclusion Sublethal levels of CIN at 37°C delayed the multiplication of E. coli cells by causing transient cell elongation, but at 6°C ≥200 mg l−1 CIN was lethal to E. coli. Significance and Impact of the Study Inhibition of cold-induced cell elongation and the enhanced lethal effect of CIN at 6°C against E. coli O157:H7 suggest that CIN may be useful for control of this pathogen at refrigeration temperatures.

Wrapped boneless pork loin roasts and slices were stored at 4 o C in bulk under constant CO 2 concentrations of 50% and 100% for 1 and 2 wks. Samples stored under 50% CO 2 for 2 wks could subsequently be displayed (aerobic) for 3 days without becoming unacceptable or for 6 days if previously held under 100% CO 2 for 14 days. Aerobic shelf-life at 4 o C of the latter samples equalled that of fresh pork chops under simulated retail display. Physicochemical characteristics during storage did not limit acceptability. Reusable master packs have application for distribution of retail ready cuts under controlled atmosphere packaging

Lactic acid bacteria (LAB) are extensively used in the food industry for fermentation processes. However, it is possible that these bacteria may serve as a reservoir for antibiotic resistance genes that can be transferred to pathogens, giving rise to public health concerns. Animal operations that use antimicrobials as growth promotants have been linked to the origin of resistance due to the selective effect of low levels of antimicrobial used in this management strategy. The objective of this study was to determine the antimicrobial susceptibilities and mechanisms of resistance for 30 isolates of meat starter cultures commonly used in dry sausage fermentations to 20 antimicrobial agents. Susceptibility tests were performed by broth microdilution using Iso-Sensitest broth (90%, vol/vol) and de Man Rogosa Sharpe (MRS) broth (10%, vol/vol). The results showed that all 30 isolates exhibited resistance to at least three antimicrobials regardless of antimicrobial class while 17 or 30% of strains were resistant to antibiotics in three or six different classes, respectively. The incidence of antimicrobial resistance was higher among Pediococcus pentosaceus and lower for Staphylococcus carnosus strains. Genetic determinants for the lincosamide, macrolide, and tetracycline antimicrobials were not found using PCR. Phenotypic resistance in the absence of known resistance genes found here suggests that other mechanisms or genes might have contributed to the negative results. Further studies are needed to explore the genetic mechanisms underlying the prevalence of antibiotic resistance in Pediococcus species.

Aim: To determine D- and z-values of Cronobacter species (Enterobacter sakazakii) in different reconstituted milk and special feeding formula and the effect of reconstitution of powdered milk and special feeding formula with hot water on the survival of the micro-organism. Methods and Results: Five Cronobacter species (four C. sakazakii isolates and C. muytjensii) were heated in reconstituted milk or feeding formula pre-equilibrated at 52–58°C for various times or mixed with powdered milk or feeding formula prior to reconstitution with water at 60–100°C. The D-values of Cronobacter at 52–58°C were significantly higher in whole milk (22·10–0·68 min) than in low fat (15·87–0·62 min) or skim milk (15·30–0·51 min) and significantly higher in lactose-free formula (19·57–0·66 min) than in soy protein formula (17·22–0·63 min). The z-values of Cronobacter in reconstituted milk or feeding formula ranged from 4·01°C to 4·39°C. Water heated to ≥70°C and added to powdered milk and formula resulted in a > 4 log10 reduction of Cronobacter. Conclusions: The heat resistance of Cronobacter should not allow the survival of the pathogen during normal pasteurization treatment. The use of hot water (≥70°C) during reconstitution appears to be an effective means to reduce the risk of Cronobacter in these products. Significance and Impact of the Study: This study supports existing data available to regulatory agencies and milk producers that recommended heat treatments are sufficient to substantially reduce risk from Cronobacter which may be present in these products.

Aim: To evaluate the effect of starvation, heat, cold, acid, alkaline, chlorine and ethanol stresses on the resistance of Enterobacter sakazakii in powdered infant milk formula (PIMF) towards gamma radiation. Methods and Results: Stressed cells of E. sakazakii ATCC 51329 and four other food isolate strains were mixed individually with PIMF, kept overnight at room temperature, and then exposed to gamma radiation up to 7·5 kGy. The D10-values were determined using linear regression and for the stressed E. sakazakii strains these values ranged from 0·82 to 1·95 kGy. Conclusions: Environmental stresses did not significantly change the sensitivity of most E. sakazakii strains to ionizing radiation. Significance and Impact of the Study: Data obtained established that most forms of environmental stress are unlikely to significantly enhance the resistance of E. sakazakii strains to lethal, low dose irradiation treatment.

AIMS: To examine the effect of processing with superheated steam (SS) on Geobacillus stearothermophilus ATCC 10149 spores. METHODS AND RESULTS: Two inoculum levels of spores of G. stearothermophilus were mixed with sterile sand and exposed to SS at 105-175 degrees C. The decimal reduction time (D-value) and the thermal resistance constant (z-value) were calculated. The effect of cooling of spores between periods of exposure to SS was also examined. A mean z-value of 25.4 degrees C was calculated for both inoculum levels for SS processing temperatures between 130 degrees C and 175 degrees C. CONCLUSIONS: Spore response to SS treatment depends on inoculum size. SS treatment may be effective for reduction in viability of thermally resistant bacterial spores provided treatments are separated by intermittent cooling periods. SIGNIFICANCE AND IMPACT OF THE STUDY: There is a need for technologies that require short thermal processing times to eliminate bacterial spores in foods. The SS processing technique has the potential to reduce microbial load and to modify food texture with less energy in comparison to commonly used hot air treatment. This work provides information on the effect of SS processing parameters on the viability of G. stearothermophilus spores.

Raw, frozen chicken nuggets and strips have been identified as a significant risk factor in contracting foodborne salmonellosis. Cases of salmonellosis as a result of consuming partly cooked chicken nuggets may be due in part to Salmonella strains originating in broiler feed. This study was undertaken to determine the occurrence and characterize the strains of Salmonella contaminating chicken nuggets, strips, and pelleted feeds, in an attempt to demonstrate whether the same Salmonella strains present in broiler feed could be isolated from raw, frozen chicken nuggets and strips available for human consumption. Salmonellae were recovered using the Health Canada MFHPB-20 method for the isolation and identification of Salmonella from foods. Strains were characterized by serotyping, phage typing, antimicrobial resistance typing (R-typing), and by pulsed-field gel electrophoresis (PFGE). Salmonellae were isolated from 25-g samples in 27% (n=92) of nugget and strip samples, 95% (n=20) of chicken nugget meat samples, and from 9% (n=111) of pelleted feed samples. Salmonella Heidelberg, Salmonella Enteritidis, and Salmonella Orion were the most commonly isolated serovars from chicken nuggets and strips, nugget and strip meat, and pelleted broiler feeds, respectively. Salmonella Enteritidis phage type (PT) 13a with PFGE pattern SENXAI.0006 and R-type sensitive as well as Salmonella Enteritidis PT13a with PFGE pattern SENXAI.0068 and R-type sensitive were isolated from pelleted feed, and chicken nugget and strip meat in two separate instances. Data showed that Salmonella strains isolated from broiler feed were indistinguishable from strains isolated from packaged raw, frozen chicken nuggets and strips. However, results did not rule out the possibility that breeding stock or contamination during processing may have contributed to chicken meat contamination by Salmonella.

Aims: The effect of a lactic acid producing bacterial (LAB) inoculant on the elimination of Escherichia coli O157:H7 from barley forage was assessed. Methods and Results: Triplicate mini-silos were prepared for four treatments and six sampling times (1, 3, 7, 15, 30 and 42 d post-ensiling). The treatments were (i) 105 cfu g−1Pediococcus pentosaceus and Propionibacterium jenzenii (P2); (ii) 105 cfu g−1E. coli O157:H7 strain 3081 and 105 cfu g−1E. coli Biotype 1 strains 719IE10, 719IE14 and 614ME49 (EC); (iii) P2 + EC; and (iv) the control (sterile distilled water). Triplicate mini-silos were opened at each sampling time for pH, volatile fatty acid (VFA) and lactate determinations and E. coli, E. coli O157:H7 and LAB were enumerated. On d 3 and 7, numbers of E. coli O157:H7 in P2 + EC were significantly lower than in EC (P

The surface temperatures and ages of 1703 retail packs of chilled, raw beef in cut or ground forms on display in a case at each of 41 Canadian retail stores were determined. For each case, data were collected from packs at pre-selected positions in the case. Data for a position were not collected if a pack of beef was not present there. Data were collected at a different time on each of 3 days, with each store being visited within l h after opening and l h before closing and between 12:00 and 14:00 h, without regard to the operation of the case defrosting cycle. The median temperatures of pack surfaces were4 °C, between 4 and 7 °C, and7 °C at 24, 16 and one stores, respectively. The maximum temperatures were4 °C, between 4 and 7 °C and7 °C at 3, 18, and 20 stores, respectively. The median ages were 0 day, 1 day, and 2 or 3 days at 19, 17 and 5 stores, respectively. The maximum ages were ⩽2 days, between 2 and 4 days, and4 days at 21, 14 and six stores, respectively. Temperatures were generally lower at the backs than at the fronts of cases, on upper than on bottom shelves, and within than on the tops of stacks of packs. Temperatures were apparently not affected by the positions of packs along the lengths of cases, and did not differ at different times of day.

Carnobacterium spp. are commonly isolated from a variety of foods, especially from meats stored under anaerobic atmospheres at refrigeration temperatures, but the role of these organisms in the spoilage of meat and meat products is yet to be determined. Cresol Red Thallium Acetate Sucrose (CTAS) agar was developed as a selective medium for enumeration of carnobacteria, however problems such as poor recovery of Carnobacterium spp. and interference by other microorganisms have precluded its general use. The aim of this study was to improve CTAS agar by broadening its spectrum of selective recovery for carnobacteria while restricting the ability of interfering species to grow. Ten Carnobacterium spp. (five ATCC cultures and five isolates from fresh pork) and 20 other genera were used in testing the agar. A wider range of Carnobacterium spp. recovery was obtained by modifying concentrations of sucrose, manganese sulphate and thallium acetate. Additions of inulin and thiamine hydrochloride also improved growth response. The additions of vancomycin and Chrisin® (nisin) eliminated interference from other microorganisms. A two-temperature incubation procedure was included to improve the characteristic growth of Carnobacterium spp. on the modified medium, identified as Cresol Red Thallium Sucrose Inulin (CTSI) agar. Lactic acid bacteria and Enterobacteriaceae were unable to grow on CTSI incubated aerobically. Growth of Carnobacterium spp. on CTSI yielded pink colonies, except for Cb. mobile, which formed gray colonies. In some instances, a red precipitate formed in the center of the colony. Yellowing and clearing of the growth medium was also frequently observed. Recovery of carnobacteria using CTSI was identical to that obtained with All Purpose Tween (APT) agar.

A nitrogen–refrigerated container was designed to control the temperature of pre–chilled meat in the range of –0.5 to –2.0 C to maximize its storage life without freezing. An acrylic box was built and fitted inside an insulated shell to form a jacketed container. A temperature control algorithm controlled a liquid N2 supply and a heater in the jacket. Except at the top shelf of the container, the meat temperatures were maintained within the designated limits. The design shows promise for commercial use with N2 consumption of 0.9, 2.4, and 4.3 kg/h at outside temperatures of 0, 15, and 30 C, respectively.

Three groups of six yearling steers (three rumen fistulated plus three nonfistulated) fed one of three different grain diets (85% cracked corn, 15% whole cottonseed and 70% barley, or 85% barley) were inoculated with 10(10) CFU of Escherichia coli O157:H7 strain 3081, and the presence of the inoculated strain was followed in the rumen fluid and feces for a 10-week period. E. coli O157:H7 was rapidly eliminated from the rumen of the animals on all three diets but persisted in the feces of some animals up to 67 days after inoculation, suggesting that the bovine hindgut is the site of E. coli O157:H7 persistence. A significant difference existed in the levels of E. coli O157:H7 shed by the animals among diets on days 5, 7, 49, and 63 after inoculation (P0.05). No significant difference was found between the levels shed among diets on days 9 through 42 and on day 67 (P0.05). The number of animals that were culture positive for E. coli O157:H7 strain 3081 during the 10-week period was significantly higher for the barley fed group (72 of 114 samplings) as opposed to the corn fed group (44 of 114 samplings) (P0.005) and the cottonseed and barley fed group (57 of 114 samplings) (P0.05). The fecal pH of the animals fed the corn diet was significantly lower (P0.05) than the fecal pH of the animals fed the cottonseed and barley and barley diets, likely resulting in a less suitable environment for E. coli O157:H7 in the hindgut of the corn fed animals. E. coli O157:H7 strain 3081 was present in 3 of 30 (corn, 1 of 10; cottonseed, 1 of 10; barley, 1 of 10) animal drinking water samples, 3 of 30 (corn, 1 of 10; cottonseed, 0 of 10; barley, 2 of 10) water trough biofilm swabs, 5 of 30 (corn, 0 of 10; cottonseed, 2 of 10; barley, 3 of 10) feed samples, and 30 of 30 manure samples taken from the pens during the entire experimental period. Mouth swabs of the steers were also culture positive for E. coli O157:H7 strain 3081 in 30 of 180 samples (corn, 7 of 60; cottonseed, 4 of 60; barley, 19 of 60) taken during the 10-week period. Minimizing environmental dissemination of E. coli O157:H7 in conjunction with diet modification may reduce numbers of E. coli O157:H7-positive cattle.

The hygienic performances of the processes for the production of cooled carcasses at eight pork packing plants were assessed from small sets of microbiological data. At each plant, a single sample was obtained from a randomly selected site on each of 25 randomly selected carcasses at each of three stages of processing, which were after polishing, after washing at the end of the dressing process, and after cooling. The aerobic bacteria, coliforms and Escherichia coli recovered from each sample were enumerated. When bacteria of one type were recovered fromor = 20 of 25 samples, the log mean number of those bacteria on the population of carcasses undergoing processing was estimated on the assumption that the set of counts was normally distributed. The log of the total number recovered from 25 samples was calculated for each set of counts. The log mean numbers of total aerobic bacteria recovered from the polished carcasses at different plants ranged from about 1.9 to 3.8 log cfu cm(-2). At six of the plants, the log mean numbers of total aerobes on the cooled carcasses did not differ substantially from the log mean numbers on the polished carcasses, but the log mean numbers on the cooled carcasses were substantially higher at one plant and substantially lower at another than on the polished carcasses. Coliforms and E. coli were recovered from too few samples in most sets from cooled carcasses for estimation of their log mean numbers. However, the log total numbers of coliforms and E. coli recovered indicated that substantial numbers of those organisms were added to carcasses during the dressing processes at four of the plants, and that the numbers on the carcasses were substantially reduced by the processes for cooling without spraying at two of the plants. At seven of the plants, the total numbers of coliforms and E. coli recovered from cooled carcasses were3.1 and2.2 log cfu 2500 cm(-2), respectively. The findings indicate that production processes for pig carcasses can be operated to give cooled carcasses with log mean numbers of total aerobes2 cm(-2), and log total numbers of coliforms and E. coli each1 2500 cm(-2).