Tenderization of beef by lactic acid injected at different times post mortem

Area of Science:

• Food Science
• Meat Science
• Biochemistry

Background:

• Tenderization of beef is crucial for improving meat quality and consumer acceptance.
• Toughness in beef often originates from the pectoralis profundus muscle in cull cows.
• Lactic acid injection is explored as a method to enhance beef tenderness.

Purpose of the Study:

• To evaluate the effectiveness of lactic acid injection for tenderizing beef muscles.
• To investigate the impact of post-mortem injection timing (pre-rigor vs. post-rigor) on tenderization.
• To elucidate the biochemical and ultrastructural mechanisms underlying lactic acid-induced tenderization.

Main Methods:

• Pectoralis profundus muscles from cull cows were injected with lactic acid (0.5 M).
• Injections were administered 1 hour (pre rigor) or 24 hours (post rigor) post mortem.
• Meat was analyzed for pH, enzyme activity, protein degradation, ultrastructural changes, collagen properties, and textural traits at 2 and 14 days post mortem.

Main Results:

• Lactic acid injection rapidly decreased muscle pH to approximately 5.0.
• Accelerated release of lysosomal enzymes and increased degradation of myosin heavy chains were observed.
• Ultrastructural analysis revealed weakening of myofibril M-lines and I-bands.
• Decreased heat stability of perimysial collagen and significant improvements in meat texture (shear value, tensile strength, sensory scores) were noted.

Conclusions:

• Lactic acid injection effectively tenderizes beef muscles, regardless of injection timing (pre-rigor or post-rigor).
• The tenderization mechanism involves accelerated biochemical changes and structural alterations within the muscle fibers and collagen.
• This technique offers a promising approach to improve the quality of tough beef cuts with minimal additional benefit from extended storage.