A:   Meat has two major components, the muscle fibers, which allows muscle fibers to contract and relax, and connective tissue, which basically supports the muscle fibers. Muscle fibers usually shorten and stiffen right after slaughter and at the start of rigor mortis, and this usually lasts for 6 to 12 hours in beef cattle. Cooling the carcass shortly after slaughter will only allow the rigor to go only so far. Also as the carcass ages, is hung, after slaughter and the tempertures in the cooler are set properly, there are enzymes within the muscle that are released causing a further breakdown of connective tissue that will increase the tenderness of the meat. How long should a carcass be hung to allow the enzymes to increase tenderness?? Data would suggest 10 to 14 days. Not much difference in tenderness in carcasses aged 10 to 14 days compared to longer. Many times, small slaughter facilities don't have the cooler space to hang carcasses very long. If the meat is tough to start with, aging will help. If the meat is tender to start with, aging will, in theory, make it more tender.