Beef Carcass Surfaces Research Articles

Comparison of methods to determine the microbiological contamination of surfaces of beef carcasses by hydrophobic grid membrane filters, standard pour plates or flow cytometry

A routine hydrophobic grid membrane filter (HGMF) method previously used to estimate the hygienic adequacy of the process of beef carcass production was compared with two variations of this method, the standard pour plate (SPP) method of enumerating aerobic cells, and the flow cytometry method of enumerating autofluorescent particles for 150 excision samples of surfaces of beef carcass. The application of 1.0% 2,3,5-triphenyltetrazolium chloride (TTC) sprayed as an aerosol after incubation of HGMF on trypticase soy agar for 24 or 42 h yielded significantly higher counts ( P<0.001) than HGMF incubated on trypticase soy agar with TTC for the same length of time. TTC applied in aerosol and 24 h incubation provided higher counts than TTC in media and 42 h incubation. The linear regression equations obtained in this study could serve to estimate the conversion of log 10most probable numbers growth units per millilitre obtained from HGMF on plates with TTC in media or applied in aerosol to SPP log 10colony forming units/per millilitre. It was assumed that bacteria taken from carcasses from 15 farm sources were representative of bacteria on beef carcasses at other Alberta abattoirs. This facilitated conversion of data obtained by the automated HGMF method to SPP data in verification of the workings of hazard analysis and critical control point systems for beef slaughter processes. Under these experimental conditions no linear relationship was found between fluorescent particles in 80 of the above surface samples and colony forming units produced by the SPP method.

Use of total or Escherichia coli counts to assess the hygienic characteristics of a beef carcass dressing process

Swab samples were obtained from 3 sites on the surfaces of beef carcasses passing through a high speed dressing process, with 24 samples from each site being obtained at each of 4 points in the process. The aerobic microflora recovered from each swab after incubation at 25 °C was enumerated and characterized, and numbers of coliforms and Escherichia coli were determined. The data on aerobic flora indicated that skinning results in similar contamination of all 3 sites, that further deposition of bacteria at the brisket site occurs after skinning, and that trimming and washing achieve modest decontamination of the neck and brisket site, and extensive decontamination of the rump site. Changes in flora compositions during processing were too limited to much affect the assessment based on the aerobic flora total counts alone. The E. coli data indicated that during skinning the rump site was more heavily contaminated with faecal organisms than the other sites, that contamination of the brisket site is little altered between skinning and carcass splitting, although there is an extensive redistribution of E. coli at the neck site and sporadic, limited decontamination of the rump site, and that trimming and washing do not decontaminate the neck or rump sites, but that the rump site is extensively decontaminated by trimming. There was good correlation between E. coli and coliform counts, but weak correlation between E. coli and aerobic, 25 °C, counts. The findings suggest that assessments of beef carcass dressing processes for Hazard Analysis: Critical Control Point (HACCP) purposes should be based on enumerations of E. coli, or perhaps coliforms, rather than of the aerobic flora, to avoid important misunderstandings of the hygienic effects of the various operations in a process.

Effectiveness of a steam-vacuum sanitizer for reducing Escherichia coli O157:H7 inoculated to beef carcass surface tissue.

A steam-vacuum sanitizer reduced aerobic plate counts associated with bovine faecal contamination from 5.5 log10 cfu cm-2 to 3.0 +/- 0.21 log10 cfu cm-2 on beef carcass short plates. The same beef carcass short plates inoculated with 7.6 +/- 0.09 log10 cfu cm-2 Escherichia coli O157:H7 in faeces, yielded an average residual level of E. coli O157:H7 of 2.1 +/- 0.21 log10 cfu cm-2, after steam-vacuum treatments. This study demonstrates the effectiveness of a steam-vacuum sanitizer for removing E. coli O157:H7 from beef carcasses.

Evaluation of six sampling methods for recovery of bacteria from beef carcass surfaces

Six bacterial sampling methods that might be used for rapid sampling of beef carcasses were evaluated in two separate studies. In Study 1, bacterial recovery from uninoculated beef rounds was 2.6, 2.3, 2.1 and 1.3 log10 cfu cm-2, respectively for excision (EX), and swabbing with cheesecloth (CC), sponge (SP) and cotton-tipped wooden swabs (CS). For Study 2, beef tissue was inoculated with bovine faeces at different levels and the mean recovery was 3.7, 3.0, 3.1 and 3.1 log10 cfu cm-2, respectively for EX, and swabbing with SP, griddle screen (GS) and 3M mesh (M). For both studies EX was determined to be the most consistently effective method while the initial study determined swabbing with CS was the least effective of the methods used. In both studies the most abrasive materials approached the effectiveness of EX even at low inoculation levels. As the inoculation levels increased, the additional effect of abrasiveness was lessened. When the carcasses were contaminated with bovine faeces, the bacterial populations that were rapidly recoverable from beef tissue using SP, GS or M were not significantly lower than those recovered using EX. Consequently SP, GS or M are an adequate method of beef carcass sampling for rapid, in-plant process monitoring to detect faecal contamination.

Comparison of Methods for Decontamination from Beef Carcass Surfaces

Methods for the removal of fecal contamination from beef carcass surfaces were evaluated using a fecal suspension containing a rifampicin-resistant strain of either Escherichia coli O157:H7 or Salmonella typhimurium. Paired cuts from four distinct beef carcass regions (inside round, outside round, brisket, and clod) were removed from hot carcasses after splitting, and subcutaneous fat and lean carcass surfaces from these cuts were used to model decontamination of prechilled carcass surface regions. Hot carcass surface regions were contaminated with an inoculated fecal suspension in a 400-cm2 area and then treated by one of four treatments either immediately or 20 to 30 min after contamination. One paired contaminated surface region from each carcass side was trimmed of all visible fecal contamination. The remaining paired carcass surface region was washed either with water (35°C) or with water followed by a 2% lactic or acetic acid spray (55°C). Surface samples were obtained for microbiological examination before and after treatment from within and outside the defined area contaminated with the fecal suspension. All treatments significantly reduced levels of pathogens; however, decontamination was significantly affected by carcass surface region. The inside round region was the most difficult carcass surface to decontaminate, regardless of treatment. Washing followed by organic acid treatment performed better than trimming or washing alone on all carcass region surfaces except the inside round, where organic acid treatments and trimming performed equally well. Overall, lactic acid reduced levels of E. coli O157:H7 significantly better than acetic acid; however, differences between the abilities of the acids to reduce Salmonella were less pronounced. All treatments caused minimal spread of pathogens outside the initial area of fecal contamination, and recovery after spreading was reduced by organic acid treatments.

Decontamination of beef carcass tissue with nisin using a pilot scale model carcass washer

Nisin spray treatments were tested for controlling Gram-positive bacteria attached to beef carcass surface tissue using a pilot scale model carcass washer. Section of lean and adipose tissues were inoculated with approximately 4 log 10 cfu cm -2 of Brochothrix thermosphacta, Carnobacterium divergens or Listeria innocua. Following 28°C water or nisin sprays, bacterial populations were enumerated immediately and after incubation for 24 h at 4°C. Spray treatments with water did not significantly alter the bacterial populations at day 0 or 1 (< 1 log 10 reduction). However, nisin spray treatments (5000 AU ml -1) reduced populations by 1·79 to 3·54 log 10 cfu cm -2 at day 0 and by 1·97 to 3·60 log 10 cfu cm -2 at day 1. This study demonstrates that spray washing is an effective means of applying bacteriocins and that these compounds may be useful as sanitizers of red meat carcasses.

Microbiological Effects of Acid Decontamination of Beef Carcasses at Various Locations in Processing

Hot (55°C), dilute (1% v/v) lactic acid was sprayed on beef carcass surfaces immediately after dehiding, after evisceration (immediately before chilling), or at both locations. Surface samples of carcasses were examined for total aerobic plate counts (APCs) and for the presence of Salmonella and Listeria. APCs of treated beef carcasses were lower (P<0.05) than those of control carcasses. APCs were determined both at slaughter day 0 (immediately after carcasses enter the chill room) and after 72 h postmortem. At day 0, reductions in log10 APC by more than 90% occurred when carcasses were treated with lactic acid after evisceration or both after dehiding and after evisceration. The effect of lactic acid decontamination was greatest on carcasses treated with lactic acid both after dehiding and after evisceration. No further reductions in APCs of carcasses were observed on samples taken 72 h postmortem. No difference in color between control and acid-treated carcasses was observed. All samples tested for the presence of Salmonella were negative. Listeria was detected in three samples from control carcasses only. Samples obtained from strip loins of acid-treated or control carcasses did not show any consistent pattern of differences in microbiological counts. Additional data collected from carcasses sprayed with lactic acid in three different sized slaughter plants showed that irrespective of differences in size of slaughter facility, mean APCs of acid-treated carcasses were significantly (P<0.05) lower than those of control carcasses.

Indole-lnduced, Green to Brown-Black Pigment Formation by an Acinetobacter Strain from Beef

In determining aerobic plate counts of surfaces of beef carcasses, green to brown-black colonies of an Acinetobacter sp. appeared on tryptic soy agar plates. Pigmentation was induced by indole-producing organisms in close proximity of or overlapping with the Acinetobacter sp. Addition of indole to culture media also supported pigmentation of the Acinetobacter sp. Indole appeared to be a key intermediate compound in pigment formation.

Niveau de contamination microbiologique de quelques établissements d'abattage et de charcuterie “Approuvé Canada”

AbstractSix to seven consecutive sanitary surveys were conducted in five different “Canada Approved” meat packing plants and slaughterhouses in order to establish the level of bacterial contamination on working surfaces as well as on surfaces of slaughtered animals (chicken and beef) during their processing. The various microbiological parameters evaluated were total aerobic plate count at 22 and 35°C, total and fecal coliforms, fecal streptococci, molds and yeasts and Salmonella. A total of 634 samples was collected at different critical control points during these sanitary surveys in 197677. Contamination of the working surfaces in various plants varied from 106 to 108/77cm2(12 in2) for the total aerobic plate count at 22 and 35°C; 104 to 105 for yeasts and molds; 103 to 105 for total coliform and 103 for fecal streptococci, while only a few fecal coliform and Salmonella were isolated. Samples at the broiler plant showed an initial level of Salmonella of 76.9%.Surfaces of beef carcasses at the packing plants were also monitored; the total aerobic plate counts fluctuated from 1O4 to 109/77cm2. This high level of contamination could contribute to the high bacterial counts on the working surfaces. At time of sampling, every plant was inspected, the results of the latest sanitary survey discussed, and improved cleaning and disinfection techniques were suggested. The level of contamination was reduced considerably, as evidenced after the final sanitary survey which showed a 1,000 fold decrease in total aerobic plate counts. Salmonella positives decreased to 4.5% at the broiler slaughtering plant. We can conclude from this work that it is possible, with good manufacturing practices and appropriate cleaning and sanitizing procedures, to maintain low microbial levels on equipment and working surfaces.

Attachment of Microorganisms to Pork Skin and Surfaces of Beef and Lamb Carcasses

A model system was developed to study attachment to and possibly detachment of bacteria from pork skin and thin-surface slices of beef and lamb carcasses. The technique involves embedding pork skin and beef and lamb surfaces in solidified wax with the skin surface exposed. After exposure of the skin or carcass surface to bacterial suspensions and subsequent manipulations, the sample is removed aseptically from the wax and subjected to agar plate counting methods. A direct relationship existed between bacterial counts of the skin or carcass surface and concentration of bacterial cells in the attachment medium. Much of the bacterial attachment occurred during the first minute of immersion in the attachment medium, although in some instances continued attachment occurred over a 30-min period. Gram-negative motile bacteria showed greater attachment than did gram-positive non-motile species. Temperature and pH of the attachment medium had little effect on the extent of bacterial attachment.

Microbial Persistence on Inoculated Beef Plates Sprayed with Hypochlorite Solutions

Exterior surfaces of beef plates were inoculated with aerobic mesophilic, psychrotrophic, coliform, fecal coliform and Staphylococcus aureus bacteria before spraying with city water (7.03 kg/cm2) or with 100, 150 or 200 ppm hypochlorite solutions applied at 3.75, 5.25 or 7.03 kg/cm2) for 12 sec. Surface strips excised from the inoculated carcass regions were analyzed for bacterial persistence at 2 hand 2,4,8,16 and 20 days after spray treatment. A one log. or greater, reduction incoliforms, fecal coliforms and S. aureus counts occurred within 4 days for each spray treatment. Initial aerobic mesophilic and psychrotrophic counts were reduced by < 1 log within 2 h but increased to original inoculum levels within 8 days for each treatment. Mesophilic and psychrotrophic counts increased to > 3.5 logs higher than inoculated levels after 16 days at 4–6 C. Spray pressure (P < .01) was more effective in reducing mesophilic, psychrotrophic and S. aureus counts than was hypochlorite concentration (P < .05) while both variables were about equally effective against coliforms (P < .01) and fecal coliforms (P < .05). Surprisingly, reductions of psychrotrophic, coliform and S. aureus counts on the beef carcass surface sprayed with hypochlorite solutions were not significantly (P < .05) different from those observed on carcasses sprayed with city water. However, a significantly (P < .05) greater reduction in aerobic mesophile and fecal coliform counts at 2 days after treatment was obtained when using the intermediate spray pressure of 5.25 kg/cm2 containing 200 ppm hypochlorite, rather than city water. No undesirable change in beef grade, muscle shear or color property was observed for carcasses treated with the hypochlorite solutions.