Anne L. Ford

Electrical stimulation of beef sides

Sides of beef were stimulated with one of three different systems of stimulation-a high voltage system (1100 V), a low voltage system (110 V) and an extra low voltage system (45 V). Warner-Bratzler shear measurements indicated that for muscles removed at 1 or 2 h post slaughter and then subjected to conditions which induce cold shortening, the high voltage system was superior to the other two. Warner-Bratzler shear values and taste panel tenderness scores indicated that, for all stimulation treatments, muscles removed from stimulated sides at 22 h post slaughter were more tender than those removed from control sides at the same time. Muscles from sides which had received the high voltage treatment, but not those from sides which had received the other stimulation treatments, were judged by the taste panel to be less juicy than muscles from the control sides. Lower shear values for individual muscles from stimulated sides were usually accompanied by longer sarcomeres and it is suggested that the major effect of electrical stimulation is the prevention of cold shortening.

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).