Tenderness and Associated Characteristics of Stretched and Contracted Bovine Muscles

SUMMARY— The effects of muscle contraction state, carcass maturity, and post‐mortem aging (4°C) on tenderness were studied on excised semitendinosus muscles of six A‐ and six E‐maturity bovine carcasses. Fiber diameter was shown to be curvilinearly related with sarcomere length (R = .95 and .87 for A‐ and E‐maturity groups, respectively). As muscles were shortened they had a larger percent area of fibers and a smaller percent area of both edomysial and perimysial material. Muscles of the A‐maturity group were more tender (P < .01) than those of the E‐maturity group. Post‐mortem aging resulted in tenderization in both A‐ and E‐maturity groups at all states of contraction f‐48 to +48% of the preexcised length); however, tenderness of contracted muscles did not reach acceptable levels even in 240 hr of aging. Tenderness was shown to be linearly related to fiber diameter (R = .82 and .87 for A‐ and E‐maturity groups, respectively); however, the relationship with sarcomere length was curvilinear (R = .90 and .75 for A and E maturities, respectively). Post‐mortem contraction of muscles was very effective in causing decreased tenderness, whereas the magnitude of tenderness increase was smaller than normal when muscles were stretched.