Preliminary study on the effect of caspase-6 and calpain inhibitors on postmortem proteolysis of myofibrillar proteins in chicken breast muscle

Postmortem Changes of Desmin, Talin-2, Vinculin, and Integrin β1 in Chicken Breast and Their Effects on Tenderness

Costameres are essential for maintaining the integrity of muscle fibers, which affects the meat tenderness. To explore the pattern of alteration in costameres after slaughter, this study investigated the distribution of costamere proteins (desmin, talin-2, vinculin, and integrin β1), their impact on tenderness, and the involved enzymes. Western blot analysis showed that talin-2 significantly degraded in postmortem, while integrin β1 significantly increased at 48 h (P < 0.05). Warner-Bratzler shear force was positively correlated with desmin, vinculin, and talin-2 expression and transcription levels of their genes but negatively correlated with pH, integrin β1 expression, and ITGB1 transcription level in terms of the overall trend. Multiplex immunohistochemistry revealed that these proteins were mainly distributed in the sarcolemma and cytoplasm, and the spatial interactions of them in the costameres began to weaken at 24 h. Caspase-3 and cathepsin B colocalized with these proteins at 3 and 24 h and may contribute to the degradation of costameres.

Apoptosis and its role in postmortem meat tenderness: A comprehensive review

Tenderness is considered a crucial attribute of postmortem meat quality, directly influencing consumers' preferences and industrial economic benefits. The degradation of myofibrillar proteins by endogenous enzymes within muscle fibers is believed to be the most effective pathway for meat tenderization. After animals are slaughtered and exsanguinated, there is a significant accumulation of reactive oxygen species (ROS), and a dramatic depletion of adenosine triphosphate (ATP) in muscle, leading to inevitable cell death. Caspases are activated in postmortem muscle cells, which disrupt the cell structure and improve meat tenderness through protein hydrolysis. In this review, we systematically summarized the three primary types of cell death studied in postmortem muscle: apoptosis, autophagy and necrosis. Furthermore, we emphasized the molecular mechanisms of apoptosis and its corresponding apoptotic pathways (mitochondrial apoptosis, death receptors, and endoplasmic reticulum stress) that affect meat tenderness during muscle conversion to meat. Additionally, factors affecting apoptosis were comprehensively discussed, such as ROS, heat shock proteins, calcium (Ca2+)/calpains, and Bcl-2 family proteins. Finally, this comprehensive review of existing research reveals that apoptosis is mainly mediated by the mitochondrial pathway. This ultimately leads to myofibrillar proteins degradation through caspase activation, improving meat tenderness. This review summarizes the research progress on postmortem muscle apoptosis and its molecular mechanisms in meat tenderization. We hope this will enhance understanding of postmortem meat tenderness and provide a theoretical basis for meat tenderization techniques development in the future.

Contribution of mitochondria to postmortem muscle tenderization: a review

Postmortem meat tenderization is a process mediated by a series of biochemical reactions related to muscle cell death. Cell death is considered a sign that muscle has started to transform into meat. Mitochondria play a significant role in regulating and executing cell death, as they are an aggregation point for many cell death signals and are also the primary target organelle damaged by tissue anoxia. Mitochondrial damage is likely to have an expanded role in postmortem meat tenderization. This review presents current findings on mitochondrial damage induced by the accumulation of reactive oxygen species during postmortem anaerobic metabolism and on the impact of mitochondrial damage on proteolysis and discusses how this leads to improved tenderness during aging. The underlying mechanisms of mitochondrial regulation of postmortem muscle tenderization likely focus on the mitochondria's role in postmortem cell death and energy metabolism. The death process of postmortem skeletal muscle cells may exhibit multiple types, possibly involving transformation from autophagy to apoptosis and, ultimately, necroptosis or necrosis. Mitochondrial characteristics, especially membrane integrity and ATP-related compound levels, are closely related to the transformation of multiple types of dead postmortem muscle cells. Finally, a possible biochemical regulatory network in postmortem muscle tenderization is proposed.

Degradation and evaluation of myofibril proteins induced by endogenous protease in aquatic products during storage: a review

Myofibril proteins degradation constitutes an important factor in quality deterioration, procedural activation or inhibition of endogenous protease potential regulates autolytic proteolysis-induced softening of post mortem fish muscle. Based on the brief introduction of myofibril proteins degradation in fish skeletal muscle, a detailed description of the main myofibril degradation properties and the distinct role played by endogenous proteases were proposed, which reflects the limitations and challenges of the current research on myofibril hydrolysis mechanisms based on the varied surrounding conditions. In addition, the latest researches on the evaluation method of myofibril proteins degradation were comprehensively reviewed. The potential use of label-free proteomics combined with bioinformatics was also emphasized and has become an important means to in-depth understand protein degradation mechanism.

Effect of Two-Step Sous Vide Cooking and Storage on Microbiological and Oxidative Stability of Chicken Breast

A two-step sous vide method, which included a low temperature initial stage, was shown to improve texture parameters, increase the solubility of proteins, and decrease the cook loss in chicken breasts. The current work was designed to determine the effect of two-step sous vide and subsequent storage on the microbiological and oxidative stability of chicken breasts. Inoculated chicken breasts were vacuum packaged and cooked at two temperatures, 50 °C and 60 °C, combined in different ratios of the same total cooking time (120 min), and then stored for 21 days at 4 °C, 10 °C, and −20 °C, and compared with the one-step temperature treatment (60 °C for 120 min). One-step sous vide treatment resulted in the total inactivation of Enterococcus faecalis NCAIM B. 01312. Meanwhile, the two-step sous vide treatments resulted in a higher than 3 log reduction in Enterococcus faecalis NCAIM B. 01312, reaching the target pasteurization performance criterion of sous vide for poultry meat. Lipid oxidation and the odor of all chicken breasts remained acceptable for 21 days of storage at 4 °C and −20 °C. Conversely, all chicken breasts had higher lipid oxidation rates and odor after 21 days of storage at 10 °C. Two-step-sous-vide-treated chicken breasts were found to be microbiologically stable regarding Enterococcus faecalis NCAIM B. 01312 and total mesophilic aerobic counts during 21 days of storage at 4 °C and −20 °C, in contrast with those stored at 10 °C. It can be concluded that two-step-sous-vide-cooked chicken breasts had acceptable oxidative and microbiological stability during chilled and frozen storage, similar to one-step sous vide ones. These outcomes highlight that two-step heat treatment can be used as an alternative cooking method to improve the quality properties without compromising the storage life of chicken breasts.

Effects of caspase activity of yak meat and internal environment changing during aging

The objective of this study was to investigate the protease family caspases in skeletal muscle and their potential contribution to postmortem proteolysis and meat tenderization. Nine yaks were slaughtered, and samples of Longissimus dorsal were injected with AC-DEVD-CHO at a ratio of 1:1 (w/v) and then stored at 4 °C for 2, 6, 12, 24, 72, and 120 h. Results indicate that the morphological changes of the muscle fibers are significantly obstructed, which is not conducive to the subsequent degradation of proteins. After inhibiting the activity of Caspase- 3, the activity of Caspase-8 and 9 and the energy metabolism was affected. In the case of without inhibition of caspase, the pH value decreased and then increased. The meat color and the water retention are better, the muscle fiber skeleton protein degradation is remarkable, the tenderness is improved. Furthermore, yak meat tenderness was improved by apoptotic pathway during aging.

The effect of caspase-3 in mitochondrial apoptosis activation on degradation of structure proteins of Esox lucius during postmortem storage

This study aimed to investigate the effect of caspase-3 inhibitor in mitochondrial apoptosis activation on structure protein degradation during postmortem storage. Mitochondrial dysfunction, apoptotic factors, structure protein degradation and the myofibrillar rupture index between the control and caspase-3 inhibitor groups were determined. The results show caspase-3 inhibitor repressed the mitochondrial membrane permeability and mitochondrial swelling, as well as increased mitochondrial membrane potential, causing a decrease in the release of cytochrome c from mitochondria to cytoplasm and caspase-9/3 activities (P < 0.05). Subsequently, small myofibrillar proteins (desmin and troponin-T) were susceptible to degradation, initiating texture deterioration. By contrast, giant structure proteins (titin and nebulin) were degraded during later postmortem storage, predominantly contributing to fish softening. The results further suggest that caspase-3 is involved in degradation of structure proteins during postmortem through mitochondrial apoptosis pathways.

The Effect of µ/m-Calpain on Protein Degradation of Chicken Breast Meat

This study was designed to determine the effects of µ/m-calpain on the degradation of cytoskeletal proteins in pectoralis major. Four chickens were slaughtered and the breasts were removed and stored for 12 hr at 4 °C. Each sample was divided into three groups and respectively immersed in control reagent, calpain inhibitor, and caspase inhibitor at 4 °C. The samples were used to evaluate troponin-T and desmin degradation, calpain activity, and myofibril ultrastructure at 12 hr, day 1, day 3, and day 7. Casein zymography revealed that µ-calpain could not be detected in all samples after 12 hr postmortem. The calpain inhibitor inhibited µ/m-calpain activity and reduced troponin-T and desmin degradation during 7 day postmortem. The caspase inhibitor inhibited µ/m-calpain activity and, troponin-T and desmin degradation before day 3 postmortem. The findings suggest that, µ/m-calpain had an effect on cytoskeletal protein degradation after 12 hr postmortem.

Effect of fast pH decline during the early postmortem period on calpain activity and cytoskeletal protein degradation of broiler M. pectoralis major

The objective of this study was to determine the effects of fast pH decline during the early postmortem period on calpain activity and the degradation of cytoskeletal proteins in broilers. Eighty broilers were randomly categorized into two groups: physical restraint (PR) and free struggle (FS). M. pectoralis major (PM) was used for determination of calpain activity, shear value, ultrastructure of myofibrils, and the degradation of desmin, titin, nebulin, and troponin-T. The pH (6.05) of FS group is significantly low than PR group (6.38) at 0.3 h postmortem. Fast pH decline during the early postmortem period led to a decrease of μ/m-calpain activities at 0.3 and 3 h postmortem (P < 0.05), but did not affect the ultimate μ/m-calpain activity. An initial fast decrease in pH increased the degradation of desmin, titin, nebulin, and increased the 30 kDa degradation fragments of troponin-T. Therefore, the fast pH decline during the early postmortem period decreased the μ/m-calpain activity and increased the degradation of cytoskeletal proteins in broiler muscle. It is possible that the fast pH decline experienced an earlier activation of calpains that resulted in earlier protein degradation and ultimately lower shear force.

Changes in apoptotic factors and caspase activation pathways during the postmortem aging of beef muscle

The pathway of apoptosis (effector caspase activation) in beef muscle cells was investigated by examining the expression of apoptotic factors during postmortem (PM) storage of beef muscle. Results showed that caspase-3 could be activated in PM beef muscle. The expression of cytochrome c increased in the cytosolic fraction but significantly decreased in the mitochondrial fraction in the early PM period, which demonstrated that cytochrome c was released from mitochondrion to cytoplasm. The expression of the anti-apoptotic factor Bcl-2 did not show any visible change, and that of pro-apoptotic factor Bax increased during PM storage. Expression of the heat-shock protein Hsp27 significantly decreased with increased PM time. These results demonstrated that the mitochondrial pathway was one of the apoptosis pathways in PM beef muscle and that Bax and Hsp27 were two key regulation factors in apoptosis in PM beef muscle.

Advances in apoptotic mediated proteolysis in meat tenderisation

Meat tenderness is considered to be one of the most important attributes of meat quality; however it is also one of the most variable. Ultimate meat tenderness is influenced by the amount of intramuscular connective tissue, the length of the sarcomere and also the proteolytic potential of the muscle. Post-mortem proteolysis by endogenous proteases causes the weakening of myofibril structures and associated proteins, which results in tenderisation. The caspase proteolytic system was first identified to be a potential contributor to post-mortem proteolysis and tenderisation in 2002. Since then research has both supported and challenged this hypothesis. The purpose of this review is to examine the experimental evidence available for caspases' involvement in post-mortem proteolysis, and to highlight cross-talk between this proteolytic system and the calpain system, a known contributor to meat tenderisation.