Genetic profiles and invasion ability of Listeria monocytogenes isolated from bovine carcasses in Southern Brazil

The goals of this study were to evaluate the persistence and the virulence potential of Listeria monocytogenes isolated from beef carcasses obtained in processing facilities in the Southern region of Rio Grande do Sul, Brazil, based on pulsed field gel electrophoresis (PFGE), invasion ability in human colorectal carcinoma cells (HCT-116), InlA expression by western blot (WB) and identification of mutation points in the inlA . PFGE profiles demonstrated that L. monocytogenes isolates were grouped based on their previously identified lineages and serogroups (lineage I: serogroups IIb, n = 2, and IVb, n = 5; lineage II, serogroup IIc, n = 5), isolates with indistinguishable genetic profiles by this method were obtained from different slaughterhouses and sampling steps, with up to 3-year interval. Seven isolates showed high invasion ability (2.4 to 7.4%, lineage I, n = 6, lineage II, n = 1) in HCT and expressed InlA. Five isolates showed low cell invasion ability (0.6 to 1.4%, lineage I, n = 1, lineage II, n = 4) and did not express InlA, and two of them (lineage II, serogroup IIc) presented mutations in inlA leading to a premature stop codon (PMSC) type 19, at position 326 (GAA → TAA). The results demonstrated that most of L. monocytogenes isolates from Lineage I expressed InlA and were the most invasive in HCT indicating their high virulence potential, while most isolates from Lineage II showed attenuated invasion due to non-expression of InlA and the presence of PMSC type 19 in inlA . The obtained results demonstrated that L. monocytogenes with indistinguishable PFGE profiles can be persisting or being reintroduced in beef processing facilities in the studied region and differences on their virulence potential based on their lineages and serogroups.

Effects of beef carcass size, and subsequent aging time, on yield and color characteristics of top round steaks

Variation in cut size and weight of fabricated subprimals is a challengeof increased beef carcass weights. Subsequently, variation in carcass size hasresulted in consistency challenges during retail display. Theobjective of this study was to assess the retail shelf-life of commerciallyavailable top rounds from varying carcass weights. In the current study, 21industry average weight (AW, 340-409 kg; no industry discount) beef carcassesand 21 oversized (OS, exceeding 454 kg; receive a discount) beef carcasses wereevaluated. Carcasses were selected at a commercial beef packing plant, wherethe left and right (paired) top round subprimals of each carcass were procured.Paired top rounds were assigned to a short (8d), average (23d), or extended(42d) postmortem aging period. After wet-aging, subprimals were fabricated intosteaks for additional analysis. Steaks were evaluated as whole top round steaksor further fabricated into “superficial” and “deep” portions at 5.08 cm fromthe superficial edge of the Semimembranosus and the Adductor muscle.Top rounds and steaks from OS carcasses were larger (P < 0.01) thanthose from AW carcasses. Quantitative color of the anatomically deep locationsof the OS steaks had the greatest mean L* (lightness; P < 0.01), a*(redness; P < 0.01) and b* (yellowness; P < 0.01) values. Extendingthe aging timeline increased L* (lightness; P < 0.01), decreased a*(redness; P < 0.01), and decreased b* (yellowness; P <0.01). Alternative top round steak fabrication which separates the deep andsuperficial anatomical locations could be an effective means of providing moreuniform steaks. 

Effects of Neck-Arm Restraint Suspension of Beef Carcasses on Meat Quality and Proteome of Different Muscles During Post-mortem Aging

Beef quality is the first deciding factor for consumers to consider before purchasing. The aim of this study was to evaluate the effects of suspension and aging time on beef quality. We compared the differences in pH, drip loss, cooking loss, color, shear force, myofibril fragmentation index (MFI), and electron microscope of three muscle tissues between Achilles tendon (AT) and neck-arm restraint (NR) suspensions during seven aging periods (days 0, 1, 2, 3, 7, 14, and 21) after slaughter using the carcasses of six Xinjiang brown cattle. We found that NR suspension could significantly increase the water loss rate and MFI, as well as reduce the shear force compared to AT suspension. The muscle fiber structure with NR suspension was more severely damaged. The proteomics of longissimus dorsi was checked for the post-mortem days 1, 7, and 14. We detected 50, 26, and 29 differentially expressed proteins between NR and AT suspension at post-mortem days 1, 7, and 14, respectively. These proteins were involved in metabolic and muscle structure associated pathways and contributed to a comprehensive understanding of suspension-dependent meat quality regulation by proteins in beef cattle. To conclude, NR suspension can accelerate the aging time of beef carcasses, which will reduce the cost of carcass suspension and bring more benefits in the beef industry.

The path from protein profiling to biomarkers: The potential of proteomics and data integration in beef quality research

This study aimed to provide an overview of the strategy of meat quality biomarkers identification from protein profiling to the establishment of putative protein biomarkers with a focus on beef tenderness and colour traits. Further, the current knowledge gained by data-integration, also known as integromics, of published meat proteomics studies during the last decade is briefly discussed in terms of the current list of protein candidate biomarkers revealed using different proteomics platforms and evaluated by proteomics-based approaches. The main biochemical pathways underlying the determination of tenderness and colour traits as important beef eating qualities revealed by bioinformatics analyses such as Gene Ontology annotations, pathway and process enrichments are further considered. This paper also addresses the potential of integromics and data-mining, in the era of big data and data analytics, to broaden our knowledge on the biochemical mechanisms underlying the conversion of muscle into meat and the consequences on beef sensory quality traits (tenderness and colour). Finally, the emerging interest of using such gathered and shortlisted protein biomarkers for first validation and then early post-mortem prediction of the potential quality of beef carcasses is highlighted.

Frequency, territorial distribution and antimicrobial resistance of Salmonella spp. on bovine cattle feces from the Altos Sur region of Jalisco State, Mexico

Multidrug resistance is a global public health problem. In 2017, in Mexico, Salmonella caused 192,771 foodborne zoonosis cases. Sonora, Hidalgo, Mexico State and Jalisco have reports of multi-resistant Salmonella strains in chicken and beef carcasses in slaughterhouses; however, the prevalence in livestock herds is unknown. From January 2012 to October 2013, 144 diarrheal stool samples were collected from bovine hatchlings from the Altos Sur region of the Jalisco State. As a result, the presence and serotype of Salmonella was determined, as well as the antibiotic resistance profile, and the genetic relationship, using PFGE. The Salmonella prevalence was 4.16 % (6/144) in feces, identifying the serotypes Anatum, Pullorum, Poona, Typhi, Gallinarum and Salmonella enterica subsp. arizonae. All the strains showed resistance to ampicillin, cephalothin, trimethoprim-sulfamethoxazole, and some of them, additionally, to amikacin, cefotaxime and/or ceftriaxone. In addition, the persistence and potential spread of two Salmonella Anatum strains was discovered in one herd. This is the first study conducted in neonate bovine in the Jalisco State, Mexico, to detect multidrug resistant Salmonella. Continuous monitoring of multi-drug resistance in animal biota for human food and ongoing training of veterinary doctors are key elements for efficient prophylaxis and antimicrobial pharmacotherapy.

An investigation into the anaerobic spoilage microbiota of beef carcass and rump steak cuts using high- throughput sequencing

The presence of anaerobic microflora on fresh beef carcass and rump steaks, which may contribute to meat spoilage, was explored in this study. A total of 120 carcass and 120 rump steak swabs were collected immediately after slaughtering and boning, respectively from five meat plants, anaerobically incubated and enriched d at 4°C for 3 weeks. This was followed by DNA extraction and 16S rRNA amplicon sequencing using the Illumina MiSeqTM, with subsequent bioinformatics analysis. The enriched microbiota of the samples was classified and grouped into 149 operational taxonomic units (OTUs). The microbiota recovered from both sample types consisted mainly of Carnobacterium, with an average relative abundance of 28.4% and 32.8% in beef carcasses and beef rump steaks, respectively. This was followed by Streptococcus, Serratia, Lactococcus, Enterococcus, Escherichia-Shigella, Raoultella and Aeromonas ranging from 1.5–20% and 0.1–29.8% in enriched carcasses and rump steak swabs, respectively. Trichococcus, Bacteroides, Dysgomonas, Providencia, Paraclostridium and Proteus were also present ranging from 0–0.8% on carcass and 0–1.8% on rump steak swabs, respectively. Alpha and Beta diversity measurements showed limited diversity between the two sample types, but some differences between samples from the beef plants investigated were evident. This study highlights the presence of potential spoilage bacteria, mainly anaerobic genera on and between carcass and rump steaks, as an indication of contamination on and between these samples.

Effect of postmortem tenderization strategies (pre-tumbling, blade tenderization, moisture enhancement) on processing yield parameters and eating quality of selected hip and loin muscles from youthful and mature beef carcasses

Several muscles from mature beef carcasses have been identified as failing to provide adequate tenderness required for a satisfactory consumer eating experience. Postmortem processing strategies can help improve the tenderness and subsequent eating quality of mature beef muscles. The current study was undertaken to investigate the impact of processing strategies (blade tenderization [BT], pre-tumbling [PT], and moisture enhancement [ME]), alone and in combination, on processing yield and eating quality-related parameters of selected loin and hip muscles (gluteus medius [GM], longissimus lumborum [LL], semimembranosus [SM], and biceps femoris [BF]) from youthful and mature beef cattle. Results indicate that muscles from mature beef were inherently less tender (P < 0.05), but some tenderization procedures produced meat that was similar in tenderness to that of youthful cattle. Of the different tenderization strategies evaluated, BT followed by ME (injection of a salt/phosphate solution) was the most effective strategy for improving (P < 0.05) tenderness of tougher muscle cuts such as BF and SM. Moisture enhancement alone improved tenderness (P < 0.05) and juiciness (P < 0.01) of SM, GM and LL, but with the exception of samples tenderized prior to injection, was not effective (P > 0.05) in BF muscles. No additional tenderization of GM and LL samples was observed (P > 0.05) by combining PT or BT with ME. Combining PT or BT with ME; however, was effective (P < 0.05) to control the increased purge loss observed following ME treatment in SM and LL muscles. Pre-tumbling as a single treatment was ineffective (P > 0.05) in all of the muscles, and only treatments that included BT were sufficient to affect an increase (P < 0.05) in tenderness of BF.

Electrical stimulator voltage settings minimally influences beef longissimus muscle tenderness

The objective of the current study was to evaluate the effect of differing electrical stimulation (ES) voltage levels on beef longissimus muscle (LM) tenderness, postmortem temperature, and pH decline, and carcass quality. Beef carcasses from three commercial beef processing plants (A, B, C) were exposed to three varying voltage levels: 1) control (no ES) 2) high ES (60-Hz for 17s each at 25, 35, 45, and 55 V) 3) low-ES (60-Hz for 17s each at 16, 20, 24, and 28 V). Ninety beef carcasses were selected from the three plants, and within a carcass, paired sides were randomly assigned to one of three ES treatments. The results indicated that ES affected (P < 0.05) muscle pH at 3 h postmortem in two of the three plants. However, ES did not affect (P > 0.05) pH at the time of grading (post rigor). Although the slice shear force (SSF) values were lower (P < 0.05) for ES steaks compared to controls, it was not (P < 0.05) influenced by the voltage levels. Variation in tenderness was observed among the plants (P < 0.05), with Plant C having the toughest steaks, whereas Plant A and B exhibited similar (P > 0.05) tenderness. Overall, the lack of difference in postmortem tenderness between high- and low-voltage settings indicated the ES-voltage minimally influenced tenderness. 

Low-Voltage Electrical Stimulation of Beef Carcasses Slows Carcass Chilling Rate and Improves Steak Color

Electrical stimulation (ES) is used in beef slaughter plants to improve tenderness; however, varying levels of low-voltage ES have not been well characterized. The objective was to evaluate the influence of two levels of low-voltage ES on temperature decline, pH, glycolytic potential, and meat quality. Forty-two beef carcasses were chosen from a commercial packing facility. One side of each carcass received either 40 or 80 volts of ES for 60 s at 45 min postmortem. The paired side of each carcass did not receive ES (Control). Temperature loggers were placed in the sirloin of 12 carcasses to record temperature decline. Longissimus muscle pH was measured at 1, 12, and 24 h, and 3 d postmortem. Strip steaks were fabricated for determination of meat quality. A treatment by time interaction was observed for carcass temperature decline (p < 0.001) where ES sides stayed warmer longer than Control sides. A treatment by time interaction was observed for pH decline with Control sides exhibiting an increased pH at 1 h postmortem (p < 0.001). Instrumental color values were increased for ES compared to Control sides (p < 0.001). These results indicate ES slows carcass temperature decline, hastens initial pH decline, and improves instrumental color. Similar results were observed between the ES treatments indicating either ES level may be used to achieve similar quality characteristics.