Location: Meat Safety and Quality
2021 Annual Report
Objectives
Objective 1: Develop strategies to manage and improve variation in meat quality, composition, and healthfulness traits.
Sub-objective 1.A: Identification of genetic markers for myoglobin content of pork muscles to increase redness of pork products.
Sub-objective 1.B: Estimate effects of three maternal lines and two mating systems on lamb carcass merit.
Sub-objective 1.C: Genomic control of dark cutting and other beef quality traits.
Sub-objective 1.D: Genomic control of pork fat quality and fatty acid profile.
Sub-objective 1.E: Identify and validate novel single-nucleotide polymorphisms (SNP) for beef lean color stability.
Sub-objective 1.F: Determine the effect of VQG' pork loin grading camera tenderness class on optimal aging time of boneless pork loins.
Sub-objective 1.G: Impact of backgrounding strategies on beef carcass merit.
Sub-objective 1.H: To determine the effects of replacing tylosin phosphate (Tylan®) with an essential oil containing limonene in the diet of finishing beef cattle on carcass characteristics.
Objective 2: Characterize biological variation in meat quality, composition, and healthfulness traits.
Sub-objective 2.A: Determine the impact of sire line on the meat quality defect characterized by a band of very pale, almost white, muscle tissue on the superficial portion of ham muscles (halo).
Sub-objective 2.B: Characterize the effect of muscle metabolic efficiency, particularly in mitochondrial efficiency on beef tenderness and lean color stability attributes across varying pH classes in beef carcasses exhibiting normal lean color.
Sub-objective 2.C: Determine if there are metabolomic differences between tender and tough beef across postmortem aging times.
Sub-objective 2.D: Identification of differentially expressed proteins in beef longissimus steaks classified as tender with stable lean color during simulated retail display compared to steaks classified as tough with labile lean color during simulated retail display.
Sub-objective 2.E: Develop technologies for measuring and predicting important traits relating to meat product quality and consistency and the biological mechanisms that control these traits.
Approach
The overall goal of this project is to develop approaches to improve quality and healthfulness while reducing the variation in meat products. This will be accomplished by providing the red meat industries with the information and tools necessary to facilitate equitable valuation of carcasses and meat, improve the quality and consistency of meat, and optimize carcass and meat composition of beef, pork, and lamb. The two objectives of this project address needs in improving consistency of quality, composition, and healthfulness of red meat products by developing strategies and instrumentation to manage and improve these traits using basic and applied research approaches. Genetic and genomic strategies will be developed that may be combined with animal and meat management strategies to optimize quality and composition traits. Research will be conducted using proteomics and other biochemical tools to characterize variation in quality and composition as well as to evaluate and facilitate implementation of instrumentation for measuring or predicting value determining traits such as carcass grade traits, tenderness, lean color stability, and fat quality.
Progress Report
Under Objective 2. Lean color is the primary factor considered by consumers when making beef purchasing decisions, and products not meeting consumer expectations are discriminated against. Muscle pH is a driver of muscle color and muscles with high muscle pH are termed “dark cutters” and are heavily discounted. Previous research from our laboratory determined that increased severity of the dark cutter condition resulted in less red, less stable lean color along with increased incidence of undesirable flavor attributes. Moreover, that work indicated that beef from mild dark cutters had increased toughness relative to severe dark cutter and normal pH beef. We determined that muscles with the dark cutting condition had increased mitochondrial content and less efficient mitochondrial function than normal pH muscles. However, the impact of mitochondrial function on color, tenderness, and flavor traits of muscles across the full range of pH values is not known. We have initiated an experiment to determine the effects of muscle pH classes on beef flavor, tenderness, and color stability. Carcasses were selected based on loin muscle pH (less than 5.55, 5.56 to 5.7, 5.71 to 5.9, and greater than 5.9). Steaks from each carcass were used for simulated retail display to determine color stability, objective measures of tenderness, and evaluation by a trained sensory panel for beef flavor attributes. Moreover, component traits describing mechanisms that contribute to these traits, as well as intermediates of muscle metabolism, mitochondrial abundance, and mitochondrial function are being measured. These data are currently being collected and analyzed. These data will be contrasted across pH categories to determine how muscle pH affects important meat quality traits and how metabolism impacts muscle pH. These results will be independent validation of previous metabolic fingerprinting experiments.
Under Objective 2. In the United States beef carcass quality grading is primarily a function of marbling score. Consumers and meat marketers sometimes complain about some steaks appearing to have less marbling than they expect for the quality grade program they purchased. The United States Standards for Grades of Carcass Beef state that “when both sides of a carcass have been ribbed prior to presentation for grading and the characteristics of the two ribeyes (area, marbling, color, texture, and firmness) would justify different quality and/or yield grades, the final grade of the carcass shall reflect the “highest” of each of these grades as determined from either side.” Marbling score can frequently differ among carcass sides. Additionally, visible marbling and intramuscular fat content can differ among the various ribeye and strip loin steaks from a carcass. USDA-ARS scientists at Clay Center, Nebraska, assessed the level of variation in beef grading camera marbling score and intramuscular fat among various ribeye and strip loin steak locations from both sides of beef carcasses. Preliminary data indicate some ribeye steaks had lower marbling scores than strip loin steaks from the same carcasses, despite no difference in ether-extractable intramuscular fat level between steaks. Also, marbling scores of ribeye steaks were lower on average than the marbling score of the corresponding carcass, with more than twice as many ribeye steaks having marbling scores below modest as was expected based on the marbling scores of the carcass sides. These data highlight the normal biological variation that occurs within muscles and across carcass sides and explains observations made at the retail level and should help alleviate concerns of deceptive marketing.
Accomplishments
1. Determined influence of muscle metabolism intermediates on beef flavor development. Beef flavor is the most important factor in determining consumer eating satisfaction of beef products. The role of beef processing strategies and cookery in flavor development has been the subject of extensive research. However, little attention has been paid to the role of inherent animal-to-animal variation in muscle metabolism in the development of beef flavor. USDA-ARS scientists at Clay Center, Nebraska, determined that variation in muscle metabolites is associated with both positive and negative flavor attributes in beef strip loin steaks. These findings provide greater understanding of the mechanisms responsible for variation in beef flavor as well as selection strategies to improve overall beef flavor and consistency, which will increase consumer satisfaction and repeat purchases for beef. These results may potentially add millions of dollars in revenue to the U.S. beef industry through increased demand for high quality beef products.
2. Improved beef grading camera. The newest (7L) version of the VBG2000 grading camera was developed to more clearly quantify errors in operation of the grading camera during online application. Beef packing companies are anxious to adopt the 7L camera to improve the ability of plant employees in both camera operation and the proper presentation of the beef carcass for grading camera operation. At the request of USDA-Agricultural Marketing Service, USDA-ARS scientists at Clay Center, Nebraska, compared the new 7L camera to the currently approved VBG2000-LED grading camera and demonstrated it provided equivalent results with enhanced capacity to identify operational errors. The 7L camera has since been approved by AMS, and will improve employee training, will result in more accurate grade data, and is being adopted by all large North American beef packing plants for evaluation of marbling score and yield grade traits for USDA grading and certification activities.
3. Novel meat tenderness measurement. Human sensory evaluation for meat quality traits, such as tenderness, is the gold standard but is time consuming and expensive to conduct. Alternatively, shear force tests of cooked meat can be used to provide an accurate measure of meat tenderness. Historically, shear force tests were conducted parallel to the meat fiber direction, but for some meat cuts this is technically very challenging. To overcome this limitation, USDA-ARS scientists at Clay Center, Nebraska, developed and evaluated methods to conduct shear force perpendicular to the cut surface of the steak rather than parallel to the meat fiber direction and demonstrated that shearing perpendicular to the cut surface of the steak provided similar mean shear force values and improved repeatability of the measurement. This new research tool will improve the accuracy of meat tenderness measurement, providing an additional tool for the meat industries to evaluate and market meat products at higher value and with improved overall consumer eating satisfaction.
Review Publications
King, D.A., Shackelford, S.D., Wheeler, T.L. 2021. Postmortem aging time and marbling class effects on flavor of three muscles from beef top loin and top sirloin subprimals. Meat and Muscle Biology. 5(1). https://doi.org/10.22175/mmb.10939.
King, D.A., Shackelford, S.D., Cushman, R.A., Wheeler, T.L. 2021. Extended aging and marbling class effects on color stability of beef Longissimus lumborum, Gluteus medius, and Biceps femoris steaks. Meat and Muscle Biology. 5(1):1-14. https://doi.org/10.22175/mmb.11139.
Lerner, A.B., Rice, E.A., Tokach, M.D., DeRouchey, J.M., Dritz, S.S., Goodband, R.D., Woodworth, J.C., O'Quinn, T.G., Gonzalez, J.M., Allerson, M.W., Dilger, A.C., Boler, D.D., Price, H.E., Lowell, J.E., Richardson, E., Barkley, K.E., Honegger, L.T., Harsh, B.N., Shackelford, S.D., Wheeler, T.L., King, D.A., Fields, B. 2020. Effects of space allowance and marketing strategy on growth performance of pigs raised to 165 kg. Translational Animal Science. 4:1252-1262. https://doi.org/10.1093/tas/txaa065.
King, D.A., Shackelford, S.D., Nonneman, D.J., Rohrer, G.A., Wheeler, T.L. 2020. Sire variation in the severity of the ham halo condition. Meat and Muscle Biology. 4(1). https://doi.org/10.22175/mmb.9743.
