Mountain Scholar :: Browsing by Author "Belk, Keith E., committee member"

Browsing by Author "Belk, Keith E., committee member"

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Open Access
An in vitro system evaluation of the rumen microbiome and rumen fermentation characteristics as a result of differing feed additives
(Colorado State University. Libraries, 2019) Reyes, Arquimides A., author; Delmore, Robert J., advisor; Belk, Keith E., committee member; Engle, Terry E., committee member; Woerner, Dale R., committee member; Holt, Timothy N., committee member
To view the abstract, please see the full text of the document.
Open Access
Antimicrobial resistance in the meat industry and the impact of meat animal fecal microbiomes and resistomes on subsequent environments
(Colorado State University. Libraries, 2022) Rice, Emily Ashton, author; Nair, Mahesh N., advisor; Belk, Keith E., committee member; Morley, Paul S., committee member; Noyes, Noelle N., committee member
The discovery of antibiotics for human and animal use is considered one of the greatest medical advancements. However, the widespread use of antibiotics has caused concerns about a potential increase of antimicrobial resistance genes (ARGs) within microbial communities offering the opportunity for consumers to acquire antimicrobial resistant infections through the direct consumption of meat animals or through the environment via manure applications to crop land. Many consumers are becoming increasingly conscious of antibiotic usage labeling when purchasing meat products resulting in animal agriculture being considered a primary contributor for the dissemination of antimicrobial resistance (AMR). Although in recent years many advancements have been made to more fully understand the resistome of production animals preharvest and few post-harvest but, there are minimal studies that fully characterize the resistome of meat animals carcasses throughout the harvest process. Therefore, the purpose of the review (Chapter 2) is to outline opportunities to utilize metagenomic sequencing to pinpoint potential sources of antimicrobial resistance throughout meat processing. This could provide insight to better understand the potential sources of antibiotic resistant bacteria as a result of meat production. As bacteria can acquire ARGs through horizontal gene transfer or mutations, as an evolutionary advantage directly resulting from environmental pressures, the objective of the following study (Chapter 3) was to evaluate the relationships between the fecal resistome of different food animal species (avian, bovine, and porcine), the resistomes of meat from those animals, and resistomes of soil where feces was used as an amendment. Composite fecal samples (n = 20 per species) were collected from each commercial production facility and meat rinsate samples were (n = 20 per species) collected for each species at the time of harvest. After harvest, feces and litter were composted and applied as an amendment on agricultural land. After one growth season, soil samples (n = 20 per species) were collected separately for each species. Additionally, human waste solids were collected from wastewater treatment plants near each animal production operation (n = 14 per species), and soil samples amended with human waste solids were collected (n = 7 per species) from fields in close proximity to the broiler and bovine facilities. DNA was extracted, and the resistome library was prepped using the SureSelectXT reagent kit to prepare samples for target-enriched resistome sequencing targeting ARGs. Reads were analyzed using AMR++ v2 pipeline and sequences were aligned to the MEGARes v2 database to identify ARGs. Richness, evenness, and Shannon's diversity were calculated, and beta-diversity was analyzed using Bray-Curtis dissimilarity distances. Hierarchal clustering was performed using Ward's agglomeration in R. Regardless of species, fecal samples had a greater (P < 0.05) richness and evenness of ARGs compared to both meat and soil samples. For beta diversity, all the sampling types clustered (P < 0.05) individually (feces, meat, and soil) by species. Furthermore, within species each environment was dominated by different classes of ARGs indicating they have different resistomes. When resistance groups medically important for human health by the World Health organization were considered, human waste samples had a greater (P < 0.05) percentage (13%) of medically important resistance groups compared to all animal fecal samples (< 5%) (World Health Organization, 2017). The resistome of feces was richer and more diverse and clustered independently from both meat and soil indicating feces had a more unique resistome across the different species. This suggests that the fecal resistome may not influence meat and amended soil resistomes.
Open Access
Complete nutrient analysis of grain finished and grass finished lamb
(Colorado State University. Libraries, 2016) Gifford, Cody Lynn, author; Woerner, Dale R., advisor; Martin, Jennifer N., committee member; Engle, Terry E., committee member; Belk, Keith E., committee member; Harris, Mary A., committee member
Health conscious consumers continue to search for foods that are nutrient dense. Nutrient labeling of foods allows consumers to select foods based on nutrient composition. The objective of this study was to analyze nutrient composition of eleven raw and cooked grain-finished and grass-finished lamb cuts to update nutrient data in the USDA National Nutrient Database for Standard Reference (SR). Packages of foreshanks, whole legs, sirloin chops, whole loins, loin chops, whole frenched ribs, frenched rib chops, whole ribs, rib chops, whole shoulders, shoulder blade chops, shoulder arm chops, stew meat, and ground lamb (IMPS # 210, 234, 1245, 232A, 1232A, 204D, 1204D, 204B, 1204B, 208, 1207B, 1207A, 295 and 296) were collected in original packaging from three U.S. suppliers during all seasons. Packages were shipped to Colorado State University Meat Laboratory for retail cut dissection, cooking, and nutrient analysis. Single composites of separable lean homogenates were formed for each cut for analysis of proximates, fatty acids, vitamins and minerals. Single composited seam and external fat from each cut were analyzed for proximates, fatty acids, vitamins and minerals. Results from this study generated greater fatty acid profiles, resulted in lower fat content, established nutrient composition for grass-finished cuts and provided updated nutrient composition for inclusion into the SR.
Open Access
Discovering consumer preferences for steak thickness and common food service cookery methods for beef strip loin steaks
(Colorado State University. Libraries, 2016) Shubert, Danielle Marie, author; Woerner, Dale R., advisor; Belk, Keith E., committee member; Tatum, J. Daryl, committee member; Delmore, Robert J., committee member; Hess, Ann, committee member
The objective of this study was to quantify consumer preferences for steak thickness and cookery method. Paired strip loins from 38 carcasses with Small marbling scores were obtained from a commercial packing facility. Each strip loin was cut into 2 sections (4 sections per carcass) and each section was randomly assigned to 1 of 4 cookery methods (COOK): 1) grill (GRILL); 2) grill mark then finish in a steam oven (MARK+FINISH); 3) par cook in a steam oven then mark on a grill (PAR+MARK); 4) broil (BROIL). Each section was vacuum-sealed and aged at 2oC for 21 days before being frozen. After freezing, three sets of paired steaks were cut from each section representing three steak thickness treatments (THICK): 1) 1.9-cm; 2) 2.5-cm; 3) 3.8-cm. For each cookery method and steak thickness combination pair, a single steak was designated for evaluation by a consumer panel while the other steak was assigned to objective testing for measures of tenderness, cook loss, and visual appearance. Known beef consumers (N = 307) evaluated each of the 12 treatment combinations of thickness and cookery method for tenderness, juiciness, flavor desirability and overall desirability using a 15-cm unstructured line scale. A significant COOK x THICK interaction (P < 0.05) affected consumer panel ratings for tenderness, juiciness, and overall desirability. As a main effect, COOK influenced (P = 0.0005) consumer ratings for flavor desirability; however, inconsistencies between the present and previous studies suggest that consumer-rated flavor desirability may have been affected more heavily by tenderness, and juiciness in what is termed a “halo effect” than by actual differences in flavor due to cookery method. The BROIL, 1.9-cm thick steaks were more desirable than 2.5 and 3.8-cm BROIL steaks as rated by consumers for overall desirability, tenderness, and juiciness, and were more tender as evaluated using WBSF and SSF (P < 0.5). The GRILL method was among the most highly rated for consumer overall desirability, and no significant difference was found existed between THICK treatments. Consumer overall desirability ratings, consumer tenderness ratings and SSF values for the PAR+MARK cookery method had, more desirable values for 3.8-cm thick steaks compared to 1.9 and 2.5-cm thick steaks. The MARK+COOK method was rated the highest for consumer overall desirability, tenderness, juiciness, and had the lowest SSF and WBSF values (P < 0.5). The MARK+COOK method was the most likely to offer consumers a desirable eating experience at steak thicknesses of 2.5 and 3.8-cm thick. The PAR+MARK method was more likely to result in a more positive eating experience as steaks were cut thicker (3.8-cm) as demonstrated by consumer ratings for overall desirability. The GRILL method had the least amount of variation in consumer ratings for overall desirability between steak thicknesses for positive eating experience. Cookery method and steak thickness should be chosen in the correct combination in order to deliver consumers with a positive eating experience in food service industry.
Open Access
Discovering dimensional differences among Holstein and conventional beef middle meat cuts and consumer preferences for appearance
(Colorado State University. Libraries, 2014) Steger, Jessica Renee, author; Woerner, Dale R., advisor; Belk, Keith E., committee member; Tatum, J. Daryl, committee member; Pendell, Dustin L., committee member
To view the abstract, please see the full text of the document.
Open Access
Discovering ground beef performance through "premium grind" concepts
(Colorado State University. Libraries, 2013) McHenry, Jordan Helaine, author; Woerner, Dale R., advisor; Belk, Keith E., committee member; Tatum, J. Daryl, committee member; Engle, Terry E., committee member; Frasier, W. Marshall, committee member
Four independent experiments were conducted to evaluate performance of ground beef from various sources and production techniques. Flavor and texture of 7 different beef products and the effects of dry-aging were evaluated and quantified by descriptive sensory analysis, fatty acid composition, and volatile compound composition. Beef products evaluated included chuck shoulder clods (NAMP 114), chuck boneless short ribs (NAMP 130), whole briskets (NAMP 120), loin tenderloin tips (NAMP 1190C), loin top sirloin caps (NAMP 184D), round sirloin tip knuckles (NAMP 167), and 81/19 chuck sourced trimmings. Fresh (100% un-aged), 100% dry-aged, and 50% fresh/50% dry-aged trimmings were used to evaluate the effects of dry-aging on ground beef performance. Furthermore, the effects of grinder plate size, blend time, and patty-forming technique were evaluated and quantified by descriptive sensory analysis and objective instrument measurement. Additional treatments compared common grocery store practices of grinding bench trimmings versus re-grinding previously ground chubs. Trained panelists evaluated ground beef patties from each treatment for 10 different flavor notes, including beefy/brothy, browned/grilled, buttery/beef fat, bloody/metallic, gamey, earthy/mushroom, nutty/roasted nut, livery, sour/acidic, and bitter, as well as 7 different texture characteristics, including hardness, cohesiveness, tenderness, connective tissue, particle size, moisture content, and beef fat/oily mouthfeel. In addition, samples were analyzed to determine fatty acid composition of raw products and volatile compounds formed during cooking. No single trimming source evaluated in this study outperformed patties comprised of 81/19 chuck sourced trimmings. Notably, briskets and sirloin caps were ranked comparably to 81/19 trimmings in the desirable flavor attributes of beefy/brothy, browned/grilled, and buttery/beef fat, whereas tenderloin tips were rated lowest in the same desirable flavors. Dry-aged beef samples produced the most complex flavor profile with the highest panel ratings for earthy/mushroom and nutty/roasted nut flavors, and had high scores for browned/grilled flavor. Grinder plate size and patty-forming technique affected perceived texture differences. Panelists indicated that ground beef patties produced with smaller sized grind plates were softer, more tender, and had a smaller particle size. In agreement, objective measures of texture showed lower peak loads for patties produced with smaller sized grind plates. Patties made with a Formax (Formax F6, equipped with the 2874-6 plate, Mokena, IL) were softer and more cohesive, while patties made with the vacuum stuffer (Model VF50, Handtmann, Germany) equipped with a portioning device were more crumbly but also ranked higher for moisture content and oily mouthfeel. Ground beef patties resulting from the re-ground chubs were perceived to have a greater amount of connective tissue, a larger particle size, greater moisture content, and a greater beef fat/oily mouthfeel. Additionally, objective measures of texture showed greater peak loads for patties from re-ground chubs.
Open Access
Effect of USDA carcass maturity on eating quality of beef from fed steers and heifers that have been classified into maturity groups using dentition
(Colorado State University. Libraries, 2015) Semler, Megan Lynn, author; Woerner, Dale R., advisor; Tatum, J. Daryl, advisor; Belk, Keith E., committee member; Enns, Kellie J., committee member
Objectives were to compare sensory properties of LM steaks from A maturity and B maturity or older carcasses that were produced by grain finished steers and heifers classified as less than and greater than 30 months of age at the time of slaughter by dentition. Carcasses were selected to represent 2 dentition groups, 2 maturity groups, and 3 marbling categories within each dentition x maturity group resulting in 12 dentition x maturity x marbling subclasses; each subclass consisting of 50 carcasses. Dental age groups consisted of carcasses classified as less than or 30 months of age (MOA) or 30 MOA or older by dentition. Maturity groups consisted of carcasses classified by USDA graders as either A⁰⁰ to A⁹⁹ overall (A) maturity or B⁰⁰ to D⁹⁹ overall (B-D) maturity; marbling categories consisted of carcasses with instrument marbling scores of Slight (SL), Small (SM), or Modest ⁰⁰ to Moderate ⁹⁹ (MT-MD). Carcasses were selected in pairs so that each carcass selected to represent the B-D maturity group was paired with an A maturity carcass of the same sex and similar marbling score (± 50 marbling units.) Strip loin (LM) steaks were obtained from both sides of each carcass. After a 14-d aging period, 1 LM steak was evaluated for Warner-Bratzler shear force (WBSF) and slice shear force (SSF). The other LM steak was used for sensory analysis by a trained descriptive attribute panel. No differences (P > 0.05) were detected in WBSF, SSF, or sensory panel ratings for tenderness juiciness, or flavor between LM steaks from carcasses classified as A maturity vs. steaks of carcasses classified from B-D maturity. Sex class influenced (P < 0.05) WBSF and sensory panel tenderness. As degree of marbling increased, sensory tenderness, juiciness, meaty/brothy flavor, and buttery/beef fat flavor increased (P < 0.05) while bloody/serumy flavor, WBSF and SSF decreased (P < 0.05). There was a significant interaction between dental age group and marbling category for SSF and panel tenderness ratings, where cattle classified as 30 MOA or older with a slight degree of marbling produced the toughest (P < 0.05) LM steaks. Within the SM and MT-MD marbling categories dental age had no effect. Results from this study suggest that USDA quality grades could be effective at determining eating quality differences to grain-finished cattle with a dental age less than 30 mo old at the time of slaughter if the A and B-D maturity groups were combined and quality grades were assigned only by marbling. In grain-finished cattle 30 mo or older at the time of slaughter the evidence was not sufficient to make conclusions.
Open Access
Effects of extended postmortem aging on selected beef muscles intended for retail sale
(Colorado State University. Libraries, 2014) Karney, Erin D., author; Woerner, Dale R., advisor; Belk, Keith E., committee member; Tatum, J. Daryl, committee member; Pendell, Dustin L., committee member
In order to mimic beef commonly found in retail supermarkets, paired strip loins (NAMP #180) and top sirloin butts (NAMP #184) were obtained from USDA Choice carcasses with a marbling score ranging from Small00 to Small50 (n = 15) and USDA Select carcasses with a marbling score ranging from Slight50 to Slight99 (n = 15) at a commercial packing plant. Samples were collected from 3 separate groups of carcasses in order to replicate each aging and display period three times. At 48 hours postmortem, paired strip loins and top sirloin butts were portioned into 3-inch sections, vacuum-sealed, and stored 14, 21, 28, 35, 49, or 63 days postmortem. For both strip loin and sirloin sections, once the aging period was designated, the sections were stored in a vacuum-sealed bag at 0°C (± 1°C) and in the dark until their assigned aging period was complete. Two steaks from each aged section for each muscle was placed in a styrofoam tray with a polyvinyl chloride overwrap and placed in a multi-deck retail display case equipped with LED lighting (Hussmann Model No. M3X8GEP) and set at 2°C for 72 hrs. A third steak cut from each aged section was immediately cooked, and Warner-Bratzler shear force (WBSF) analysis was measured to determine the effects of the aging period on tenderness without the display period. During the display period, each steak was evaluated every 8 hours by a minimum of 8 trained panelists for lean color, external fat color, lean percent discoloration, and L* a* b* color values. A trained sensory panel for tenderness and flavor attributes, including off-flavors, also was used to evaluate steaks. As steaks were subjected to longer periods of postmortem aging, WBSF values decreased and trained sensory panel tenderness ratings improved. A 72 h display time reduced (P < 0.05) WBSF values of strip loin and sirloin steaks. A minimum of 28 d of postmortem aging was required to improve the WBSF values of low Choice and Select strip loin steaks compared with the same strip loins steaks aged for 14 d, and a minimum of 35 d of postmortem aging was required to improve sensory tenderness ratings for low Choice and Select strip loin steaks. Strip loin steaks aged up to 28 d before retail display had little impact on display life and the incidence of off-flavors; however, there was no tenderness advantage over 14 d aged steaks from low Choice and Select strip loins. Thirty-five days of postmortem aging were required to achieve an improvement in WBSF compared to that achieved with 14 d aging for low Choice and Select top sirloin steaks, and trained sensory panel scores indicated that at least 49 d of postmortem aging was required to improve the myofibrillar tenderness of low Choice and Select sirloin steaks. Sirloin steaks aged 35 d and beyond produced undesirable lean color scores in as early as the first 24 h of retail display, and top sirloin steaks aged only 14 d and displayed an additional 72 h had relatively intense levels of oxidized and sour/acidic flavors present. Top sirloins cannot be aged for enough time to improve tenderness and maintain a considerable level of display life, and extended aging time is not a viable option for top sirloins intended for retail display and sale.
Open Access
Effects of Lubabegron supplementation on carcass traits, muscle fiber type, proteome profile and meat quality attributes of finished feedlot steers
(Colorado State University. Libraries, 2020) Corona, Ashley, author; Nair, Mahesh N., advisor; Belk, Keith E., committee member; Scanga, John A., committee member; Prenni, Jessica, committee member
Two thousand one hundred and sixty (2,160) British and Continental crossbred steers were supplemented (1, 4, 3.2 or 5.0 g/ton (DM basis) Lubabegron and a control diet (Experior; EX, Elanco Animal Health) for the last 28, 56, or 84 d of the finishing period resulting in twelve treatment combinations. Fifteen pens (12 hd/pen) were allocated to each treatment combination consisting of a dose and feeding duration. A total of five harvest cycles were conducted, consisting of 432 head per cycle. Each harvest cycle consisted of 3 blocks, each block contained all dosages and each block was associated with a specific feeding duration. Hot carcass weights (HCW), marbling scores (MS), adjusted fat thickness (aFT), longissimus muscle area (LMA), kidney pelvic and heart fat percentage (KPH), and USDA calculated yield grade (YG) were evaluated for all carcasses (N = 2160). No dose x feeding duration (FD) interaction (P > 0.05) was present for any of the characteristics measured. Supplemented cattle produced heavier (P < 0.05) carcass weights, larger (P < 0.05) LMAs and decreased (P < 0.05) YGs. As feeding duration was extended from 28 to 56 and 84 d, carcass weights were increased (P < 0.05). Control cattle produced MS that were significantly higher than those that were supplemented EX at the highest dose; nonetheless MS remained within USDA Premium Choice (MT00-99). Whereas, EX supplementation did not affect aFT and KPH. A subset of carcasses (N= 540) (3 carcasses/pen) that graded USDA Low Choice (SM00-99) were selected for the purpose of objective color, muscle fiber typing, proteome analysis, and the evaluation of the effect of postmortem aging on tenderness and palatability. As dose increased (P < 0.05) to 3.2 and 5.0 g/ton steaks became less (P < 0.05) red (a*), less (P < 0.05) yellow (b*), and less (P < 0.05) saturated than the controls. Striploin steaks collected during fabrication (before aging) were analyzed for muscle fiber typing (N = 96, n = 8). No detrimental shifts (P > 0.05) were observed for muscle fiber type as it relates to meat quality. The muscle fiber type IIX cross sectional area remained similar across the majority of treatment groups, except for decrease in CSA seen in cattle fed 5.0 g/ton for the final 56 and 84 d of feed. Meat quality attributes were measured using trained sensory panels, slice shear force (SSF) and Warner-Bratlzer shear force (WBSF). Striploins from the right side of each carcass were collected, fabricated into 2.54-cm steaks, and aged for 0, 7, 14, 21, and 28 d postmortem. Steaks for all postmortem aging periods were evaluated using SSF and WBSF, whereas, only those aged for 14 d were evaluated by trained panelists. Non- supplemented cattle produced striploin steaks that were juicier and more tender (P < 0.05) than those from EX supplemented cattle regardless of dose, and no differences (P > 0.05) were observed as a consequence of FD. All steaks (supplemented and non-supplemented) subjected to a minimum 7 d of PM aging produced WBSF that were less than 3.9 kg, and therefore eligible to be labeled as "Certified Very Tender." Once 21 d of postmortem aging was reached, no differences (P > 0.05) in tenderness were observed between the treatments. Based on meat quality attributes, six samples each (N = 24, n = 6) from four treatments (control, low dose for 28 days, high dose for 28 days, and high dose for 84 days) were selected for proteome analysis using a chemical labelling approach know as tandem mass tag (TMT). Experior supplementation influenced expression of proteins involved in muscle contraction, calcium signaling, transport, growth factor, and proteasome activation. Myosin light chain 3 (MYL3) was associated with an improved tenderness and carcass grading, which could be reflective of the increased intramuscular fat content. The proteins identified such as hemoglobin subunit α (HBA), hemoglobin subunit β (HBB), and alpha-1-acid glycoprotein (ORM1) were suggestive of increased vascularization in muscles as a response to EX supplementation.
Open Access
Epidemiological investigation of antimicrobial resistance in beef production using metagenomic sequencing
(Colorado State University. Libraries, 2019) Doster, Enrique, author; Hoover, Edward A., advisor; Morley, Paul S., advisor; Belk, Keith E., committee member; Abdo, Zaid, committee member; Gow, Sheryl P., committee member
Globally, the emergence of antimicrobial resistance (AMR) resulting in treatment failure is recognized as a growing public health threat. Antimicrobial use practices used in beef production are thought to be a direct driver of increasing antimicrobial resistance in pathogens and the environment, in part due to the higher volumes of antimicrobial drug necessary to treat cattle weighing 10 times more than an average person. This has led policy makers and public health organizations to promote "judicious use" or outright ban of antimicrobial drugs in livestock production. Use of antimicrobials is unavoidable for the treatment of disease and we must therefore learn how we can best adjust our AMD use to reduce selection of AMR pathogens. However, outside of important indicator organisms and pathogens, little is known about how different antimicrobial drug use practices affect communities of microorganisms, or microbiomes, and the AMR gene determinants, or resistome, shared between pathogen and non-pathogens alike. With advances in high-throughput sequencing (HTS), we can perform culture-independent studies and gain a better understanding of how antimicrobial drug use practices in livestock production affect AMR epidemiology. This dissertation consists of five studies that employ HTS to characterize the microbiome and resistome of samples with differing AMD exposure along the beef production line. Projects begin with a look into the short-term effects on the microbiome and resistome of feedlot cattle following treatment with a macrolide drug, tulathromycin, in the manuscript "Investigating Effects of Tulathromycin Metaphylaxis on the Fecal Resistome and Microbiome of Commercial Feedlot Cattle Early in the Feeding Period". Fecal samples collected in this project also were processed with aerobic culture, polymerase chain reaction (PCR), and lateral flow immunoassay for identification of Salmonella enterica and the comparison of these results are presented in "A Cautionary Report for Pathogen Identification Using Shotgun Metagenomics; a Comparison to Aerobic Culture and Polymerase Chain Reaction for Salmonella enterica Identification". Samples collected as part of a longitudinal study in feedlot cattle were analyzed to characterize the associations between AMD use and AMR in two bacterial species. These archived samples are leveraged for a broader understanding of AMR dynamics by adding a community-level perspective to results from aerobic culture. Results in individual cattle are presented in "Antimicrobial Drug Use in Beef Feedlots; Effects on the Microbiome and Resistome Dynamics in Individual Cattle" and results at the pen-level in "Metagenomic Investigation of the Effects of Antimicrobial Drug Use Practices on the Microbiome and Resistome of Beef Feedlot Cattle". Finally, in "Metagenomic Characterization of the Microbiome and Resistome in Retail Ground Beef" we examined the end of the beef production line by comparing the microbiome and resistome of retail ground beef products from either conventional production systems or those labeled as "raised with antibiotics" (RWA). The five studies presented in this dissertation each contribute to the collective understanding of how AMD use in livestock production system can affect the ecology of AMR in microbial communities. These projects are useful first steps in learning to manage AMR in beef production systems; encompassing a targeted look at the use of one type of AMD, characterizing the resistome dynamics in individual cattle and pens over time in a feedlot, a comparison of the resistome in ground beef products, and many other aspects of AMR epidemiology. The final study, describing limits to incorporating HTS for pathogen identification, serves as a cautionary reminder that with new technologies come new challenges and that research must keep pace.
Open Access
Escherichia coli O157:H7 attachment, survival, growth, and control on stainless steel and in meat brining solutions and its thermal inactivation in non-intact beef
(Colorado State University. Libraries, 2010) Adler, Jeremy Michael, author; Sofos, John Nikolaos, advisor; Kendall, Patricia A. (Patricia Ann), 1947, committee member; Nightingale, Kendra K., committee member; Belk, Keith E., committee member
The three studies described in this dissertation examined (1) the effects of the initial level of environmental hydration, nutrient density, natural flora, and fluid flow on the strength and attachment of Escherichia coli O157:H7 on stainless steel and the subsequent inactivation of pathogen within a biofilm through sanitizer exposure; (2) E. coli O157:H7 survival in model meat brines containing antimicrobials, natural flora, and meat residues; and (3) the extent of thermal inactivation of the pathogen at different depths of non-intact steaks under-cooked by pan-broiling and roasting to a 60°C geometric center temperature from either the frozen or thawed state. In the first study, E. coli O157:H7, transferred to stainless steel and allowed to dry, exhibited stronger strength of attachment to the surface than pathogen cells that were kept hydrated, indicating that the pathogen's optimal physical removal would occur before the surface dried. Once on stainless steel, E. coli O157:H7 cells remained viable and were able to proliferate in a reduced nutrient substrate; however, when competing flora from beef were present, growth was limited and the pathogen demonstrated an increased strength of attachment. Given this, the inactivation of the pathogen within a biofilm through the use of sanitizers was studied. Peroxyacetic acid/octanoic acid, a quaternary ammonium compound, and sodium hypochlorite based sanitizers were effective in inactivating greater than 99.99% (4 log CFU/cm2) E. coli O157:H7 cells in biofilms with and without competing flora by 10 min of exposure; however, peroxyacetic acid/octanoic acid mixture was the most effective as it gave similar reductions after 1 min of exposure. In the second study, the brining ingredients salt and phosphate in combination were sufficient to inhibit E. coli O157:H7 and natural flora growth for up to 48 h in meat brining solutions at 4 and 15°C with and without meat residues; however, both the pathogen and natural flora remained viable with the potential to spread contamination through recirculated brine solutions. Consequently, antimicrobials were studied for the inactivation of the pathogen in the brine solutions. Cetylpyridinium chloride and sodium metasilicate caused immediate and sustained cell reductions to below the detection limit (1.3 log CFU/ml) and were thus identified as to best reduce the probability of product cross-contamination through pathogen transfer in contaminated re-circulated brine injection. In the third and final study, the 5-day storage of non-intact steaks either at 4 or -20°C did not alter their initial contamination level. Pathogen populations were similar in non-intact steaks in the frozen state or allowed to thaw at 4 or 25°C to simulate thawing in the refrigerator or on the kitchen countertop, respectively, suggesting that the microbial safety of non-intact beef was not decreased by the method of thawing as long as steaks were cooked immediately after the desired thawing temperature was reached. Steak size and cooking method affected the thermal inactivation of E. coli O157:H7 as thicker steaks and steaks cooked by pan-broiling had greater pathogen inactivation than thinner and those cooked by roasting, respectively, even though non-intact steaks were cooked to the same internal geometric center temperature of 60°C. These data suggest that steak size and cooking method should be included in lethality guidelines that are designed to ensure the safe preparation of beef products, and when cooking non-intact steaks, pan-broiling is preferred to roasting to ensure their safe consumption. Overall, the results of the studies reported in this dissertation may be useful in the development of cleaning and sanitization programs and improving brining recipes to control E. coli O157:H7 in brining solutions. Further, these data may be useful in developing lethality guidelines for the safe preparation and consumption of non-intact beef products.
Open Access
Escherichia coli O157:H7 control in nonintact meat products and inhibition of Listeria monocytogenes biofilms on kitchen surfaces
(Colorado State University. Libraries, 2012) Gupta, Shivani, author; Sofos, John N., advisor; Nightingale, Kendra K., committee member; Belk, Keith E., committee member; Kendall, Patricia A., committee member
To view the abstract, please see the full text of the document.
Open Access
Estimating potential biosafety risk of a CRISPR-Cas9 system for targeted killing of certain pathogens in beef cattle production using omic-based analysis methodologies
(Colorado State University. Libraries, 2021) Dong, Jixin, author; Yang, Hua, advisor; Belk, Keith E., committee member; Metcalf, Jessica L., committee member; Weir, Tiffany L., committee member
The CRISPR-Cas9 system has emerged as a programmable and versatile tool for precise gene editing purposes. In addition to gene editing, the CRISPR-Cas9 system can be developed to kill targeted bacteria. In our previous studies, we developed a CRISPR-Cas9 targeted killing system with a guide RNA designed to specifically recognize the Shiga-toxic genes (stx1 and stx2). Delivery of this system into E. coli cells could effectively kill Shiga-toxin producing E. coli (STEC) cells. This current study was conducted to estimate potential biosafety risk associated with our CRISPR-Cas9-based targeted killing system when applied to kill STEC cells in a bovine cell line model system using next generation sequencing (NGS) analysis. A bovine cell line CPA 47 (ATCC® CRL-1733™) was cultured to reach 90% confluence. Then the bovine cells were subjected to one of four treatments: 1) bovine cell control: without any CRISPR treatment; 2) CRISPR/gRNA: treated with phages that carry the CRISPR system with the guide RNA targeting stx genes (106 PFU/flask); 3) CRISPR+O157: treated with phages that carry the CRISPR system but without the guide RNA targeting stx genes (106 PFU/flask) and E. coli O157:H7 strain Sakai cells (105 CFU/flask); and 4) CRISPR/gRNA+O157: treated with phages that carry the CRISPR system with the guide RNA targeting stx genes (106 PFU/flask) and E. coli O157:H7 strain Sakai cells (105 CFU/flask). Each treatment was conducted in four replicates for a total of 16 samples. After application of treatments, bovine cells from each sample were collected and divided into two portions: half for whole genome sequencing (WGS) and half for protein analysis. Whole genome DNA from each sample was extracted, purified, and sent to Novogene Bioinformatics Technology (Beijing, China) for library construction and WGS. Raw reads were subjected to quality control (QC) procedures to remove unusable reads. Clean reads after QC were aligned to the bovine reference genome (NCBI access number: ARS-UCD 1.2 USDA ARS) using Burrows-Wheeler Aligner (BWA) with default parameter. Based on the mapping results, SAMtools was used to detect individual SNP/InDel variants, and ANNOVAR was used for functional annotation of the detected variants. A total of 1078 Gb of output with 3593.12 million paired end reads (150 bp) were obtained for all 16 samples after NGS. After QC, a total of 1073 Gb of clean data output were obtained for all 16 samples. The average output for the four replicates within the control, CRISPR/gRNA, CRISPR+O157, and CRISPR/gRNA+O157 treatments was 59.1, 72.3, 72.3, and 65.9 Gb, respectively. The mapping rate of each sample ranged from 99.48% to 99.75%, and the 4X coverage ranged from 89.45% to 98.23%. For SNP detection, a total of 94,796,157 SNPs were identified in all 16 samples when compared with the reference genome. The number of SNPs with each sample ranged from 5,225,269 to 6,192,930. Of the total number of SNPs, 60.01% were located in intergenic regions (regions between genes), 36.40% in intronic regions (non-coding sequences of genes), and 0.79% in exonic regions (coding sequences of genes). Further analysis of exonic regions showed that the average SNPs for each treatment of control, CRISPR/gRNA, CRISPR+O157, and CRISPR/gRNA+O157 was 0.1964%, 0.2002%, 0.2002%, and 0.1948%, respectively. SNPs within each functional class, for example, stop loss, stop gain, synonymous, non-synonymous, at slicing sites, and upstream or downstream from transcription termination sites, the number of SNPs all showed no significant differences (P > 0.05) among the control and the three CRISPR treatments. For InDel detection, a total of 11,949,421 InDels were identified in all 16 samples, with each sample having between 604,387 and 817,716 InDels. Of the total number of InDels, 62.78% were located in intergenic regions, 38.54% in intronic regions, and 0.15% in exonic regions. The average exonic InDels in the control, and CRISPR/gRNA, CRISPR+O157, and CRISPR/gRNA+O157 treatments was 0.0371%, 0.0372%, 0.0375%, and 0.0372%, respectively. InDels within each functional class, for example, stop loss, stop gain, frameshift insertion/deletion, non-frameshift insertion/deletion, at slicing sites, and upstream or downstream from transcription termination sites, the number of InDels all showed no significant differences (P > 0.05) among the control and the three CRISPR treatments. Neither the SNP nor InDel data showed significant differences (P > 0.05) in the number of SNPs/InDels between the control and the CRISPR treatments when their WGS data were compared with the bovine reference genome. These results go along with our initial prediction that the biosafety concern of our CRISPR-Cas9 system should be low because our CRISPR system was designed to make a cleavage on target bacterial genomes but not on cattle genomes. In addition to coding regions, we are continuing with our analysis of the variants in non-coding regions. Results from this study will provide insights on how to further improve approaches or develop criteria on biosafety evaluation of the CRISPR-Cas9 system. Completion of this project will provide the beef industry with biosafety information regarding application of CRISPR as an alternative to antibiotics in cattle production.
Open Access
Evaluations that increase value for pork export products
(Colorado State University. Libraries, 2017) Sewald, Dan, author; Woerner, Dale R., advisor; Belk, Keith E., committee member; Mason, Gary, committee member
Experiment 1: An evaluation of the suitability of porcine lung tissue for human consumption. This study was conducted to provide evidence of the safety of pork lungs for human consumption via an assessment of prevalence of potentially pathogenic bacteria and infectious agents. Specifically, the goal was to collect evidence that could be used to petition the current regulation disallowing use of pork lungs for human food. Pork lungs have been labeled by the U.S. Meat Export Federation as a widely consumed product across Asia as well as South and Central America. It was believed that there is profit potential in saving pork lungs and exporting them to specified countries. Pork lungs must first be deemed safe and edible before they can be sold on the export market. Lungs (N = 288) were collected from a total of six federally inspected young market barrow/gilt or sow processing facilities. In an attempt to obtain a representative sample of production at each facility on a given day, lungs were randomly selected throughout the entire production day. All collected lungs were removed and processed using aseptic techniques to prevent any exogenous contamination. Lung samples were tested for the presence of pathogens and other physical contamination. Lungs did not test positive for Yersinia spp., Influenza, or Mycobacterium spp., and they contained low yeast and mold counts. However, multiple lung samples collected from both barrows/gilts and mature sows tested positive for Salmonella spp., Shiga toxin-producing Escherichia coli, Campylobacter, and Streptococcus suis. Also, half of the samples collected were found to contain aspirated plant material within the airways of the lungs. These results suggested that pork lungs are not safe and should not be saved for human consumption. Experiment 2: Pork Fibrin used as a meat binder in pork variety and offal meats. Fibrin is a cold set binding product that is created by recombining the two blood components of thrombin and fibrinogen. This study was conducted as a proof-of-concept to validate using fibrin derived from pork blood to create value-added export items from various pork offal and variety meats, hence adding value to both pork blood and pork offal/variety meats. Fibrin currently is marketed as Fibrimex® by Sonac, but the patent for producing fibrin expired leaving potential for U.S. pork operations to begin to produce their own fibrin and use it to create their own value-added products. A total of eight finished products were created in this study using Fibrimex® and pork offal/variety meats. Products for which use of the fibrin complex proved useful included a boneless baby back rib-like product made from pork jowl, a steak-like product made from diaphragms, a boneless hock, a log of skinned pork tongues, a pinwheel with pork diaphragm and cheese, a steak made from course ground heart and back fat, fresh bacon made from pork jowl, and a bung roll stuffed with liver, heart, and kidneys. These products were examples that demonstrated the binding capabilities of fibrin on offal/variety meats that differed in texture. All products were believed to have potential as successful export items. It was noted that fibrin could be added to many other meats to create additional products, including products that are of value within our country's own markets.
Open Access
Ground beef degradation: evolution of chemical and microbial properties and sensory characteristics during shelf-life
(Colorado State University. Libraries, 2019) Levey, Jennifer R., author; Martin, Jennifer N., advisor; Belk, Keith E., committee member; Woerner, Dale R., committee member; Prenni, Jessica E., committee member
Two separate experiments were conducted on the same lots of ground beef. The first experiment aimed to examine changes in culture-dependent microbes and the changes in sensory characteristics and chemical properties in aerobically stored ground beef after 16/17d and 23/24d dark storage periods in anaerobic chub packaging. Three lots of ground beef one lot from the West (n=30) and two lots from the Midwest (n=100)) were treated as three separate replications. The three lots were stored in 4.54kg chub packages for 16 or 17 days and 23 or 24 days dark storage prior to regrinding and packaging into PVC overwrapped trays. The overwrapped trays were placed into a retail case under fluorescent lights for 5d. Subjective odor score (off-odor intensity; 1 = no off-odor to 5 = extreme off-odor), traditional culture bacterial counts (Pseudomonas spp., Enterobacteriacae, Lactic Acid Bacteria, and psychrotrophic plate counts), and lipid oxidation indicators were analyzed as a split-plot design, whereas subjective (1= Very bright red to 6= Very dark red or brown) and objective color (Hunter CIE L*, a*, and b* values) were analyzed as a repeated measures design. All bacterial counts increased (P≤0.05) during retail case display following both dark storage periods. Overall, off-odor intensity increased (P≤0.05) over both retail case display periods; however, the off-odor intensity score after 16/17d dark storage was lesser than the off-odor intensity score after 23/24d dark storage. Subjective color panel scores for ground beef redness decreased (P≤0.05) over both retail case display periods; however, a more rapid decrease (P≤0.05) in ground beef color during the retail case display period was observed after 23/24d dark storage comparative to 16/17 day dark storage. Similarly, the redness (a* value) decreased (P≤0.05) more rapidly following 23/24d dark storage comparative to after 16/17d dark storage. An increase (P≤0.05) in TBARS values was observed for both retail case display periods. For the second experiment, instead of using culture-dependent microbiological methods, culture-independent methods of investigating microbial diversity were employed in conjunction with a GC/MS analysis of the volatile organic acids (VOCs) produced during storage. 16S rRNA amplicon sequencing was utilized to analyze the diversity and microbial constituents of the microbial community during the retail case display period after both 16/17d and 23/24d dark storage, and a targeted analysis utilizing GC/MS was used to evaluate the changes of VOCs production. The relative peak areas of the VOCs were analyzed as a split-plot design, where replication was the main plot, dark storage period was the sub-plot, and retail case storage day was the sub-subplot. Differences (P≤0.05) in Faith Phenotypic Diversity Index were observed during retail case display; however, the range of diversity was (1.02 to 1.28) was not large enough to be biologically relevant. The taxonomic analysis resulted in bacteria previously identified to contribute to beef spoilage. Lactobacillales, Enterobacteriales, and Pseudomonadales were in the top ten bacteria orders present across all samples throughout retail case display. Eighteen different VOCs were identified through the targeted analysis. The compounds identified via targeted analysis included aldehydes, ketones, volatile fatty acids, sulfones, and alcohols. Hexanal, an indicator of spoilage, increased (P≤0.05) during both retail case display periods. Moreover, acetoin and acetic acid also increased (P≤0.05) during both retail case display periods.
Open Access
Growth and control of Escherichia coli O157:H7 in processing environments and fresh beef products and of Listeria monocytogenes on processed meats during home storage and thawing
(Colorado State University. Libraries, 2010) Simpson Beauchamp, Catherine, author; Sofos, John Nikolaos, advisor; Smith, Gary C., committee member; Nightingale, Kendra Kerr, 1977-, committee member; Kendall, Patricia A. (Patricia Ann), 1947-, committee member; Belk, Keith E., committee member
To view the abstract, please see the full text of the document.
Open Access
Identifying and characterizing the influence of cattle production history and lean muscle characteristics on specific beef flavor attributes
(Colorado State University. Libraries, 2016) Adams, Tanner Scott, author; Woerner, Dale R., advisor; Legako, Jerrad F., committee member; Tatum, J. Daryl, committee member; Belk, Keith E., committee member; Enns, Kellie J., committee member
Experiments were conducted on ground beef patties as well as pure fat and lean samples manufactured using various sources and production techniques. Differences among 5 cattle types, 3 muscle types, and 3 lean percentages were evaluated for descriptive sensory analysis, fatty acid composition, volatile compound composition, and amino acid composition. Furthermore, an olfactory detection port (ODP) was used while analyzing volatiles to detect odorous compounds. Cattle types, breed and days-on-feed (DOF), evaluated included F1 Wagyu-Angus crosses (450 DOF), long-fed natural Holsteins (350 DOF), short-fed retail Holsteins (250 DOF), long-fed conventional beef (200 DOF), and short-fed beef (90 DOF). Muscles included in this study were Pectorales profundi (high connective tissue), Longissimus dorsi (intermediate connective tissue), and Psoas major (low connective tissue). Lean percentages of ground beef included 90%, 80%, and 70%. All sources were used in combination as a factorial design with 5 cattle types mixed with 3 muscles at 3 different lean percentages (5x3x3) with one treatment consisting of 45 samples with 5 replications (N=225). Trained panelists evaluated ground beef patties from each treatment and replication for 8 different flavor notes, including beefy/brothy, browned/grilled, buttery/beef fat, bloody/metallic, grassy/fishy, earthy/mushroom, nutlike/roasted nut, and livery/organy. Initial analyses consisted of least-square-means to determine differences among breed, muscle, and lean percentage and the interactions among them. These results were significant (P < 0.05) for two-way and three-way interactions; however, no plausible data could be interpreted from the analysis. Further analyses with principal component analysis were used to determine relationships between amino acids, fatty acids, volatiles, and sensory panels with cattle type and muscle separately. Relationships were identified and used to identify certain attributes as possible contributions to beef flavor. Additionally, nonmetric multidimensional scaling was used to access clustering using pairwise comparisons. This showed significant (P < 0.05) differences among cattle type treatments with small variance between samples while muscle treatments were not significant (P > 0.05) and encountered large variance between samples.
Open Access
Influence of post-mortem aging time and method on flavor and tenderness of beef, and comparison of retail cutting yields, times, and value in thirteen beef subprimals from beef and Holstein cattle
(Colorado State University. Libraries, 2018) Foraker, Blake Austin, author; Woerner, Dale R., advisor; Belk, Keith E., committee member; Engle, Terry E., committee member; Heuberger, Adam L., committee member
The objective of this study was to identify flavor and tenderness differences in beef aged for different lengths of time and using different methods. Strip loin sections from commodity, USDA Choice beef carcasses (n = 38) were randomly assigned to 1 of 8 aging treatments: 1) 3 d wet-aged; 2) 14 d wet-aged; 3) 28 d wet-aged; 4) 35 d wet-aged; 5) 49 d wet-aged; 6) 63 d wet-aged, 7) 21 d dry-aged; and 8) 14 d wet-aged followed by 21 d dry-aged (combination). Trained sensory panelists rated the cooked product for flavor and textural attributes, and samples were evaluated for Warner-Bratzler and slice shear force, fatty acid composition, amino acid composition, and volatile flavor compounds. Wet-aging of beef up to 35 d caused no changes (P > 0.05) in flavor notes. However, beef wet-aged for 49 d or longer was rated lowest (P < 0.01) for the attribute of beef flavor ID and greatest (P ≤ 0.02) for metallic, sour, oxidized, nutty, musty/earthy, and liver-like. No differences (P > 0.05) were identified between wet-aging, dry-aging, or the combination of both for any flavor attributes. Fatty acid profiles did not differ (P > 0.05) by aging length of time or method. Concentrations of amino acids and volatile flavor compounds increased (P < 0.01) during the wet-aging period, but minimal differences in these compounds were noted between wet- and dry-aged beef. Additionally, beef that was wet-aged for 3 d was toughest (P < 0.01). Nonetheless, tenderness improvement only occurred up to 28 d of wet-aging, where no subsequent differences (P > 0.05) were noted. Results suggested that wet-aging to extreme lengths of time may have a dramatic effect on flavor profile of beef, without necessarily improving tenderness. Additionally, eating quality characteristics do not necessarily differ between wet- and dry-aged beef. Holsteins comprise approximately 20% of the U.S. fed beef slaughter, and the carcass characteristics of Holsteins tend to differ (on average) from those of traditional beef breeds. Retail cutting yields, cutting times, and resulting value were evaluated in thirteen subprimal cuts from carcasses of fed Holstein (n = 398) and beef-breed (n = 404) origin. Generally, subprimals from carcasses of beef-breeds were heavier (P < 0.05) than those derived from Holsteins. Greater (P < 0.01) saleable yields of retail cuts were noted for ribeye rolls, short loins, and inside rounds (individual muscle) from carcasses of Holsteins, and bottom round flats from carcasses of beef-breeds. Saleable yields of all other subprimal cuts did not differ (P > 0.05) between cattle types. Only the amount of time taken to cut center-cut top sirloin butts derived from beef-breeds were faster (P < 0.01) than those for cuts from carcasses of Holsteins; in all other instances, times for cutting subprimals derived from Holstein carcasses were either faster (P < 0.05) or not different (P ≥ 0.05). Retail prices among cuts from differing breed types were minimal, but true differences (P < 0.05) in cutting yields for ribeye rolls and short loins from carcasses of Holsteins may generate greater values to a steak cutter or retailer. Such advantages could be attributed to smaller, more manageable, and leaner cuts produced from carcasses of Holsteins. Therefore, further research regarding retail cutting differences between cattle types may provide insight for operations seeking maximum retail yields and profit.
Open Access
Investigating the impact of husbandry and management practices on the interaction of animal well-being and product quality in beef, swine, and dairy production systems
(Colorado State University. Libraries, 2011) Vogel, Kurt D., author; Grandin, Temple, advisor; Belk, Keith E., committee member; Engle, Terry E., committee member; Rollin, Bernard E., committee member
The impact of husbandry and management practices were investigated in a beef feedlot, a small slaughter facility, and a dairy. In the first experiment, the impact of â-adrenergic agonist supplementation and implant strategy on the physiological, metabolic, and behavioral responses of feedlot steers was evaluated. Due to the ineffectiveness of head-only electrical stunning of pigs in small slaughter establishments, a two-stage stunning method was proposed where head-only stunning for 3 s was immediately followed by application of the same stunning wand to the cardiac region of the animal for 3 s while lying in lateral recumbancy. A paired-comparison study was conducted on 89 pigs in a small slaughter facility to compare the head-only method applied for 6 s to the head/heart method. Head/heart stunning eliminated rhythmic breathing, natural blinking, eye tracking to moving objects, and righting reflex, which were all observed in head-only stunned pigs. Blood lactate was not different (P > 0.05) between stunning methods (head only: 8.8 ± .7 mmol/l, head/heart: 7.8 ± .7 mmol/l). Stun to bleed time did not differ (P > 0.05) (head only: 32 ± 1 s, head/heart: 33 ± 1 s). No heartbeat was observed with the head/heart method. Longissimus thoracis pH, color, and drip loss were not different (P > 0.05) between stunning methods. This study determined that the head/heart electrical stunning method reduced the incidence of signs of return to sensibility without significant effects on meat quality, plant operation speed, or blood lactate concentration. As concern toward the care afforded to animals on U.S. dairy farms increases, benchmark data and means of assessing the welfare status of the dairy industry are necessary to dovetail with existing National Animal Health Monitoring System and National Cattlemens' Beef Association National Non-fed Beef Quality Audits. The 3rd study was developed to explore the framework of a potential study to dovetail with these two programs and identify variables of relevance to such an analysis. A single Northern Colorado Dairy Herd enrolled in the Cooperatives Working Together (CWT) Dairy Herd Retirement program was selected for this pilot study. Overall, data suggested that risk factors for herd health issues exist based on lactation number, days in milk, daily milk production, and previous lactation 305 d milk. Our analysis showed that muscling and finish scores are potentially valuable tools for assessing body condition score in cows post mortem. Body condition score was different between daily production levels (low: 3.08, medium: 2.70, high: 2.51) (P < 0.05). The mean percentage of broken tails in the herd was 44.1% and the occurrence of tail breaks increased as cows became more lame (P < 0.05) and as lactation number increased (P < 0.05). Overall, this study demonstrated the importance of including welfare-relevant variables in assessing on-farm animal welfare that are not strictly restricted to production. The results of these studies indicate the importance of management in maintaining acceptable animal welfare in livestock production and processing facilities.
Open Access
Mapping temperature decline in beef cattle during conventional chilling
(Colorado State University. Libraries, 2019) Klauer, Brenna Lynne, author; Woerner, Dale R., advisor; Belk, Keith E., committee member; Nair, Mahesh N., committee member; Bonanno, Alessandro, committee member
A continued increase in beef carcass weights has likely caused need to adjust chilling practices in order to chill carcasses appropriately with respect to food safety and beef quality. The objectives of this study were to track continuous temperature decline of beef carcasses of varying size, gain insight on how fat thickness and carcass size affect overall chilling rates, and to model temperature decline in deep muscle tissue of 6 muscles and one beef carcass surface location. Temperature recorder thermocouples were placed in 7 carcass locations and temperature was measured every 30 seconds from post electrical stimulation until the carcasses were removed from the postmortem chilling coolers (hot boxes) to be graded. Carcass temperatures were measured at the geometric center of the 1) brisket/plate (deep pectoral), 2) deep chuck (medial side of scapula/clod heart), 3) deep tissue (Semimembranosus), 4) Gluteus medius (Sirloin), 5) Longissimus dorsi at the 12th rib, 6) surface (5mm under the fascia) at the 11th rib, 7) Psoas major (Tenderloin), and 8) ambient per group of carcasses. Carcasses were classified into groups consisting of (1) light (650- 750 pounds), (2) medium (850-950 pounds), and (3) heavy (1050 to 1150 pounds) hot carcass weights. Surface temperatures from all weight categories reached levels below 4˚C within 24 hours of chilling. In the deep tissue (SM), Gluteus medius, and Longissimus dorsi carcass locations, differences in temperature between light versus medium and heavy weight ranges at the final hour of chilling (hour 28) were detected (P < 0.05). At hour 28, no differences (P ≥0.05) were detected among surface, deep pectoral, Psoas major, or deep chuck locations. At hour 28, light weight carcasses reached below the recommended chilling target of 7˚C in the deep tissue location; however, the medium and heavy range carcasses never declined below 7˚C. When larger carcasses are not chilled adequately, potential quality implications exist including reduced quality grades, increased carcass weight loss due to shrink, and fabrication issues. Therefore, beef processing facilities should consider sorting cattle before chilling in order to maximize the quality of the products being processed.