Location: Meats Safety & Quality Research2013 Annual Report
1a. Objectives (from AD-416):
Objective 1: Develop strategies to manage and improve variation in meat quality and composition traits. 1.1: Determine the temperature and pH profiles for optimal quality of modern pork. 1.2: Develop genetic markers for pork lean color stability, tenderness, water holding capacity, intramuscular fat content, sarcomere length, and postmortem proteolysis. 1.3: Evaluation of plasma glucose and lactate levels at exsanguination as predictors of meat quality attributes. 1.4: Evaluate the relationships between mitochondrial abundance and efficiency and animal variation in beef lean color stability. 1.5: Determine seasonal variation in fatty acid profile of belly adipose from first-pull and run-out hogs fed diets differing in fatty acid profile. 1.6: Determine variation in fatty acid profile of belly fat from first-pull and run-out gilts, barrows, and immuno-castrated barrows. Objective 2: Develop non-invasive technology to improve meat quality, composition, and healthfulness traits. 2.1: Develop regression equations for prediction of ribeye (longissimus) area and other value determining characteristics using the laser-enhanced VBG2000 beef carcass grading camera. 2.2: Determine the effect of light source on robustness of regression equations for prediction of marbling score using the laser-enhanced VBG2000 beef carcass grading camera. 2.3: Develop regression equations for prediction of beef fatty acid profiles with on-line visible and near infrared (VISNIR) spectroscopic evaluation of the ribeye (longissimus) and subcutaneous fat during beef carcass grading. 2.4: Develop regression equations for on-line prediction of fatty acid profiles of pork belly fat with VISNIR spectroscopy.
1b. Approach (from AD-416):
The effects of the interaction of muscle pH and temperature decline on various pork quality traits will be determined. Genetic markers will be identified that can be used to optimize various pork quality traits. Plasma glucose and lactate levels at exsanguination will be evaluated as predictors of meat quality traits. Mitochondrial abundance and efficiency will be evaluated as mechanisms controlling variation in lean color stability. Season, marketing group, and immuno-castration will be investigated as sources of variation in pork fat quality. The USMARC beef carcass grading camera accuracy will be enhanced by developing prediction models using more stable light sources and laser-enhanced placement adjustments. Healthfulness and quality of beef and pork will be improved by developing visible and near-infrared prediction of fatty acid profile of lean and fat.
3. Progress Report:
Several objectives were advanced this year. For objective 1.3, we determined whether biochemical traits in muscle contribute to sire effects on variation in meat tenderness. Slice shear force, which is an objective assessment of tenderness, was determined for top loin steaks obtained from the carcasses of 800 beef steers. Steers were sired by bulls sampled from the most common U.S. beef breeds. It was determined that variation among sires for both postmortem protein degradation and degree of muscle shortening contributed to variation among sires in tenderness. Thus, there may be merit to identifying sources of genetic variation in both of these components of tenderness. For objective 1.4, we determined the impact of biochemical variation in mitochondria on insufficient color-life of retail meat products. Many of the enzyme systems known to influence lean color stability of meat products are located in the mitochondria of muscle cells. Site specific defects in the electron transport chain have been demonstrated to cause oxidative conditions in muscles cells, and reduce feed efficiency in meat producing species and are hypothesized to affect lean color stability in meat products. Lean color stability, reducing capacity, and mitochondrial efficiency (electron loss) were determined on beef ribeye muscles. Greater electron loss is associated with decreased reducing capacity and, consequently, decreased beef lean color stability. These results indicate that mitochondrial efficiency influences lean color stability in meat products, and technology targeting the improvement of mitochondrial efficiency could improve lean color stability of meat products. Furthermore, genetic selection for increased feed efficiency may also improve lean color stability. For Objective 2.1, we collected the data and are currently developing regression equations for prediction of ribeye lean color using the laser-enhanced VBG2000 beef carcass grading camera. Lean color segregation by the grading camera would enable beef processing plants to sort carcasses for lean color variation that would enhance their marketing capabilities and maximize carcass values.
1. Freezing then thawing and aging beef improves meat tenderness. An unacceptable high percentage of beef top loin and sirloin steaks are tough and result in consumer dissatisfaction. ARS scientists at Clay Center, Nebraska determined that freezing, then thawing and aging beef resulted in significant improvement in meat tenderness. This strategy could be implemented for all high-priced meat cuts with high quality expectations to ensure tenderness and improve consumer satisfaction or it could be selectively implemented only on those meat cuts identified as high risk to produce tough steaks.
2. High pH beef (dark colored ribeye) affects flavor and tenderness traits of steaks. Animal stress before harvest results in abnormally high pH of the meat which makes the meat dark. The carcass grade is discounted for carcasses with dark ribeye lean which reduces the value of the carcass for both the producer and the processor. ARS scientists at Clay Center, Nebraska determined that slightly dark top loin steaks were less tender than normal colored top loin steaks or severely dark steaks and are likely to be included in routine U.S. Select and U.S. Choice product lines. These results indicate carcasses with slightly dark lean should not be included in U.S. Choice and U.S. Select products and that a mitigation strategy is needed to improve the tenderness of meat from those carcasses thereby increasing consumer satisfaction with beef.
King, D.A., Shackelford, S.D., Kalchayanand, N., Wheeler, T.L. 2012. Sampling and aging effects on beef longissimus color stability measurements. Journal of Animal Science. 90:3596-3605.