Relationships among calpastatin single nucleotide polymorphisms, calpastatin expression and tenderness in pork longissimus.

Genome scans in the pig have identified a region on chromosome 2 (SSC2) associated with tenderness. Calpastatin is a likely positional candidate gene in this region because of its inhibitory role in the calpain system that is involved in postmortem tenderization. Novel single nucleotide polymorphisms (SNP) in calpastatin were identified and used to genotype a population (n = 1042) of Duroc-Landrace-Yorkshire swine for association with longissimus lumborum slice shear force (SSF) measured at days 7 and 14 postmortem. Three genetic markers residing in the calpastatin gene were significantly associated with SSF (P < 0.0005). Haplotypes constructed from markers in the calpastatin gene were significantly associated with SSF (F-ratio = 3.93; P-value = 0.002). The levels of normalized mRNA expression of calpastatin in the longissimus lumborum of 162 animals also were evaluated by real-time RT-PCR and were associated with the genotype of the most significant marker for SSF (P < 0.02). This evidence suggests that the causative variation alters expression of calpastatin, thus affecting tenderness. In summary, these data provide evidence of several significant, publicly available SNP markers associated with SSF that may be useful to the swine industry for marker assisted selection of animals that have more tender meat.

Prevalence of Mycobacterium avium subsp. paratuberculosis in ileocecal lymph nodes and on hides and carcasses from cull cows and fed cattle at commercial beef processing plants in the United States.

Clinical associations between Crohn's disease in humans and Mycobacterium avium subsp. paratuberculosis (MAP) have been suggested but not confirmed. Cattle could be sources for MAP, but little information on MAP prevalence with beef has been reported. Samples of ileocecal lymph nodes and swabs of hides and carcasses from 343 animals at cull cattle slaughtering facilities and 243 animals at fed cattle slaughtering facilities across the United States were analyzed for the presence of MAP. Amplification of genetic sequences detected MAP DNA predominantly on hides and in lymph nodes of samples taken at both types of processing facilities. More than 34% of the cattle at cull cow slaughtering facilities had ileocecal lymph nodes that tested positive for MAP DNA. From these same cattle, hide prevalence was more than twofold greater than the prevalence in ileocecal lymph nodes, suggesting that cross-contamination could be occurring during transport and lairage. The prevalence of MAP DNA decreased during processing, and less than 11% of the carcasses tested positive after interventions in the cull cow processing facilities. Using standard double-decontamination and culture techniques, less than 1% of the postintervention carcasses tested positive for viable MAP at cull cow facilities. In samples from the facilities processing only fed cattle, MAP prevalence of 1% or less was detected for ileocecal lymph node, hide, and carcass samples, and viable MAP was not detected. Based on this study, fed cattle carcasses are unlikely sources of MAP, and carcasses at cull cow plants have only a slight risk for transmitting viable MAP, due to current interventions.

Prevalence and level of Escherichia coli O157:H7 in feces and on hides of feedlot steers fed diets with or without wet distillers grains with solubles.

The objective of this study was to determine if wet distillers grains with solubles (WDGS) from corn in diets affected Escherichia coli O157:H7 in growing and finishing cattle; steers (n = 603) were randomly assigned to diets with or without WDGS. Hide and fecal samples were collected monthly (October through June) from each animal for enumeration and enrichment of E. coli O157:H7. In the growing phase (0 or 13.9% WDGS diets), fecal prevalence for E. coli O157:H7 in steers fed a diet with WDGS was twice that of the prevalence in control steers (P < 0.001). In the finishing phase (0 or 40% WDGS diets), the average prevalence in feces (P < 0.001) and on hides (P < 0.001) was higher for cattle fed WDGS. The average percentage of fecal E. coli O157:H7 enumerable samples during the finishing phase for cattle fed WDGS was 2.7% compared with 0.1% for control steers (P < 0.001). The average percentage of E. coli O157:H7 enumerable hide samples was not different between diets, but the cattle fed WDGS had higher levels (P < 0.05) of the pathogen. Animals fed WDGS had higher levels of E. coli (P < 0.001), higher pH values (P < 0.001), and lower concentrations of L-lactate (P < 0.001) in feces than those values of the control steers. These results indicate that feeding 40% WDGS could increase the level and prevalence of E. coli O157:H7 in and on feedlot cattle when E. coli O157:H7 is seasonally low.

Consumer acceptance and steak cutting yields of beef top sirloin and knuckle subprimals.

Beef knuckles (n=150) and center-cut top sirloin butts (n=150) were used to determine portion-controlled steak cutting yields, palatability characteristics, and consumer acceptance of rectus femoris (RF), vastus lateralis (VL), and gluteus medius (GM) steaks. Steak yields were higher (P<0.05) for top sirloins than knuckles. Trained sensory panel ratings for overall tenderness, juiciness, and flavor were similar between RF and GM. Consumer panel ratings for tenderness and juiciness were higher (P<0.05) for GM than RF; however, consumer perceptions of overall like and flavor were similar for GM and RF. Vastus lateralis received lower (P<0.05) trained panel and consumer ratings for all traits than either RF or GM. Palatability of VL will need improvement to be a viable foodservice offering. Yet, these data suggest that RF would amply substitute for GM in foodservice settings, and that knuckle steak yields would be adequate for foodservice applications.

Evaluation of biochemical parameters and genetic markers for association with meat tenderness in South African feedlot cattle.

A large proportion of South African feedlot cattle are crossbreds of Brahman (BrX, Bos indicus), and Simmental (SiX, Bos taurus). A sample of 20 grain fed bulls from each of these crossbreeds was used to compare meat quality with that of the small frame indigenous Nguni (NgX, Sanga) by evaluating a variety of biochemical and genetic parameters previously shown to be associated with meat tenderness. Shear force values were generally high (5.6kg average at 14days post mortem), with SiX animals higher than BrX or NgX (P=0.051) despite higher calpastatin:calpain ratio in BrX (P<0.05). Calpain activity and cold shortening were both correlated with tenderness for all classes. The sample size was too small to accurately estimate genotypic effects of previously published markers in the CAST and CAPN1 genes, but the allele frequencies suggest that only modest progress would be possible in these South African crossbreds using these markers.

Enumeration of Salmonella from poultry carcass rinses via direct plating methods.

AIM: To evaluate direct plating methods for the estimation of Salmonella load in poultry carcass rinses. METHODS AND RESULTS: Two direct plating tools, the spiral plate count method (SPCM) and the hydrophobic grid membrane filtration (HGMF) method, were adapted to support quantification of Salmonella during poultry processing. Test samples consisted of 180 broiler carcasses from a commercial abattoir, 60 from each of three points in the processing line [pre-inside-outside bird wash (pre-IOBW), prechill and postchill]. The SPCM was used to estimate Salmonella load in pre-IOBW rinses, while HGMF was used to estimate Salmonella levels in prechill and postchill rinses. Carcass rinses were also evaluated for Salmonella prevalence by enrichment methods. Mean prevalences of Salmonella were 95%, 100% and 41.7%, and the geometric mean loads were 3.7 x 10(1), 5.6 x 10(0) and 5.0 x 10(-2) CFU ml(-1) for pre-IOBW, prechill and postchill rinses, respectively. CONCLUSIONS: The methods described are useful for estimating the concentration of viable and typical Salmonella in poultry carcass rinses. SIGNIFICANCE AND IMPACT OF THE STUDY: Direct plating enumeration methods can facilitate the monitoring of Salmonella load on poultry carcasses throughout the production process, and the evaluation of new processing intervention strategies.

Opportunities for collaborative phenotyping for disease resistance traits in a large beef cattle resource population.

The Germplasm Evaluation (GPE) Project at the US Meat Animal Research Center (USMARC) is planned to produce about 3,000 calves per year in support of the following objectives: identification and validation of genetic polymorphisms related to economically relevant traits (ERT), estimation of breed and heterosis effects among 16 breeds for ERT, and estimation of genetic correlations among ERT and physiological indicator traits (PIT). Opportunities exist for collaboration in the development and collection of PIT phenotypes for disease resistance. Other areas of potential collaboration include detailed diagnosis (identification of disease causing organisms, etc.) of treated animals, collaborative development of epidemiological statistical models that would extract more information from the records of diagnoses and treatments, or pharmacogenetics. Concentrating a variety of different phenotypes and research approaches on the same population makes each component much more valuable than it would be individually.

Interventions to reduce/eliminate Escherichia coli O157:H7 in ground beef.

The Escherichia coli O157:H7 (E. coli O157:H7) outbreak in the Northwestern United States ushered in an era that has dramatically changed the way beef processors in the United States convert live cattle into meat. Unprecedented cooperation among the beef processors and massive investment in research by the US government and the beef industry have resulted in an acceptable level of control of E. coli O157:H7 in ground beef. The evidence to support the progress in control of E. coli O157:H7 is the CDC data for reduction in human illness as well as the dramatic reduction in the number of E. coli O157:H7-positive samples in USDA-FSIS ground beef monitoring. This manuscript highlights some of the recent findings from our laboratory on the control of E. coli O157:H7 in ground beef. We have also summarized the key events/decisions/milestones that have contributed to the control of E. coli O157:H7 in ground beef in the United States. While there is much to be done to bring E. coli O157:H7 under complete control in the beef sector of the food industry, E. coli O157:H7 also is becoming a major issue in the fresh vegetable sector, as evidenced by the 2006 outbreaks in the United States. We have discussed how the fresh vegetable industry can benefit from the beef industry's experience to expedite the control of E. coli O157:H7 in their products.

Contribution of postmortem muscle biochemistry to the delivery of consistent meat quality with particular focus on the calpain system.

Tenderness has been repeatedly reported as the most important quality aspect of meat. However, a number of studies have shown that a significant portion of retail meat can be considered tough. As a consequence, a significant consumer segment is willing to pay a premium for guaranteed tender meat. However, apart from measuring the shear force, there is no reliable method to predict tenderness. Most of the branded meat programs therefore attempt to ensure eating quality by controlling some of the factors that affect tenderness. Meat tenderness is determined by the amount and solubility of connective tissue, sarcomere shortening during rigor development, and postmortem proteolysis of myofibrillar and myofibrillar-associated proteins. Given the effect of postmortem proteolysis on the muscle ultrastructure, titin and desmin are likely key substrates that determine meat tenderness. A large number of studies have shown that the calpain proteolytic system plays a central role in postmortem proteolysis and tenderization. In skeletal muscle, the calpain system consists of at least three proteases, µ-calpain, m-calpain and calpain 3, and an inhibitor of µ- and m-calpain, calpastatin. When activated by calcium, the calpains not only degrade subtrates, but also autolyze, leading to loss of activity. m-Calpain does not autolyze in postmortem muscle and is therefore not involved in postmortem tenderization. Results from a number of studies, including a study on calpain 3 knockout mice, have shown that calpain 3 is also not involved in postmortem proteolysis. However, a large number of studies, including a study on µ-calpain knockout mice, have shown that µ-calpain is largely, if not solely, responsible for postmortem tenderization. Research efforts in this area should, therefore, focus on elucidation of regulation of µ-calpain activity in postmortem muscle. Discovering the mechanisms of µ-calpain activity regulation and methods to promote µ-calpain activity should have a dramatic effect on the ability of researchers to develop reliable methods to predict meat tenderness and on the meat industry to produce a consistently tender product.

On-line classification of US Select beef carcasses for longissimus tenderness using visible and near-infrared reflectance spectroscopy.

The current experiment was conducted to evaluate the on-line application of visible and near-infrared spectroscopy (VISNIR) to US Select carcasses during commercial beef carcass grading procedures to predict tenderness of longissimus steaks after 14 days of refrigerated storage. A regression model was calibrated using 146 carcasses and tested against an additional 146 carcasses. Carcasses were segregated into VISNIR-based tenderness classes based on whether their VISNIR-predicted slice shear force value was less than (tender) or greater than (tough) the median predicted slice shear force value. Carcasses classified as tender by VISNIR had a lower mean SSF value, were less likely to have slice shear force values greater than 245 N, had higher trained sensory panel tenderness ratings, and were less likely to have trained sensory panel tenderness ratings below slightly tender than were carcasses classified as tough (P<0.001). This technology might be useful for identification of US Select carcasses that excel in longissimus tenderness.

Post-harvest interventions to reduce/eliminate pathogens in beef.

In 1999 the foodborne pathogens Salmonella, Listeria, Campylobacter, and Escherichia coli (both O157 and non-O157) were estimated to cause more than 6 million illnesses and approximately 9000 deaths each year. However, the most recent Centers for Disease Control and Prevention report on the sources and incidence of foodborne disease, released in 2004, has shown a dramatic decrease in E. coli O157:H7 infections. Since raw beef products are the most frequently foodborne sources of these pathogens, the results of this report demonstrate that the microbiological quality of raw beef has improved greatly. During the intervening years, post-harvest interventions have continually improved, with new attention to hide decontamination and innovative treatments of carcasses. In addition, a system to hold and test beef trim or ground beef for E. coli O157:H7 before its release into commerce has provided an even greater level of safety. In this paper, we review the latest information on the prevalence of E. coli O157:H7 and other pathogens on beef, the evidence identifying the hide as the primary source of pathogens on beef carcasses, the efficacy of various hide and carcass interventions, and other developments that have led or have the potential to lead to even greater improvements in the microbial quality of beef.

Quantification of calpastatin using an optical surface plasmon resonance biosensor.

An immunological biosensor for calpastatin was developed on a surface plasmon resonance based system (Biacore Q). The performance of the biosensor assay was evaluated using ovine and bovine muscle and heart extracts with known calpastatin activity. In addition, the relationship between immunologically detectable calpastatin at 1 day postmortem and shear force at 14 days postmortem was investigated for bovine longissimus dorsi. Calpastatin biosensor results for several experiments were linearly related to calpastatin activity measurements with correlation coefficients ranging from 0.51 to 0.99. The intra- and inter-assay CVs were <6% (n=12). During postmortem storage, the amount of immunologically detectable calpastatin decreased faster than the inhibitory activity in the enzymatic assay. Probably, the epitope recognized by the antibody is degraded faster than the inhibitory sites of calpastatin during postmortem storage. Calpastatin content at 1 day postmortem was correlated to shear force at 14 days postmortem (r=0.75). It is anticipated that developments in the near future will allow for at-line calpastatin determinations in beef plants. At present, the calpastatin biosensor assay appears suitable for research purposes where large numbers of samples need to be processed for breed evaluation or selection programs because this assay requires less labor than other methods.

The role of Ca(2+)-dependent proteases (calpains) in post mortem proteolysis and meat tenderness.

This manuscript summarizes research results from our laboratory regarding the role of endogenous proteases in post mortem proteolysis resulting in meat tenderization. Proteolysis of key myofibrillar proteins is the principal reason for ultrastructural changes in skeletal muscle associated with meat tenderization. Proteases should have the following characteristics to be considered as possible candidates for bringing about post mortem changes: i) to be located within skeletal muscle cells; ii) to have access to the substrate ie, myofibrils); and iii) to be able to hydrolyze the same proteins that are degraded during post mortem storage. Of the proteases located within skeletal muscle cells and thus far characterized, only calpains have all of the above characteristics. Numerous experiments conducted in our laboratory have indicated that the calcium-dependent proteolytic system (calpains) is responsible for post mortem proteolysis. Some of this evidence includes: 1) incubation of muscle slices with buffer containing Ca2+ accelerates post mortem proteolysis; 2) incubation of muscle slices with Ca2+ chelators inhibits post mortem proteolysis; 3) infusion or injection of carcasses with a solution of calcium chloride accelerates post mortem proteolysis and the tenderization process such that post mortem storage beyond 24 h to ensure meat tenderness is no longer necessary; 4) infusion of carcasses with zinc chloride, a potent inhibitor of calpains, blocks post mortem proteolysis and the tenderization process; and 5) feeding a beta-adrenergic agonist to lambs results in a reduction of the proteolytic capacity of the calpain system, which leads to a decreased rate of post mortem proteolysis and produces tough meat.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of different levels of beef bacterial microflora on the growth and survival of Escherichia coli O157:H7 on beef carcass tissue.

The influence of various levels of endogenous beef bacterial microflora on the growth and survival of Escherichia coli O157:H7 on bovine carcass surface tissue was investigated. Bacterial beef microflora inoculum was prepared by enriching and harvesting bacteria from prerigor lean bovine carcass tissue (BCT) and was inoculated onto UV-irradiated prerigor BCT at initial levels of 10(5), 10(4), 10(3), and <10(3) CFU/cm2. Additional control BCT was inoculated with sterile H2O. E. coli O157:H7 was inoculated onto all tissues at an initial level of 10(2) CFU/cm2. Following a 48-h incubation at 4 degrees C, BCT was incubated up to 14 days at 4 or 12 degrees C, either aerobically or vacuum packaged. Regardless of the microflora level, there was no substantial growth of E. coli O157:H7 on BCT during storage at 4 degrees C under either aerobic or vacuum-packaged conditions. Instead, viable cell numbers at 4 degrees C remained constant, with no reduction in numbers associated with the different beef microflora levels. E. coli O157:H7 grew on all BCT stored at 12 degrees C, regardless of microflora inoculation treatment, reaching higher populations on aerobic samples than on vacuum-packaged samples in 10 days. However, the presence of the beef microflora did appear to delay the onset of growth or slow the growth of the pathogen, and E. coli O157:H7 counts on BCT without added microflora were generally higher following 7 to 10 days of 12 degrees C storage than those counts on BCT inoculated with beef microflora. These data demonstrate the importance of temperature control during meat handling and storage to prevent the outgrowth of this pathogen and indicate that proper sanitation and processing practices that prevent and reduce contamination of carcasses with E. coli O157:H7 are essential, regardless of background microflora levels.

Microbial and quality attributes of ground pork prepared from commercial pork trim treated with combination intervention processes.

The effects of combination intervention treatments of commercial pork trim on microbial and quality attributes of the subsequent ground pork were examined. Fresh commercial pork trim was inoculated with swine feces and subjected to five different intervention treatments: (i) control (untreated), (ii) water (15 degrees C, 120 s), (iii) water followed by 2% lactic acid wash (15 degrees C, 75 s), (iv) Combination 1 (water plus lactic acid plus hot air [510 degrees C, 90 s]), and (v) Combination 2 (hot air plus water plus hot air). Following treatment, the pork trim was stored at 4 degrees C for 24 h, then ground, stuffed, vacuum packaged, and stored at 4 degrees C for 21 days. Populations of aerobic bacteria, coliforms, Escherichia coli, and lactic acid bacteria in the ground pork were monitored before treatment, after treatment (day 0), and at 2, 7, 14 and 21 days. In addition, uninoculated pork trim was treated as described above, and the color and emulsion stability of the ground product was evaluated. Ground pork prepared from trim treated with any of the treatment processes had lower initial microbial populations compared to the untreated samples. The applications of water plus lactic acid or Combination 1, which included a lactic acid wash, were more effective than water or Combination 2 at both reducing initial populations and suppressing the growth of aerobic bacteria, coliforms, and E. coli in ground pork during refrigerated storage. By day 21, populations of aerobic bacteria in ground pork prepared from control, water-treated, and Combination 2-treated trim were 8.22 to 8.32 log CFU/g, but in water plus lactic acid and Combination 1 ground pork, populations were 6.32 and 4.90 log CFU/g, respectively. Among the trim interventions examined, Combination 1 was most detrimental to the color and emulsion stability of the ground pork. The water plus lactic acid treatment provided the greatest microbial reduction and inhibition without large negative effects on quality attributes of the ground pork.

Application of multiple antimicrobial interventions for microbial decontamination of commercial beef trim.

Commercially produced, irregularly sized (range, 100 to 400 cm2), uninoculated beef trim was treated by a previously optimized multihurdle antimicrobial process under spray system or hot air gun with set-up speed (1 cm/s): W (water wash at 65 psi for five passes) + HW (82 degrees C water at 30 psi for three passes) + HA (510 degrees C air for five passes) + L (2% [vol/vol] room temperature lactic acid wash at 30 psi for three passes). After treatment, the trim was finely ground, vacuum packaged, and stored at 4 degrees C for up to 20 days. At regular intervals (0, 5, 10, 15, and 20 days of storage at 4 degrees C), the ground beef was analyzed to measure mesophilic aerobic bacteria (APC), coliforms, psychrotrophic bacteria (PCT), and presumptive lactic acid bacteria (PLAB) and compared with the untreated control. The numbers of APC, coliforms, PCT, and PLAB were reduced to nearly nondetectable levels immediately after treatment, with significant differences compared with the control (P < 0.05), then started to increase after 5 to 10 days of storage at 4 degrees C. After 20 days, microbial populations of treated ground beef were significantly lower than those of nontreated ground beef for the numbers of APC, coliforms, PCT, and PLAB (P < 0.05), with differences of 1.2, 2.4, 1.6, and 1.6 log CFU/g, respectively. Based on microbial reduction and quality aspects, the multihurdle antimicrobial process was identified as an effective intervention to reduce coliforms on beef trim.

Development of a multiple-step process for the microbial decontamination of beef trim.

A multiple-hurdle antimicrobial process for beef trim was developed. The microbial profiles of inoculated lean beef trim tissue (BTL) and fat-covered lean beef trim (BTF) were monitored during prolonged refrigerated storage following the application of successive multiple antimicrobial treatments applied to inoculated beef trim on a processing conveyor belt set at a belt speed of 1 cm/s. Beef trim (meat size approximately 15 by 15 cm) was preinoculated with bovine feces before all treatments that included the following: control, no treatment; water wash at 65 psi for five passes; water plus lactic acid (2% [vol/vol] room temperature lactic acid wash at 30 psi for three passes); combination treatment 1 (water plus 65 degrees C hot water at 30 psi for one pass plus hot air at 510 degrees C for four passes plus lactic acid), combination treatment 2 (water plus hot water at 82 degrees C for one pass plus hot air at 510 degrees C for five passes plus lactic acid), and combination treatment 3 (water plus hot water at 82 degrees C for three passes plus hot air at 510 degrees C for six passes plus lactic acid). The effects of treatments on bacterial populations were monitored by enumerating mesophilic aerobic bacteria (APC), presumptive lactic acid bacteria (PLAB), psychrotrophic bacteria (PCT), coliforms, and Escherichia coli biotype 1 on product stored for up to 7 days at 4 degrees C. In the case of BTL, the numbers of APC, PCT, and PLAB increased during storage at 5 degrees C, whereas the numbers of coliform and E. coli decreased on average by 1.8 log CFU/cm2, then remained constant following the initial reduction. Negligible effects on color quality were observed from multihurdle treatment combination 1. In the case of the BTF, the microbial reductions by treatments were much greater than the reduction on BTL. The pH of treated BTF increased more slowly than the pH of treated BTL, resulting in further reduction of the microflora on BTF. Except for control and water treatments, all sample treatments involving lactic acid resulted in continuously decreasing microbial populations. Based on microbial reduction and quality aspects, it was concluded that successively applied combination antimicrobial treatments for meat trim could offer potential food safety benefits.

Bacterial cross-contamination of meat during liquid nitrogen immersion freezing.

Prerigor beef carcass surface tissue (BCT) was used to simulate lamb carcasses on a processing line with a 15-min liquid nitrogen (LN) immersion freezing step, and the potential for the dissemination of bacteria during freezing was examined. Streptomycin-resistant strains of Listeria innocua and Escherichia coli O157:H7 spiked into a fecal slurry were inoculated onto BCT pieces that were introduced into the freezing process to represent contaminated carcasses. Following this introduction, subsequently frozen uninoculated BCT, LN, and LN containers were examined for the inoculated organisms. In the first study, BCT samples were inoculated with ca. 7 log CFU/cm2 of both L. innocua and E. coli O157:H7, spray washed with water and frozen, distributed among uninoculated BCT, in LN for 15 min. In two separate trials, L. innocua was recovered by enrichment from all uninoculated BCT and LN samples. E. coli O157:H7 was also recovered from uninoculated BCT and LN, but this cross-contamination was more sporadic. Both species were recovered from the LN container following freezing. Attempts to enumerate cross-contaminating bacteria in the second trial indicated that contaminating levels were low (< 1.0 CFU/cm2 BCT). In a second study, a 2.0% lactic acid spray wash was used to reduce further the numbers of L. innocua introduced into the freezing system and resulted in fewer positive samples, although this organism was still recovered from many uninoculated BCT samples. When either bacterium was inoculated at lower initial levels (1.35 to 1.77 log CFU/cm2) and BCT was water or 2.0% lactic acid spray washed prior to freezing, neither L. innocua nor E. coli O157:H7 was recoverable by enrichment from uninoculated BCT, LN, or from the freezing container. Results demonstrate that bacterial cross-contamination of meat during LN immersion freezing can occur but indicate that the use of good sanitation practices and product with low microbial numbers can limit this occurrence.

Evaluation of combination treatment processes for the microbial decontamination of pork trim.

Combination treatment processes for the microbial decontamination of pork trim were developed and evaluated. Lean pork trim tissue (LPT) and fat-covered pork trim tissue (FPT) inoculated with swine feces were treated with intervention processes as follows: (i) control (untreated), (ii) water (15 degrees C, 120 s), (iii) water followed by lactic acid wash (15 degrees C, 75 s), (iv) combination 1 (water plus hot water [65.5 degrees C, 15 s] plus hot air [510 degrees C, 60 s] plus lactic acid), (v) combination 2 (water plus hot water [82.2 degrees C, 15 s] plus hot air [510 degrees C, 75 s] plus lactic acid), and (vi) combination 3 (water plus hot water [82.2 degrees C, 45 s] plus hot air [510 degrees C, 90 s] plus lactic acid). Populations of aerobic bacteria, psychrotrophic bacteria, coliforms, Escherichia coli, and lactic acid bacteria were determined before and after treatment and at days 2 and 7 of 4 degrees C storage. Regardless of the intervention treatment, lower microbial populations were observed on FPT than on LPT immediately after treatment and during the 7-day storage period. Both LPT and FPT treated with water plus lactic acid, combination 1, combination 2, and combination 3 had lower remaining populations of all microbial groups immediately after treatment than did water-treated samples. Populations of aerobic bacteria, coliforms, E. coli, and lactic acid bacteria on either LPT or FPT did not statistically increase during the 7-day storage period. On LPT, populations of psychrotrophic bacteria grew during 4 degrees C storage but remained lower at day 7 on LPT treated by combinations 2 and 3 (2.29 and 1.89 log10 CFU/cm2, respectively) than on LPT treated with water (4.07 log10 CFU/cm2) or water plus lactic acid (3.52 log10 CFU/cm2). Populations of psychrotrophic bacteria remained below detectable levels throughout the 7-day storage on FPT treated with water plus lactic acid or any of the three combination treatments. Treatment of pork trim with any of the combination treatments significantly (P < 0.05) affected the color and emulsion stability of the ground pork. Water and water plus lactic acid were the most favorable treatments in reducing microbial populations on pork trim without affecting the quality attributes of the ground pork.

Screening bovine carcass sponge samples for Escherichia coli O157 using a short enrichment coupled with immunomagnetic separation and a polymerase chain reaction-based (BAX) detection stept.

A bovine carcass sponge sample screening protocol for detecting Escherichia coli O157:H7 was composed of a short selective enrichment followed by an immunomagnetic separation (IMS) and target detection using the BAX E. coli O157 polymerase chain reaction assay. This screening protocol was compared to a culture-based method for detection of the organism in carcass sponge samples. Enriched samples were subjected to IMS; the bead suspension was divided and plated on selected media or stored at -20 degrees C, then subjected to BAX analysis. The results showed a high degree of agreement between the plating method and the BAX system. Fifty-two of the 59 culture-positive samples were also positive using the BAX system (88.1% sensitivity). Of the 76 samples that appeared negative for the presence of E. coli O157:H7 by the culture method, 66 were determined as negative using the BAX system (86.8% specificity). Four of the 10 samples found negative by the initial culture method and positive by the BAX method were subsequently found to be culture positive upon reanalysis. Based on these data, the BAX system combined with a short, selective enrichment and IMS may be a rapid, reliable, and simple method to screen for E. coli O157:H7 in carcass sponge samples. Our data indicate that optimization and subsequent testing of this protocol for use as a carcass screening tool are warranted.