A Comparison of Glycolysis and Associated Changes in Light and Dark Portions of the Porcine Semitendinosus

Abstract

SUMMARYPost‐mortem glycolysis and related properties in light and dark portions of porcine semitendinosus were studied to determine differences in composition as well as rate and extent of change at two post‐mortem holding temperatures. These post‐mortem changes in the light and dark portions of the semitendinosus were studied in animals evidencing a death reaction, after insensibilization by a captive‐bolt pistol, as well as in animals which were insensibilized by sodium pento‐barbital which yielded no evident death reaction. Dark‐muscle portions contained higher initial values for pH and glycogen and exhibited a shorter delay phase of rigor mortis. Lowering the post‐mortem holding temperatures from 37 to 4°C slowed post‐mortem glycolysis and increased the water‐binding capacity in both muscle portions. Lactic acid concentrations (24 hr) in both portions were similar at both post‐mortem holding temperatures. Insensibilization with sodium pento‐barbital slowed post‐mortem glyeolysis but increased the accumulation of lactic acid in both portions. The delay phase of rigor mortis from animals injected with sodium pento‐barbital was lengthened more in the light portions than in the dark portions. These studies indicate that only light muscle portions have an increased glycolytic rate which may be attributable to the struggle associated with the death reaction upon insensibilization with a captive‐bolt pistol.