ABSTRACT Peripheral lymph nodes (LNs) located in the fatty tissues of beef carcasses have been shown to harbor Salmonella and, thus, potentially contaminate ground beef. Salmonella prevalence within LNs is known to differ among feedlots. Two South Texas feeding operations (identified as locations A and B) known to harbor salmonellae in the feedlot environment, while historically producing cattle with opposing rates (one “high” and one “low”) of Salmonella prevalence in LNs, were used in this study. To determine whether this difference was due to cattle source or factors associated with different stages of feeding, weanling steers of common and known origin were followed through normal feeding stages at both operations. Eighty Angus-sired beef steers were harvested at each of four feeding stages: 1, postweaning; 2, background or stocker; 3, 60 days on feed; and 4, 120 days on feed. Left and right subiliac and superficial cervical LNs ( n = 304) were collected from each carcass, and similar node types were pooled by animal ( n = 152). Results showed a difference ( P < 0.05) in prevalence of Salmonella in bovine lymph nodes between location A and location B and among feeding stages in location B. Salmonella was not isolated from any feeding stage 1 (postweaning) or location A LN samples. Within location B, there was an increase in Salmonella prevalence as cattle moved into later stages of feeding: at 22.2% (4 of 18), 77.8% (14 of 18), and 94.4% (17 of 18) for feeding stages 2, 3, and 4, respectively. Although the reasons for the differences seen between feeding operations and for increased Salmonella prevalence in LNs at later feeding stages remain unexplained, these results indicate that factors other than cattle source are likely influencing Salmonella prevalence in LNs.

The U.S. Department of Agriculture Food Safety and Inspection Service (USDA-FSIS) has a specific lethality performance standard for ready-to-eat products. To assist meat processing establishments in meeting the performance standard, USDA-FSIS developed Appendix A, which provides guidelines for cooking temperatures, times, and relative humidity. This project determined whether the USDA-FSIS performance standards for lethality were met when using parameters other than those identified in Appendix A to cook large hams and beef inside rounds. The effects of alternative lethality parameters on the reduction of Salmonella Typhimurium and coliforms and on the toxin production of Staphylococcus aureus were evaluated. Large (9- to 12-kg) cured bone-in hams ( n = 80) and large (8- to 13-kg) uncured beef inside rounds ( n = 80) were used in this study. The products were subjected to 1 of 10 treatments defined by combinations of final internal product temperatures (48.9, 54.4, 60.0, 65.6, or 71.1°C) and batch oven relative humidities (50 or 90%). For all treatments, at least a 6.5-log reduction in Salmonella Typhimurium was achieved. The coliform counts were also substantially reduced for both hams and rounds. Across all treatments for both products, S. aureus toxin production was not detected. The relative humidity did not alter the lethality effectiveness for any of the treatments. The final internal temperatures and relative humidity combinations used in this project achieved the lethality performance standard established by USDA-FSIS for fully cooked, ready-to-eat products.

Two trials were conducted to determine the efficacy of cattle wash treatments in reducing pathogens on hides of cattle before slaughter. In trial I, live cattle ( n = 120) were washed in an automated, commercial cattle wash system with one of four treatments (single water wash, double water wash, water wash with 0.5% l -lactic acid, or water wash with 50 ppm chlorine). Samples were collected at three locations (brisket, belly, and inside round) pre- and posttreatment to evaluate the effectiveness of treatments on the reduction of aerobic plate counts, coliforms, Escherichia coli and the incidence of Salmonella . For all three locations, bacterial numbers increased from 0.1 to 0.8 log CFU/cm 2 posttreatment. In trial II, hide samples were inoculated in the laboratory with 6.0 log CFU/cm 2 of rifampicin-resistant Salmonella serotype Typhimurium. Hide wash treatments included higher concentrations of chlorine (100, 200, and 400 ppm) and l -lactic acid (2, 4, and 6%), as well as other antimicrobial agents such as ethanol (70, 80, and 90%), acetic acid (2, 4, and 6%), and Oxy-Sept 333 (0.5, 2, and 4%). Spray wash treatments with ethanol and 4 to 6% concentrations of lactic acid had greater ( P < 0.05) mean log reductions than 2% solutions of acetic or lactic acid, as well as 100, 200, and 400 ppm chlorine and the control water wash treatment. Spray wash treatments with Oxy-Sept 333 and 100, 200, or 400 ppm chlorine were not effective ( P > 0.05) in reducing Salmonella Typhimurium compared to the (control) distilled water spray wash treatment. Several effective cattle hide interventions were identified in a controlled laboratory setting, but the high concentrations required for effectiveness would likely present problems from an animal welfare standpoint.

Lactic acid and trisodium phosphate (TSP) were evaluated for the ability to reduce Escherichia coli and aerobic plate counts (APCs) on lamb breasts that were inoculated with a lamb fecal paste. A 90-s water rinse was applied followed by either a 9-s (55°C) 2% lactic acid spray, a 60-s (55°C) 12% TSP dip, or a combined treatment of both lactic acid and TSP treatments. Lactic acid reduced E. coli and APCs by 1.6 log 10 /cm 2 , and TSP caused a 1.8-log 10 /cm 2 reduction in E. coli and a 0.7-log 10 /cm 2 reduction in APCs. Combined reductions by the lactic acid spray followed by the TSP dip were 1.8 and 1.5 log 10 /cm 2 for E. coli and APCs, respectively. Lactic acid and trisodium phosphate, used alone or in combination, were effective in reducing numbers of E. coli and could be useful as pathogen intervention steps in lamb slaughter processing.

Hot beef carcass surface regions (outside round, brisket, and clod) contaminated with feces spread over a 5-cm 2 (1-in 2 ) area were cleaned using a steam-vacuum spot-cleaning system alone or combined with subsequent sanitizing treatments of hot water (95°C at the nozzle), or warm (55°C) 2% lactic acid spray, or combinations of these two sanitizing methods. These treatments were compared for effectiveness in reducing aerobic plate counts (APC) and counts of Enterobacteriaceae , total coliforms, thermotolerant coliforms, and Escherichia coli . All treatments significantly reduced the numbers of each group of bacteria on beef carcass surfaces. However, reductions obtained by steam vacuuming were significantly smaller than those obtained by a combination of steam vacuuming with any sanitizing treatment. No differences in bacterial reductions were observed between different carcass surface regions. Steam vacuuming reduced the number of different indicator organisms tested by ca. 3.0 log cycles but also spread the bacterial contamination to areas of the carcass surface adjacent to the contaminated sites. This relocated contamination after steam vacuuming was most effectively reduced by spraying with hot water and then lactic acid. This combined treatment consistently reduced the numbers of Enterobacteriaceae , total and thermotolerant coliforms, and E. coli to undetectable levels (<1.0 log 10 CFU/cm 2 ) on areas outside the initial 5-cm 2 inoculated areas.

Cleaning treatments, such as high-pressure water wash at 35°C or trim, alone and combined with sanitizing treatments, such as hot water (95°C at the source), warm (55°C) 2% lactic acid spray, and combinations of these two sanitizing methods, were compared for their effectiveness in reducing inoculated numbers (5.0 to 6.0 log CFU/cm 2 ) of Salmonella typhimurium , Escherichia coli O157:H7, aerobic plate counts, Enterobacteriaceae , total coliforms, thermotolerant coliforms, and generic E. coli on hot beef carcass surface areas in a model carcass spray cabinet. Log reductions in numbers of all tested organisms by water wash or trim alone were significantly smaller than the log reductions obtained by the different combined treatments. Regardless of the cleaning treatment (water wash or trim) or surface area, the range for mean log reductions by hot water was from 4.0 to >4.8 log CFU/cm 2 , by lactic acid spray was from 4.6 to >4.9 log CFU/cm 2 , by hot water followed by lactic acid spray was from 4.5 to >4.9 log CFU/cm 2 , and by lactic acid spray followed by hot water was from 4.4 to >4.6 log CFU/cm 2 , for S. typhimurium and E. coli O157:H7. Identical reductions were obtained for thermotolerant coliforms and generic E. coli . No differences in bacterial reductions were observed for different carcass surface regions. Water wash and trim treatments caused spreading of the contamination to other areas of the carcass surface while providing an overall reduction in fecal or pathogenic contamination on carcass surface areas. This relocated contamination after either water wash or trim was most effectively reduced by following with hot water and then lactic acid spray. This combined treatment yielded 0% positive samples for S. typhimurium , E. coli O157:H7, thermotolerant coliforms, and generic E. coli on areas outside the inoculated areas, whereas percent positive samples after applying other combined treatments ranged from 22 to 44% for S. typhimurium , 0 to 44% for E. coli O157:H7, and 11 to 33% for both thermotolerant coliforms and generic E. coli . From data collected in this study, it is possible to choose an effective, inexpensive treatment to reduce bacterial contamination on beef carcasses. In addition, the similar reduction rates of total coliforms, thermotolerant coliforms, or generic E. coli may be useful in identifying an indicator to verify the effectiveness of the selected treatment as a critical control point in a Hazard Analysis and Critical Control Point program.

Hot water treatment of beef carcass surfaces for reduction of Escherichia coli O157:H7, Salmonella typhimurium , and various indicator organisms was studied using a model carcass spray cabinet. Paired hot carcass surface regions with different extemal fat characteristics (inside round, outside round, brisket, flank, and clod) were removed from carcasses immediately after the slaughter and dressing process. All cuts were inoculated with bovine feces containing 10 6 /g each of rifampicin-resistant E. coli O157:H7 and S. typhimurium , or with uninoculated bovine feces. Surfaces then were exposed to a carcass water wash or a water wash followed by hot water spray (95°C). Counts of rifampicin-resistant Salmonella and E. coli or aerobic plate count (APC) and coliform counts were conducted before and after each treatment. All treatments significantly reduced levels of pathogens from the initial inoculation level of 5.0 log 10 CFU/cm 2 . Treatments including hot water sprays provided mean reductions of initial counts for E. coli O157:H7 and S. typhimurium of 3.7 and 3.8 log, APC reductions of 2.9 log, and coliform and thermotolerant coliform count reductions of 3.3 log. The efficacy of hot water treatments was affected by the carcass surface region, but not by delaying the treatment (30 min) after contaminating the surface. Verification of efficacy of hot water interventions used as critical control points in a hazard analysis critical control point (HACCP) system may be possible using coliform counts.

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-cm 2 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.

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 log 10 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.

Steers were slaughtered, dressed, and fabricated using conventional procedures or strict sanitary procedures. Strict sanitary procedures involved antemortem washing of steers, use of disposable gloves, careful handling of carcasses to prevent cross-contamination, and spraying of carcasses with hot (55°C) 1% L-lactic acid before evisceration and before entering the chill cooler. Mean aerobic plate counts (APC, log 10 /cm 2 ) of carcasses slaughtered under strict sanitary conditions and of subprimals (boneless strip loins and ribs) from animals handled under strict sanitary conditions and stored at 1°C in high-oxygen barrier (HOB) film (0 to 80 d) were lower than those of carcasses and subprimals from animals slaughtered and fabricated using conventional procedures. In most cases, APCs of steaks displayed in polyvinyl chloride (PVC) film for 0 to 6 d from animals and subprimals handled under strict conditions were lower than those of steaks from animals and subprimals handled under conventional procedures. Bacillus spp., Micrococcus spp., and yeasts were the dominant (50% or more of microflora) microbial types on carcasses that were slaughtered and dressed using strict sanitary conditions. For carcasses slaughtered using conventional procedures, Micrococcus spp. and to a lesser extent Streptococcus , coagulase-negative Staphylococcus and/or coryneform bacteria were the dominant microbial types. After 20 d of storage, there were no consistent differences in the percentage distribution of microbial types on the two groups of subprimals. Lactobacilli dominated the microflora of subprimals at that time. When scores for lean color, surface discoloration, fat color, overall appearance, and odor of steaks from subprimals handled under strict sanitary conditions were significantly different (P<0.05) from controls, treated steaks were more desirable than those of comparable steaks from control subprimals.

Thirty packages (454 g) each of beef and chicken pre-marinated vacuum packaged fajitas were obtained from a commercial meat purveyor and placed in a retail case for 16 d. At days 1, 5, 9, 12 and 16, aerobic plate counts (APCs) and microbial types of three randomly selected samples of each product were determined. Samples were also evaluated for surface discoloration, overall appearance, immediate and cooked off-odor and off-flavor. As storage progressed, the pH of products declined, APCs increased and Lactobacillus spp. Became dominant in the microflora. Some packaged fajitas, especially chicken, exhibited gas formation in random packages throughout the storage periods. Products became “unacceptable” between 12 and 16 d of retail storage.

Steaks and roasts were fabricated from strip loins and top rounds that were held vacuum packaged for 10 d at 2°C. Steaks and roasts then were treated with 2–3% Dermatex R Food Grade (DFG), an acetylated monoglyceride, vacuum packaged and stored at 2 ± 2°C for up to 4 weeks (steaks) and 7 weeks (roasts). Aerobic plate counts (APC) and APT counts of control and DFG-treated steaks and roasts did not differ (P>0.05) during refrigerated storage. The microflora of steaks and roasts during storage was dominated by lactic acid bacteria. Treatment with DFG did not influence the microbiological characteristics of the steaks and roasts.

Vacuum packaged strip loins and top rounds were fabricated into loin steaks and round roasts and treated, respectively, with 3 and 2% Dermatex® Food Grade (DFG), an acetylated monoglyceride. Samples were then vacuum packaged and stored at 2 ± 2°C for up to 49 (steaks) and 56 (roasts) d. Mean lean color (vacuum packaged and oxygenated), surface discoloration and overall appearance scores were not consistently different between treated and control steaks and roasts regardless of storage time. No consistent differences were observed in pH values of the lean and purge, percentage moisture or sensory evaluations of steaks and roasts treated with DFG before storage.

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.

Seventy-two beef knuckles were packaged (n = 12) in each of six different bag types with oxygen transmission rates (OTR) of 1, 10, 12, 13, 30 and 400 cc/m 2 /24 h at 4°C and 100% relative humidity to study brown discoloration of knuckles during refrigerated storage. Knuckles in bag types of OTR of 1 and 12 cc did not discolor as compared to those in bags with higher OTR (30 and 400 cc) probably due to differences in oxygen tension in the package and in the types of bacteria present. Deterioration of lean color of knuckles in some bag types of low OTR appeared associated with large percentages of Leuconostoc mesenteroides in the microflora.

The effect of various initial chilling treatments on the numbers and types of microorganisms of beef, pork and lamb tongues (n = 60) and livers (n = 60) packaged either in polyethylene (PE) film or in vacuum packages in Texas and transported fresh-chilled via transoceanic shipment to Antwerp, Belgium, was evaluated. Initial chilling treatments included: cooler-tempered (4 to 6 h at 2°C), cooler-chilled (24 h at 2°C) freezer-tempered (0.5 to 1 h at −20°C), freezer-chilled (2 h at −20°C), ice-chilled (2 h in ice water slush) and no prechilling (NPC) before packaging and subsequent refrigerated storage at 2°C. After the initial chilling treatments, the microflora was varied with Micrococcus spp. with or without coryneform bacteria being the predominant bacterial types of most samples. After refrigerated storage for 13 to 15 d, lactic acid bacteria became dominant in most vacuum-packaged samples and in pork and lamb samples stored in PE film. Brochothrix thermosphacta and Pseudomonas spp. constituted a greater part of the microflora of beef tongues and livers stored in PE film than that of comparable vacuum-packaged samples. Increases in aerobic plate counts (APC) of refrigerated vacuum-packaged samples nearly always were greatest for samples (NPC) that were not pre-chilled before packaging and usually were smallest for samples that were either freezer-chilled, freezer-tempered or ice-chilled.

The effects of chilling/tempering treatments on the pH, weight loss and quality characteristics of beef, pork and lamb variety meats (livers, hearts, tongues and kidneys) that were packaged either in polyethylene (PE) bags or vacuum packaged (VP) in the USA and transported fresh-chilled to Antwerp, Belgium, were evaluated. Product arrived at the final destination 11 d after departure from the United States seaport (13 to 15 d after packaging). Changes in pH during overseas shipment were generally small and suggested a lack of product quality deterioration resulting from major microbial proliferation during this period. Variety meats that were not prechilled before packaging generally had the lowest weight loss among chilling/tempering treatments. In general, fresh-chilled variety meats that were vacuum packaged incurred less weight loss than those that were packaged in PE bags. Livers lost a greater percentage of their weight during shipment than did other variety meats. Vacuum-packaged variety meats had more desirable quality characteristics after shipment than those that were packaged in PE bags. Shipping fresh-chilled variety meats in PE does not appear feasible. Although some statistical differences were noted, the chilling/tempering treatments appeared to have little appreciable effect on quality characteristics of variety meats, with two exceptions: (a) cooler-chilled variety meats packaged in PE bags had superior quality characteristics as compared to those that were not prechilled and packaged in PE bags; and (b) livers that were not prechilled before vacuum packaging did not maintain their qualitative characteristics as well as did those in other chilling/tempering treatments.

Pork loins were fabricated immediately (fresh) or stored in parchment paper for 6 d or stored in vacuum packages for 8 d. Chops were packaged in either a high oxygen-permeable (PVC) film or a high oxygen-barrier film (vacuum) to be displayed 4 d or 2, 6 and 10 d, respectively. High oxygen-barrier (HOB) film was superior to PVC film in maintaining desirable visual properties of chops. Chops had less off-odor in HOB film when they were held no longer than 3 or 4 d in HOB packages compared to extended periods of display. Pork loin chops packaged in high oxygen-barrier film can be displayed up to 6 d if chops are from fresh pork loins. Although visual scores for vacuum-packaged chops were acceptable for 10 d for all storage treatments, chops from the parchment paper and vacuum-packaged storage treatments had off-odors which were limiting factors in achieving long shelf life.

Pseudomonas spp. and Brochothrix thermosphacta were a major or dominant part of the microbial flora of normal and dark, firm and dry (DFD) beef steaks with or without added glucose, citrate or citrate plus lactic acid and displayed for 3 to 6 d in polyvinyl chloride (PVC) film. When normal and DFD steaks with or without the additives were displayed in high oxygen-barrier film, Lactobacillus and/or Leuconostoc spp. were dominant. Addition of glucose (50–500 μg/g meat) had little, if any, effect on the aerobic plate count (APC), pH, lean color, odor and surface discoloration scores of both normal and DFD steaks displayed in PVC or in high-oxygen barrier film. Addition of citrate or citrate plus lactic acid also had little effect on steaks except for lowering pH values and surface discoloration scores of steaks.

Ninety each of beef livers, hearts, tongues and kidneys were transported in a refrigerated van from Palestine, Texas to Rungis, France. Product arrived at destination 21 d after departure (24 d after removal from the animal) and was evaluated for color and odor by a four-member experienced USA panel and by variety meat buyers at the Rungis market. Vacuum packaging most successfully protected color and odor of tongues and hearts, kidneys had acceptable color and odor if not wrapped, and livers were most desirable in color and most acceptable in odor if wrapped with polyvinyl chloride film. Buyers on the Rungis, France market paid a premium for those variety meats which were vacuum packaged in relation to comparable USA product that was transported in the frozen state. Beef variety meats can be successfully transported to European markets without freezing.