Degradation Of Myosin Heavy Chain Research Articles

Risk of low bone mineral density in young pediatric cancer survivors with sarcopenia.

10070 Background: Required treatments to cure pediatric cancer at such a young age increase the risk of later health-related complications. Early exposure to DNA damaging agents, during a vital period of active skeletal growth, interferes with accrual of bone mass. Treatments not only impair bone health, but also affect skeletal muscle function and mass. Long-term pediatric cancer survivors present these limitations due to myofibrillary atrophy caused by degradation of myosin heavy chain and decrease in myosin synthesis death. Muscle weakness (both muscle strength deficits and low lean mass hereafter referred to as sarcopenia) and low areal bone mineral density (aBMD) have been observed to coexist in adult survivors of paediatric cancer. However, in young pediatric cancers survivors, associations between sarcopenia and low aBMD are not well described. Therefore, this study aimed to examine the risk of low aBMD in young pediatric cancer survivors with sarcopenia confirmed/probable, compared to not having sarcopenia. Methods: This cross-sectional study included 116 pediatric cancer survivors (12.1±3.3 years old; 42% female) enrolled on a randomized controlled trial designed to improve bone health (iBoneFIT project). Handgrip strength was used to assessed muscle strength. Dual-energy X-ray absorptiometry estimated aBMD (g/cm2) at the total body (less head), lumbar spine, total hip and femoral neck, and appendicular lean mass index (ALMI, kg/m2). Sarcopenia status was determined using age and sex specific international reference data from a healthy population. “No sarcopenia” was defined when muscle strength was >decile 2. “Sarcopenia probable” was defined when muscle strength was ≤decile 2 and ALMI Z-score was > -1.5 standard deviation (SD). “Sarcopenia confirmed” was defined when muscle strength was ≤decile 2 and ALMI Z-score ≤-1.5 SD. Logistic regression, adjusted for time from treatment completion and radiation exposure, was used to evaluate the risk of low aBMD (age-, sex- and race-specific aBMD Z-score < -1.0) by sarcopenia status. Results: More than one-third of survivors met criteria for sarcopenia confirmed (37.9%); 19.0% met criteria for sarcopenia probable. Survivors with sarcopenia confirmed had higher risk of low aBMD at the total body (odd ratio [OR]: 6.91, 95% confidence interval [CI]: 2.31-24.15), total hip (OR: 2.98, 95% CI: 1.02-9.54) and femoral neck (OR: 4.72, 95% CI: 1.72-14.19) than those without sarcopenia. Survivors with sarcopenia probable had higher risk of having low aBMD only at the total body (OR: 4.13, 95% CI: 1.04-17.60) than those without sarcopenia. Conclusions: Over one-third of young paediatric cancer survivors presented sarcopenia confirmed with higher risk of low aBMD. These findings suggest that interventions to mitigate osteosarcopenia in this population should be implemented at early stages after treatment completion.

Insight into the evolution of textural properties and juiciness of ready-to-eat chicken breasts upon different thermal sterilization: From the perspective of protein degradation.

Texture deterioration of meat products upon high-temperature sterilization is a pressing issue in the meat industry. This study evaluated the effect of different thermal sterilization temperatures on the textural and juiciness of ready-to-eat (RTE) chicken breast. In this study, by dynamically monitoring the texture and juiciness of chicken meat products during the process of thermal sterilization, it has been observed that excessively high sterilization temperatures (above 100°C) significantly diminish the shear force, springiness and water-holding capacity of the products. Furthermore, from the perspective of myofibrillar protein degradation, molecular mechanisms have been elucidated, unveiling that the thermal sterilization treatment at 121°C/10 min triggers the degradation of myosin heavy chains and F-actin, disrupting the lattice arrangement of myofilaments, compromising the integrity of sarcomeres, and resulting in an increase of approximately 40.66% in the myofibrillar fragmentation index, thus diminishing the quality characteristics of the products. This study unravels the underlying mechanisms governing the dynamic changes in quality of chicken meat products during the process of thermal sterilization, thereby providing theoretical guidance for the development of high-quality chicken products.

Lactic acid fermentation of kamaboko, a heated Alaska pollock surimi, enhances angiotensin I-converting enzyme inhibitory activity via fish protein hydrolysis.

To enhance the value of surimi, efforts have been made to develop a fermentation method with lactic acid bacteria (LAB) to proteolyze fish protein. However, fermenting unheated surimi poses a spoilage risk due to its high bacterial content. Surimi heat treatment can prevent spoilage, but gel formation induced by heating introduces another technical issue: it hinders uniform fermentation. Thus, this study aims to observe the proteolysis and enhance the functionality of seafood product through lactic acid fermentation of kamaboko, a heated surimi. Upon analyzing the kamaboko fermented with Lactobacillus helveticus JCM1004, we observed that LAB produced protease, resulting in the degradation of myosin heavy chain and actin during fermentation. Lactic acid fermentation significantly augmented the peptide content of kamaboko, subsequently elevating the angiotensin Ⅰ-converting enzyme (ACE) inhibitory activity in 200-fold diluted extract of fermented kamaboko to approximately 70% and higher. Notably, our investigation revealed that proteolysis was confined to the surface of kamaboko, as evidenced by SDS-PAGE analysis. This observation implies that the surface area of kamaboko influences the ACE inhibitory activity. Through a comparative analysis of various bacterial strains, we demonstrated that the increase in ACE inhibitory activity is contingent on the protease generated by LAB. These results suggest that LAB-mediated proteolysis of fish proteins liberates bioactive peptides, thereby manifesting in the ACE inhibitory activity. In summary, this study underscores that the fermentation of kamaboko employing proteolytic LAB holds promise in the development of novel functional seafood products.

Unlocking the secrets of crude myofibril-bound serine protease from grass carp: The role in degrading myofibrillar proteins

Grass carp (Ctenopharyngodon idella) are used as raw material for conventional surimi products in Southern China. However, endogenous serine proteases deteriorated the texture of the surimi gel. To unlock the mechanism behind, the present study isolated the crude myofibril-bound serine protease (cMBSP) in grass carp and studied its effects on surimi gel. The cMBSP activity was the highest at 40 °C and pH 8.0, and it remained stable at 20–55 °C neutral pH. Additionally, it was susceptible to serine protease inhibitors and high concentrations of Na+. The maximum degradation of myosin heavy chain by cMBSP was observed at 50 °C. Protein unc-45 homolog B (a myosin chaperone) is one of the apparent degradation products according to mass spectrometry. The cMBSP caused lower water holding capacity and deteriorated texture in the surimi gel. This study expanded insights about the mechanism of surimi gel degradation by cMBSP, which provided theoretical basis for enhancing surimi quality.

Dihydromyricetin as a potential enhancer for surimi gels with anti-modori activity: A molecular docking and experimental validation

Modori is a major quality issue in surimi gels, and the development of safe and effective food ingredients to prevent this phenomenon is highly desirable. In this study, molecular docking was used to identify compounds that could bind to the predicted myofibril-bound serine proteinase (MBSP). Three compounds- Epigallocatechin gallate (EGCG), phytate, and dihydromyricetin (DMY)- were selected for investigation. The effects of these compounds on surimi gels containing 1.5% salt were studied, and a degradation analysis was conducted after incubation at 55 °C. Phytate did not inhibit the degradation of myosin heavy chain, whereas both EGCG and DMY promoted the formation of macromolecular aggregates associated with certain thermal stability. The addition of 0.4% of both polyphenols significantly improved the resistance of surimi gels to modori. However, when 3% salt was applied, EGCG displayed a primary promotion effect on gel deformation but reducecd breaking force. In contrast, DMY exhibited favorable impacts on breaking force, deformation, hardness, gumminess, and chewiness of resulting gels. Among the three covalent cross-linking bonds detected, Lys-DMY-Lys, Lys-DMY-Cys or Cys-DMY-Lys, and Cys-DMY-DMY-Cys, were formed between oxidized DMY and myofibrillar protein. DMY at 100 μM significantly inhibited the activity of MBSP, thus supporting the results obtained from the molecular docking study. Overall, these results suggest that dihydromyricetin is a better gel enhancer for surimi than other candidates tested.

Utilization of deep sea at 4000 and 6000 m depths for long-term storage and quality improvement of greater amberjack (Seriola dumerili) muscle

Long-term storage and quality maintenance of fresh fish are tremendously challenging. This study aimed to develop a novel technology for long-term storage and quality improvement of fresh fish by utilizing deep sea and to clarify its detailed mechanisms focusing on protein properties. Thus, deep-sea aging of greater amberjack muscle was performed at depths of 4000 and 6000 m for approximately 4 months. The total viable count of bacteria in the deep-sea-aged samples was significantly suppressed, especially at 6000 m. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the degradation of myosin heavy chain was accelerated in the deep-sea-aged samples. A significant increase in the content of free amino acids such as aspartic acid and serine, which relates to the enhancement of umami and sweet taste, was also observed in the deep-sea-aged samples. The differential scanning calorimetry (DSC) analysis indicated that protein conformational changes induced by deep-sea high pressure presumably increase the reactivity between protease and substrate in the fish sample, leading to enhanced proteolysis. Therefore, deep-sea aging contributes to improving the safety and quality of greater amberjack muscle during long-term storage. Consequently, this novel technology can be used to achieve the sustainable utilization of marine resources.

Enhanced sodium release and saltiness perception of surimi gels by microwave combined with water bath heating

The study aims to use thermal processing to enhance sodium release from surimi matrix during oral processing and therefore improve the saltiness perception. Surimi gels were prepared by one- and two-stage heating, containing water bath heating (WB90), microwave heating (MW10), two-stage water bath heating (WB40+WB90), and water bath combined with microwave heating (WB40+MW10). The physicochemical properties including gel strength, protein degradation, and microstructure of surimi gels were compared. The water and sodium mobility of surimi gels were characterized by 1H low field NMR and 23Na NMR. Sodium release from matrix during oral processing and sensory evaluation of saltiness difference were employed to verify the enhancement effect of saltiness perception caused by thermal processing. WB40+MW10 improved surimi gel strength by reducing the degradation of myosin heavy chain. Microstructure observations showed that WB40+WB90 gels had a relatively rough and loose microstructure with curved small gaps, whereas WB40+MW10 gels exhibited a denser microstructure. The water and sodium mobility of WB40+MW10 gels (T21 88.08 ms, D 6.68 × 10−10 m2/s) were significantly higher than those of WB40+WB90 gels (T21 83.10 ms, D 6.35 × 10−10 m2/s). WB40+MW10 gels eliminated the tortuosity effect of water and sodium diffusion, resulting in 1.12 times higher sodium release than WB40+WB90 gels. The triangle sensory evaluation also showed that WB40+MW10 gels were perceived as saltier than WB40+WB90 gels, achieving a 15% salt reduction effect. This study provides a promising heating method to improve the saltiness perception of fish products by enhancing sodium release during oral processing.

Mechanisms of fish protein degradation caused by grass carp spoilage bacteria: A bottom-up exploration from the molecular level, muscle microstructure level, to related quality changes

To demonstrate the roles of bacteria in fish protein degradation and related quality changes, three major grass carp spoilage bacteria were individually inoculated into grass carp flesh, and their effects on protein molecules, muscle structures, and quality indices were evaluated through peptidomics, optical microscopy and transmission electron microscope, and texture and water distribution analyses, respectively. Results showed that Pseudomonas putida degraded obscurin, nebulin, and titin, caused disarrangement of myofilaments and fragmented myofibers, and induced great loss of free water in muscle. Shewanella putrefaciens was active in hydrolyzing collagen and degraded both thick and thin filament proteins. Mutual separation of myofibers and severe texture softening were also observed in S. putrefaciens-inoculated samples. Aeromonas rivipollensis degraded myosin heavy chain and some thin filament proteins but less affected muscle microstructure and quality indices. Therefore, this study revealed the mechanisms of bacteria-induced grass carp protein degradation and provided guidance for developing quality control strategies.

A Phytomolecule Icariin Protects from Sarcopenia Partially by Suppressing Myosin Heavy Chain Degradation in Orchiectomized Rats.

Treatments are lacking for sarcopenia, which is an age-related disease characterized by loss of skeletal muscle mass, strength, and/or physical performance. Icariin is a phytomolecule fromherbal Epimedium, a traditional Chinese medicine widely used to treat musculoskeletal disorders for thousands of years. Here the effects of icariin against sarcopenia are investigated and the underlying mechanism is elucidated. A classic rat model of bilaterally orchiectomized (ORX) is used to induce sarcopenia. After administration for 8 weeks, compared to the control group, the forelimb grip strength, the specific tetanic forces of the soleus (SOL) and extensor digitorum longus muscle (EDL) are higher, and the fiber cross-sectional areas (CSAs) of the gastrocnemius and tibialis anterior muscle are larger in the icariin group. In addition, icariin promotes mRNA and protein expressions of myosin heavy chain (MyHC) both in SOL and EDL. Mechanistically, icariin significantly suppresses the mRNA and protein expressions of FOXO3a, atrogin-1, and MuRF-1, which are related to the degradation of myosin heavy chain. Collectively, icariin protects from sarcopenia in ORX rats characterized by enhancing grip strength and skeletal muscle contraction, as well as increasing skeletal muscle CSA by inhibiting the ubiquitination degradation of the MyHC in skeletal muscle fibers.

Characteristics and Mechanism of Crayfish Myofibril Protein Gel Deterioration Induced by Autoclaving.

Crayfish myofibril protein (CMP) gel deterioration induced by autoclaving was investigated. A series of CMP gels were obtained through treating CMP solutions at different autoclaving conditions from 100 °C/0.1 MPa to 121 °C/0.21 MPa, and then characteristics and the mechanism of gel texture deterioration along with the intensification of autoclaving were explored through determining appearance, texture, protein composition, cross-linking forces, degree of hydrolysis, water state, microstructure of the gels, and average particle size of aggregates. When autoclaving was at above 105 °C/0.103 MPa, texture of CMP gel showed a tendency to severely weaken with the intensification of autoclaving (p < 0.05), hydrophobic interaction and aggregation between proteins weakened gradually (p < 0.05), and moderately bound water in the gel decreased and T22 relaxation time significantly increased (p < 0.05). After heating for 30 min at above 105 °C/0.103 MPa, pores in the microstructure of CMP gel enlarged obviously, and myosin heavy chain (MHC) degraded. It can be concluded that CMP gel deterioration induced by autoclaving was associated with the degradation of MHC and 105 °C might be the critical temperature to ensure good texture of crayfish products.

Inhibitory mechanism of tyramine-degrading strains on reducing tyramine accumulation in Harbin dry sausage during fermentation

To reduce tyramine accumulation in Harbin dry sausage, two tyramine-degrading strains, Lactobacillus sakei and Staphylococcus epidermidis, were inoculated in Harbin dry sausage. Changes in pH, aw, protein degradation, microbial growth, and tyramine content during fermentation were determined. The results showed that two strains could increase the abundance of corresponding genera and form population dominance in the early fermentation stage. Particularly, L. sakei could significantly reduce the pH and aw of Harbin dry sausage (P < 0.05) and promote the degradation of myosin heavy chain and actin. The α-amino group content was increased due to L. sakei, which resulted in an increase in tyramine content in the early fermentation stage. After fermentation, the tyramine content in the compound fermentation group decreased to 31.91 mg/kg, which was 55% less than that in the spontaneous fermentation group (70.21 mg/kg). Therefore, co-inoculation with tyramine-degrading strains could reduce tyramine accumulation in Harbin dry sausage.

Proximate composition and changes in muscle proteins of dried salted abo (Otolithes ruber)

Dried salted abo is a popular fishery product in San Miguel Bay (SMB), Philippines. However, the development of this food product has not been fully explored. In this study, the proximate composition and muscle protein profile of dried salted abo was investigated after confirming the molecular identification of abo found in SMB. Sequence analysis of 16S ribosomal RNA and cytochrome c oxidase subunit I genes suggested that abo in SMB could be Otolithes ruber. Abo fillets were brined in 4%, 8%, and 12% salt concentrations (w/w) and sun-dried for 6 and 12 hrs. In both 6 hrs and 12 hrs drying time, moisture content decreased in samples brined with 12% salt, suggesting that the salt concentration could be lowered between 8–12% with 6 hrs drying time. Additionally, the proteolytic profiling by SDS-PAGE analysis detected 17 bands in the myofibrillar protein fraction. Subsequent mass spectrometry identified nine proteins, of which the myosin heavy chain, actin, and keratin were degraded while the other proteins remained stable. Moreover, at 12% salt concentration, changes in staining intensities in several proteins were observed at both 6 hrs and 12 hrs drying time. These findings revealed that the applied salting and drying conditions led to the degradation of myosin heavy chain and polymerization of actin, in addition to an overall alteration of protein profile, which could affect the texture of dried abo product. Overall, this study demonstrated molecular evidence for species identification of abo for the first time. The information on proximate composition and changes in the protein profile of dried salted abo obtained from this study could help the local dried fish industry develop high-quality dried abo products with low salt content.

UBE2L3, a Partner of MuRF1/TRIM63, Is Involved in the Degradation of Myofibrillar Actin and Myosin.

The ubiquitin proteasome system (UPS) is the main player of skeletal muscle wasting, a common characteristic of many diseases (cancer, etc.) that negatively impacts treatment and life prognosis. Within the UPS, the E3 ligase MuRF1/TRIM63 targets for degradation several myofibrillar proteins, including the main contractile proteins alpha-actin and myosin heavy chain (MHC). We previously identified five E2 ubiquitin-conjugating enzymes interacting with MuRF1, including UBE2L3/UbcH7, that exhibited a high affinity for MuRF1 (KD = 50 nM). Here, we report a main effect of UBE2L3 on alpha-actin and MHC degradation in catabolic C2C12 myotubes. Consistently UBE2L3 knockdown in Tibialis anterior induced hypertrophy in dexamethasone (Dex)-treated mice, whereas overexpression worsened the muscle atrophy of Dex-treated mice. Using combined interactomic approaches, we also characterized the interactions between MuRF1 and its substrates alpha-actin and MHC and found that MuRF1 preferentially binds to filamentous F-actin (KD = 46.7 nM) over monomeric G-actin (KD = 450 nM). By contrast with actin that did not alter MuRF1–UBE2L3 affinity, binding of MHC to MuRF1 (KD = 8 nM) impeded UBE2L3 binding, suggesting that differential interactions prevail with MuRF1 depending on both the substrate and the E2. Our data suggest that UBE2L3 regulates contractile proteins levels and skeletal muscle atrophy.

Prediction of top round beef meat tenderness as a function of marinating time based on commonly evaluated parameters and regression equations.

This study investigates the influence of 24‐hr marination (with different plant extracts and vinegar) at refrigerated conditions on commonly evaluated physicochemical and textural attributes, including pH, water‐holding capacity (WHC), collagen solubility, moisture, drip loss, and shear force values of beef meat. The results reflected the appropriate correlation between each pair and indicated the efficiency of the household marination procedure to acquire more palatability and tender beef meat. Therefore, to predict beef meat tenderness by applying the Warner–Bratzler shear force (WBSF), a strong positive correlation with the drip loss (p < .01) and a notable negative correlation with the moisture content (p < .01) emphasized the importance of moisture improvement and shear force reduction in affecting tenderness of baked beef meat. The regression equations and R‐squared values were revealed the favorable correlation between collagen solubility and WHC (y = 0.1035x−0.8431, R 2 = .98) as well as moisture and WBSF (y = −0.3297x + 102.58, R 2 = .99) in marinated beef meat. Electrophoresis patterns of isolated myofibrillar proteins disclosed remarkable degradation of myosin heavy chain (MHC), desmin, actin, and tropomyosin during the first day of aging. The noticeable ultrastructural destruction and connective tissue solubilization were observed by microscopy images. These outcomes were a good tenderness predictor be utilized in retailing and industrial scale.

Isoquercitrin Delays Denervated Soleus Muscle Atrophy by Inhibiting Oxidative Stress and Inflammation.

Although denervated muscle atrophy is common, the underlying molecular mechanism remains unelucidated. We have previously found that oxidative stress and inflammatory response may be early events that trigger denervated muscle atrophy. Isoquercitrin is a biologically active flavonoid with antioxidative and anti-inflammatory properties. The present study investigated the effect of isoquercitrin on denervated soleus muscle atrophy and its possible molecular mechanisms. We found that isoquercitrin was effective in alleviating soleus muscle mass loss following denervation in a dose-dependent manner. Isoquercitrin demonstrated the optimal protective effect at 20 mg/kg/d, which was the dose used in subsequent experiments. To further explore the protective effect of isoquercitrin on denervated soleus muscle atrophy, we analyzed muscle proteolysis via the ubiquitin-proteasome pathway, mitophagy, and muscle fiber type conversion. Isoquercitrin significantly inhibited the denervation-induced overexpression of two muscle-specific ubiquitin ligases—muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx), and reduced the degradation of myosin heavy chains (MyHCs) in the target muscle. Following isoquercitrin treatment, mitochondrial vacuolation and autophagy were inhibited, as evidenced by reduced level of autophagy-related proteins (ATG7, BNIP3, LC3B, and PINK1); slow-to-fast fiber type conversion in the target muscle was delayed via triggering expression of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α); and the production of reactive oxygen species (ROS) in the target muscle was reduced, which might be associated with the upregulation of antioxidant factors (SOD1, SOD2, NRF2, NQO1, and HO1) and the downregulation of ROS production-related factors (Nox2, Nox4, and DUOX1). Furthermore, isoquercitrin treatment reduced the levels of inflammatory factors—interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α)—in the target muscle and inactivated the JAK/STAT3 signaling pathway. Overall, isoquercitrin may alleviate soleus muscle atrophy and mitophagy and reverse the slow-to-fast fiber type conversion following denervation via inhibition of oxidative stress and inflammatory response. Our study findings enrich the knowledge regarding the molecular regulatory mechanisms of denervated muscle atrophy and provide a scientific basis for isoquercitrin as a protective drug for the prevention and treatment of denervated muscle atrophy.

Inhibitory effect of edible natural compounds with di- and tri-carboxyl moiety on endogenous protease inducing disassembly and degradation of myofibrils from grass carp (Ctenopharyngodon idella)

Inhibition of endogenous protease is a rapid and feasible approach to control the proteolysis proceeding of post mortem fish flesh. In the present study, the in vitro inhibitory effects of common edible di- and tri-carboxylic acids and salts on endogenous proteolytic activities as well as myofibrillar disassembly and degradation mediated by crude enzyme of grass carp muscle were investigated. The results showed that among the compounds tested, maleic acid, fumaric acid, tartaric acid and malic acid were the most effective inhibitor for cathepsin B, L and calpain, with IC50 ranging from 7.76 to 30.13 mM, from 32.38 to 65.12 mM, from 1.06 to 6.76 mM, respectively. Also, relatively lower Ki (ranging from 1.04 to 43.21 mM) of these compounds were found towards cathepsin B, L and calpain. Incubation of myofibrillar protein with crude enzyme in the presence of di- and tri-carboxylic compounds could remarkably suppress the dissociation and degradation of myosin heavy chain (MHC), and ameliorate the loss of heat shock protein (HSP) in myofibrils, with tartaric acid and fumaric acid proved more effective than other compounds, possibly implicating their application as potential and efficient inhibitors for quality control of fish muscle products.

Effect of Chinese Rice Wine on the Endogenous Protease Activity, Myofibrillar Degradation, and Quality Characteristics in Topmouth Culter (Culter alburnus)

ABSTRACT The aim of this study was to investigate the influence of rice wine (Jinbiao, Yinbiao, Wunianchen, Nv’erhong) on the endogenous protease activity, myofibrillar degradation, and quality characteristics of topmouth culter (Culter alburnus). Rice wine had a pH of 4.3 and calcium ions ranging from 89.30 to 123.70 μg/mL. Nv’erhong rice wine had the highest total phenolic content of 583.38 μg gallic acid equivalent (GAE)/mL, while Wunianchen rice wine (WNC) showed the strongest total antioxidant capacity of 87.29 U/mL. WNC presented the optimum inhibitory effect on endogenous proteases of calpain and cathepsin B, D, and L, delaying the degradation of myosin heavy chain and α-actinin, which are important to muscle softening. The quality characteristic evaluation indicated that the addition of rice wine could maintain the hardness and chewiness, increase the springiness of the fish fillet, as well as inhibit the total volatile basic nitrogen production. These results suggest that rice wine had effects of inhibiting endogenous proteases, delaying myofibrillar degradation, and maintaining the sensory quality of topmouth culter.

Effect of Catla catla roe protein isolate on textural and sensorial properties of surimi gel from Piaractus brachypomus

Influence of protein isolate from catla (Catla catla) roe at different levels (0–8%, w/w) on the textural and sensorial properties of surimi gel from red-bellied pacu (Piaractus brachypomus) were studied. Protein isolate from catla roe (CRPI) was prepared and evaluated for trypsin inhibitory activity. Surimi gels added with CRPI were subjected to shear stress, texture profile analysis, color, SDS-PAGE, microstructure, water holding capacity and sensorial analysis. CRPI had trypsin inhibitory activity of 771.7 ± 12.57 unit/g. The CRPI effectively prevented the degradation of myosin heavy chain (MHC) in a concentration-dependent manner in both modori (65/90 °C) and kamaboko (40/90 °C) gels. Nevertheless, surimi gels incorporated with 6% CRPI (w/w) exhibited higher textural properties. This was witnessed by higher shear stress, hardness, springiness, cohesiveness, gumminess, chewiness, adhesiveness, fracture force, and water-holding capacity for both gels (P < 0.05). Furthermore, increasing CRPI levels (8%, w/w) showed a detrimental effect on gelation. The whiteness of modori and kamaboko gels slightly decreased with increasing CRPI levels (P < 0.05). The microstructure of modori and kamaboko gels added with 6% CRPI was more ordered and compact with fewer voids, demonstrating a preventive effect of CRPI on hydrolysis of myofibrillar proteins. Moreover, both gels added with 6% CRPI presented the higher texture and overall likeness scores than that of gels devoid of CRPI (P < 0.05). Therefore, CRPI could be used as an alternative additive to improve the textural properties of red-bellied pacu surimi by mitigating autolysis caused by endogenous proteinase or serve as a co-gelling agent or binder.

Effects of µ-calpain oxidation on Coregonus peled myofibrillar protein degradation in vitro.

The aim of this study was to evaluate the effect of µ-calpain oxidation on Coregonus peled myofibrillar protein degradation. In the present study, a hydroxyl radical oxidation system was selected to investigate oxidative modification on µ-calpain activity and its degradation on C. peled myofibrillar protein. When subjected to oxidation, the carbonyl content of µ-calpain significantly increased with the increasing of oxidation levels, and oxidation modification promoted the µ-calpain activity. Incubation of C. peled myofibrillar protein with oxidized µ-calpain resulted in the enhanced degradation of myosin heavy chains, actin, and troponin T, but the degradation of desmin at higher levels of oxidation was slightly inhibited, based on sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blotting. This study suggests that oxidation treatment of µ-calpain could accelerate myofibrillar proteolysis through regulating the enzyme activity during postmortem aging. PRACTICAL APPLICATION: Endogenous proteases, especially µ-calpain, are reported to be involved in fish softening during early postmortem storage, which is critical to muscle quality. The cysteine residues of proteins are particularly sensitive to oxidation. The investigation of the effect of oxidation on µ-calpain (a cysteine protease) activity allows for the monitoring of its role in the postmortem proteolysis of fish myofibrils and the associated softening of fish meat, in an attempt to minimize this softening.

Effects of Bromelain and Double Emulsion on the Physicochemical Properties of Pork Loin.

Our aim was to investigate the effects of bromelain embedded in double emulsion (DE) on physicochemical properties of pork loin. We evaluated DE characteristics such as size, zeta potential, and microscopy after fabrication. We marinated meat with distilled water (DW), 1% (w/v) bromelain solution, blank DE, and 1% (w/v) bromelain loaded in double emulsion (DE E) for 0, 24, 48, and 72 h at 4°C, and prepared raw meat for control. The marinated samples were assessed for color, water holding capacity, cooking loss, moisture content, pH, protein solubility, Warner-Bratzler shear force (WBSF) and gel electrophoresis. The droplet size of 1% (w/v) bromelain embedded in DE was increased compared with blank DE (p<0.05) and values of zeta potential decreased. The increase in lightness and color difference range of the DE-treated group was lower than that of the DW-treated group (p<0.05). Moreover, treatment by immersion in 1% (w/v) DE E resulted in the highest water holding capacity values (p<0.05) and lower cooking loss values than water base treatment (p<0.05). Results for myofibrillar protein solubility and WBSF showed a similar trend. 1% (w/v) DE E showed degradation of myosin heavy chain after 48 h in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Thus, bromelain-loaded DE is useful for controlling and handling enzyme activity in food industry.