Effect of Ageing Time on Microstructure, Rate of Desmin Degradation and Meat Quality of Pig Longissimus Lumborum and Adductor Muscles

This study evaluated the effect of ageing time (45 min, 24 h, 96 h and 168 h) on desmin degradation pattern, meat quality and muscle fibre traits in longissimus lumborum (LL) and adductor (AD) muscles of 28 Polish Landrace fatteners slaughtered at 105 kg body weight. The results indicate that the rate of desmin degradation depends on pH and type of muscle, and thus on muscle fibre composition. In AD muscle, characterized by significantly higher pH(45), pH(24) and shear force values, lower drip loss, significantly higher percentage of type I and IIA oxidative fibres, and lower percentage of type IIB glycolytic fibres, desmin degradation is slower than in LL muscle. The rate of desmin degradation is also associated with its localization in muscle fibre. Regardless of muscle type, in all muscle fibres desmin was degraded more rapidly within, rather than at the periphery of the fibres. Additionally, levels of intact desmin and drip loss during postmortem meat storage contribute significantly to a reduction in the diameter of three fibre types analysed in AD and LL muscles 24 h postmortem and of type IIB fibres in AD muscle 96 h postmortem. Furthermore, the decrease in the level of intact desmin is paralleled by a cumulative increase in drip loss and a decrease in shear force at 45 min, 24 h and 96 h postmortem.