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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

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

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.

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 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.

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.

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.

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.

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.

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.

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

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.

There is growing interest in centralized preparation of retail-ready meat cuts for distribution to widely dispersed retail stores due to the convenience of having high-quality ready-to-go products that are consistently provided to consumers at lower cost. Various centralized packaging techniques are described. Of all packaging techniques, master packaging is the most economical and shows promise for commercial application. Nevertheless, the master-packaging technique must be integrated with strict temperature control in a narrow range just above freezing (- 1.5 +/- 0.5 degrees C), good processing hygiene, and maintenance of a completely anoxic atmosphere in the package headspace throughout the distribution period to maximize storage life. Packaging using the CAPTECH process reduces the residual O2 present in the headspace to 300 ppm. Oxygen scavengers must be incorporated in the package to absorb the residual O2 and preserve the metmyoglobin reducing activity of meat tissues. Integration of all these technologies can provide a storage life of retail-ready meat up to 10 weeks in the master package followed by 3 days of retail display life. This extension of storage life is sufficient for transporting meat to distant markets.

Use of pulsed electric fields (PEFs) for inactivation of microorganisms is one of the more promising nonthermal processing methods. Inactivation of microorganisms exposed to high-voltage PEFs is related to the electromechanical instability of the cell membrane. Electric field strength and treatment time are the two most important factors involved in PEF processing. Encouraging results are reported at the laboratory level, but scaling up to the industrial level escalates the cost of the command charging power supply and of the high-speed electrical switch. In this paper, we critically review the results of earlier experimental studies on PEFs and we suggest the future work that is required in this field. Inactivation tests in viscous foods and in liquid food containing particulates must be conducted. A successful continuous PEF processing system for industrial applications has yet to be designed. The high initial cost of setting up the PEF processing system is the major obstacle confronting those who would encourage the system's industrial application. Innovative developments in high-voltage pulse technology will reduce the cost of pulse generation and will make PEF processing competitive with thermal-processing methods.