Tenderization of beef by lactic acid injected at dierent times post mortem
Résumé
The potential to tenderize beef muscles by the injection of lactic acid (0.5 M, 10% w/w) was studied using the pectoralis profundus
muscle from cull cows. The injection was performed either 1 h (pre rigor) or 24 h (post rigor) post mortem, and the meat was stored
for 2 or 14 days post mortem. Both treatments caused a rapid pH drop to around 5.0 within 4 h of injection. Other eects were: (1)
an accelerated release of lysosomal enzymes into the cytosol; (2) a greater degradation of myosin heavy chains; (3) ultrastructural
alterations of the myo®brils which included a general weakening or rupture in the M-lines and, to a lesser extent, in the I-bands; (4)
a decreased heat stability of perimysial collagen indicated by a lower insoluble collagen content, lower dierential scanning calori-
metry transition temperature, and lower transition temperatures in isometric tension tests on muscle strips. The lactic acid injections
improved signi®cantly the textural traits of the meat (shear value, tensile strength, sensory scores) at 2 days post mortem with little
further improvement when storage was extended to 14 days post mortem. Changes in texture were of similar amplitude at both post
mortem injection times. The tenderization mechanisms of lactic acid injection are discussed.