pH inactivation of phosphofructokinase arrests postmortem glycolysis

Influence of post-mortem muscle glycogen content on the quality of beef during aging

Introduction: Glycolic changes which occur post-mortem have an impact on the physical and sensory features of beef, which in turn determine the successive processes and influence such beef quality traits as colour, tenderness, and cooling loss. The aim of this study was evaluation of the post-mortem changes in bovine meat during aging, quantitative analysis of glycogen and lactic acid, as well as examination of their impact on technological and sensory quality of selected muscles from Holstein-Friesian × Limousin breed carcasses.

Material and Methods: The study included three muscles of different metabolic qualities and sarcomere length: m. semitendinosus, m. longissimus dorsi, and m. psoas major, collected from nine bull carcasses aged 24 ±2 months.

Results: Significant correlations were found between the volume of cooling loss on individual days of aging and the pH value of muscle tissue, lactic acid and glycogen content, as well as beef lightness. However, no significant dependency between the volume of glycogen and the intensity of red and yellow colours was detected.

Conclusion: The colorimetric analysis of glycogen and lactic acid can be an effective tool in predicting the quality of beef.

Mitochondria influence postmortem metabolism and pH in an in vitro model

Our objective was to determine the influence of mitochondria on metabolites and pH decline using an in vitro model of postmortem muscle metabolism. Mitochondria were isolated from porcine longissimus lumborum and added (0, 0.5, or 2.0mg) to powdered muscle in reaction media containing either a combination of inhibitors for mitochondria complexes (I, IV, and V) or diluent (without inhibitors). In the absence of inhibitors, adding mitochondria (0.5 and 2.0mg) reduced ATP loss from 30 to 120 min, but did not alter glycogen or lactate during this time. In reactions with mitochondria, inhibitors decreased ATP levels by 30 min and increased glycogen degradation by 60 min. Regardless of mitochondria content, inhibitors enhanced lactate accumulation from 15 to 240 min, and decreased pH from 15 min to 1440 min. In the in vitro model, mitochondria influence the maintenance of ATP, and inhibition of mitochondria enzyme activity contributes to accelerated metabolism and pH decline.