Categorization of beef longissimus lumborum and gluteus medius muscles based on metabolic attributes is more informative than muscle pH

Authors: King, David; Shackelford, Steven; Nonneman, Danny; Katz, Tatum; Wheeler, Tommy

Submitted to: Meat and Muscle Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2024
Publication Date: 1/22/2025
Citation: King, D.A., Shackelford, S.D., Nonneman, D.J., Katz, T.S., Wheeler, T.L. 2025. Categorization of beef longissimus lumborum and gluteus medius muscles based on metabolic attributes is more informative than muscle pH. Meat and Muscle Biology. 9(1). Article 18388. https://doi.org/10.22175/mmb.18388.
DOI: https://doi.org/10.22175/mmb.18388

Interpretive Summary: Energy producing mechanisms in muscle contribute greatly to variation in meat quality traits. Muscle pH is often used as an indicator of these energy producing processes. However, these processes have contributions to meat quality that are not described by muscle pH. Thus, we conducted a study to evaluate grouping cuts of meat based on several metabolic (energy producing) traits. Some meat cuts generally used energy producing processes that require oxygen more than other cuts. Grouping meat cuts based on metabolic traits was generally, but not completely consistent with categorization based on pH. Some groups of meat cuts did not differ in pH, indicating significant differences in energy production that are not explained by pH. Relationships of energy production traits in some meat cuts were generally consistent with relationships of those traits in other cuts. Some meat cuts displayed differences in the ability to convert glucose to lactic acid at two different temperatures. These results indicate that using metabolic traits to create categories of meat cuts is more informative than categories based on pH and can be used to develop strategies to improve meat quality traits.

Technical Abstract: Muscle metabolism is generally monitored using muscle pH. However, pH does not account for all metabolic effects on meat quality. We evaluated the effectiveness of agglomerative hierarchical clustering in creating clusters of beef longissimus and gluteus medius muscles based on metabolic traits. Beef carcasses (n = 100) were selected at grading based on longissimus thoracis pH (5.9). Metabolic traits characterizing oxidative and gly colytic metabolism were measured on each muscle. A subset of longissimus lumborum muscles were placed in an in vitro glycolytic system with 2 temperature decline rates to evaluate glycolytic efficiency. Gluteus medius muscles exhibited more oxidative metabolism than longissimus lumborum muscles. Metabolic traits measured in one muscle were generally pos itively correlated to the same trait measured in the other muscle. Clustering of metabolic traits within each muscle produced similar dendrograms. Clustering of longissimus lumborum muscles based on metabolic traits produced 4 distinct clusters (High pH, Glycolytic, Chaperone, and Soluble). Clustering of the high pH was generally, but not totally, in agreement with classifications based on pH. The remaining longissimus lumborum clusters did not differ in pH. Similar to the longissimus lumborum clusters, the gluteus medius clusters included High pH and Glycolytic clusters and a cluster with low values for protein solubility and peroxiredoxin 2 abundance. In the in vitro system, pH decline was affected by a cluster × temperature decline rate interaction (P < 0.05). The soluble cluster had the least extensive pH decline under the fast temperature decline but had the most rapid pH decline at the slower pH decline. These results indicate that clustering muscles based on several metabolic factors was more effective than categorizing muscles based on muscle pH. Metabolic variation identified by clustering was related to differences in the glycolytic machinery that can be differentially impacted by chilling rate.