Browsing by Author "Nair, Mahesh N., advisor"
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Item Open Access Ability, repeatability, and reproducibility of rapid evaporative ionization mass spectrometry to predict beef quality attributes(Colorado State University. Libraries, 2022) Hernandez Sintharakao, Michael J., author; Nair, Mahesh N., advisor; Prenni, Jessica E., advisor; Morgan, James B., committee member; Sharp, Julia L., committee memberTenderness, juiciness, and flavor are beef quality attributes that influence consumer satisfaction eating beef. Rapid evaporative ionization mass spectrometry (REIMS) is a novel technique that provides chemical information of biological tissues with the potential to predict beef quality attributes. Two studies were conducted to evaluate the ability of REIMS to predict quality attributes of beef (study I) and to evaluate the repeatability and reproducibility of REIMS in a beef matrix (study II). In study I, USDA Select or upper two-thirds Choice (n = 42, N=84) striploins and tenderloins were collected approximately 36h post-mortem from a commercial beef abattoir. Slivers of the longissimus dorsi muscle between the 12-13th rib were collected during grading (GR, 36h post-mortem) and analyzed using REIMS. Striploins (LM) and tenderloins (PM) were cut into portions and assigned to 6 aging periods (3, 14, 28, 42, 56, and 70 days). However, only samples aged 3, 14, and 28 days were used to represent industry practices in study I. After aging, portions were cut into 2.54-cm steaks to analyze juiciness, tenderness, and 10 flavor attributes with a trained sensory panel. In addition, tenderness measures were performed using slice shear force (SSF) and Warner-Bratzler shear force (WBF). Samples were categorized by SSF, WBF, and sensory panel tenderness (PT) into "tough" and "tender"; by juiciness into "dry" and "juicy"; and by flavor into "acceptable" and "unacceptable" classes using a composite score of all flavor descriptors. Combinations of three dimensionality reduction methods (principal component analysis [PCA], feature selection, [FS], and a combination of both [PCA-FS]) with 13 machine learning algorithms were used to create classification models based on REIMS data for tenderness, juiciness, and flavor classes at the three aging periods. The predictive ability of the models was assessed with the overall accuracy resulting from 10-fold cross-validation. Among all machine learning algorithms evaluated, the maximum classification accuracies for days 3, 14, and 28 were 94, 87, and 83% for PT; 86, 85, 92% for SSF; 87, 82, and 95 for WBF; 85, 84, and 86% for juiciness; and 87, 89, and 81% for flavor classes, respectively. FS performed the best as a dimensionality reduction method for all PT, juiciness, flavor, and SSF on day 3 and WBF on days 3 and 14. PCA-FS was the best dimensionality reduction method for SSF on days 14 and 28, and WBF on day 28. Extreme gradient boosting machine learning algorithm was the highest performing algorithm for all juiciness models, flavor model on day 28, PT on days 3 and 14, SSF on days 14 and 28, and WBF on days 3. Partial least squared discriminant analysis (PLSDA) performed better for PT day 28 and flavor day 14, while elastic-net regularized generalized linear model, random forest, and support vector machine were the highest performing algorithms for SSF day 3, and WBF days 14 and 28, respectively. Results demonstrated that the chemical fingerprints obtained with REIMS could potentially be used as in situ and real-time technique to sort carcasses by flavor, juiciness, and tenderness. However, overlaps between classes affected REIMS results, and unbalanced data negatively affected model accuracies. Therefore, exploring the full potential of REIMS will require increasing the sample size and developing a sampling method that allows increased separation between sensory evaluations. Study II was performed with REIMS data from all LM and PM samples from the six aging periods (n=1008), two sets of GR samples (n=168, N=84), and quality control (QC) samples (n=29) made from homogenized ground beef. Except for the second set of GR samples, REIMS analysis of all samples was performed at Colorado State University (CSU) using a meat probe as the sampling device. Analysis of all samples was performed over 5 days, including two batches per day. GR samples were evaluated on the first day, and LM and PM data were randomly analyzed on the remaining days. QC samples were analyzed at the beginning, middle, and end of each batch. The second set of GR samples was analyzed at Texas Tech University (TTU) using different mass spectrometry (MS) instruments, technicians, and an iKnife as the sampling device. The stability of REIMS data between burns, batches, and days was evaluated with QC data. Day effect and robustness of REIMS data were evaluated with data from LM and PM samples, and interlab reproducibility was evaluated with data from GR samples. Multiple classification models of muscle type and aging were built with LM and PM data to evaluate the robustness of REIMS and day-to-day variability. Models to predict sensory attributes of beef were used to assess the robustness of REIMS with respect to interlab variability. Coefficients of variation (CV) between burns of the mass bins representing 90% of the total ion current were between 0.7 to 0.98, while the most relevant mass bins showed CV less than 0.3. Variances between batches and collection days were not significant (P < 0.05). PCA of LM and PM showed that data variability by collection day was stronger than muscle type and aging time variability. However, data could classify samples into muscle types and two distant aging times with accuracies higher than 95.6% and 91.0%, respectively. PCA of GR samples showed that data collected in both labs differed, and the predictive models developed with the CSU data did not appropriately predict the quality classes with the TTU data. REIMS collected with the meat probe provides a chemometric profile of beef samples with good repeatability and interday reproducibility but low interlab reproducibility. Consequently, optimization and standardization of sampling methods will be required to improve the interlab reproducibility of REIMS.Item 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 memberThe 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.Item Open Access Association between beef ribeye area measurements and steak portion size(Colorado State University. Libraries, 2024) Schiefelbein, Abbey Faith, author; Nair, Mahesh N., advisor; Geornaras, Ifigenia, committee member; Clark, Daniel, committee member; Hess, Ann, committee memberAs cattle weights have increased over the past decades, hot carcass weight and ribeye area (REA) have also increased. The REA is an important determinant of carcass value as it impacts the thickness of steaks when portioned to a pre-determined weight. Additionally, previous research has indicated that steak thickness impacts consumers' eating experience potentially due to its impact on the degree of doneness. The objective of this study was to examine the relationship between carcass REA and steak portion size. Beef carcasses (n = 100) were selected from a commercial beef harvesting facility based on REA in 1 in2 (6.45 cm2) increments ranging from less than 11 in2 (70.97 cm2) to greater than 19 in2 (122.58 cm2) based on a United States Department of Agriculture-approved camera (E+V) with 10 total categories. Data (hot carcass weight, back fat thickness, and marbling) were collected from each selected carcass. The REA measurements were obtained using the grading camera, a manual grid, and pen tracing and measured using ImageJ software. Strip loins (IMPS#180) from selected carcasses were collected, and weight, length, and three width (anterior, middle, and posterior) measurements of the strip loins were measured manually. Each strip loin was then scanned through a Marel I-Cut 56 portion cutter to determine the thickness of 12 oz (340.19 g) and 16 oz (453.59 g) portions and to determine the weight of a 1-in (2.54 cm) thick portion. To quantify and describe the relationship between steak thickness (cut to 12 oz and 16 oz portions) and steak weight (cut at 1-in. thickness), linear regression models were developed using traced REA as the independent variable. Additionally, more exhaustive linear regression models were developed to predict steak thickness or weight based on the traced REA, hot carcass weight, fat thickness, strip loin weight, strip loin length, strip loin width, and average maximum height of the strip loin. Each model was evaluated separately for the main effects of each variable, with significance determined at ɑ=0.05. There was a significant (P < 0.001) correlation and linear relationship (P < 0.05) between traced REA measurement and 12 oz (R2 = 0.71), 16 oz (R2 = 0.71), and 1-in.-thick (R2 = 0.75) portions examined in this study. For 12 oz steaks, the steak thickness decreased by an estimated 0.055 in. (0.14 cm) for every 1-in. increase in REA. Similarly, for the 16 oz steaks, the steak thickness decreased by an estimated 0.074 in. (0.19 cm) for every square in. increase in REA. The 1-in. steak portions had a mean weight of 340 g, and the steak weight increased an estimated 18 g for each square in. increase in REA. In addition, using the strip loin measurements, linear regression models were able to predict steak thickness for 12 oz and 16 oz portions with an R2 of 0.95 each and predict the steak weight for the 1-in. portion with an R2 of 0.98. As expected, REA strongly correlated with the portion size of strip loin steaks cut to a specified weight or thickness. Additionally, our results indicated that the weight and length of the strip loin were good predictors of steak thickness (for 12 oz and 16 oz portions) or steak weight (for 1-in.-thick portions). Further research exploring consumer acceptance and degree of doneness for steaks with varying thicknesses would provide data to determine REA ranges and targets that would optimize steak portion sizes and consumer acceptability.Item 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 memberTwo 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.Item Open Access Investigating the impact of the microbiome on beef steak color stability(Colorado State University. Libraries, 2022) Smith, Colton Levi, author; Nair, Mahesh N., advisor; Morgan, J. Brad, committee member; Geornaras, Ifigenia, committee member; Weir, Tiffany, committee member; Metcalf, Jessica L., committee member; Clark, Daniel L., committee memberMeat color is the most influential characteristic for consumer purchasing decisions. In fact, consumer discrimination of discolored beef results in approximately $3.73 billion/year lost in revenue in the US. Interestingly, most often these products are not yet microbially spoiled, leading to unnecessary food waste. Complicating matters, different muscles originating from the same carcass discolor at different rates. Several studies have investigated the physiochemical, enzymatic, and intrinsic muscle properties of muscles with differing color stabilities such as color stabile beef longissimus lumborum (LL) and color labile psoas major (PM). However, the impact of microbial growth on the meat color stability has not been investigated yet. Therefore, the objective of this study was to characterize the microbial populations and their biochemical parameters of color labile and color stabile beef muscle cuts during aerobic retail display. Paired USDA Select LL and PM (n = 5) were collected from a local abattoir and aged for 14 days in darkness under vacuum at 3°C. After aging, the muscles were fabricated into 2.54-cm thick steaks and packaged aerobically in a foam tray wrapped with polyvinyl chloride film. Steaks were then placed into an open faced multi-decked retail display case for 7 days at 4°C ± 1°C. Each day, beginning day of fabrication, steaks were evaluated for visual color, percentage discoloration, instrumental color, water activity, pH, metmyoglobin reducing activity, microbial levels as determined by using culture-dependent methods (aerobic plate counts, lactic acid bacteria plate counts, Pseudomonas spp. plate counts and Enterobacteriaceae plate counts), and 16S rRNA bacterial gene sequencing (microbiome). Visual color was darker (P < 0.05) for PM than LL for all days, and percentage discoloration was greater (P < 0.05) for PM than LL from the second daif retail display. Color stability (determined by MRA) was greater (P > 0.05) in LL compared to PM for all days. The pH was greater (P < 0.05) for PM for the first 5 days of display compared to LL. However, water activity was the same (P > 0.05) for both muscles across all display days. Microbiological analyses revealed that aerobic plate counts, and lactic acid bacteria plate count were greater (P < 0.05) for PM starting on day 1 of display compared to LL. The Pseudomonas spp. plate counts were similar (P > 0.05) until day 2, after which PM was greater (P < 0.05) than LL and remained greater for the remaining days. Moreover, the 16S rRNA gene sequencing showed no differences (P > 0.05) in the alpha or beta diversities of the microbial communities between muscles. The results indicated that PM has less color stability and a greater amount of microbial growth than LL during retail display. Despite the increased number of bacteria on PM earlier during display, the microbiome analyses showed no major differences in the microbial communities between the muscles on the same display day. These data may suggest that microbial metabolic pathways, evidenced by faster microbial growth on PM compared to LL, may be a bigger contributor to color stability differences than the microbial community composition. Further work establishing these metabolic differences is needed to understand the biochemical interaction between the microbiota and the beef steaks.Item Open Access Multi-omic approaches to investigate meat quality variation(Colorado State University. Libraries, 2022) Zhai, Chaoyu, author; Nair, Mahesh N., advisor; Prenni, Jessica E., committee member; Chicco, Adam J., committee member; Belk, Keith E., committee memberVariation in the proteome profile of longissimus lumborum (LL) and psoas major (PM) post-rigor influences meat quality attributes such as tenderness and color stability during retail display. Tandem mass tag (TMT) labeling is a chemical labeling approach using isobaric mass tags for accurate mass spectrometry-based quantification and identification of biological macromolecules. The objective of first study was to use TMT labeling to examine proteome profile variation between beef LL and PM during the early postmortem period (45 min, 12 h, and 36 h). We identified a total of 629 proteins, of which 71 were differentially abundant (fold change > 1.5, P < .05) from three comparisons between the muscles (PM vs. LL at 45 min, 12 h and 36 h). These proteins were mainly involved in oxidative phosphorylation and ATP-related transport, tricarboxylic acid cycle, NADPH regeneration, fatty acid degradation, muscle contraction, calcium signaling, chaperone activity, oxygen transport, as well as degradation of the extracellular matrix. At early postmortem, more abundant antiapoptotic proteins in LL could cause high metabolic stability, enhanced autophagy, and delayed apoptosis, while overabundant metabolic enzymes and pro-apoptotic proteins in PM could accelerate the generation of reactive oxygen species and initiation of cell death. Pulmonary hypertension is a noninfectious disease of cattle at altitudes > 1524 m (5,000 ft). Mean pulmonary arterial pressures (PAP) are used as an indicator for pulmonary hypertension in cattle. High PAP cattle (≥50 mmHg) entering the feedlot at moderate elevations have lower feed efficiency as compared to low PAP cattle (< 50 mmHg). In second study, the impact of pulmonary arterial pressure on mitochondrial function, oxidative phosphorylation (OXPHOS) protein abundance, and meat color was examined using LL from high (98 ± 13 mmHg; n = 5) and low (41 ± 3 mmHg; n = 6) PAP fattened Angus steers (live weight of 588 ± 38 kg) during early postmortem period (2 and 48 h) and retail display (days 1 to 9), respectively. High PAP muscle had greater (P = 0.013) OXPHOS-linked respiration and proton leak-associated respiration than low PAP muscles at 2 h postmortem but rapidly declined to be similar (P = 0.145) to low PAP muscle by 48 h postmortem. OXPHOS protein expression was higher (P = 0.045) in low PAP than high PAP muscle. During retail display, redness, chroma, hue, ratio of reflectance at 630 and 580 nm, and metmyoglobin reducing activity decreased faster (P < 0.05) in high PAP steaks than low PAP. Lipid oxidation significantly increased (P < 0.05) in high PAP steaks but not (P > 0.05) in low PAP. The results indicated that high PAP caused a lower OXPHOS efficiency and greater fuel oxidation rates under conditions of low ATP demand in premortem beef LL muscle; this could explain the lower feed efficiency in high PAP feedlot cattle compared to low PAP counterparts. Mitochondrial integral function (membrane integrity or/and protein function) declined faster in high PAP than low PAP muscle at early postmortem. LL steaks from high PAP animals had lower color stability than those from the low PAP animals during simulated retail display, which could be partially attributed to the loss of muscle mitochondrial function at early postmortem by ROS damage in high PAP muscle. Rapid Evaporative Ionization Mass Spectrometry (REIMS) is a type of ambient ionization mass spectrometry, which enables real-time evaluation of several complex traits from a single measurement. The objectives of third study were (1) to investigate the capability of REIMS to accurately identify and predict cooked sheep meat flavor and carcass characteristics based on consumer response utilizing metabolomic data acquired from different types of raw sample by I-Knife and (2) to compare the data generated by these two electrodes (Meat Probe vs. I-Knife) in their ability to differentiate carcass background and sheep meat flavor. Current study demonstrated that REIMS analysis of raw meat samples can be used to accurately predict and classify cooked sheep meat flavor and carcass characteristics (based on consumer response). Specifically, the lean and fat tissue collected at 45 min postmortem can be used to predict carcass characteristics and post rigor meat flavor. Models for diet, flavor intensity acceptance, off flavors presence, overall acceptance, age, and flavor acceptance achieved prediction accuracies higher than 80%. In addition, data generated using the Meat Probe resulted in models with better or similar prediction accuracies of carcass background (age, diet, and gender) and consumer preference (intensity acceptance, flavor acceptance, off flavors presence, and overall acceptance) as compared to models based on data generated using the I-Knife. The Meat Probe was more user-friendly, faster, and cleaner than I-Knife for REIMS analysis. Further investigations are necessary to evaluate the use of the Meat Probe for REIMS analysis in other applications.Item Open Access Processes to improve storage shelf-life and palatability of beef(Colorado State University. Libraries, 2023) González Sánchez, Sara Victoria, author; Nair, Mahesh N., advisor; Geornaras, Ifigenia, advisor; Morgan, J. Brad, committee member; Gutierrez-Rodriguez, Eduardo, committee memberThree studies were conducted to evaluate processes to improve the storage shelf-life and palatability of beef. The first two studies evaluated the effects on retail shelf-life and palatability characteristics of beef following Suspended Fresh® storage. Suspended Fresh® (SF) is a patented, proprietary, trademarked process that allows the storage of beef muscles at temperatures at or slightly above their freezing point to slow down microbiological spoilage while maintaining the product's fresh status. These studies evaluated the impact of 60, 75, or 90 d of storage in SF (-2.7±0.3°C) on the retail shelf-life and palatability characteristics of steaks derived from inside rounds (IR), bone-in ribeyes (RE), and striploins (SL) from 10 (n=10) upper two-thirds Choice beef carcasses. Two steaks fabricated from each subprimal were vacuum-packaged, wet-aged for 21 d (3°C), and frozen (-20°C) for Warner-Bratzler shear force (WBSF) and sensory analyses. These steaks served as the control with regard to storage condition and time. The remainder of each subprimal was fabricated into three portions, and after vacuum packaging, were randomly allocated to an SF storage time of 60, 75, or 90 d. After each storage time, five steaks were fabricated from the subprimal pieces, overwrapped, and placed in a retail display case (3°C) under continuous fluorescent light for 7 d. Another two steaks were vacuum-packaged and stored at -20°C until WBSF and consumer sensory evaluations. Consumers (N=238) evaluated each sample for juiciness, tenderness, flavor liking, and overall liking. Instrumental and trained visual color were evaluated daily during retail display, and aerobic bacterial populations (APC), lactic acid bacteria, and Pseudomonas spp. were enumerated on days 0, 2, 4, and 7. Data were analyzed in R using a factorial design for the microbial counts or a split-plot for the rest of the analyses. Least-squares means were separated using a significance level of α=0.05. For all cuts, initial redness (a* values) of SF60 steaks were lower (P < 0.05) than SF75 and SF90 steaks. In general, irrespective of SF storage time or retail display day, trained panelists did not detect differences in lean color and discoloration of steaks. For all cuts, the APC of SF60 steaks on days 0, 2, and 4 of retail display were lower (P < 0.05) than those of SF75 and SF90 samples. The WBSF values decreased (P < 0.05) with increased storage time for all the cuts. Similarly, the consumer tenderness rating scores of IR and SL generally increased with the SF storage time. However, storage time did not influence (P ≥ 0.05) the juiciness, flavor, and overall liking of any cuts. The results of this study suggest it would be feasible to extend the storage time of beef while preserving or improving the sensory quality when held at optimal conditions above the freezing temperature. The third study was conducted to evaluate the effects of different temperature and time treatment combinations (1A: 56.1°C and 71 min; 1B: 56.1°C and 150 min; 1C: 56.1°C and 240 min; 2A: 61.7°C and 8 min; 2B: 61.7°C and 150 min; 2C: 61.7°C and 240 min) of sous vide cooking on the palatability of beef biceps femoris. Beef biceps femoris were sliced into 1.6-cm steaks, vacuum packaged as 4.5 kg bags, and randomly assigned to one of the six treatments with 16 packages (n=16) per treatment. Cooked and chilled packages were weighed, and then the weight of the meat was taken to measure cooking loss. Weighed samples were divided into two halves: one was left non-marinated, and the other was assigned to marination. Two 1.6-cm non-marinated steaks were randomly selected and cut in half to measure the internal cooked color. Additionally, non-marinated and marinated steaks were randomly selected for WBSF and sensory analysis by a trained panel. Data were analyzed using a complete randomized design in R with a significance level of α=0.05. The cooking loss of samples increased as the temperature and dwell time combinations increased (P < 0.05). Internal redness of steaks decreased (P < 0.05) with increased temperature and dwell time. The only major difference in WBSF and the trained sensory panel results was between treatment 1C (56.1°C and 240 min) and 2A (61.7°C and 8 min), where 1C samples had lower WBSF values and higher perceived tenderness scores than 2A samples. These results suggest that biceps femoris samples can be cooked at conditions examined in this study with minimal impact on palatability, allowing producers more flexibility with cooking time to optimize production time and energy while reducing cooking loss. Overall, the findings of these studies should be useful to the beef industry as they consider strategies for improving the storage shelf-life and palatability of beef.Item Open Access Understanding the impact of carcass size, chilling rate, and electrical stimulation on beef quality(Colorado State University. Libraries, 2019) Allahodjibeye Djimsa, Blanchefort, author; Nair, Mahesh N., advisor; Woerner, Dale R., advisor; Engle, Terry E., committee member; Hess, Ann M., committee member; Belk, Keith E., committee memberIncreasing carcass sizes and mass make it difficult for packers to appropriately chill beef carcasses, resulting in issues associated with tenderness and color. The wide variability in carcass size and weight and the lack of management practices to address it represent a challenge that the industry must address. To our knowledge, few studies have looked at the combined impact of chilling and electrical stimulation on postmortem biochemistry, tenderness, juiciness and color among the current consist of US beef carcasses, hence justifying this study. The study was conducted in two major parts: The first part focused on the effects of carcass size, chilling rate, and electrical stimulation on temperature and pH decline and postmortem biochemistry. Cattle (N =162, < 30 month) were randomly selected at two beef processing plants in the US. The left or right side of each carcass was electrically stimulated (ES) whereas the matching side was not electrically stimulated (NES). Matched sides were conventionally spray-chilled (CC) or delayed spray-chilled (DC). Deep tissue and surface temperature were continuously monitored during chilling in addition to temperature and pH measurements obtained from the muscles Semimembranosus (SM), Longissimus lumborum (LL), and Psoas major (PM) at an initial time (45 to 60 min), 6 h, 12 h, and final chilling time (18 to 28 h postmortem). A six-member panel evaluated the color of the tenderloin (PM). The L*, a*, and b* values of the PM were measured. A nonlinear regression model was fitted to the continuous deep and surface temperatures. Electrical stimulation improved (P < 0.05) the tenderloin color of light weight carcasses but not (P > 0.05) that of heavy weight carcasses. Temperature decline was faster (P < 0.05) in the SM and LL of heavy weight and delay chilled carcasses while pH decline was slower (P < 0.05). The exponential decay models for deep and surface temperatures showed that the rate of cooling differed (P < 0.05) due to the combination of treatment factors. Heavy weight carcasses had slower rates of chilling (P < 0.05). Variability in carcass size resulted in differences in chilling rate. In the second part of the study, the effects of the treatment factors on beef tenderness were determined. Steaks from the loins (LL) collected from the previous study were randomly assigned to 14, 21, 28, or 35 d aging periods. While sensory evaluation was performed on the 14 d steaks, all the aging groups were used to determine Warner-Braztler shear force (WBSF) and slice shear force (SSF) values. Results showed that sensory panel scores were not affected (P > 0.05) by treatment factors. However, WBSF and SSF were affected (P < 0.05) by carcass size and chilling rate. Aging curves were developed using an exponential decay model to predict aging response and describe the tenderization process for the treatments groups. The models indicated significant differences in the rate and extent of tenderization between different treatment groups.