Influence of animal age on the tenderness of beef: Muscle differences

Animal age effects on the mechanical properties of cooked samples from muscles able to cold shorten (Mm. longissimus dorsi, LDA, and semimembranosus, SMA from Achilles tendon hung sides) and muscles partially restrained from shortening (LD muscles from pelvic hung sides, LDP) from groups of animals aged 9, 16, 27 and 42 months were studied. Age effects on stretched muscles (SM muscles from pelvic hung sides, SMP) were determined using groups aged 2 and 120 months in addition to those of 9, 16, 27 and 42 months. Taste panel, Warner-Bratzler shear and Instron compression results for stretched SMP muscles indicated that tenderness decreased systematically as animal age increased. In contrast, Warner-Bratzler peak force values of LDA muscles decreased by half; linearly, as animal age increased from 9 to 423 months, a reflection of less postmortem shortening in samples from the heavier carcasses of older animals. It is suggested that results of age/tenderness studies depend on the age range, differences in carcass weight, the muscle(s) chosen and the cooling rate of muscles and hence on chilling conditions, cooking conditions and the method(s) used to assess the mechanical properties of the cooked muscle(s).