Characterization of Rigor Mortis Development in Four Broiler Muscles

Abstract

Three experiments were conducted to characterize the development of rigor mortis by broiler muscles containing different muscle fiber types. In the first experiment, isotonic shortening was used to detect the development of rigor mortis. Two homogeneous fiber-type muscles were used to model the behavior of red, aerobic, and white anaerobic muscle fibers and two heterogeneous fiber-type muscles were used to evaluate the contribution of these fiber types within a muscle. Rigor mortis development in predominantly red, aerobic muscles was significantly more rapid (P<.05) than that in predominantly white, anaerobic muscle. Commercial chilling procedures slowed (P<.10) rigor mortis development only in red, aerobic muscles.In the second and third experiments the same four test muscles were removed from broilers at .33, .67, 1, 2, 3, 4, 6, and 8 h post-mortem and analyzed for R value and for glycogen and lactic acid. The aerobic muscles showed no change in any biochemical parameters tested after 2 h post-mortem. The anaerobic muscles showed continued metabolic activity beyond 2 h post-mortem and the Pectoralis superficialis exhibited substantial R value and lactic acid increases up to 8 h post-mortem.The rigor mortis development times from the isotonic shortening experiment did not coincide with changes in the monitored biochemical parameters. These results led to the conclusions that rigor mortis development in broiler muscles was more rapid in red fibers than in white fibers, was slowed by chilling only in red fibers, and could not be accurately predicted from biochemical changes.