title: Effect of stress-induced high post-mortem pH on protease activity and tenderness of beef.
abstract: Forty-four Swiss Brown young bulls were stressed by regrouping unfamiliar animals before slaughter. M. longissimus thoracis (6-9th ribs) of carcasses were analysed for post-mortem pH, protease activities (m- and α-calpain, calpastatin and cathepsin B + L), Warner-Bratzler shear force and sensory tenderness and juiciness. Muscles were classified into three groups, according to ultimate pH values: > 6.3, 6.3-5.8 and < 5.8. The most significant difference related to high pH was a higher activity of m-calpain at 7th day post mortem. It was also found that meat showing the highest pH was significantly more tender and juicy. Sensory tenderness was highly correlated with activity of m-calpain at 7th day post mortem (r = 0.776) and with ultimate pH (r = 0.708). It is concluded that high ultimate pH induced by stress significantly increases m-calpain activity, and this results in a greatly enhanced tenderisation of beef meat.
authors: Departamento Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, 50013, Zaragoza, Spain.
authors: J A
authors: JA
authors: Beltrán
authors: I
authors: I
authors: Jaime
authors: P
authors: P
authors: Santolaria
authors: C
authors: C
authors: Sañudo
authors: P
authors: P
authors: Albertí
authors: P
authors: P
authors: Roncalés