Glycogen Supplementation in Vitro Promotes pH Decline in Dark-Cutting Beef by Reverting Muscle’s Metabolome toward a Normal Postmortem Muscle State
Frank Kiyimba, Steven D. Hartson, G. G. Mafi, Ranjith Ramanathan
Abstract
High Resolution Image Download MS PowerPoint Slide Dysregulated muscle glycogen metabolism preslaughter contributes to aberrant postmortem muscle pH (>5.8) in dark-cutting beef phenotypes. However, the underlying mechanisms have remained elusive. Herein, we examine the glycogen dependent regulation of postmortem muscle pH decline and darkening in beef. We show that supplementation of glycogen in vitro restores postmortem pH decline in dark-cutting beef by reverting the metabolome toward a typical postmortem muscle state characterized by increased activities of enzymes glycogen phosphorylase and lactate dehydrogenase ( p < 0.05) coupled with a pronounced abundance of glycolytic metabolites and reduced abundance of tricarboxylic acid cycle and amino acid metabolites. Furthermore, concurrent inhibition of mitochondrial respiration at complexes I, IV, and V with glycogen supplementation stimulates greater pH decline. Together, our findings show that supplementing glycogen at low concentrations (10 mM) can reprogram the dark-cutting beef muscle’s metabolome toward typical postmortem state and promote muscle acidification. Thus, enhancing glycogen levels could represent a promising strategy for mitigating dark-cutting beef phenotypes and improving meat quality.