The mechanism for the promotion of tenderness in meat during the post-mortem process: a review

Chianina beef tenderness investigated through integrated Omics

In the present study we performed an integrated proteomics, interactomics and metabolomics analysis of Longissimus dorsi tender and tough meat samples from Chianina beef cattle. Results were statistically handled as to obtain Pearson's correlation coefficients of the results from Omics investigation in relation to canonical tenderness-related parameters, including Warner Bratzler shear force, myofibrillar degradation (at 48 h and 10 days after slaughter), sarcomere length and total collagen content. As a result, we could observe that the tender meat group was characterized by higher levels of glycolytic enzymes, which were over-phosphorylated and produced accumulation of glycolytic intermediates. Oxidative stress promoted meat tenderness and elicited heat shock protein responses, which in turn triggered apoptosis-like cascades along with PARP fragmentation. Phosphorylation was found to be a key process in post mortem muscle conversion to meat, as it was shown not only to modulate glycolytic enzyme activities, but also mediate the stability of structural proteins at the Z-disk. On the other hand, phosphorylation of HSPs has been supposed to alter their functions through changing their affinity for target interactors. Analogies and breed-specific differences are highlighted throughout the text via a direct comparison of the present results against the ones obtained in a parallel study on Maremmana Longissimus dorsi. It emerges that, while the main cornerstones and the final outcome are maintained, post mortem metabolism in tender and tough meat yielding individuals is subtly modulated via specific higher levels of enzymes and amino acidic residue phosphorylation in a breed-specific fashion, and whether calcium homeostasis dysregulation was a key factor in Maremmana, higher early post mortem phosphocreatine levels in the Chianina tender group could favor a slower and prolonged glycolytic rate, prolonging the extent of the minimum hanging period necessary to obtain tender meat from this breed by a few days.

Estimation of postmortem interval using the protein marker cardiac Troponin I

The importance of determining the time since death is crucial to criminal, civil and forensic cases. A technique exploiting the degradation of a protein, cardiac Troponin I (cTnI), to estimate the postmortem interval (PMI) was investigated. Cardiac Troponin I is a basic regulatory protein found as part of a ternary complex responsible for calcium dependent muscle contraction. An efficient extraction protocol to analyze the banding pattern of cTnI in postmortem tissue was developed. The analysis involves extraction of the protein, separation by denaturing gel electrophoresis (SDS-PAGE) and visualization by Western blot using cTnI specific monoclonal antibodies. A bovine model was used to develop and optimize the protocol. The homology of cTnI amongst mammalian species allows for the cross-reaction of human anti-cTnI antibodies with bovine cTnI. The results indicate a characteristic banding pattern amongst human cadavers (n=6), a pseudo-linear relationship between percent cTnI degraded and the log of the time since death (r>0.95), and a qualitative degradation band pattern that in a simple comparative analysis with a standard human heart (known time since death) can be used to estimate the postmortem interval. The degradation-banding pattern of tissue cTnI is useful in the determination of the early postmortem (pm) interval (0-5 days). Overall, this technique offers advantages such a wide postmortem interval, measurable degradation pattern, a temporal semiquantitative relationship and manageable temperature dependence over direct temperature methods.