Desmin Degradation Research Articles

Exploring the Effects of S-Nitrosylation on Caspase-3 Modification and Myofibril Degradation of Beef In Vitro.

This study aimed to explore the effects of S-nitrosylation on caspase-3 modification and its subsequent effects on beef myofibril degradation in vitro. Recombinant caspase-3 was reacted with different concentrations of S-nitrosoglutathione (GSNO, nitric oxide donor) at 37 °C for 30 min and subsequently incubated with purified myofibrillar protein from bovine semimembranosus muscle. Results indicated that the activity of caspase-3 was significantly reduced after GSNO treatments (P < 0.05) and showed a dose-dependent inhibitory effect, which was attributed to the increased S-nitrosylation extent of caspase-3. LC-MS/MS analysis revealed that caspase-3 was S-nitrosylated at cysteine sites 116, 170, 184, 220, and 264. Moreover, the degradation of desmin and troponin-T was notably suppressed by S-nitrosylated caspase-3 (P < 0.05). To conclude, protein S-nitrosylation could modify the cysteine residues of caspase-3, which accounts for the reduced caspase-3 activity and further represses its proteolytic ability on beef myofibrillar protein.

Effect of non‐selenium glutathione peroxidase activity of peroxiredoxin 6 on beef tenderness: underlying mechanisms

SummaryThis study investigated the effect of non‐selenium glutathione peroxidase (NSGPx) activity of Peroxiredoxin 6 (Prdx6) on beef tenderness. Longissimus thoracis et lumborum (LTL) muscle from six cattle were obtained at 30 min post‐mortem. Samples from each muscle were randomly assigned to each of four treatment groups: being incubated in H2O2 (simulation of oxidative stress), mercaptosuccinic acid (MA; inhibiting NSGPx activity), N‐acetyl‐L‐cysteine (NAC; inhibiting oxidative stress and increasing NSGPx activity), and saline (control), respectively. Results indicated that cells increased the expression of Prdx6 and NSGPx activity to resist oxidative stress. The inhibition of NSGPx activity group (MA) significantly decreased the Warner‐Bratzler shear force and increased the degradation of desmin. Moreover, both the H2O2 and the MA treatment significantly increased the Ca2+ concentration in the sarcoplasm, cell apoptotic rate, and caspase 9 and 3 activity. These results demonstrated that inhibiting NSGPx activity of Prdx6 could accelerate beef tenderization by promoting mitochondrial apoptosis.

Desmin degradation in the skeletal muscle of patients with chronic critical illness

Critical illness myopathy (CIM) is a primary myopathy that develops in critically ill patients. Histologic features of CIM include a general decrease in muscle fiber cross-sectional area and a predominant loss of the motor protein myosin. These features are observed in the absence of inflammatory infiltrates but with detectable cytokine activation. The purpose of this study was to examine the state of the extracellular matrix of the human soleus muscle under conditions of CIM caused by chronic impairment of consciousness. Incisional muscle biopsies were taken from the soleus muscle of 6 patients who were in a chronic critical condition and were treated in the Department of Anesthesiology and Reanimation at the A.L. Polenov Russian Research Institute - branch of the Almazov National Medical Research Center. The study included patients with a chronic impairment of consciousness lasting at least 2 months. Muscle biopsies taken from healthy men were used as controls. The biopsies were obtained using needle biopsy under local anesthesia. Using histological staining of tissue sections, it was determined that patients with CIM exhibited a significant increase in collagen area, surpassing the control value by 82%. An increased mRNA content of collagens I, III, and VIa was also observed, along with an increase in the protein content of collagen I and III. At the same time, we did not observe any changes in the content of fibronectin and extracellular tissue growth factor mRNA. However, we did observe an increase in the mRNA of the integrin A7 subunit. The results obtained indicate significant skeletal muscle fibrosis under CIM conditions. Further studies on the signaling pathways that regulate this process are needed.

Endoplasmic reticulum stress improved chicken tenderness, promoted apoptosis and autophagy during postmortem ageing

In this study, endoplasmic reticulum (ER) stress inducer tunicamycin (TM) and inhibitor 4-phenylbutyric acid (4-PBA) were used to treat postmortem chicken breast muscle to investigate changes in tenderness and effects on apoptosis and autophagy during 5 days ageing. TM-induced ER stress reduced shear force, enhanced myofibril fragmentation index (MFI), disrupted myofibril structure, increased desmin degradation, and activated μ-calpain and caspase-12. In addition, TM-induced ER stress increased the expression of Bax, Bim, and cytochrome c, and decreased the expression of Bcl-xL. Furthermore, TM-induced ER stress improved the conversion of LC3I to LC3II, raised the expression of Beclin-1, and decreased the expression of p62, PI3K, and mTOR. The opposite results were observed after 4-PBA treatment. These results suggested that ER stress could improve chicken tenderness, promote apoptosis and autophagy during chicken postmortem ageing.

In vitro susceptibility of grass carp fish (Ctenopharyngodon idella) to oxidized myosin on structural change of protein secondary structure associated with reactive oxygen species (ROS) treatment

This study aimed to investigate the in vitro susceptibility of grass carp (Ctenopharyngodon idella) oxidized myosin, with the treatment of H2O2 levels being 0, 25, 50, and 100 μmol/L, respectively. The results showed that in vitro oxidation of myosin, reactive oxidative species promoted protein modifications that propagated the conformation changes on myosin secondary structure, leading to a significant increase (P < 0.05) in the protein carbonyl content in the high oxidation treatment, when compared to the low and medium treatments. The results of the Western blot analysis and sodium-polyacrylamide amide-dodecyl sulfate gel electrophoresis demonstrated that in vitro oxidation actively promoted the degradation of protein molecular weight and Desmin (53 kDa) deterioration in the sample with the highest concentration treatment of H2O2. Circular dichroism spectra showed a decrease in α-helix content from 70.1% to 29.8% and an increase in β-sheet percentage from 5.6% to 17.4%. Meanwhile, cysteine and methionine as the free amino acids were most susceptible to oxidative change due to their high sensitivity to the reaction of the sulfur group of amino acids. Protein degradation induced by oxidation resulted in significant changes to the protein secondary structure, as evidenced by the observation of oxidized myosin under different H2O2 levels.

Mitochondrial and endoplasmic reticulum stress pathways regulate tenderness of post-mortem chicken muscle

Apoptosis is closely associated with meat tenderization and calcium chloride (CaCl2) and tea polyphenols (TP) have been shown to have a positive effect on meat tenderness. To examine the mechanism by which apoptosis regulates meat tenderness, chicken breasts were treated with 50 mM CaCl2 and 5 mg/mL TP during 5 days of post-mortem ageing where corresponding tender indexes were measured. The results demonstrated that the shear force was highly reduced by 30.74% and 53.64% in chicken breasts treated with CaCl2 and TP, respectively, which promoted postmortem degradation of troponin-T and desmin as well as destruction of myofibrils. Western blot analysis demonstrated that CaCl2 and TP treatments resulted in the activation of calpain-1, caspase-12, -9 and -3, cleavage of PARP, increased the Bax/Bcl-2 ratio, and reduced Bcl-xL levels. In addition, BiP, p-IRE1, and XBP1 factors associated with the endoplasmic reticulum (ER) pathway, were activated during apoptosis. This suggests that the mitochondrial and ER pathways were involved in the induction of apoptosis by CaCl2 and TP during post-mortem ageing. Moreover, ultrastructural damage occurring in mitochondria and nuclei was observed in the morphological features of apoptosis. Consequently, these results suggest that CaCl2 and TP promote meat rejuvenation during ageing process by activating apoptosis via mitochondrial and ER pathways.

Multivariate Examination of Metabolic Contributions to Beef Longissimus Lumborum Flavor

We examined the impact of muscle metabolic capacity on beef longissimus lumborum flavor. Beef carcasses were selected to have normal or dark cutting lean color (n=160, each) and aged until 13 d postmortem. Muscle pH, glycolytic potential, mitochondrial DNA copy number, instrumental lean color, myoglobin concentration, carbonyls on sarcoplasmic proteins, initial metmyoglobin formation, bloom, proximate composition, slice shear force, sarcomere length, desmin degradation, overall tenderness, juiciness, and flavor profile were determined. Carcasses were clustered based on metabolic characteristics into dark cutting classes (Control, Shady, Moderate, and Severe), which were compared using analysis of variance and multiple factor analysis. Clusters were in general, but not complete, agreement with classifications based on muscle pH. Multiple factor analysis produced 2 dimensions that explained 30.8% and 13.8% of the variation, respectively. Dimension 1 had strong negative loadings for muscle pH and strong positive loadings for glycolytic potential, L*, a*, b*, initial metmyoglobin formation, and bloom. Ratings for fat-like, overall sweet, sweet, and musty/earthy/humus had relatively weak positive loadings for dimension 1, whereas salt, sour, and metallic ratings had weak negative loadings for dimension 1. Overall tenderness and juiciness ratings, marbling score, intramuscular lipid content, carbonyls on sarcoplasmic proteins, and L* had positive loadings for dimension 2. Ratings for fat-like, beef flavor identity, and brown/roasted had positive loadings for dimension 2, and intramuscular moisture content, slice shear force, and mitochondrial copy number had negative loadings. Sample scores stratified dark cutting clusters along dimension 1, which agreed with univariate comparisons for these traits. Sample scores for dimension 2 were greater for Moderate and Control steaks than for Shady steaks. These data indicate that clustering was effective in segmenting them into groupings more indicative of the metabolic machinery than pH alone. Moreover, the semetabolic differences influenced animal variation in beef flavor profile.

Effects of phosphoglycerate kinase 1 and pyruvate kinase M2 on metabolism and physiochemical changes in postmortem muscle

The objective of this work was to investigate the influence of phosphoglycerate kinase-1 (PGK1) and pyruvate kinase-M2 (PKM2) activity on glycolysis, myofibrillar proteins, calpain system, and apoptosis pathways of postmortem muscle. The activity of PGK1 and PKM2 was regulated by their inhibitors and activators to construct the postmortem glycolysis vitro model and then incubated at 4 °C for 24 h. The results showed that compared to PGK1 and PKM2 inhibitors groups, the addition of PGK1 and PKM2 activators could accelerate glycogen consumption, ATP and lactate production, while declining pH value. Moreover, the addition of PGK1 and PKM2 activators could increase desmin degradation, μ-calpain activity, and caspase-3 abundance. Interestingly, troponin-T degradation was significantly increased both in PKM2 inhibitor and activator groups. It was suggested that PGK1 and PKM2 might be used as robust indicators to regulate meat quality by affecting the glycolysis, myofibrillar proteins, μ-calpain and apoptosis pathways in postmortem muscle.

Desmin Degradation in the Skeletal Muscle of Patients with Chronic Critical Illness

Chronically critically ill patients lose a significant amount of muscle mass during their stay in the intensive care unit, which can have long-term detrimental consequences. This, among other factors, leads to the degradation of the muscle cytoskeleton’s integrity, and at present there are no comprehensive studies that describe the mechanisms b-ehind the development of this process. The purpose of this study was to investigate the signaling processes that contribute to the degradation of desmin in patients with critical illness myopathy (CIM). Incisional muscle biopsies were taken from the soleus muscle from 6 patients undergoing treatment at the A.L. Polenov Russian Research Institute - branch of the Almazov National Medical Research Center, with chronic impairment of consciousness (lasting at least 2 months). Muscle biopsies taken from healthy men using a needle biopsy technique were used as controls. Biopsies were frozen in liquid nitrogen for subsequent Western blot and PCR analysis, as well as immunohistochemical studies. The analysis showed that fibers with an altered histological pattern of desmin were visually identified in 4 out of 6 patients studied. We also observed a significant decrease in desmin content by 69% and a 24% decrease in its mRNA content in patients with CIM. Desmin breakdown may be associated with increased calpain activity and activation of the ubiquitin-proteasome system. In this study, the content of calpain-1 increased under conditions of CIM at the protein level, but remained unchanged at the mRNA level. We observed changes in GSK3-β (Ser9) phosphorylation, which is a crucial step in the d-epolymerization of desmin filaments by calpain-1. A study on ubiquitin ligases revealed a significant 155% increase in the expression of Trim32, along with a decrease in the e-xpression of Atrogin1 and MuRF1. Thus, in this study, we observed a decrease in desmin content under conditions of CIM. The breakdown of desmin may be due to increased phosphorylation by GSK3β and subsequent cleavage by calpain-1. In addition, we observed an increase in the expression of the E3 ubiquitin ligase Trim32, the activity of which, according to literature, also increases after phosphorylation of desmin.

Desmin Degradation in Skeletal Muscles of Patients with Chronic Critical Illness

Desmin Degradation in Skeletal Muscles of Patients with Chronic Critical Illness

Protein Phosphorylation Induced by Pyruvate Kinase M2 Inhibited Myofibrillar Protein Degradation in Post-Mortem Muscle.

Myofibrillar protein degradation is primarily related to meat tenderness through protein phosphorylation regulation. Pyruvate kinase M2 (PKM2), a glycolytic rate-limiting enzyme, is also regarded as a protein kinase to catalyze phosphorylation. The objective of this study was to investigate the relationship between myofibrillar protein degradation and phosphorylation induced by PKM2. Myofibrillar proteins were incubated with PKM2 at 4, 25, and 37 °C. The global phosphorylation level of myofibrillar proteins in the PKM2 group was significantly increased, but it was sensitive to temperature (P < 0.05). Compared with 4 and 25 °C, PKM2 significantly increased the myofibrillar protein phosphorylation level from 0.5 to 6 h at 37 °C (P < 0.05). In addition, the degradation of desmin and actin was inhibited after they were phosphorylated by PKM2 when incubated at 37 °C. These results demonstrate that phosphorylation of myofibrillar proteins catalyzed by PKM2 inhibited protein degradation and provided a possible pathway for meat tenderization through glycolytic enzyme regulation.

In-depth characterization of myofibrillar muscle proteome changes in lambs fed hazelnut skin by-products

This study investigated the effect of hazelnut skin by-products supplementation on lamb myofibrillar proteome changes during post-mortem storage (0, 4, and 7 days). Gel-based proteomics and bioinformatics approaches were applied to reveal the underlying biochemical pathways and their importance in lamb meat texture development. Twenty-two Valle del Belice male lambs were randomly assigned to two dietary treatments: control (C) for lambs fed with maize-barley diet, and hazelnut skin (H) for lambs fed hazelnut skin by-product as maize partial replacer in the concentrate diet (150 g/kg DM basis). A greater myofibrillar fragmentation index (MFI) was found in meat from the C group at day 0 of storage (91.33 vs 98.38 in H and C groups, respectively). Conversely, starting from 4 days of storage, higher MFI values were observed in meat from lambs fed hazelnut skin (113.74 and 116.1 vs 99.28 and 107.26 in H and C groups at 4 and 7 days, respectively). Myofibrillar proteome changes estimated by SDS-PAGE and immunoblotting revealed a degradation of desmin (P<0.01) and troponin T (P<0.001) intact proteins, and an increase in the abundance of the appearing 30 kDa fragment (P<0.001) after 4 days of storage in meat from H than the C group. In-depth proteomics and bioinformatics revealed 44 proteoforms (26 unique proteins), mainly involved in actin filament-based process/cytoskeleton organization, energy metabolism, and heat shock proteins, as the major interconnected pathways impacted by hazelnut by-product feeding strategy on lamb meat quality. Twelve proteins were proposed in this trial as potential biomarkers of lamb meat texture as a consequence of hazelnut skin by-products supplementation.

L‐Arginine and l‐lysine can weaken the intermolecular interactions of main myofibrillar proteins: the roles in improving the tenderness of pork Longissimus lumborum muscle

SummaryThis work aims at investigating the mechanisms underlying the effects of l‐arginine and l‐lysine on the tenderness of pork Longissimus lumborum muscle. The results indicated that on day 7, L‐arginine and l‐lysine were able to decrease the shear force from 71.47 to 27.59 or 32.53 N, but raise the myofibrillar fragmentation index from 70.93 to 88.2 or 92.4, compared to the control. Additionally, l‐arginine inhibited the degradation of desmin, troponin‐T and titin; while l‐lysine inhibited the degradation of desmin, troponin‐T, titin and nebulin. l‐Arginine, especially l‐lysine alleviated the Z‐disc damage, while accelerated the M‐line damage. l‐Arginine and l‐lysine promoted the extraction of myosin, titin and some unidentified proteins, decreased ionic bonds but increased hydrophobic interactions. The results suggest that the weakening of the intermolecular interactions between main myofibrillar proteins by l‐arginine or l‐lysine may play crucial roles in improving meat tenderness. The finding may broaden the way to tenderise meat.

Exploratory study on the potential regulating role of Peroxiredoxin 6 on proteolysis and relationships with desmin early postmortem

The objective of the present study was to explore the effect of Peroxiredoxin 6 (Prdx 6) on beef tenderization during the early postmortem period. The longissimus lumborum (LL) were obtained at 45 min postmortem from 6 beef carcasses and then incubated with or without the inhibitor of Prdx6 (NSC348884) for different times, followed by incubation with or without the H2O2 (simulation of oxidative stress). The expression of Prdx6, proteolysis indicated by desmin degradation, cell apoptosis rate and expression of caspases were measured. The results indicated that the inhibitor significantly reduced the Prdx6 level, while the cells adaptively increased Prdx6 expression to resist the oxidative stress caused by H2O2. Moreover, the samples in which Prdx6 was inhibited demonstrated more severe desmin degradation accompanied by a higher apoptosis rate which was induced by the increase in caspase degradation as well as the ratio of Bax/Bcl-2. These results demonstrated that inhibiting Prdx6 could promote cell apoptosis and further accelerate beef tenderization.

Early postmortem muscle proteome and metabolome of beef longissimus thoracis muscle classified by pH at 6 hours postmortem

The objective was to identify metabolome and proteome differences at 1 h and 1 d postmortem between longissimus thoracis (LT) muscle classified based on 6 h pH values. Twenty beef LT rib sections were sorted based on 6 h postmortem pH values into low (LpH; pH < 5.55; n = 9) and high (HpH; pH > 5.84; n = 8) pH classifications. Warner-Bratzler shear force (WBSF), desmin degradation, and calpain-1 autolysis were measured. Two-dimensional difference in gel electrophoresis (3–10, 4–7, and 6–9 pH range) and Tandem mass tagging (TMT) protein analyses were employed to determine how the sarcoplasmic protein profile varied across pH classification. Non-targeted metabolomic analyses were conducted on extracts prepared at 1 h and 1 d postmortem. The LpH classification had a lower WBSF value at 1 d postmortem, which was explained by greater calpain-1 autolysis and desmin degradation at 1 d postmortem. Proteome and metabolome analysis revealed a phenotype that promotes more rapid energy metabolism in the LpH group. Proteome and metabolome analyses identified energy production, apoptotic, calcium homeostasis, and proteasome systems influencing pH classifications that could explain the observed pH, proteolysis, and beef tenderness differences. SignificanceThis study is the first to identify proteomic and metabolomic variations early (1 h and 1 day) postmortem that are linked to differences in early (6 h) postmortem pH values and to tenderness differences at 1 day postmortem. This study integrates postmortem biochemical features (protein degradation, proteome, and metabolome variations) to postmortem pH decline and eating quality of beef steaks. Potential biomarkers of more rapid postmortem metabolism linked to earlier tenderization in beef are suggested. Identification of these biochemical features will assist in predicting the eating quality of beef products.

Effects of iron-catalyzed oxidation and methemoglobin oxidation systems on endogenous enzyme activity and myofibrillar protein degradation in yak meat

In this study, the effects of different oxidation intensities on the degradation of myofibrillar protein by endogenous enzymes in iron-catalyzed oxidizing (IOS) and metmyoglobin oxidizing system (MOS) were compared. The results showed that carbonyl content and endogenous enzyme activities (caspase-3, caspase-6 and calpain-1) increased significantly and the total sulfhydryl content decreased significantly with H2O2 concentration in both oxidation systems. Meanwhile, the rate of carbonyl formation and the inhibition of endogenous enzymes activities of IOS were significantly lower than MOS for the same oxidation intensity. In addition, IOS and MOS mainly produced myosin light chains degradation products of 20–25 kDa and 20–17 kDa. At the same oxidation intensity, MOS of myofibrillar protein significantly enhanced the degradation of troponin-T and desmin by caspase-3/-6 compared with IOS, while inhibiting the degradation of troponin-T by calpain-1. In conclusion, MOS inhibited endogenous enzyme degradation in vitro more than IOS during post-slaughter maturation of yak meat.

Effects of hydroxyl radical oxidation on physicochemical properties and degradation of chicken myofibrillar protein

The most significant issue influencing the preservation and sale of chicken is its oxidative behavior. The effect of hydroxyl radical oxidation on the hydrolysis of myofibrillar protein by μ-calpain in vitro was explored in this work, which looked at the alteration of chicken myofibrillar protein by hydroxyl radical oxidation. The carbonyl, dimerized tyrosine content and surface hydrophobicity of myofibrillar protein increased significantly as H2O2 concentration increased, tryptophan fluorescence intensity and total sulfhydryl content decreased. Compared with the control group, the carbonyl content of 10 mmol/L H2O2 treatment group increased to 1.7 nmol/mg protein, the surface hydrophobicity and the dimer tyrosine content increased 32.41% and 14.73%, respectively, the total sulfhydryl content decreased to 67.93 nmol/mg protein. The protein cross-linked and aggregated, and the oxidative modification of chicken myofibrillar protein promoted degradation. Desmin degradation by μ-calcinase is inhibited by MHC, actin, and troponin-T. The findings revealed that oxidation influenced the hydrolysis of myofibrillar protein and the tenderness of chicken after slaughter. Novelty impact statement The chicken myofibrillar proteins were cross-linked and aggregated by hydroxyl radical oxidation. The oxidative modification of hydroxyl radical changes the sensitivity of protein to μ-calpain. The oxidative modification of chicken myofibrillar protein improved the tenderness of postmortem chicken by promoting the degradation of MHC, actin, and troponin-T caused by μ-calcium-activating enzyme.

PSIII-A-1 Acute Stress Effects on Physiological Responses and Meat Quality Changes in Goats

Abstract Duration of stress prior to processing can significantly affect physiological status and meat quality in goats. This experiment was conducted to determine the effects of duration of preslaughter stress on physiological responses and meat quality in goats. In a Randomized Complete Block Design, fifty-four uncastrated male Spanish goats (8-mo old; BW 29.7 ± 2.03 kg) were randomly subjected to one of three treatments (n = 18 goats/treatment): (i) transported for 3 h, (ii) transported for 30 min, or (iii) or held in pens (control) on two different days. Blood samples were collected before and after transport for assessment of stress responses. Goats were slaughtered, using humane procedures, for meat quality analysis. The data were analyzed using MIXED procedures in SAS with treatment and day as fixed variables. Cortisol concentrations were higher (P &amp;lt; 0.01) in both 3 h (117.7 ± 7.96 ng/mL) and 30 min (130.1 ± 8.05 ng/mL) transported groups compared to the control group (27.5 ± 7.59 ng/mL). A similar treatment effect was noticed in plasma non-esterified fatty acid (P &amp;lt; 0.05) concentrations. Glucose concentrations were highest in 180-min, lowest in control, and intermediate in 30-min group (P &amp;lt; 0.01). There were significant positive correlations among muscle desmin concentration after 6 days of aging and 24 h pH (P &amp;lt; 0.05) and calpastatin activity (P &amp;lt; 0.05), suggesting that desmin degradation plays a role in determining the tenderness of aged meat from goats subjected to preslaughter stress. Warner-Bratzler shear force values of loin chops were highest in 180-min, lowest in control, and intermediate in 30-min groups; however, treatment did not influence the color values or cooking loss of loin chops. The results indicate that acute stress prior to processing can affect both physiological responses and meat quality in a duration-dependent manner in goats.

Carcass Characteristics and Quality Attributes of Beef from Cattle Supplemented Zinc and Ractopamine Hydrochloride

The objective of this experiment was to identify the impact of supranutritional zinc (SUPZN) and ractopamine hydrochloride (RAC) supplementation of beef steers on postmortem protein degradation and tenderness development of extended (&amp;gt;14 d) aged steaks. It was hypothesized that RAC and SUPZN supplementation would influence meat quality development during extended aging of the longissimus thoracis muscle. Crossbred steers (n=27) were fed in a 2 × 2 factorial: control (CON; analyzed 36 mg Zn/kg dry matter) or supranutritional Zn supplementation (SUPZN; CON diet + 60 mg Zn/kg dry matter [from ZnSO4] + 60 mg Zn/kg dry matter [from Zn–amino acid complex]) dietary treatments for the entire 91-d trial. Before harvest (30 d), steers were blocked by body weight within Zn treatments to RAC treatments of 0 or 300 mg per steer per day. Steers were harvested at a commercial processing facility. Carcass characteristics were collected 2 d postmortem. Warner-Bratzler shear force of the Longissimus thoracis was measured at 7, 14, 28, and 42 d postmortem. Calpain-1 autolysis (2 d postmortem) and desmin degradation (2, 7, 14, 28, and 42 d postmortem) were analyzed. RH resulted in greater (P&amp;lt;0.02) Warner-Bratzler shear force values at 7, 14, and 28 d postmortem, lesser (P&amp;lt;0.01) calpain-1 autolysis (76-kDa band) at 2 d postmortem, and lesser (P&amp;lt;0.02) desmin degradation at 2, 7, 14, and 28 d postmortem. Supplementation of Zn resulted in greater (P&amp;lt;0.01) calpain-1 autolysis (78- &amp;amp; 76-kDa band) at 2 d postmortem and a trend for greater (P=0.08) desmin degradation at 2 d postmortem. Tougher steaks from RH supplemented steers were explained by slowed postmortem proteolysis, and Zn supplementation showed evidence to enhance proteolysis early postmortem (2 d). These results demonstrate that nutritional supplementation can impact the rate of tenderness development and postmortem proteolysis in muscle.

Effect of chilling rate on heat shock proteins abundance, myofibrils degradation and caspase‐3 activity in postmortem muscles

SummaryThe objective of this study was to investigate the effect of chilling rate on heat shock proteins (HSP) abundance, myofibrillar proteins degradation and caspase‐3 activity of lamb muscle in postmortem. Eighteen longissimus dorsi (LD) muscles from lamb were treated under three different chilling rates—very fast chilling I (VFC‐I, 22.2 °C h−1), very fast chilling II (VFC‐II, 32.4 °C h−1) and control (1.44 °C h−1)—and stored at −1 °C, −1 °C and 4 °C for 120 h postmortem, respectively. The results showed that myofibril fragmentation index (MFI), the abundance of αβ‐crystallin and HSP20, as well as the degradation of HSP27, HSP70, troponin‐T and desmin under the VFC‐I and VFC‐II groups were higher than control. Notably, HSP90 abundance may not be affected by the chilling rate in the late postmortem aging. Additionally, with increasing of chilling rate for postmortem muscle could inhibit caspase‐3 activity. Overall, results indicated that chilling rate may affect the process of meat tenderization by changing the abundance levels of heat shock proteins, myofibrillar degradation and apoptotic pathway.