The objective of this study was to determine the effects of hot-boning, low voltage electrical stimulation and chilling temperature on the tenderness of bovine M. longissimus dorsi(LD) and M. semimembranosus(SM) muscles. LD(n=32)and SM(n=32)were subjected to different post-mortem treatments; hot-boning (before90 min post-mortem), cold-boning (at 48 h post-mortem), low voltage ES and rapid or slow chilling.Hot-bonend muscle which were not electrically stimulated(NES) had higher Warner Bratzler shear force(WBSF) values (P<0.001)and shorter sarcomeres (P<0.001) than cold-boned muscles. Hot-boned muscles subjected to ES had lower pH values (P<0.001) post-stimulation and up to 8 h post-mortem than NES muscles. At both chilling temperatures WBSF values were lower in ES hot-boned LD and SM muscles at days 2, 7 and 14 post-mortem than NES muscles. Hot-boned muscles subjected to slow chilling had longer sarcomeres (P<0.001) than those subjected to fast chilling. In hot-boned SM muscles, ES resulted in longer sarcomere lengths (P<0.001). However, ES did not have a significant effect on the sarcomere longth of LD muscles. As indicated by WBSF alues all muscles tenderised during ageing, including muscles which were (cold shortened). Proteolysis was not the main reason for differences in WBSF values between ES and NES muscles as jidged by qualitative sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE).A combination of slow chilling and ES hat a positive effect on hot-boned muscles with respect to WBSFvalues.
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