Impact of visual dark-cutting severity on the aging, color and biochemical properties of beef longissimus lumborum

Dark-cutting beef remains one of the challenges for the global beef industry, with much work focused on identifying mechanisms responsible for its occurrence. Therefore, the objective of this study was to evaluate the impact of varying visual severities of dark-cutting beef longissimus lumborum on the biochemical, retail color stability, metabolome and lipidome at 0, 21, and 39 d of aging. At the time of grading, beef carcasses (n = 8/treatment) were selected based on the visual degree of dark-cutting severity. Beef strip loins (IMPS #180) representing four treatments including a normal, bright cherry-red colored control, shady, moderate, and moderately severe dark-cutting were collected. At 48 to 60 h postmortem, two 2.54 cm steaks were sliced from the anterior end of each loin. The remaining portion of each loin was cut in half and the halves were randomly assigned to 21- or 39-d of wet aging. Following aging, one steak was fabricated from each half. Biochemical, color stability, and untargeted metabolomics analysis occurred throughout aging. Untargeted lipid analysis was evaluated on the unaged samples. Moderately severe and moderate dark-cutting beef had a greater (P < 0.05) pH than shady and normal beef on d 0 of analysis. Metabolite profiling indicated downregulation of several key glycolytic metabolites, while there was an upregulation of amino acid and lipid-based metabolites such as isoleucine, and glyceryl monopalmitate, in all three dark-cutting severities compared to normal beef. Pairwise comparisons of the three dark-cutting severities to normal beef revealed 20, 21, and 25 lipid species that were over abundant in shady, moderate, and moderately severe dark-cutting beef, respectively. Acylcarnitine species of varying carbons and saturations were the most common of the shared species. During aging evaluation of metabolites noted shady dark-cutting steaks exhibited the least changes during aging compared with normal-beef, while moderately severe dark-cutting beef had a greater change in metabolite profile during aging. Changes in bloom color throughout aging are coupled with subsequent changes in metabolite profile. As dark-cutting severity increases, there is subsequent changes in color biochemistry traits as well as shifts in energy metabolism including a downregulation of glycolysis.