The thermal shrinkage force in perimysium from different beef muscles is not affected by post-mortem ageing

- Bovine M. pectoralis profundus and M. semitendinosus have different intramuscular collagen contents.
- Perimysium from the two muscles showed differences in collagen solubility but not in the shrinkage force.
- Ageing does not create a significant pattern of changes with time in the shrinkage forces in perimysium.
- The results support a hypothesis of labile and resistant pools of collagen in intramuscular connective tissue.

Differences in the thermal shrinkage and collagen solubility between bovine Semitendinosus (ST) and Pectoralis profundus (PP) muscles and their interactions with ageing were evaluated by studying collagen solubility, hydrothermal isometric tension and thermal denaturation properties of intramuscular connective tissue after 5-20 days post-mortem storage at 4 °C.Collagen solubility was higher in ST than in PP muscle at 5-13 days, but the differences between the two muscles decreased at longer ageing times. A small decrease in the peak denaturation temperature of perimysium occurred with increasing ageing times in both muscles. Maximum force in isometrically-heated perimysium was broadly equivalent in both muscles. Although the amount and solubility of collagen varies between muscles and ageing decreases the stability of some of the collagen, thermal shrinkage forces in heated perimysium are not significantly diminished by ageing.These findings support the idea of one collagen fraction easily degraded by ageing and heat, and another more resistant fraction that determines the physical properties of the tissue after ageing and cooking.