Glycogen Supplementation\nin Vitro Promotes pH Decline\nin Dark-Cutting Beef by Reverting Muscle’s Metabolome toward\na Normal Postmortem Muscle State

Dysregulated muscle glycogen metabolism preslaughter\ncontributes\nto aberrant postmortem muscle pH (>5.8) in dark-cutting beef phenotypes.\nHowever, the underlying mechanisms have remained elusive. Herein,\nwe examine the glycogen dependent regulation of postmortem muscle\npH decline and darkening in beef. We show that supplementation of\nglycogen in vitro restores postmortem pH decline in dark-cutting beef\nby reverting the metabolome toward a typical postmortem muscle state\ncharacterized by increased activities of enzymes glycogen phosphorylase\nand lactate dehydrogenase (<i>p</i> < 0.05) coupled with\na pronounced abundance of glycolytic metabolites and reduced abundance\nof tricarboxylic acid cycle and amino acid metabolites. Furthermore,\nconcurrent inhibition of mitochondrial respiration at complexes I,\nIV, and V with glycogen supplementation stimulates greater pH decline.\nTogether, our findings show that supplementing glycogen at low concentrations\n(10 mM) can reprogram the dark-cutting beef muscle’s metabolome\ntoward typical postmortem state and promote muscle acidification.\nThus, enhancing glycogen levels could represent a promising strategy\nfor mitigating dark-cutting beef phenotypes and improving meat quality.