Metabolomic investigation of tenderness and aging response in beef longissimus steaks

Authors: King, David - Andy; Shackelford, Steven; BROECKLING, COREY - Colorado State University; PRENNI, JESSICA - Colorado State University; BELK, KEITH - Colorado State University; Wheeler, Tommy

Submitted to: Meat and Muscle Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2018
Publication Date: 3/14/2019
Publication URL: https://handle.nal.usda.gov/10113/6666457
Citation: King, D.A., Shackelford, S.D., Broeckling, C.D., Prenni, J.E., Belk, K.E., Wheeler, T.L. 2019. Metabolomic investigation of tenderness and aging response in beef longissimus steaks. Meat and Muscle Biology. 3(1):76-89. https://doi.org/10.22175/mmb2018.09.0027.
DOI: https://doi.org/10.22175/mmb2018.09.0027

Interpretive Summary: Beef tenderness is a primary determinant of customer satisfaction. Traditional methods for studying beef tenderness involving physical and biochemical differences generally explain a relatively small portion of the variation in tenderness. Advanced molecular technologies, such as metabolomics enable discovery of previously unknown mechanisms regulating beef tenderness. This study identified 102 metabolites that were highly related to beef tenderness. These results provide molecular markers for predicting meat tenderness and indicate new mechanisms regulating tenderness variation. These new insights into the complexity of meat tenderness lay the groundwork for opportunities to better understand and control variation in meat tenderness which will lead to greater consumer satisfaction and improved demand for beef.

Technical Abstract: A study was conducted to identify molecular changes reflective of beef tenderness variation and tenderization during postmortem aging. Carcasses (U.S. Select) were selected to represent extremes in tenderness (n = 20; 10 per class). Two pairs of adjacent longissimus lumborum steaks from each strip loin were blocked by location and assigned to each aging time (2, 7, 14, or 28 d postmortem). One steak from each pair was designated for slice shear force determination and the other was used for sarcomere length, western blotting for desmin, and non-targeted LC- and GC–MS metabolite profiling. Tough steaks had higher (P < 0.001) slice shear force values than tender steaks, and increasing aging time decreased (P < 0.001) slice shear force values. Tender steaks had a greater (P < 10–4) proportion of desmin degraded than tough steaks, and increasing aging time increased (P < 10–22) desmin degradation in steaks from both classes. From 2,562 profiled metabolites, 102 metabolites were included in the final analysis after statistical screening. Twenty-eight metabolites could be annotated and loosely categorized into amino acids/peptides (n = 16), metabolism intermediates (n = 7), glycosides (n = 4), and fatty acids and phospholipids (n = 3). Amino acids were primarily associated with desmin degradation. Increased glucose levels were strongly associated to the tender classification and moderately associated to increased proteolysis, while increased glucose-6-phosphate was strongly related to the tender class but was related to decreased proteolysis. Increased malic acid was strongly associated to the tough classification, increased slice shear force, and decreased proteolysis. Increased levels of 3-phosphoglyceric acid and glycerol-3-phosphate was moderately associated with increased slice shear force and decreased proteolysis. These data indicate that accumulation of amino acids during aging is strongly related to postmortem proteolysis and may provide evidence of the fate of proteins degraded postmortem. Measures of glucose, glucose-6-phosphate, and malic acid concentrations may provide a metabolic fingerprint indicative of tenderness differences in beef longissimus.