Beef Trim Research Articles

Detection of Shiga toxin-producing Escherichia coli, stx1, stx2 and Salmonella by two high resolution melt curve multiplex real-time PCR

In the United States, Shiga toxin-producing Escherichia coli (STEC) O157 and six non-O157 serogroups O26, O45, O103, O111, O121 and O145 are considered adulterants in non-intact beef. Further, Salmonella is responsible for one of the highest numbers of foodborne infections worldwide. Multiple foods, especially meats, are routinely tested for these pathogens using methods like PCR. However, with such a large group of organisms, multiplexing using probe-based PCR assays is expensive due to the need for differently labeled oligonucleotide probes and sophisticated instrumentation. The aim of this study was to design low-cost multiplex real-time PCR assays for the detection of seven STEC serogroups, stx1, stx2 genes and virulent Salmonella. Two multiplex real-time PCR melt curve assays with internal amplification controls (IAC) were standardized. The first assay detected E. coli O121, E. coli O145, E. coli O157, stx1, and stx2. The second assay targeted E. coli O26, E. coli O111, E. coli O103, E. coli O45, and Salmonella. Ground beef and beef trim inoculated with 5–27 CFU/325 g of STEC and 9–36 CFU/325 g of Salmonella could be detected following an 8–10 h enrichment at 40 °C ± 2 °C in buffered peptone water containing 8 mg/L vancomycin. The assays showed reproducible results for beef products with different fat contents. These assays do not rely on fluorescent-labeled probes or immunomagnetic beads, yet accurately detect seven STEC serogroups, seven stx gene subtypes and Salmonella, making them suitable for routine testing of STEC and Salmonella in beef.

Comparing the Recovery of Indicator Microorganisms from Beef Trimmings Using Swabbing, Rinsing, and Grinding Methodologies

Different bacterial sampling methods that are destructive or nondestructive in nature have been developed to evaluate the microbial quality of meat and determine if it fulfills criteria for distribution to the public. The purpose of this study was to evaluate the effectiveness of swabbing, rinsing, and grinding as sampling methodologies for recovery of indicator microorganisms on beef trimmings. A total of fifteen samples (n = 15) of beef trimmings were collected using the N60 trim sampling technique adopted by the USDA Food Safety and Inspection Service. Each of the 15 samples were divided into 3 parts, with each part assigned to a methodology (swabbing, rinsing, or grinding), and subjected to multiple sequential sampling for a total of three times. A comparison was made between the first sampling and the total bacteria recovered by each methodology. For total aerobic counts (TAC) obtained by the rinse and the grinding methodology, the first sampling as well as the total resulted in aerobic bacteria counts that were not significantly different (P > 0.05); however, swabbing yielded counts that were significantly lower (P < 0.05) than both rinsing and grinding. For total coliforms, rinsing was not significantly different (P < 0.05) from either swabbing or grinding, yet swabbing recovered the least number of bacteria. Within each sampling methodology, the decline in aerobic bacteria counts due to multiple sequential samplings was calculated. Rinsing and grinding resulted in significantly lower counts (P < 0.05) after the initial samplings, whereas swabbing did not (P > 0.05). Linear models showed strong relationships, with a coefficient of determination (r2) of 0.81 (swabbing vs. grinding), 0.67 (swabbing vs. rinsing), and 0.70 (rinsing vs. grinding). Although the sampling methodologies investigated are reliable to determine true bacterial counts of tested samples, consistency and uniformity of sampling is required for the proper interpretation of the acquired results.

Effect of ultraviolet light, organic acids, and bacteriophage on Salmonella populations in ground beef

This study investigated individual and combined effects of organic acids, bacteriophages, and ultraviolet light interventions on Salmonella populations in ground beef. Beef trim was inoculated with four Salmonella strains to result in a contamination level of 3.5 log CFU/g after grinding. Lactic (LA) and peroxyacetic (PAA) acids, bacteriophages (S16 and FO1a) (BA), and ultraviolet light (UV) were applied on fresh trim prior to grinding. Applications of individual or combined organic acids did not significantly decrease Salmonella populations in ground beef. Individual applications of BA and UV light decreased approximately 1 log CFU/g (P<0.05). Combined applications of BA and UV provided an optimal decrease of 2 log CFU/g (P<0.05). Organic acid applications do not reduce Salmonella populations in ground beef when applied on trim prior to grinding. Combined applications of UV and BA may be used in industry settings to improve Salmonella control in ground beef.

The Effect of Potassium/Sodium Lactate (Pl/Sl), Sodium Erythorbate (Nae), and Sodium Bicarbonate (Sb) on Quality of Aerobically Stored Beef Trimmings

ObjectivesThe objective of the study was to investigate various concentrations of solutions that can be applied to aerobically stored beef trimmings as a processing aid to prevent further deterioration of color, lipid, odor and/or microbial growth.Materials and MethodsBeef trimmings (∼15 kg) were fabricated from beef forequarters and aerobically stored (5°C) for 6 d in a plastic container covered with linear low-density polyethylene film (LLDPE; Oxygen Transmission Rate: 5,000 cc/m2 per 24 h at 25°C and 0% R.H.) to simulate the collection, storage, transportation and receipt of a combo of beef trimmings. A total of 12 treatments (4 solutions × 3 concentration levels) consisting of PL and SL at 0.1, 0.2 and 0.5 M; NaE at 1, 2, and 100 mM; and SB solutions at 0.1, 0.2 and 1.5 M; and a control (water). Concentrations of the solutions were based on previous research. After aerobic storage the beef trimmings (∼20% fat) were coarse ground (12 mm) and 9 mL of each treatment and control solution was applied to ∼454-g samples. The treated samples were reground (3 mm) placed into Petri dishes and overwrapped with LLDPE film. The patties (2 per treatment/control (13) × 2 storage d; N = 52 per replication) were stored under simulated retail conditions: 5°C under cool white fluorescent light (200 to 300 lux) and analyzed at 0 and 5 d of storage to assess the effectiveness of each treatment solution in preventing further quality deterioration. Objective color (L*, a*, b*; metmyoglobin concentration, MMB), 2-thiobarbituric acid (TBA) determinations, GC–MS identification of volatile compounds for off-odor assessment and aerobic plate counts (APC) were conducted. The results of 2 replications were analyzed using one-way ANOVA and Tukey HSD with a significance level of P < 0.05.ResultsNo differences were observed for treated and control patties for color, lipid oxidation or microbial analyses on storage d 0. Additionally, no differences were observed between treatments and the control for any volatile off odor compounds (ketones, aldehydes and acids) at 0 and 5 d of storage (P > 0.05). Samples treated with varying concentration of PL did not significantly impact any quality factors evaluated (P > 0.05). Analyses of SL, SB and NaE treated patties at 5 d of retail storage exhibited differences in color, lipid oxidation and microbial growth (P < 0.05). Pattie samples treated with SB (1.5 M) exhibited the highest a* value (13.63) and lowest MMB content (33.92%) compared to other treatments (P < 0.05). Samples treated with NaE (100 mM) had the lowest TBA value (0.79) compared to other treatments and control. Samples treated with SL (0.4 M) exhibited the lowest AM and AP counts (8.4 and 7.4 log10 CFU/g, respectively) compared to other treatments and control.ConclusionIn conclusion, samples treated with the SB (1.5 M), NaE (100 mM), and SL (0.4 M), had the greatest effect on improving color stability, reducing lipid oxidation, and controlling microbial spoilage, respectively at 5 d of retail storage. Results of this study suggest that a solution could be developed as a processing aid using a combination of SB, NaE, and SL to prevent further deterioration of beef trimmings prior to use in the manufacturing of ground beef products.

Comparing the Recovery of Indicator Microorganisms from Beef Trimmings Using Swabbing, Rinsing, and Grinding Methodologies

Different bacterial sampling methods that are destructive or nondestructive in nature have been developed to evaluate the microbial quality of meat and determine if it fulfills criteria for distribution to the public. The purpose of this study was to evaluate the effectiveness of swabbing, rinsing, and grinding as sampling methodologies for recovery of indicator microorganisms on beef trimmings. A total of fifteen samples (n = 15) of beef trimmings were collected using the N60 trim sampling technique adopted by the USDA Food Safety and Inspection Service. Each of the 15 samples were divided into 3 parts, with each part assigned to a methodology (swabbing, rinsing, or grinding), and subjected to multiple sequential sampling for a total of three times. A comparison was made between the first sampling and the total bacteria recovered by each methodology. For total aerobic counts (TAC) obtained by the rinse and the grinding methodology, the first sampling as well as the total resulted in aerobic bacteria counts that were not significantly different (P &gt; 0.05); however, swabbing yielded counts that were significantly lower (P &lt; 0.05) than both rinsing and grinding. For total coliforms, rinsing was not significantly different (P &lt; 0.05) from either swabbing or grinding, yet swabbing recovered the least number of bacteria. Within each sampling methodology, the decline in aerobic bacteria counts due to multiple sequential samplings was calculated. Rinsing and grinding resulted in significantly lower counts (P &lt; 0.05) after the initial samplings, whereas swabbing did not (P &gt; 0.05). Linear models showed strong relationships, with a coefficient of determination (r2) of 0.81 (swabbing vs. grinding), 0.67 (swabbing vs. rinsing), and 0.70 (rinsing vs. grinding). Although the sampling methodologies investigated are reliable to determine true bacterial counts of tested samples, consistency and uniformity of sampling is required for the proper interpretation of the acquired results.

Relationship between Descriptive Flavor and Texture Attributes on In-Home Consumer Acceptance of Ground Beef

ObjectivesGround beef comprises between 50 and 60% of the beef sold and consumed in the U.S. It is one of the most popular protein sources due to its affordability and versatility. Emerging trends in the industry are changing the way ground beef is formulated to include different formulations and grind treatments to change the flavor and texture attributes. In this study, 16 treatments were utilized, including 4 meat sources (chuck, regular, sirloin, round), 2 fat percentages (10 and 20%), and 2 grind treatments (6.4 mm grind and bowl chopped) to better understand consumer attitudes and preferences of ground beef in a home use test.Materials and MethodsKnuckle, outside round flat, and chuck shoulder clod subprimals and 50/50 beef trim were used to formulate the sirloin, round, and chuck treatments, respectively for both fat percentages. Regular 80/20 coarse ground beef was used for the 20% fat and it was supplemented with trimmed knuckle to formulate the 10% fat treatment. For each source, the ground beef was divided into 2 final grind batches either 6.4 mm or bowl chopped to approximately 6.4 mm grind. Patties were then formed with a patty maker using a 2.5 cm mold or 454 g chubs. Patties and chubs were vacuum packaged and frozen until use. Each consumer received 8 samples including 4 patties and 4 chubs from the same treatment. Treatments were randomly selected for each consumer. Eighty consumers were recruited from Griffin, GA; Portland, OR; Manhattan, KS, and State College, PA. Of the 314 consumers that were given product, 218 actively participated and returned the ballots.ResultsConsumers varied in their preparation methods. More consumers used an outdoor grill to cook the patties and more consumers pan fry/sautéed the meat when given chubs. More consumers ate the patties as a main course when compared to the chubs.Meat source affected raw appearance, overall, flavor and texture liking. Raw appearance liking was highest (P < 0.05) for the regular meat source treatments and lowest (P < 0.05) for the round and sirloin. For overall, flavor, and texture liking, the consumers rated chuck the highest (P < 0.05) and regular and round the lowest (P < 0.05). Patties with 6.4 mm grind size were rated higher (P < 0.05) than the bowl chop method for overall, flavor and texture liking. Fat level affected the raw appearance, cooked appearance and texture liking. Consumers preferred the 10% lipid level over the 20% lipid level. Form did not affect overall liking.A grind by fat interaction was present for overall liking (P < 0.05). Consumers preferred the 6.4 mm grind size with 10% lipid over the 6.4 mm with 20% lipid and both bowl chop treatments. The meat source by fat interaction was significant for texture liking (P < 0.05). Regular 20% lipid, round 10% lipid, and sirloin 20% lipid beef patties rated lowest in texture liking compared to chuck and sirloin ground beef patties. Texture liking also had a grind by form interaction (P < 0.05). Both the 6.4 mm treatments for patties and chubs were liked more than (P < 0.05) the bowl chop patties and chubs.ConclusionWith ground beef accounting for such a large percentage of beef consumption, it is crucial to understand how flavor and texture affect overall liking. Overall, consumers preferred 10% lipid ground chuck beef in patties or chubs ground to a 6.4 mm grind size.

Effect of Lactic Acid Treatment on E. coli and Coliform Growth in Ground Beef after Different Storage Periods and Retail Display Days

ObjectivesThe study evaluated the changes in of Escherichia coli and coliforms counts in ground beef prepared from beef trimmings stored either 24 or 48 h after treatment with a 2–3% lactic acid dip (LA) for 3 storage periods of 7, 14, or 21 d after grinding. Materials and MethodsTwo sets of beef trimmings were dipped with 2 to 3% LA and stored for either 24 or 48 h prior to grinding. Additionally, 2 untreated sets were included as controls (CON), and were not treated with LA. Samples from each of the 4 sets of trim (n = 84; 4.54 kg) were ground, vacuum packaged, and further stored and sampled at 7, 14, or 21 d. After storage period was over, samples were re-ground using a 3.175 mm disk and a 25-g sample was collected to represent retail d 0. Three 454 g portions of each sample were placed on a polystyrene tray overwrapped with low-barrier polyvinylchloride film to represent retail d 1, 2, and 3. Packages were displayed in a coffin-style retail case maintained at 2 to 3°C. Packages were respectively sampled every 24 h according to its designated retail display day. A 25-g sample was collected, placed into a filter bag, and 225 mL of buffered peptone water (BPW) was aseptically added. The bag was stomached for 2 min at 230 RPM. Serial dilutions were made from meat rinse in 9 mL tubes of BPW. One mL from the bag or appropriate tube was plated to each EC petrifilm in duplicate. Both coliforms and E. coli petrifilm plates were incubated at 36°C ± 1°C. Counts were made at 24 h for coliforms and 48 h for E. coli. Counts and duplicate plates were averaged and converted to log CFU/g of ground beef prior to statistical analysis. Data were analyzed using statistical procedures of a 2-way ANOVA. A split-plot design was used with a whole plot as a 2 × 2 factorial of trim age and treatment and subplot of post-grind age. ResultsThe Statistical Analysis showed that the coliform concentration increased in function of the storage period 7, 14, 21 d for 24 to 48 h LA treatments and 24 to 48 h control (P 0.05). ConclusionBased on the results, E. coli was not reduced in the samples treated with LA at 2 to 3% prior grinding after 7 and 14 d stored. However, an E. coli reduction was observed over a period of 21 d. Similarly, coliforms counts were not reduced with the chemical treatment during the storage periods.

Effects of Lactic Acid Dipped Beef Trim Stored 24 or 48 H and Chub Storage Duration on Ground Beef Color in Retail Display

ObjectivesThe study evaluated objective and subjective retail display color of ground beef produced from beef trim treated with or without lactic acid dip and stored 24 or 48 h prior to chub packaging and storage for 7, 14, or 21 d.Materials and MethodsGround beef produced from trim treated (TRT) with lactic acid dip (LA) or without (CON) and stored 24 h (24TS) or 48 h (48TS) was used. Samples (n = 84; 21/TRT, TS combination) were chub vacuum packaged (4.54 kg) and stored for 7, 14, or 21 d (CS) and finely ground when storage time completed. Ground beef was placed on a polystyrene tray overwrapped with low-barrier polyvinylchloride film. Packages were displayed for 3 d (2 to 3°C) under continuous fluorescent lighting. CIE L* a* b* values were taken daily during simulated retail display to calculate hue angle (tan–1 a/b) and saturation index [(a2 + b2)1/2]. Trained panelists (n = 6) evaluated worst-point lean color daily during retail display with an 8-point verbally anchored numeric scale with 0.5 increment scores (1 = very bright red, 8 = tan to brown). Data were analyzed as a split plot design with whole plot as a 2 × 2 factorial of TS and TRT and subplot combined CS with retail day.ResultsVisual color scores and L* values differed (P < 0.0001) among CS times and retail display day, as expected. Treatment, CS and retail display day interacted (P < 0.05) for a*, saturation index, and hue angle. Hue angle and a* values indicated a loss of redness (P < 0.05) within TRT and CS as retail display increased. Initial display a* values within TRT did not differ (P > 0.05) across CS, but LA treated chubs were more red (P < 0.05) than CON regardless of CS. Chubs stored 7 or 14 d had similar (P > 0.05) hue angles and were less discolored (P < 0.05) than 21 d stored chubs regardless of TRT at 0 d of display. Hue angle and a* values did not differ (P > 0.05) between LA and CON within CS after 0 d of display. Saturation index, or vividness, for 7 d stored chubs decreased (P < 0.05) the longer packages were displayed in retail, but chubs stored 14 and 21 d had similar vividness (P > 0.05) within d 2 and 3 of display. At initial display, chubs treated with LA were more vivid (P < 0.05) than CON within CS. Lactic acid treated and CON chubs did not differ (P > 0.05) within CS at d 1 and 3 of display. Chubs stored 7 d were more vivid (P < 0.05) than 14 and 21 d stored chubs, which did not differ (P > 0.05) at d 1, 2, and 3 of display. The vividness of LA treated chubs was greater (P < 0.05) than CON for 7 d stored chubs at d 2 of display. A TS × CS retail day interaction (P < 0.05) was observed for a* and saturation index. Saturation index and a* values for TS were similar (P > 0.05) within chubs stored 7 and 21 d at retail d 1 and 2 of display, but no redness differences (P > 0.05) within CS were observed at d 3 of display. Saturation index and a* values decreased (P < 0.05) as package display time increases within TS and CS, except 48TS vividness did not differ (P > 0.05) between d 2 and 3 of display. L* and b* values indicated LA treated chubs were lighter and more yellow (P < 0.05) than CON. Hue angle indicated 48TS was less red (P < 0.05) than 24TS.ConclusionLonger trim and chub storage is detrimental, but LA combined with other factors can delay discoloration.

Effects of Inclusion of Tannic Acid on Color, Lipid Stability, and Sensory Attributes of Ground Beef Patties

ObjectivesOxidation negatively affects meat quality leading to changes in sensory and nutritional properties. Inclusion of antioxidants in ground beef improves lipid stability and extends case life. In this study, we examined the effects of tannic acid as a novel antioxidant source on lipid oxidation, color stability, and sensory attributes of ground beef patties.Materials and MethodsA beef trim 80% lean composite from 4 different carcasses aged for 14 d was acquired from Wolfpack Meats, the University of Nevada, Reno (UNR) USDA harvest and processing facility. Trim was transferred to the UNR Meat Quality laboratory, ground, and divided in 4 batches. Each batch was treated with 0 (Control), 0.5, 1, or 1.5% of a burgundy food-grade tannic acid powder. Ground beef portions weighing 120 g were formed into 11.5 cm diameter/1.5 cm thickness patties (n = 5 per treatment). Patties used for sensory analysis were vacuum-packaged and held at –80°C until testing. Prior to sensory analysis, patties were thawed for 24 h at 4°C and cooked on an electric grill to an internal temperature of 71°C. Pie-shaped pieces were obtained from each sample and served to a 7-member sensory panel. Each panelist evaluated tenderness, chewiness, juiciness, off-flavor, and overall desirability using an unstructured linear 10 cm scale (0 = extremely tough, chewy, dry, mild, and undesirable to 10 = extremely tender, soft, juicy, intense, and desirable). For color and lipid stability (TBA values), patties were placed in polystyrene trays, overwrapped with an oxygen permeable PVC film, and stored at 4°C. Samples were displayed for 6 d under fluorescent lights with intensity of approximately 1,300 lux. Objective color (L*, a*, b*) measurements were taken daily by using a Minolta CR-400 and lipid oxidation was evaluated on d 0, 3, and 6. Data were analyzed as a CRD with repeated measures using PROC GLIMMIX of SAS (SAS Inst. Inc., Cary, NC). Fixed effects included tannic acid treatment (TA) and day of display.ResultsSignificant interactions between fixed effects of tannic acid treatment and day of display were observed for a*, b*, and Chroma values. For all 3 variables, values decreased as display time increased. Control samples were redder from d 1 to 4 when compared to treated samples. Regarding yellowness, samples treated with 1.5% of TA showed the highest b* values from d 1 to d 6, whereas minimal differences between control and 0.5% TA samples were observed during display time. Chroma values were higher on samples treated with 1.5% of TA on d 5 and 6 when compared to control and 0.5% samples. At the end of display (d 6). All TA treatments similarly improved lipid stability when compared to control samples. However, inclusion levels above 0.5% led to detrimental effects on sensory attributes.ConclusionInclusion of 0.5% of tannic acid is effective to improve lipid stability without compromising objective color parameters and sensory attributes of ground beef. Levels above 0.5% decrease redness and scores of sensory attributes, possibly due to the burgundy color and the astringent flavor of the powder.

Antimicrobial Effects of Lauric Arginate, Peroxyacetic Acid, and Buffered Sulfuric Acid against Pathogenic Bacteria Populations in Beef Trimmings Destined for Ground Beef

Antimicrobial Effects of Lauric Arginate, Peroxyacetic Acid, and Buffered Sulfuric Acid against Pathogenic Bacteria Populations in Beef Trimmings Destined for Ground Beef

Thermal Inactivation of Salmonella in High-Fat Rendering Meat Products

Thermal inactivation of Salmonella is a critical component of the calculated thermal process to ensure the safety of cooked human and animal products. However, lethality performance standards for meat processing by-products that may harbor Salmonella have not been properly set under the actual conditions of rendering processes. The goal of this study was to evaluate the thermal inactivation parameters for Salmonella in high-fat beef trimmings as a model system for animal food products treated under simulated "worst-case scenario" commercial rendering conditions. Ground high-fat beef trimmings (50% fat) were artificially inoculated with a 108 CFU/g Salmonella cocktail containing human outbreak strains including the highly thermotolerant serotype Salmonella Senftenberg. The meat samples were packaged and immersed in either water or silicon oil at predetermined temperatures ranging from 60 to 121°C (from 140 to 250°F). D-values of Salmonella at each temperature were calculated from the negative inverse slope of the log CFU per gram versus time plot. The z-values were determined from the negative inverse slope of the log D versus temperature plot. The D-values in thermal death curves for low-fat (20%) content materials (between 60 and 95°C) were 2.175, 0.658, 0.237, 1.563, 0.356, 0.284, 0.264, and 0.201 min, whereas materials with 50% fat (between 100 to 121°C) were 0.277, 0.286, 0.159, 0.143, 0.137, and 0.087 min. The z-values for low- and high-temperature schedules were 43.7 and 42.9°C, respectively. Thermal lethality data for Salmonella inactivation in high-fat rendering raw materials will help animal food processors design adequate thermal processing schedules and support critical control points to ensure the safety of final beef-based rendered products.

Low Prevalence of Salmonella and Shiga Toxin–Producing Escherichia coli in Lymph Nodes of Australian Beef Cattle

Salmonella contamination of ground beef has been viewed as originating from the surface of carcasses. Recent studies have identified lymph nodes as a potential source of Salmonella contamination because these tissues play an active role in containment of pathogens in the live animal and because some lymph nodes are unavoidably present in manufacturing beef trimmings or primal cuts that may be incorporated into ground beef. A survey was conducted of the microbiological status of lymph nodes from Australian cattle at the time of slaughter to determine the prevalence of microbiological contamination. Sets of lymph nodes (n = 197), consisting of the superficial cervical (prescapular), prepectoral, axillary, presternal, popliteal, ischiatic, subiliac (precrural), coxalis, and iliofemoralis (deep inguinal), were collected from five geographically separated Australian abattoirs over a period of 14 months. Samples were tested for the presence of Salmonella spp. and Shiga toxin-producing Escherichia coli by BAX PCR assay. Aerobic plate count, E. coli, and coliforms were enumerated with a lower limit of detection of 80 CFU per node. The observed prevalence of Salmonella within peripheral lymph nodes was 0.48% (7 of 1,464). Two of the seven lymph nodes in which Salmonella organisms were detected came from the same animal. Grass-fed, grain-fed, and cull dairy cattle were all found to have detectable Salmonella in lymph nodes. All Salmonella detections occurred during cooler months of the year. No Shiga toxin-producing E. coli were detected. Aerobic microorganisms were detected above the limit of quantification in 3.2% of nodes (median count 2.24 log per node), and E. coli was detected in 0.8% of nodes (median count 3.05 log per node). The low prevalence of Salmonella and low concentration of aerobic microorganisms in Salmonella-positive lymph nodes of Australian cattle at the time of slaughter suggest that the likelihood of lymph nodes contributing significantly to the presence of Salmonella in ground beef is low.

High-resolution melt curve PCR assay for specific detection of E. coli O157:H7 in beef

Among the disease-causing Shiga toxin-producing Escherichia coli (STEC), E. coli O157:H7 is estimated to cause one-third of the total STEC illnesses and the most cases of hemolytic uremic syndrome (HUS) in the U.S. The uidA gene which is present in the majority of E. coli strains, codes for the synthesis of β-d-glucuronidase (GUD). In E. coli O157:H7, the uidA gene has a single point mutation at the +93 position that leads to an alteration in the amino acid sequence encoding the GUD enzyme. The aim of this study was to distinguish E. coli O157:H7 from other E. coli using a high resolution melt curve (HRM) real-time PCR assay. Based on the uidA mutation in E. coli O157:H7, a reliable PCR assay targeting the uidA gene was developed to differentiate E. coli O157:H7 from other E. coli serotypes and the closely related Shigella spp. The specificity of the assay was validated using a set of 128 pure bacterial DNA samples. Following enrichment and immunomagnetic separation (IMS), the assay was further applied to spiked ground beef and beef trim. Isolates of E. coli O157:H7 formed distinctive melt peaks that were easily distinguishable from those of other E. coli serogroups and Shigella isolates in the PCR plot. Therefore, this assay was able to clearly discriminate E. coli O157:H7 strains from other E. coli and Shigella. With a 5–8 h enrichment time, followed by IMS, 10 CFU of E. coli O157:H7 were detectable in 325 g spiked beef samples. The HRM E. coli O157:H7 detection assay standardized in this study will allow for accurate identification of contaminated food samples and help in preventing foodborne outbreaks caused by this pathogen.

Evaluation of chlorine dioxide, acidified sodium chlorite and peroxyacetic acid for control of Escherichia coli O157:H7 in beef patties from treated beef trim

The effectiveness of 30 to 400ppm chlorine dioxide (CDO), acidified sodium chlorite (ASC) and peroxyacetic acid (PAA) to control Escherichia coli O157:H7 in beef was examined. Ground beef made from treated meat was vacuum packaged and stored at 4°C for 4d. CDO or ASC concentration by storage time interaction for inactivation of E. coli O157:H7 was significant (P<0.05). Exposure of beef to 200 and 400ppm CDO caused 0.73 and 1.25logcfu/g reduction in the numbers of pathogen, respectively, and an additional 2.08 and 2.25logcfu/g reduction, respectively, occurred at day 4. At 400ppm ASC caused a 0.87logcfu/g reduction and an additional 0.86logcfu/g inactivation at day 4. PAA caused ≤0.8logcfu/g reduction in pathogen numbers at ≤400ppm. Among tested antimicrobials, CDO was most effective and had a positive interaction with cold storage where additional E. coli O157:H7 inactivation occurred.

Biofilm Formation, Antimicrobial Resistance, and Sanitizer Tolerance of Salmonella enterica Strains Isolated from Beef Trim.

In the beef industry, product contamination by Salmonella enterica is a serious public health concern, which may result in human infection and cause significant financial loss due to product recalls. Currently, the precise mechanism and pathogen source responsible for Salmonella contamination in commercial establishments are not well understood. We characterized 89 S. enterica strains isolated from beef trim with respect to their biofilm-forming ability, antimicrobial resistance, and biofilm cell survival/recovery growth after sanitizer exposure. A total of 28 Salmonella serovars was identified within these strains. The most common serovars identified were Anatum, Dublin, Montevideo, and Typhimurium, with these accounting for nearly half of the total strains. The vast majority (86%) of the strains was able to develop strong biofilms, and the biofilm-forming ability was highly strain dependent and related to cell surface expression of extracellular polymeric structures. These strains also demonstrated strong tolerance to quaternary ammonium chloride (QAC) and chlorine dioxide (ClO2), but were more sensitive to chlorine treatment. Sanitizer tolerance and bacterial postsanitization recovery growth were closely associated with strains' biofilm-forming ability. Thirty percent of the examined strains were found resistant to multiple antimicrobial agents and the resistance phenotypes were serovar associated, but not related to strains' biofilm-forming ability. Pulsed-field gel electrophoresis analysis tended to group strains by serovar rather than by biofilm-forming ability. Collectively, these data indicate that the strong biofilm formers of certain S. enterica strains/serovars possess significant potential for causing meat product contamination in meat processing environment.

Isolation and characterization of non-O157 Shiga toxin-producing Escherichia coli from beef carcasses, cuts and trimmings of abattoirs in Argentina.

Several foods contaminated with Shiga toxin-producing Escherichia coli (STEC) are associated with human diseases. Some countries have established microbiological criteria for non-O157 STEC, thus, the absence of serogroups O26, O45, O103, O104, O111, O121, and O145 in sprouts from the European Union or ground beef and beef trimmings from the United States is mandatory. While in Argentina screening for O26, O103, O111, O145 and O121 in ground beef, ready-to-eat food, sausages and vegetables is mandatory, other countries have zero-tolerance for all STEC in chilled beef. The aim of this study was to provide data on the prevalence of non-O157 STEC isolated from beef processed in eight Argentinean cattle slaughterhouses producing beef for export and local markets, and to know the non-O157 STEC profiles through strain characterization and genotypic analysis. Samples (n = 15,965) from 3,205 beef carcasses, 9,570 cuts and 3,190 trimmings collected between March and September 2014 were processed in pools of five samples each. Pools of samples (n = 3,193) from 641 carcasses, 1,914 cuts and 638 trimming were analyzed for non-O157 STEC isolation according to ISO/CEN 13136:2012. Of these, 37 pools of carcasses (5.8%), 111 pools of cuts (5.8%) and 45 pools of trimmings (7.0%) were positive for non-O157 STEC. STEC strains (n = 200) were isolated from 193 pools of samples. The most prevalent serotypes were O174:H21, O185:H7, O8:H19, O178:H19 and O130:H11, and the most prevalent genotypes were stx2c(vh-b) and stx2a/saa/ehxA. O103:H21 strain was eae-positive and one O178:H19 strain was aggR/aaiC-positive. The prevalence of non-O157 STEC in beef carcasses reported here was low. None of the non-O157 STEC strains isolated corresponded to the non-O157 STEC serotypes and virulence profiles isolated from human cases in Argentina in the same study period. The application of microbiological criteria for each foodstuff should be determined by risk analysis in order to have a stringent monitoring system. Likewise, zero-tolerance intervention measures should be applied in beef, together with GMP and HACCP. Further, collaborative efforts for risk assessment, management and communication are extremely important to improve the safety of foodstuffs.

Application of Surfactant Micelle-Entrapped Eugenol for Prevention of Growth of the Shiga Toxin-Producing Escherichia coli in Ground Beef.

Beef safety may be compromised by O157 and non-O157 Shiga toxin-producing Escherichia coli (STEC) contamination. The capacity of surfactant micelles loaded with the plant-derived antimicrobial eugenol to reduce STEC on beef trimmings that were later ground and refrigerated for five days at 5 ± 1 °C was tested to determine their utility for beef safety protection. STEC-inoculated trimmings were treated with free eugenol, micelle-encapsulated eugenol, 2% lactic acid (55 °C), sterile distilled water (25 °C), or left untreated (control). Following treatment, trimmings were coarse-ground and stored aerobically at 5 ± 1 °C. Ground beef was then sampled for STEC immediately post-grinding, and again at three and five days of storage. STEC minimum inhibitory concentrations (MICs) in liquid medium for free eugenol and 1% sodium dodecyl sulfate (SDS)-loaded micelles were 0.5% and 0.125%, respectively. STEC numbers on beef trimmings treated by sterile water (6.5 log10 CFU/g), free eugenol (6.5 log10 CFU/g), micelle-loaded eugenol (6.4 log10 CFU/g), and lactic acid (6.4 log10 CFU/g) did not differ compared to untreated controls (6.6 log10 CFU/g) (p = 0.982). Conversely, STEC were significantly reduced by refrigerated storage (0.2 and 0.3 log10 CFU/g at three and five days of storage, respectively) (p = 0.014). Antimicrobial treatments did not significantly decontaminate ground beef, indicating their low utility for beef safety protection.

Quality of steak restructured from beef trimmings containing microbial transglutaminase and impacted by freezing and grading by fat level.

ObjectiveThe objective of this research was to evaluate the physico-chemical, microbiological and sensorial qualities of restructured steaks processed from beef trimmings (grade I and II) and frozen beef (fresh beef as control and frozen beef).MethodsBeef trimmings from commercial butcher were collected, designated into 4 treatments differing in beef trimmings grade and freezing, processed into restructured steaks with 1% microbial transglutaminase and then analyzed for product quality.ResultsThe results showed that all meat from different groups could be tightly bound together via cross-linking of myosin heavy chain and actin as observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Microbial counts of psychrotrophic and mesophilic bacteria were not affected by treatments (p>0.05), and no detectable of thermophilic bacteria were found. Regarding effect of beef trimmings grade, steaks made from beef trimmings grade II (16.03% fat) showed some superior sensorial qualities including higher tenderness score (p<0.05) and tendency for higher scores of juiciness and overall acceptability (p<0.07) than those made from beef trimmings grade I (2.15% fat). Moreover, a hardness value from texture profile analysis was lower in steaks processed from beef trimmings grade II than those made from grade I (p< 0.05). Although some inferior qualities in terms of cooking loss and discoloration after cooking were higher in steaks made from beef trimmings grade II than those made from beef trimmings grade I (p<0.05), these differences did not affect the sensory evaluation. Frozen beef improved the soft texture and resulted in effective meat binding as considered by higher cohesiveness and springiness of the raw restructured product as compared to fresh beef (p<0.05).ConclusionThe results indicated the most suitable raw beef for producing restructured steaks without detrimental effect on product quality was beef trimmings grade II containing up to 17% fat which positively affected the sensory quality and that frozen beef trimmings increased tenderness and meat binding of restructured beef steaks.

Crystal Diagnostics Xpress S Kit for the Rapid Detection of Salmonella spp. in Selected Food Matrixes.

The Crystal Diagnostics (CDx) Xpress S Kit is a rapid-screening assay for Salmonella spp. in whole raw tomatoes, whole chicken carcasses, raw ground beef, raw beef trim, and whole liquid pasteurized eggs with citric acid when present at levels of 1 CFU/portion size. The Xpress S system comprises an automatic CDx Xpress Reader and a single-use CDx BioCassette that incorporates antibody-coupled microspheres and liquid crystal for the selective identification of the intended microbe. In internal evaluations, the CDx Xpress S Kit detected all 142 Salmonella strains tested, including non-enterica subspecies, and excluded all non-Salmonella species assayed. Method-developer studies, as well as a third-party evaluation, demonstrated that 15 h single-stage enrichment permits rapid detection equivalent to the U.S. Department of Agriculture and U.S. Food and Drug Administration reference methods. The results demonstrate that the CDx Xpress S Kit is one of the fastest, most sensitive, and most accurate methods for detecting Salmonella in food matrixes.

Development and Testing of a Prototype Automatic Beef Trim Sampler

Development and Testing of a Prototype Automatic Beef Trim Sampler