http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Methods for improving and mechanisms associated with the tenderness of meat from Brahman, Hereford and Brahman cross beef cattle
Ten each, purebred Hereford, purebred American Grey Brahman, Hereford x Brahman and Brahman x Hereford steers were fed a typical feedlot diet and slaughtered when real-time ultrasound measurements indicated that they had approximately 1 cm of subcutaneous fat over the longissimus muscle at the 12th rib. All four breeds or breed-types were utilized to determine the potential of postmortem procedures for improving meat tenderness. The calcium dependent protease (CDP) system, cathespins B and B+L, postmortem increases in muscle ionic strength and early postmortem pH and temperature were investigated as possible mechanisms for the variation in meat tenderness between the two purebred breeds. Cooked meat (longissimus muscle) from purebred Brahman cattle was less tender and more variable in tenderness than that from the other breed-types, but postmortem electrical stimulation reduced many of these differences in tenderness. The half-Brahman cross steers produced meat that was not different in tenderness or variability in tenderness to that from purebred Hereford steers, although all were only rated as "slightly tender" by the trained sensory panel. Electrical stimulation reduced the length of postmortem aging time needed to reach a given level of tenderness, regardless of breed or breed-type. Meat that was blade tenderized was not different in tenderness from meat that was electrically stimulated, and when the procedures were combined, they produced no synergistic effects. Longissimus muscle from Brahman cattle was less tender initially (7 d postmortem) than muscle from Hereford cattle, but muscle from both breeds responded to aging (7 to 35 d postmortem) in a similar manner. Cathepsin B and B+L activities were not different between breeds and thus, could not explain breed differences in tenderness. Lower CDP I activity of immediately postmortem Brahman muscle at optimal and actual muscle assay conditions, and higher CDP inhibitor activity in immediately postmortem Brahman muscle at optimal assay conditions may be responsible, in part, for the inherent differences in tenderness between breeds. The effect of elevated ionic strength on myofibrillar solubility between breeds did not explain breed differences in tenderness. However, the higher solubility of myofibrillar proteins incubated at .3 vs .1 M ionic strength, regardless of breed or aging time, may be related to the postmortem increases in tenderness of both breeds. CDP I activity, as modulated by CDP inhibitor, seems to play a major role in the inherent tenderness differences between breeds.