Palatability of beef steaks marinated with solutions of calcium chloride, phosphate, and (or) beef-flavoring

This study evaluated the efficacy of marination for increasing consumer acceptability of beef. Top-sirloin steaks from 28 USDA select steers were randomly assigned to one of six marination treatments: control (CT), 150 mM calcium chloride (CA), 10% solution of beef-flavoring/seasoning mixture (FL), CA and FL (CF), 2.5% sodium phosphate and FL (PF), and tap water (TW). Steaks were marinated in vacuum pouches, aged for 7 days, cooked to 70°C and evaluated by a trained sensory panel. Marination with CA did not affect tenderness ratings, but increased (P<0.05) bitter and metallic flavors compared to CT or TW treatments. Use of FL, alone or in conjunction with CA or sodium phosphate, increased (P<0.05) tenderness and juiciness ratings and reduced (P<0.05) bitterness and metallic flavors compared to CT, CA and TW marinades. Marination of beef, in vacuum pouches, is an effective method for increasing consumer acceptability and value beef.     

Control of Listeria monocytogenes on vacuum-packaged frankfurters sprayed with lactic acid alone or in combination with sodium lauryl sulfate

U.S. regulations require that processors employ lethal or inhibitory antimicrobial alternatives in production of ready-to-eat meat and poultry products that support growth of Listeria monocytogenes and may be exposed to the processing environment after a lethality treatment. In this study, lactic acid (LA; 5%, vol/vol) and sodium lauryl sulfate (SLS; 0.5%, wt/vol) were evaluated individually or as a mixture (LASLS) for control of L. monocytogenes on frankfurters. Frankfurters were inoculated with a 10-strain mixture of L. monocytogenes, sprayed for 10 s (20 bar, 23 +/- 2 degrees C) with antimicrobials or distilled water (DW) before (LASLS or DW) or after (LA, SLS, LASLS, or DW) inoculation (4.8 +/- 0.1 log CFU/cm2), vacuum packaged, and stored at 4 degrees C for 90 days. Samples were analyzed for numbers of the pathogen (on PALCAM agar) and for total microbial counts (on tryptic soy agar with yeast extract) during storage. Spraying with DW, LA, or SLS after inoculation reduced numbers of L. monocytogenes by 1.3 +/- 0.2, 1.8 +/- 0.5, and 2.0 +/- 0.4 log CFU/cm2, respectively. The LASLS mixture applied before or after inoculation reduced pathogen populations by 1.8 +/- 0.4 and 2.8 +/- 0.2 log CFU/cm2, respectively. No further reduction by any treatment was observed during storage. The bacterial growth curves (fitted by the model of Baranyi and Roberts) indicated that the lag-phase duration of the bacterium on control samples (13.85 to 15.18 days) was extended by spraying with all solutions containing LA. For example, LA suppressed growth of L. monocytogenes for 39.14 to 41.01 days. Pathogen growth rates also were lower on frankfurters sprayed after inoculation with LA or LASLS compared to those sprayed with DW. Therefore, spraying frankfurters with a mixture of LA and SLS may be a useful antilisterial alternative treatment for ready-to-eat meat and poultry products.     

Factors contributing to the incidence of dark cutting beef

The 1995 National Beef Quality Audit reported that dark cutting beef (dark cutters) cost $6.08 per animal harvested in the United States. Feedlot data were obtained over a 3-yr period from nine commercial feedyards (15,439 pens of cattle; 2,672,223 total cattle). Feedyard, sex, implant treatment, days from final implant to harvest, maximum and minimum daily temperatures, and temperature fluctuations from 2 d before harvest to the day of harvest all contributed (P < .05) to the incidence of dark cutters. Heifers yielded a higher (P < .05) percentage of dark cutters per pen and, when reimplanted a second time with an estrogenic implant, produced greater (P < .05) mean percentages of dark cutters per pen than heifers reimplanted with either androgens or combination (androgen and estrogen) growth promotants. Furthermore, heifers produced higher (P < .05) mean percentages of dark cutters per pen than steers during periods of hot (> 35 degrees C) weather 2 to 1 d before harvest. Steers, when treated with a combination (androgen and estrogen) implant when entering the feedyard and as a reimplant, produced higher (P < .05) mean percentages of dark cutters per pen when compared to other moderate growth-promoting implant strategies. When producers opted to implant steers with estrogenic growth promotants, either as the cattle entered the feedlot or as a final reimplant before harvest, the occurrence of dark cutters was reduced from 9.2 per thousand cattle shipped to 2.0 and .5 per thousand cattle shipped, respectively. Producers that reimplanted heifers before harvest with products that were not primarily estrogenic reduced the occurrence of dark cutters from 10.4/1,000 cattle shipped to 5.2/1,000 cattle shipped when androgen-based growth promotants were used and to 3.5/1,000 cattle shipped when combination (androgen and estrogen) implants were administered. In addition to implant selection, those producers that held cattle on-feed over 100 d past reimplantation reduced the incidence of dark cutters per pen by an average of 38% among heifers and 69% among steers. By reducing the occurrence of dark cutters, there is an opportunity for beef producers to realize large economic savings.     

Antimicrobials in the formulation to control Listeria monocytogenes postprocessing contamination on frankfurters stored at 4 degrees C in vacuum packages.

Postprocessing contamination of cured meat products with Listeria monocytogenes during slicing and packaging is difficult to avoid, and thus, hurdles are needed to control growth of the pathogen during product storage. This study evaluated the influence of antimicrobials, included in frankfurter formulations, on L. monocytogenes populations during refrigerated (4 degrees C) storage of product inoculated (10(3) to 10(4) CFU/cm2) after peeling of casings and before vacuum packaging. Frankfurters were prepared to contain (wt/wt) sodium lactate (3 or 6%, as pure substance of a liquid, 60% wt/wt, commercial product), sodium acetate (0.25 or 0.5%), or sodium diacetate (0.25 or 0.5%). L. monocytogenes populations (PALCAM agar and Trypticase soy agar plus 0.6% yeast extract [TSAYE]) exceeded 10(6) CFU/cm2 in inoculated controls at 20 days of storage. Sodium lactate at 6% and sodium diacetate at 0.5% were bacteriostatic, or even bactericidal, throughout storage (120 days). At 3%, sodium lactate prevented pathogen growth for at least 70 days, while, in decreasing order of effectiveness, sodium diacetate at 0.25% and sodium acetate at 0.5 and 0.25% inhibited growth for 20 to 50 days. Antimicrobials had no effect on product pH, except for sodium diacetate at 0.5%, which reduced the initial pH by approximately 0.4 U. These results indicate that concentrations of sodium acetate currently permitted by the U.S. Department of Agriculture-Food Safety and Inspection Service (USDA-FSIS) (0.25%) or higher (0.5%) may control growth of L. monocytogenes for approximately 30 days, while currently permitted levels of sodium lactate (3%) and sodium diacetate (0.25%) may be inhibitory for 70 and 35 to 50 days, respectively. Moreover, levels of sodium lactate (6%) or sodium diacetate (0.5%) higher than those presently permitted by the USDA-FSIS may provide complete control at 4 degrees C of growth (120 days) of L. monocytogenes introduced on the surface of frankfurters during product packaging.     

Prevalence and antibiotic susceptibility of Salmonella isolated from beef animal hides and carcasses

This study determined the prevalence of Salmonella on beef animal hides and carcasses and antimicrobial susceptibility profiles against a panel of 13 antibiotics. In each of the eight commercial packing facilities, of which five processed primarily heifers and steers and the remaining three processed primarily cows and bulls, hide and carcass sponge swab samples were obtained immediately before hide removal and before carcass chilling, respectively. Overall, prevalence of Salmonella on external surfaces (hides) of cattle was 15.4% (49 of 319), whereas prevalence after dehiding and other slaughtering/dressing processes, including the application of decontamination treatments, was, as expected, reduced (P < 0.05) to 1.3% (4 of 320) on carcass surfaces. From 53 total Salmonella-positive hide and carcass samples, 526 biochemically confirmed isolates were obtained to determine antimicrobial susceptibility profiles. Of 53 Salmonella-positive samples, individually, 24 (45.3%), 17 (32.1%), 17 (32.1%), 11 (20.8%), 8 (15.1%), 8 (15.1%), 8 (15.1%), 4 (7.5%), and 2 (3.8%) samples yielded at least one isolate resistant to amoxicillin/clavulanic acid, tetracycline, streptomycin, sulfonamides, ampicillin, ampicillin/sulbactam, chloramphenicol, gentamicin, and trimethoprim/sulfamethoxazole, respectively. None of the Salmonella-positive samples yielded an isolate resistant to ceftriaxone, ciprofloxacin, enrofloxacin, or levofloxacin. Although none of the samples yielded an isolate simultaneously resistant to three or four antimicrobials, a total of eight samples yielded at least one isolate resistant to five or more antimicrobials tested. Included among the 18 group B-positive samples were three samples that, individually, yielded at least one Salmonella Typhimurium var. Copenhagen DT104 isolate resistant to at least six antimicrobials tested. Results from this study support current prudent therapeutic and subtherapeutic antimicrobial use recommendations.     

High-throughput small molecule screening reveals structurally diverse compounds that inhibit the growth of Escherichia coli O157:H7 in vitro

Escherichia coli O157:H7 colonizes the gastrointestinal tract of ruminants asymptomatically and may enter the human food supply through fecal contamination. A fraction of individuals infected by E. coli O157:H7 develop hemolytic uremic syndrome, a life-threatening condition. When individuals infected by E. coli O157:H7 are treated with certain antibiotics, an increased incidence of hemolytic uremic syndrome may result. This finding supports the need to identify novel compounds that can either reduce the load of E. coli O157:H7 entering the human food supply or serve as alternative therapeutic treatments for infected individuals. We developed a high-throughput turbidometric assay to identify novel compounds that inhibit E. coli O157:H7 growth. Pin transfers were performed to introduce small molecule libraries into 384-well plates, where each well contained approximately 5.0 log CFU of E. coli O157:H7. Plates were incubated at 37°C for 18 h, and the optical density was measured to determine the effect of each small molecule. A total of 64,562 compounds were screened in duplicate, and 43 unique compounds inhibited E. coli O157:H7 growth. Thirty-eight of the 43 inhibitory compounds belonged to known bioactive libraries, and the other 5 compounds were from commercial libraries derived from splitting and pooling. Inhibitory compounds from known bioactive libraries were most frequently therapeutic antibiotics (n = 34) but also included an antiviral compound, a compound that disrupts the citric acid cycle, and two biguanide compounds, which have been used for various nonclinical applications. We identified two novel compounds (i.e., biguanides) that should be studied further for their ability to reduce pathogen populations in foods.     

Microbial contamination occurring on lamb carcasses processed in the United States

Lamb carcasses (n = 5,042) were sampled from six major lamb packing facilities in the United States over 3 days during each of two visits (fall or winter, October through February; spring, March through June) in order to develop a microbiological baseline for the incidence (presence or absence) of Salmonella spp. and for populations of Escherichia coli after 24 h of chilling following slaughter. Samples also were analyzed for aerobic plate counts (APC) and total coliform counts (TCC). Additionally, incidence (presence or absence) of Campylobacter jejuni/coli on lamb carcasses (n = 2,226) was, determined during the slaughtering process and in the cooler. All samples were obtained by sponge-sampling the muscle-adipose tissue surface of the flank, breast, and leg of lamb carcasses (100 cm2 per site; 300 cm2 total). Incidence of Salmonella spp. in samples collected from chilled carcasses was 1.5% for both seasons combined, with 1.9% and 1.2% of fall or winter and spring samples being positive, respectively. Mean (log CFU/cm2) APC, TCC, and E. coli counts (ECC) on chilled lamb carcasses across both seasons were 4.42, 1.18, and 0.70, respectively. APC were lower (P < 0.05) in samples collected in the spring versus fall or winter, while TCC were higher in samples collected in the spring. There was no difference (P > 0.05) between ECC from samples collected in the spring versus winter. Only 7 out of 2,226 total samples (0.3%) tested positive for C. jejuni/coli, across all sampling sites. These results should be useful to the lamb industry and regulatory authorities as new regulatory requirements for meat inspection become effective.     

Thermal inactivation of Escherichia coli O157:H7 in beef treated with marination and tenderization ingredients

Internalization of Escherichia coli O157:H7 in nonintact beef products during mechanical tenderization or during injection of marination and tenderization ingredients is of concern if such products are undercooked. This study tested organic acids (0.2% citric acid and 0.3% acetic acid), potassium and calcium salts (1.8% potassium lactate, 0.63% calcium lactate, 0.86% calcium ascorbate, and 0.23% calcium chloride), and sodium chloride (2.5%) for their influence on thermal destruction of E. coli O157:H7 in ground beef serving as a model system. Ground beef batches (700 g; 5% fat) were mixed with equal volumes (22 ml) of each treatment solution or distilled water and portions (30 g) of treated ground beef were extruded in test tubes (2.5 by 10 cm). A five-strain mixture of E. coli O157:H7 (0.3 ml; 7 log CFU/g) was introduced at the center of the sample with a pipette. After overnight storage (4 degrees C), simulating product marination, samples were heated to 60 or 65 degrees C internal temperature, simulating rare and medium rare doneness of beef, in a circulating water bath. At 65 degrees C, treatments with citric and acetic acid showed greater (P < 0.05) reduction (4 to 5 log CFU/g) of E. coli O157:H7 than all the other ingredients and the control (3 to 4 log CFU/g). Sodium chloride reduced weight losses (16 to 18% compared with 20 to 27% by citric or acetic acid) and resulted in a 4-log reduction in counts during cooking to 65 degrees C. Ingredients such as citric or acetic acid may improve thermal inactivation of E. coli O157:H7 internalized in nonintact beef products, while sodium chloride may reduce cooking losses in such products.     

Inactivation of Escherichia coli O157:H7 in moisture-enhanced nonintact beef by pan-broiling or roasting with various cooking appliances set at different temperatures

This study evaluated inactivation of Escherichia coli O157:H7 in moisture-enhanced restructured nonintact beef cooked to 65 °C using different cooking appliances set at different temperatures. Batches (2 kg) of coarse-ground beef (approximately 5% fat) were mixed with an 8-strain composite (100 mL) of rifampicin-resistant E. coli O157:H7 (6.4 ± 0.1 log CFU/g) and a solution (100 mL) of sodium chloride plus sodium tripolyphosphate to yield concentrations (wt/wt) of 0.5% and 0.25%, respectively, in the final product. Beef portions of 2.54 cm thickness (15 cm dia) were prepared and were vacuum-packaged and frozen (-20 °C, 42 h). Partially thawed (-2.5 ± 1.0 °C) portions were pan-broiled (Presto electric skillet and Sanyo grill) or roasted (Oster toaster oven and Magic Chef kitchen oven) to 65 °C. The appliances were set at, and preheated before cooking to 149 or 204 °C (electric skillet), 149 or 218 °C (grill), 149 or 232 °C (toaster oven), and 149, 204, or 260 °C (kitchen oven). Temperatures of appliances and beef samples were monitored with thermocouples, and meat samples were analyzed for surviving microbial populations. In general, the higher the appliance temperature setting, the shorter the time needed to reach 65 °C, and the higher the edge and surface temperatures of the meat samples. Temperatures of 204 to 260 °C, regardless of appliance, resulted in greater (P < 0.05) pathogen reductions (3.3 to 5.5 log CFU/g) than those obtained at 149 °C (1.5 to 2.4 log CFU/g). The highest (P < 0.05) reduction (5.5 log CFU/g) was obtained in samples cooked in the kitchen oven set at 260 °C. The results should be useful to the food service industry for selection of effective nonintact beef cooking protocols, and for use in risk assessments for nonintact meat products. Practical Application: Results of this study should be useful for developing cooking recommendations to enhance the safety of nonintact beef products, and for use in risk assessments of such products.