Techniques for postmortem tenderisation in meat processing: effectiveness, application and possible mechanisms

Developing efficient and promising tenderising techniques for postmortem meat is a heavily researched topic among meat scientists as consumers are willing to pay more for guaranteed tender meat. However, emerging tenderising techniques are not broadly used in the meat industry and, to some degree, are controversial due to lack of theoretical support. Thus, understanding the mechanisms involved in postmortem tenderisation is essential. This article first provides an overview of the relationship of ageing tenderisation and calpain system, as well as proteomics applied to identify protein biomarkers characterizing tenderness. In general, the ageing tenderisation is mediated by multiple biochemical activities, and it can exhibit better palatability and commercial benefit by combining other interventions. The calpain system plays a key role in ageing tenderisation functions by rupturing myofibrils and regulating proteolysis, glycolysis, apoptosis and metabolic modification. Additionally, tenderising techniques from different aspects including exogenous enzymes, chemistry, physics and the combined methods are discussed in depth. Particularly, innovation of home cooking could be recommended to prepare relatively tender meat due to its convenience and ease of operation by consumers. Furthermore, the combined interventions provide better performance in controlled tenderness. Finally, future trends in developing new tenderising techniques, and applied consideration in the meat processing industry are proposed in order to improve meat quality with higher economical value. Graphical abstract

Feeding strategies alter gene expression of the calpain system and meat quality in the longissimus muscle of Braford steers

Objective: The aim of the present study was to determine the effect of supplementing pasture-finished steers with corn silage on the expression level of the calpain system proteins and beef tenderization.Methods: Thirty Braford steers grazing on summer pasture were used for the study. For 120 days fifteen animals were supplemented with corn silage at 1% of body weight per head per day (Suppl) whereas the remaining 15 steers only received pasture (Contr). Carcass and meat traits were evaluated and compared between groups. Gene expression and activities of proteases (calpain 1 and calpain 2) and inhibitor (calpastatin) were measured using real-time polymerase chain reaction and casein zymography.Results: Carcass and meat traits were significantly different between feeding systems. Supplemented steers showed higher hot carcass weight (p<0.01), fat content (p = 0.02), and Warner-Bratzler shear force (p = 0.03). Furthermore, the control group showed higher protease:inhibitor ratios, at mRNA (p = 0.01) and protein levels (p<0.10). Warner-Bratzler shear force and mRNA calpains:calpastatin ratio were associated in both feeding systems (p<0.01).Conclusion: Based on the results obtained in the study, beef tenderness differences among finishing strategies could be modulated through differential expression of the calpain system proteins.

Assessment of the occurrence of gene polymorphisms CAPN316 and UoGCAST in the population of cattle

To solve the problem of increasing the rate of breeding, but reduce the breeding work with farm animals, it is necessary to form herds with the desired level of productivity, that are adapted to specific regions of breeding, resistant to various diseases, with a decrease in the time for the breeding process. The active use of molecular genetic methods has contributed to the expansion of the list of DNA markers for farm animals, which are candidate genes for economically useful traits. Among these genes are widely known members of the calpain-calpastatin system, which is associated with postmortem proteolysis and tenderisation of muscles. The calpain system consists of an actively expressed μ-calpain (CAPN1) and m-calpain (CAPN2) and a single endogenous inhibitor, CAPN1 and CAPN2-calpastatin (CAST). The study of polymorphisms of these genes contributes to the expansion of marker characterisation in breeding. DNA samples (n=139) obtained from the blood of cattle were used in the work. Real-time PCRs were carried out using a ANK-32 programmable thermocycler (Synthol, Moscow, Russia). The CAPN316 gene polymorphism was present in 15% of animals tested, with allele G being found in 85% of animals. Similar calculations on the occurrence of the UoGCAST gene polymorphism in this sample of animals found the desirable allele G in 22% of animals and allele C in the remaining 78%. From the analysis of the occurrence of both genes and their polymorphisms in the study population, animals that had a combination of both desirable genotypes (CC*GG*) of CAPN316 and UoGCAST genes were not identified. There were also no animals that had the desired CAPN316 CC genotype and the heterozygous state of the UoGCAST gene (CC*GC). While 7.6% of the animals were CC*GG for the desirable expression of gene CAPN316, they contained the homozygous form of the gene UoGCAST.

Calpain-1 and Calpain-2 in the Brain: Dr. Jekill and Mr Hyde?

While the calpain system has now been discovered for over 50 years, there is still a paucity of information regarding the organization and functions of the signaling pathways regulated by these proteases, although calpains play critical roles in many cell functions. Moreover, calpain overactivation has been shown to be involved in numerous diseases. Among the 15 calpain isoforms identified, calpain-1 (aka &#181;-calpain) and calpain-2 (aka m-calpain) are ubiquitously distributed in most tissues and organs, including the brain. We have recently proposed that calpain-1 and calpain- 2 play opposite functions in the brain, with calpain-1 activation being required for triggering synaptic plasticity and neuroprotection (Dr. Jekill), and calpain-2 limiting the extent of plasticity and being neurodegenerative (Mr. Hyde). Calpain-mediated cleavage has been observed in cytoskeleton proteins, membrane-associated proteins, receptors/channels, scaffolding/anchoring proteins, and protein kinases and phosphatases. This review will focus on the signaling pathways related to local protein synthesis, cytoskeleton regulation and neuronal survival/death regulated by calpain-1 and calpain-2, in an attempt to explain the origin of the opposite functions of these 2 calpain isoforms. This will be followed by a discussion of the potential therapeutic applications of selective regulators of these 2 calpain isoforms.