Postmortem titin proteolysis is influenced by sarcomere length in bovine muscle1

Abstract

The calpain protease system, in particular, μ-calpain is involved in the disassembly of specific myofibrillar proteins, resulting in tenderization of meat postmortem. Given the size, complexity, and integral nature of titin to the structure of the sarcomere, it is plausible that the length of a sarcomere may alter the susceptibility of various domains of titin to cleavage by the calpains. Therefore, we hypothesized titin degradation differs in a sarcomere-length-dependent manner in beef. After slaughter, beef carcasses were split and sides were either suspended by the Achilles tendon (normal suspension, NS) or by the aitchbone (hip suspension, HS). Immediately after suspension, samples were dissected from the LM, psoas major (PM), and semitendinosus (STN) muscles to serve as 0-d controls. After 24 h, 4 steaks were removed from each muscle and randomly assigned to 1-, 4-, 7-, or 10-d aging treatments. After the assigned aging period, myofibrils were purified for determination of sarcomere length. Warner-Bratzler shear force analysis was also performed to evaluate differences in tenderness. Muscle proteins were solubilized and subjected to SDS-VAGE (vertical agarose gel electrophoresis) to evaluate titin degradation. Sarcomere lengths differed (P < 0.0001) between contralateral muscles of NS and HS carcasses. Quantification of SDS-VAGE gels revealed less (P < 0.05) intact titin in the PM muscle of NS carcasses at each aging period compared with the PM of HS carcasses. No significant differences (P > 0.05) were detected in the disappearance of intact titin among suspension methods in the LM or STN. These data demonstrate that suspension method alters proteolysis of titin and suggest an increase in sarcomere length may contribute to the susceptibility of titin to postmortem proteolysis in beef.

Physico‐chemical characteristics of Longissimus lumborum muscle in goats subjected to halal slaughter and anesthesia (halothane) pre‐slaughter

“…() muscles with longer sarcomere lengths have lower resistance of shear force (more tender) and are more susceptible to post mortem proteolysis (England et al . ). The effect of slaughter methods on sarcomere length in LL muscle is shown in Figure .…”

“…It is a good indicator of tenderization due to its close relationship with meat tenderness (Kandeepan et al 2009). According to Weaver et al (2008) muscles with longer sarcomere lengths have lower resistance of shear force (more tender) and are more susceptible to post mortem proteolysis (England et al 2012). The effect of slaughter methods on sarcomere length in LL muscle is shown in Figure 1.…”

Anoxia stress and effect on flesh quality and gene expression of tilapia

“…On muscle fibre, sarcomeres are bounded by two successive Z-lines, where fine filaments are anchored and thick filaments are located in the middle (Sabow et al, 2015). Sarcomere length is related to meat tenderness as muscles with longer sarcomeres are less resistant to shear force (these meat products are softer) (Weaver et al, 2008) and are more susceptible to post-mortem proteolysis (England et al, 2012). Therefore, it can be inferred that stress induced by anoxia for 3 and 6 min in Nile tilapias produces fillets with a less firm texture.…”

Effects of dietary fat source on beef quality

“…Wheeler and Koohmaraie (1999) reported a range in sarcomere lengths from 1.36 μm (cold-shortened longissimus) to 1.69 μm (normal longissimus). Similar results were found by King et al (2003) and England et al (2012) who reported post-mortem sarcomere lengths of 1.78 μm and 1.82 μm in bovine longissimus, respectively. Furthermore, many studies on feeding distillers grains reported no differences in sarcomere length (OLTRA et al, 2008.…”