The calpains are involved in the development of meat tenderness by degrading various myofibrillar proteins in skeletal muscles. Members of this proteolytic system include the ubiquitous u-calpain and m-calpain, the skeletal-muscle-specific calpain-3, and calpastatin. Calpastatin is known to inhibit and regulate the activities of the ubiquitous calpains but not calpain-3. Although the postmortem proteolytic role of u-calpain is well established, those of"m-calpain and calpain-3 remain to be clarified. In addition, calpastatin mRNA and proteins exist as three different isoforms in skeletal muscles, but their individual involvement in determining meat quality characteristics in beef cattle has not been ascertained. It is expected that animals and muscle types with higher levels of calpains, and or lower levels of calpastatins would produce meat with improved quality characteristics, i.e. the meat is likely to age faster and become more tender and juicier. This study was therefore carried out to evaluate meat quality characteristics and the expression of the calpain/calpastatin genes in the skeletal muscles of young bulls, steers and heifers. The animals were slaughtered at equivalent live weight of approximately 550 kg, attained at the age of 547, 764 and 889 days for bulls (n = 6), steers (n = 6) and heifers (n = 6), respectively . .Two anatomically distinct muscles, the Longissimus thoracis (LT) and the Semimembranosus (SM), were sampled from each animal to determine their postmortem aging patterns in the different sex groups. Overall, bulls had lower shear force values" than heifers and tended to be lower than steers. Heifer shearforce values tended to be higher than those of steers. A significant (P < 0.001) muscle effect was found, showing higher shear force values for the SM than the LT. In Heifers, the LT did not tenderise effectively and was found to be as tough as the SM. Generally, the LT tenderised early (between 7 to 14 d), while the SM tenderised late postmortem (between 28 to 35 d). Longer aging also reduced the amount of drip from raw meat but had the opposite effect on cooking losses. With the exception of drip loss in bulls which was equal between the two muscles, the LT had a higher water-holding capacity than the SM. Therefore meat quality may be improved by employing a musclespecific aging regime. A trained panel assessed the sensorial qualities of SM steaks subjected to a prolonged aging treatment of 35 d. The panel rated aged meat as more tender (P < 0.01) but could not detect any significant sex differences (P> 0.05).
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:606729 |
| Date | January 2012 |
| Creators | Mberema, Christopher Heinz Hunke |
| Publisher | University of Newcastle Upon Tyne |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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