S. C. Seideman

Factors associated with tenderness in young beef

One hundred and twenty-two crossbred steers of varying percentages of Bos Indicus and Bos Taurus breeding were slaughtered to determine the relationship of carcass and meat characteristics to tenderness. Carcasses were graded and longissimus dorsi muscle samples were evaluated for fibre type characteristics, sensory and shear force determination, sarcomere length, intramuscular fat content, collagen content and solubility and fragmentation index. Sarcomere length and collagen content and solubility were not significantly related to shear force values or sensory tenderness ratings. The fragmentation index was highly correlated to sensory tenderness ratings (r = -0·60) and shear force values (r = 0·53) indicating that variation in tenderness is associated with myofibrillar protein degradation. A four variable regression equation that included fragmentation index, lean colour, marbling and per cent red fibres accounted for 56% of the variation in sensory tenderness. Fragmentation index directly accounted for 30% of the variation in sensory tenderness in the four variable equation.

Effect of subcutaneous fat and high temperature conditioning on bovine meat tenderness.

Effects of subcutaneous fat cover and high temperature conditioning on tenderness of meat were studied using 16 steer carcasses. Longissimus subcutaneous fat cover was completely removed from eight carcasses and the right and left sides were stored at either 0°C or 26°C. After 6 h at 26°C, the sides were transferred to the 0°C room; and after 24 h, all sides were transferred to a 1°C room for the duration of the experiment. Cold temperature and removal of fat cover reduced (P < 0·05) the longissimus muscle temperature at 6, 9 and 12 h post-mortem. The pH of the longissimus muscle was lower (P < 0·05) as the result of high temperature conditioning and fat cover 6, 9 and 12 h post-mortem. Consequently, conditions existed which would have been expected to promote cold shortening, yet high temperature conditioning and fat cover had no consistent effects on myofibrillar fragmentation index, sarcomere length or shear values.