Beef Carcass Tissue Research Articles

Antimicrobial Efficacy of a Lactic Acid and Citric Acid Blend against Shiga Toxin-Producing Escherichia coli, Salmonella, and Nonpathogenic Escherichia coli Biotype I on Inoculated Prerigor Beef Carcass Surface Tissue

Studies were conducted to (i) determine whether inoculants of nonpathogenic Escherichia coli biotype I effectively served as surrogates for E. coli O157:H7, non-O157 Shiga toxin-producing E. coli, and Salmonella when prerigor beef carcass tissue was treated with a commercially available blend of lactic acid and citric acid (LCA) at a range of industry conditions of concentration, temperature, and pressure; (ii) determine the antimicrobial efficacy of LCA; and (iii) investigate the use of surrogates to validate a hot water and LCA sequential treatment as a carcass spray intervention in a commercial beef harvest plant. In an initial laboratory study, beef brisket tissue samples were left uninoculated or were inoculated (∼6 log CFU/cm(2)) on the adipose side with E. coli O157:H7 (5-strain mixture), non-O157 Shiga toxin-producing E. coli (12-strain mixture), Salmonella (6-strain mixture), or nonpathogenic E. coli (5-strain mixture). Samples were left untreated (control) or were treated with LCA, in a spray cabinet, at one of eight combinations of solution concentration (1.9 and 2.5%), solution temperature (43 and 60°C), and application pressure (15 and 30 lb/in(2)). In a second study, the E. coli surrogates were inoculated (∼6 log CFU/cm(2)) on beef carcasses in a commercial facility to validate the use of a hot water treatment (92.2 to 92.8°C, 13 to 15 lb/in(2)) followed by an LCA treatment (1.9%, 50 to 51.7°C, 13 to 15 lb/in(2), 10 s). In the in vitro study, surrogate and pathogen bacteria did not differ in their response to the tested LCA treatments. Treatment with LCA reduced (P < 0.05) inoculated populations by 0.9 to 1.5 log CFU/cm(2), irrespective of inoculum type. The hot water and LCA sequential treatments evaluated in the commercial facility reduced (P < 0.05) the inoculated nonpathogenic E. coli surrogates on carcasses by 3.7 log CFU/cm(2). This study therefore provides the meat industry with data for this sequential multiple hurdle system for the operation parameters described.

Prediction of beef carcass composition and tissue distribution using ultrasound scanning

1 page, 1 table.-- Contributed to: Proceedings of the British Society of Animal Science (Belfast, UK, 12-14 April, 2010).

Assessing beef carcass tissue weights using computed tomography spirals of primal cuts

More than 800 beef primal cuts from 44 Aberdeen Angus and Limousin-cross steers carcasses were scanned using spiral computed tomography (CT) and dissected. Thresholds for the segmentation of fat, muscle and bone in the CT spirals were estimated with the objective of assessing the weight of these tissues in the primal cuts and in the entire carcasses. Thresholds were estimated using half of the dataset (DBE) and then validated in the other half (DBV). Automatic image analysis procedures were used to assess tissue weights. The R 2 of the regression between primal tissue weight by dissection and CT were high in both datasets for fat (DBE, 0.89; DBV, 0.92), muscle (DBE, 0.99; DBV, 0.99) and bone (DBE, 0.95; DBV, 0.97). The estimation of total carcass tissue weights were also very accurate for the three tissues ( R 2 values of 0.95 to 0.96), indicating that CT scanning may deliver very accurate information on beef carcass composition faster and with lower cost than physical dissection and without damaging or depreciating the primal joints.

Identification of Escherichia coli O157:H7 Meat Processing Indicators for Fresh Meat through Comparison of the Effects of Selected Antimicrobial Interventions

Fresh meat products can become contaminated with the pathogen Escherichia coli O157:H7 during the slaughter process; therefore, an E. coli O157:H7 indicator to verify the effectiveness of process controls in slaughter establishments would be extremely useful. The hides of 20 beef cattle were sampled, and 113 bacterial isolates were obtained. Thirteen of these isolates representing four genera, Escherichia, Enterobacter, Providencia, and Serratia, were selected based on growth and biochemical characteristics similar to those of five clinical strains of E. coli O157:H7. The temperature sensitivity was determined for the individual isolates and the five E. coli O157:H7 strains at 55 and 65°C. D65-values for all 13 isolates were not significantly different from D65-values of the E. coli O157:H7 strains. E. coli isolates were the only isolates whose D55-values were not significantly different from those of the E. coli O157:H7 strains. E. coli isolates P3 and P68 were more resistant to the effects of 55°C than were the other E. coli isolates but were not significantly different from E. coli O157:H7 WS 3331 (P > 0.05). The remaining E. coli isolates (P1, P8, and P14) were not significantly different from E. coli O157:H7 strains ATCC 35150, ATCC 43894, ATCC 43895, and WS 3062 (P > 0.05). Prerigor lean and adipose beef carcass tissue was artificially contaminated with stationary-phase cultures of the five E. coli beef cattle isolates or a cocktail of five E. coli O157:H7 strains in a fecal inoculum. Each tissue sample was processed with the following microbial interventions: 90°C water; 90°C water followed by 55°C 2% lactic acid; 90°C water followed by 20°C 2% lactic acid; 20°C water followed by 20°C 2% lactic acid; 20°C water followed by 20°C 20 ppm chlorine; and 20°C water followed by 20°C 10% trisodium phosphate. The appropriateness of the E. coli isolates as potential E. coli O157:H7 indicators was dependent upon the microbial intervention utilized. For all microbial intervention methods applied irrespective of tissue type, the mean log reductions of at least two E. coli isolates were not significantly different from the mean log reduction of the E. coli O157:H7 cocktail (P > 0.05). Because of the frequent employment of multiple microbial interventions in the cattle industry, no single isolate can realistically represent the effectiveness of all microbial interventions for reduction of E. coli O157:H7. Thus, the use of a combination of E. coli isolates may be required to accurately predict the effectiveness of microbial intervention methods on the reduction of E. coli O157: H7 in beef carcass tissue.

Effect of Simulated Spray Chilling with Chemical Solutions on Acid-Habituated and Non–Acid-Habituated Escherichia coli O157:H7 Cells Attached to Beef Carcass Tissue

Samples (10 by 20 by 2.5 cm) of beef carcass tissue were inoculated (104 to 105 CFU/cm2) with Escherichia coli O157: H7 that was either non–acid habituated (prepared by incubating at 15°C for 48 h in inoculated filter-sterilized composite [1:1] of hot and cold water meat decontamination runoff fluids, pH 6.05) or acid habituated (prepared in inoculated water fluids mixed with filter-sterilized 2% lactic acid [LA] runoff fluids in a proportion of 1/99 [vol/vol], pH 4.12). The inoculated surfaces were exposed to conditions simulating carcass chilling (−3°C for 10 h followed by 38 h at 1°C). Treatments applied to samples (between 0 and 10 h) during chilling included the following: (i) no spraying (NT) or spraying (for 30 s every 30 min) with (ii) water, (iii) cetylpyridinium chloride (CPC; 0.1 or 0.5%), (iv) ammonium hydroxide (AH; 0.05%), (v) lactic acid (LA; 2%), (vi) acidified sodium chlorite (ASC; 0.12%), (vii) peroxyacetic acid (PAA; 0.02%), (viii) sodium hydroxide (SH; 0.01%), or (ix) sodium hypochlorite (SC; 0.005%) solutions of 4°C. Samples were taken at 0, 10, 24, 36, and 48 h of the chilling process to determine changes in E. coli O157:H7 populations. Phase 1 tested water, SH, PAA, LA, and 0.5% CPC on meat inoculated with non–acid-habituated pathogen populations, whereas phase 2 tested water, SC, AH, ASC, LA, and 0.1% CPC on meat inoculated with acid- and non–acid-habituated populations. Reductions in non–acid-habituated E. coli O157:H7 populations from phase 1 increased in the order NT = water = SH < PAA < LA < CPC. Reductions from phase 2 for acid-habituated cells increased in the order NT = water = SC < ASC = LA = AH < CPC, whereas on non–acid-habituated cells the order observed was NT = water = SC < AH = ASC < LA < CPC. Previous acid habituation of E. coli O157:H7 inocula rendered the cells more resistant to the effects of spray chilling, especially with acid; however, the trend of reduction remained spray chilling with water = non–spray chilling < spray chilling with chemical solutions.

Effect of Different Levels of Beef Bacterial Microflora on the Growth and Survival of Escherichia coli O157:H7 on Beef Carcass Tissue

The influence of various levels of endogenous beef bacterial microflora on the growth and survival of Escherichia coli O157:H7 on bovine carcass surface tissue was investigated. Bacterial beef microflora inoculum was prepared by enriching and harvesting bacteria from prerigor lean bovine carcass tissue (BCT) and was inoculated onto UV-irradiated prerigor BCT at initial levels of 105, 104, 103, and <103 CFU/cm2. Additional control BCT was inoculated with sterile H2O. E. coli O157:H7 was inoculated onto all tissues at an initial level of 102 CFU/cm2. Following a 48-h incubation at 4°C, BCT was incubated up to 14 days at 4 or 12°C, either aerobically or vacuum packaged. Regardless of the microflora level, there was no substantial growth of E. coli O157:H7 on BCT during storage at 4°C under either aerobic or vacuum-packaged conditions. Instead, viable cell numbers at 4°C remained constant, with no reduction in numbers associated with the different beef microflora levels. E. coli O157:H7 grew on all BCT stored at 12°C, regardless of microflora inoculation treatment, reaching higher populations on aerobic samples than on vacuum-packaged samples in 10 days. However, the presence of the beef microflora did appear to delay the onset of growth or slow the growth of the pathogen, and E. coli O157:H7 counts on BCT without added microflora were generally higher following 7 to 10 days of 12°C storage than those counts on BCT inoculated with beef microflora. These data demonstrate the importance of temperature control during meat handling and storage to prevent the outgrowth of this pathogen and indicate that proper sanitation and processing practices that prevent and reduce contamination of carcasses with E. coli O157:H7 are essential, regardless of background microflora levels.

Monitoring the microbial contamination of beef carcass tissue with a rapid chromogenic Limulus amoebocyte lysate endpoint assay.

A chromogenic Limulus amoebocyte lysate (LAL) endpoint assay was found to be an accurate and rapid means of gauging levels of beef carcass microbial contamination within 10 min. The assay demonstrated a high correlation with the total mesophilic bacterial and coliform surface populations from inoculated beef carcass surface tissues. This assay was tested on a set of actual beef carcass surface samples (n = 121) demonstrating the utility of the chromogenic LAL test as a means of monitoring carcass microbial contamination in a near real-time fashion. Classifying the chromogenic LAL results into four contamination groups was found to be a sound means of utilizing the resultant chromogenic LAL data for detecting carcasses with high levels of microbial contamination. For beef carcass testing, this assay can be used with no instrumentation other than the required 37 degrees C incubator and, as an option, a microplate reader.

Effects of acid adaptation of Escherichia coli O157:H7 on efficacy of acetic acid spray washes to decontaminate beef carcass tissue.

Exposure to low pH and organic acids in the bovine gastrointestinal tract may result in the induced acid resistance of Escherichia coli O157:H7 and other pathogens that may subsequently contaminate beef carcasses. The effect of acid adaptation of E. coli O157:H7 on the ability of acetic acid spray washing to reduce populations of this organism on beef carcass tissue was examined. Stationary-phase acid resistance and the ability to induce acid tolerance were determined for a collection of E. coli O157:H7 strains by testing the survival of acid-adapted and unadapted cells in HCl-acidified tryptic soy broth (pH 2.5). Three E. coli O157:H7 strains that were categorized as acid resistant (ATCC 43895) or acid sensitive (ATCC 43890) or that demonstrated inducible acid tolerance (ATCC 43889) were used in spray wash studies. Prerigor beef carcass surface tissue was inoculated with bovine feces containing either acid-adapted or unadapted E. coli O157:H7. The beef tissue was subjected to spray washing treatments with water or 2% acetic acid or left untreated. For strains ATCC 43895 and 43889, larger populations of acid-adapted cells than of unadapted cells remained on beef tissue following 2% acetic acid treatments and these differences remained throughout 14 days of 4 degrees C storage. For both strains, numbers of acid-adapted cells remaining on tissue following 2% acetic acid treatments were similar to numbers of both acid-adapted and unadapted cells remaining on tissue following water treatments. For strain ATCC 43890, there was no difference between populations of acid-adapted and unadapted cells remaining on beef tissue immediately following 2% acetic acid treatments. These data indicate that adaptation to acidic conditions by E. coli O157:H7 can negatively influence the effectiveness of 2% acetic acid spray washing in reducing the numbers of this organism on carcasses.

Comparison of Sponging and Excising as Sampling Procedures for Microbiological Analysis of Fresh Beef-Carcass Tissue

Sponging and excising were evaluated as sampling procedures for microbiological analysis of beef-carcass tissue. Brisket tissue portions (10 × 10 cm) were inoculated with 2 ml of an Escherichia coli ATCC 25922 cell suspension (3 × 108 CFU/ml). After 30 min, the portions were sampled by excising (EX) or swabbing (SP) with a sterile sponge and were analyzed for aerobic plate counts on tryptic soy agar and for total coliform counts and E. coli counts on Petrifilm E. coli count plates. Another set of inoculated samples was analyzed after being spray washed, in sequence, with water (6 s, 35°C, 3.4 bar), acetic acid (2%, 6 s, 35°C, 2.1 bar), water (20 s, 42°C, 20.7 bar), and acetic acid (2%, 6 s, 35°C, 2.1 bar). Additional samples were sampled for analysis after chilling at 7°C for 24 h. Bacterial counts recovered were influenced (P ≤ 0.05) by procedure of sampling (EX versus SP), time of sampling (0.5 versus 24 h), and by their interactions. Counts recovered 0.5 h after inoculation from unwashed or spray-washed samples were similar between the two sampling procedures (EX and SP). However, counts recovered after 24 h of sample storage were significantly (P ≤ 0.05) lower for the SP compared with the EX procedure. The results indicated that as the carcass tissue was stored, recovery of bacteria by SP was less efficient than was recovery by EX.

Incorporation of nisin into a meat binding system to inhibit bacteria on beef surfaces.

In two separate experiments, the bacteriocin, nisin, was incorporated into a commercially available meat binding system (Fibrimex) and applied to meat surfaces as a way of inhibiting the meat spoilage organism, Brochothrix thermosphacta during extended refrigerated storage. In experiment 1, pre-rigor lean beef carcass tissue (BCT) was inoculated with B. thermosphacta, left untreated (U), treated with 10 micrograms ml-1 nisin (N), Fibrimex (F) or Fibrimex containing 10 micrograms ml-1 nisin (FN), held aerobically at 4 degrees C for up to 7 d, and populations of B. thermosphacta and nisin activity determined. Experiment 2 determined the effects of the same treatments but on post-rigor, frozen and thawed lean BCT that was inoculated, vacuum-packaged, and stored at 4 degrees C for up to 14 d. In both experiments, N- and FN-treated tissues exhibited significantly lower populations of B. thermosphacta compared to U- and F-treated tissues, for the duration of refrigerated storage. Nisin activity was detected up to 7 d in N- and FN-treated samples from experiment 1. However, activity was detected only to days 0 and 2 in FN- and N-treated samples, respectively, from experiment 2. These studies indicate that the addition of a bacteriocin to a meat binding system and application to meat surfaces may be useful in reducing undesirable bacteria in restructured meat products.

Reduction of foodborne micro-organisms on beef carcass tissue using acetic acid, sodium bicarbonate, and hydrogen peroxide spray washes

In an attempt to control beef carcass contamination, a search for effective carcass washing treatments has become a major focus in the area of microbiological meat safety. Spray-wash treatments utilizing 1.0% acetic acid, 3% hydrogen peroxide, 1% sodium bicarbonate, alone or in combination, were performed to evaluate their efficacy in reducing numbers ofEscherichia coli,ListeriainnocuaandSalmonella wentworth. The fascia surface of lean and adipose tissue was inoculated with sterilized fecal slurry containing the designated bacteria to obtain 5 log8cfu cm−2. A pilot scale model carcass washer was used to apply the spray treatment (80 psi, 15 s, 25°C). Control samples received no spray treatments. Following treatments, lean and adipose samples were immediately analyzed or held for 24 h at 5°C for analysis of the treatments, for residual bacterial populations, surface pH, color analysis, and residual hydrogen peroxide. The combination wash of acetic acid/3% hydrogen peroxide (AAHP) resulted in the greatest reductions of 3.97 and 3.69 log8cfu cm−2forE. colion lean or adipose tissue, respectively. Spray washes with AAHP reducedL. innocuaby 3.05 log8cfu cm−2on lean tissue and 3.52 log8cfu cm−2on adipose tissue, whileS. wentworthwas reduced by 3.37 log8cfu cm−2on lean and 3.69 log8cfu cm−2on adipose tissue. A spray-wash treatment consisting of the right combination of safe and acceptable solutions may be effective for improving the microbial safety of beef.

Parameters Affecting the Efficacy of Spray Washes against Escherichia coli O157:H7 and Fecal Contamination on Beef

A series of progressive experiments was conducted with a model carcass washer using tap water and 2% acetic acid sprays to determine if tissue type, inoculation menstruum, bacterial level, or spray temperature affect removal of bacteria from beef carcass tissue during spray washing. For the first experiment, prerigor (15 min postexsanguination), postrigor (24 h postexsanguination), or postrigor frozen (−20°C, 7 days), thawed, lean beef carcass tissue (BCT) was inoculated with bovine feces and subjected to spray washing (15 s, 56°C) with water or acetic acid. Spray washing with either compound resulted in bacterial populations that were similar for prerigor and postrigor BCT; however, remaining bacterial populations from spray-treated postrigor, frozen BCT were significantly (P ≤ 0.05) less than for the other two tissue types. For the second experiment, prerigor, lean BCT was inoculated with Escherichia coli O157:H7 suspended in bovine feces or physiological saline and spray washed (15 s, 56°C) with water or acetic acid. Bacterial populations were reduced to similar levels with acid sprays, regardless of menstruum. For the third experiment, E. coli O157:H7 in feces was used to contaminate prerigor lean BCT to obtain different initial bacterial levels (7, 5,3, and 1 log CFU/cm2). Spray washes (15 s, 56°C) with acetic acid reduced the level of the pathogen to 2.51 and 0.30 log CFU/cm2 when initial bacterial levels were 7 and 5 log CFU/cm2, and to undetectable levels when initial bacterial levels were 3 and 1 log CFU/cm2. In a fourth experiment, water or acetic acid (15 s), ranging from 30 to 70°C was applied to beef tissue contaminated with E. coli O157:H7 in feces. Remaining bacterial populations were not different between the water treatments or between the acid treatments at any temperature. While variables such as bacterial level and inoculation menstruum may affect the efficacy of spray washing with organic acids, these results indicate that tissue type or spray temperature do not.

Effects of Acetic Acid, Lactic Acid and Trisodium Phosphate on the Microflora of Refrigerated Beef Carcass Surface Tissue Inoculated with Escherichia coli O157:H7, Listeria innocua, and Clostridium sporogenes

The microbial profiles of inoculated beef carcass tissue (BCT) were monitored during prolonged refrigerated vacuum-packaged storage following antimicrobial treatment. An industrial spray wash cabinet was used to deliver water (W), 1.5 and 3.0% lactic (LA) or acetic (AA) acid, or 12% trisodium phosphate (TSP) washes. Fresh unaltered bovine feces spiked with antibiotic-resistant strains of Escherichia coli O157:H7, Listeria innocua, and Clostridium sporogenes were used to inoculate BCT prior to all treatments. The effect of treatments on bacterial populations was tracked by monitoring levels of specific-antibiotic-resistant(marked) bacteria along with mesophilic aerobic bacteria (APC), lactic acid bacteria (LAB), and pseudomonads for up to 21 days of storage at 5°C. Initial APC levels of approximately 5.6 log CFU/cm2 were reduced by 1.3to 2.0 log CFU/cm2 by LA, AA, and TSP treatments. Marked bacteria were reduced to <1.3 log CFU/cm2, remaining that way throughout the 21-day storage. TSP treatments were not different in effectiveness from acids for controlling growth of E. coli O157:H7 and C. sporogenes, but were less effective for APC, L. innocua, or LAB. The aerobic bacteria, L. innocua, and LAB had counts ≥7 log CFU/cm2 by 7 days in all but one case and by 14 days all had counts >7 log CFU/cm2 on the untreated controls and water-washed samples. Treatments generally added a degree of safety regarding the foodborne pathogens and pathogen models used for the present study when beef tissue was stored up to 21 days and in no case did the treatments appear to offer any competitive advantage to select microorganisms on BCT.

Effects of Steam-Vacuuming and Hot Water Spray Wash on the Microflora of Refrigerated Beef Carcass Surface Tissue Inoculated with Escherichia coli O157:H7, Listeria innocua, and Clostridium sporogenes

The fates of several bacterial populations on beef carcass surfaces were examined immediately following hot water washes (W) delivered through a beef carcass wash cabinet or application of steam-vacuum (SV). Additionally, the long-range effectiveness of W and SV on several bacterial populations was also determined during storage up to 21 days at 5°C under vacuum-packaged conditions. Fresh, unaltered bovine feces spiked with antibiotic-resistant strains of Escherichia coli O157:H7, Listeria innocua, and Clostridium sporogenes were used to inoculate beef carcass tissue prior to W or SV treatment. All treatments were equally effective as is indicated by bacterial populations immediately following any of the treatments (P > 0.05); however, the combination of SV followed by W consistently produced arithmetically greater bacterial reductions. In general, all treatments produced initial reductions of up to 2.7 log CFU/cm2 for APC, lactic acid bacteria, and L. innocua, but by 14 days bacterial numbers had increased to levels of at least 7 log CFU/cm2. E. coli O157:H7 was initially reduced by as much as 3.4 log CFU/cm2 and did not grow to original inoculation levels for the duration of the experiment. Vegetative counts of C. sporogenes were initially reduced by as much as 3.4 log CFU/cm2, and numbers continued to decline for the duration of the study. These results indicate that the use of W and SV effectively reduces bacterial populations from beef carcass tissue immediately after treatment. Additionally, storage of treated tissue up to 21 days at 5°C did not appear to offer any competitive advantage to potentially pathogenic microorganisms.

Efficacy of using a sponge sampling method to recover low levels ofEscherichia coliO157:H7,Salmonella typhimurium, and aerobic bacteria from beef carcass surface tissue

No abstract

Removal of Bacteria from Beef Tissue by Spray Washing after Different Times of Exposure to Fecal Material

This study examined the effect of exposure time of beef-fat fascia to an inoculated fecal paste on the efficiency of removal of bacteria by spray washing or rinsing. Brisket fat (obtained <15 min postmortem) samples (10 by 10 by 2 cm) were inoculated, in the geometric center of their fascia surface, with four 0.64-cm diameter loops of a bovine fecal paste containing an inoculum (108 CFU/g) of streptomycin-resistant Escherichia coli ATTC 11370. Triplicate samples were spray washed with water (35°C, 20.7 bar) and then rinsed with solutions of 2% acetic acid, 5% hydrogen peroxide, or 12% trisodium phosphate, or spray washed with water at 35°C or 74°C (20.7 bar), in an automated spray-washing cabinet for 12 s, after 0, 2, or 4 h of exposure to the inoculated fecal paste. The samples were analyzed for streptomycin-resistant bacterial counts. Washing or washing/rinsing at time 0 (immediately after exposure to the inoculated fecal paste) with trisodium phosphate, 35°C water, hydrogen peroxide, acetic acid, and 74°C water removed 3.04 ± 0.40, 3.52 ± 0.55, 3.62 ± 0.67, 3.69±0.72 and 4.17±0.55 log CFU/cm2, respectively. Applying the spray-washing treatments 2 or 4 h after exposure to the fecal paste resulted in significantly (P < 0.05) less removal (1.76 to 3.89 log CFU/cm2 after 2 hand 0.94 to 2.58 Jog CFU/cm2 after 4 h) of bacteria. Thus, the time of exposure to fecal contamination affected the attachment of bacteria to beef-carcass tissue, as indicated by the decreasing numbers of bacteria removed by spray washing with increasing time of exposure, regardless of the washing treatment. The most effective washing agent was 74°C water at all washing times.

Efficient Nondestructive Sampler for Carcasses and Other Surfaces

Two versions of an electrically powered device (Rotorinser) to sample carcasses or other surfaces in situ for microbiological analysis and several different sampling protocols were evaluated against excision plus stomaching for ability to remove bacteria from pig skin and beef carcass tissue. Both devices sampled circular areas of approximately 14 cm2. Ten tissue samples were used for each set of conditions. Rotorinser bacterial removal efficiency was calculated as R/(R + S), where R is the Rotorinser count (CFU cm−2) and S is the count on stomached excised tissue after rotorinsing. Stomacher efficiencies were calculated as S1/(S1 + S2), where S1 is the first stomacher count of excised tissue and S2 is the count from a second stomaching. Both Rotorinsers were much better than traditional swabs. Rotorinser 1 gave removal efficiencies of 0.79 to 0.88 for beef, and 0.79 to 0.95 for pork. Prewetting surfaces for 5 min improved removal, but mixtures of enzymes did not. Rotorinser 2 applied with NaCl or NaCl-Tween 80 diluent for either 30 or 60 s was significantly better (0.93 and 0.98) than the stomacher (0.86) at removing aerobic mesophilic bacteria from pork skin. The Rotorinser causes negligible tissue damage and can be used on surfaces at any angle.

Factors Influencing Attachment of Escherichia coli O157:H7 to Beef Tissues and Removal Using Selected Sanitizing Rinses

Attachment of E. coli O157:H7 and E. coli K12 to beef tenderloin filet, chuck, and adipose tissues was studied. Most attachment occurred within 1 min of incubation; the number of attached organisms depended on the concentration of bacteria in the liquid inoculum. Similar levels of E. coli bound to the three types of beef tissues tested. E. coli O157:H7 was heavily piliated; however, there was no significant difference between levels of bound E. coli O157:H7 and E. coli K12, indicating that these surface structures apparently are not involved in attachment. Scanning electron photomicrographs of meat tissue and of purified collagen suggested that bacteria attached primarily to collagen fibers. Rinsing solutions consisting of 10% trisodium phosphate (TSP), 2% acetic acid (HAc), phosphate-buffered saline (PBS) and combinations of each were tested for effectiveness in reducing the number of attached E. coli. The level of bacteria removed from tenderloin tissue following TSP, HAc, or PBS rinses did not differ considerably. When beef tissues were stored at 4°C for 18 h after the various rinse combinations, TSP rinse treatments reduced the levels of E. coli K12 and O157:H7 attached to adipose tissue up to 3.4 and 2.7 log units, respectively, compared to PBS rinse treatments. Therefore, TSP may be effective for reducing populations of E. coli O157:H7 on beef carcass tissue.

Chlorine Dioxide Spray Washes for Reducing Fecal Contamination on Beef

The ability of chlorine dioxide (ClO2) to reduce bacterial populations (i.e., aerobic plate count, APC) on fecally contaminated beef carcass tissue (BCT) was examined in two separate experiments. In the first study, individual pieces of BCT were inoculated with fresh bovine feces to obtain approximately 6.60 log APC/cm2 and spray treated (10 s; 520 kPa; 16°C) with ClO2 at tank concentrations ranging from 0 to 20 ppm. Bacterial populations were reduced by no more than 0.93 log CFU/cm2, regardless of ClO2 concentration, and were not statistically different (P ≥ 0.05) from water-treated BCT. In the second study, tap water (16°C) and ClO2 at a tank concentration of 20 ppm (16°C) were sprayed (690 kPa) for 15, 30, and 60 s onto BCT inoculated with fresh bovine feces to obtain approximately 5.80 log APC/cm2 and the remaining bacterial populations compared. While spray treatments with ClO2 or water reduced APC by 1.53 to 2.07 log CFU/cm2, spray treatments with either water or ClO2 at 15, 30 or 60 s were not statistically different (P ≥ 0.05). Similar reductions (1.61 log CFU/cm2) were observed when BCT was spray treated for 60 s with tap water followed by a 60 s spray wash with ClO2. These results demonstrate that spray treatments with ClO2 are no more effective than water for reducing fecal contamination on beef.

Microbial ATP Bioluminescence as a Means to Detect Contamination on Artificially Contaminated Beef Carcass Tissue

The use of microbial ATP bioluminescence was evaluated as a means to rapidly detect gross microbial contamination from feces on bovine-carcass surface tissue (BCT). Microbial ATP was selectively distinguished from nonmicrobial ATP by the assay procedure used. Regression analyses of microbial ATP and viable count scatterplots showed lean and adipose BCT artificially contaminated with bovine feces had the same regression line parameters (P < 0.05), and therefore, the microbial ATP responses were similar for both tissue types. Correlation coefficients (r) of these regression lines were >0.90 for both tissue types. Results indicated that swab samples can be held at 5°C for up to 6 h without compromising microbial ATP bioluminescence assay results. The microbial ATP bioluminescence assay shows potential for use as a means to rapidly detect fecal contamination on red meat carcasses and to gauge decontamination effectiveness and hence could monitor critical control points in a processing-plant HACCP plan.