Biochemistry of postmortem muscle — Lessons on mechanisms of meat tenderization

Impact of UV pre-treatment on the Longissimus thoracis et lumborum muscle proteomes of dry-aged beef cuts: A characterisation within two sampling locations

This research aimed to explore the changes in two sampling locations (internal and external) of the Longissimus thoracis et lumborum (LTL) beef muscle proteomes subjected to ultraviolet light before dry-aging. It further compared the biological processes and associated proteins at interplay at the external locations of UV pre-treated and control dry-aged samples. Before dry-aging, proteins related to external stimuli were differentially abundant between both locations possibly due to the early post-mortem energy metabolism attempting to compensate for energy deficiencies and stress derived from slaughter and processing. The biochemical status of muscle during chilling and hanging of the carcasses and the impact of the UV pre-treatment may have also influenced the abundance of these proteins before dry-aging. Proteins associated to muscle structure, energy and fatty acids metabolism were differentially abundant between locations after 21 days of dry-aging. These dynamic changes in the meat proteome and related biological processes suggested that both evolved differently between the two sampling locations during dry-aging, and these may underlie the development of dry-aged beef properties. The proteome of the external locations sampled from UV pre-treated beef loins was compared to control counterparts during dry-aging. The results show that aging time appeared to outweigh the effect of UV since the differentially abundant proteins between both groups decreased as dry-aging progressed. These proteins were associated with mRNA stabilization, the matrisome, energy pathways and heat shock proteins (HSPs). Further research is warranted to better understand the role of these proteins in the production of dry-aged beef and their relation to the UV pre-treatment.

In vitro proteolysis mirrors intact muscle maturation in beef carcasses

An in vitro assay was developed to study protease activity during the maturation of beef postmortem. Myofibrils were purified from the semitendinosus and used as a sentinel for assessing the activity of endogenous proteases in longissimus thoracis et lumborum (LTL) and the extensor carpi radialis (ER) over time postmortem in beef carcasses. Samples were collected from each muscle at 0, 1, 2, 7, and 14 d of aging and snap frozen. Samples were powdered and added to an in vitro proteolysis assay containing buffer and purified myofibrils. Aliquots were collected at 0, 2, 120, 480, and 1440 min of incubation, and intact desmin and troponin-T were quantified. Digestions at 0 and 1 d using either muscle had little desmin degradation during the entire digestion period. In contrast, LTL muscle collected at 2, 7, and 14 d had the greatest proteolytic capacity as indicated by disappearance of intact desmin by 480 and 1440 min incubation. Though degradation ensued using powdered ER muscle, disappearance of intact proteins was limited. Degradation in vitro paralleled that observed in intact muscle. Addition of ethylene glycol tetra-acetic acid (EGTA), a cysteine protease inhibitor, and calpastatin inhibited proteolysis and suggest proteolytic activity observed in muscles and detected in our proteolysis assays is due to an active calpain protease. Collectively, our data show an active protease is minimal in bovine muscle until 48 h postmortem in the LTL muscle and suggest an in vitro assay containing purified myofibrils is a potential tool for studying temporal changes in proteolysis during the maturation and tenderization of beef across muscles.

Study on protein hydrolysis and microbial community changes during the fermentation of pork loin ham mediated by electrical stimulation

This study explored the effect of electrical stimulation (ES) and Pediococcus pentosaceus LL-07 (P. pentosaceus LL-07) and Staphylococcus simulans QB7 (S. simulans QB7) on the quality and microbial community of loin ham during the ripening. After the ES and starter culture treatments, the Aw and pH were decreased. Surface hydrophobicity, myogenic fiber fragmentation index (MFI), TCA-soluble peptide, amino nitrogen and free amino acids (FAAs) were also significantly higher than the control group (CK) (P < 0.05). This increase was more significant in the E-S group (electrical stimulation followed by inoculation with P. pentosaceus LL-07 and S. simulans QB7) than the rest of the experimental group (E、S、S-E group). Furthermore, the CK and E-S groups were subjected to a bacterial community comparison experiment. The microbial diversity of these two groups was increased. Pediococcus spp. and Staphylococcus spp. became the dominant bacteria in E-S groups during the ripening. Correlation analyses show a strong correlation between protein hydrolysis, microorganisms and FAAs. In conclusion, the combination of ES and starter culture could promote protein hydrolysis, the accumulation of FAAS, and improves the bacterial community of loin ham.

Revealing the Mechanism of Protein Degradation in Postmortem Meat: The Role of Phosphorylation and Ubiquitination

The aim of this study was to investigate the possible effects of phosphorylation and ubiquitination on the degradation of myofibrillar proteins in mutton with different tenderness. The longissimus thoracis lumborum muscles were chosen and divided into tender and tough groups (n = 9), and then stored at 4 °C for 1 h, 12 h, 1 d, 3 d, and 5 d postmortem. Shear force, pH, myofibril fragmentation index, AMPK activity, E3 ubiquitin ligase abundance, protein phosphorylation, and the ubiquitination levels of muscle samples were measured. The results demonstrated that the meat of samples in the tender group had a higher degradation of desmin and a lower phosphorylation level of desmin at 1 d compared with the tough group. The ubiquitination level of desmin, AMPK activity, and E3 ubiquitin ligase abundance in the tender group were noticeably higher than those in the tough group at 12 h. There was a negative correlation between the shear force and desmin degradation. The desmin degradation was negatively correlated with desmin phosphorylation and ubiquitination levels. The phosphorylation level of desmin was positively correlated with its ubiquitination. In summary, this study suggests that AMPK and E3 ubiquitin ligase concurrently play significant roles in regulating meat tenderness by regulating phosphorylation and ubiquitination in meat postmortem.

Insights into the differences of caspase and apoptosis levels in pork longissimus thoracis muscles with different tenderness: A perspective on S-nitrosylation modification

This study investigated the differences of caspase and apoptosis levels in pork with different tenderness from the perspective of S-nitrosylation and further explored their role during pork tenderization. Ten longissimus thoracis muscles selected from 36 individual carcasses based on shear force were divided into high (HT) and low (LT) tenderness groups (n = 5), respectively. Results demonstrated that total nitric oxide synthase activity and protein S-nitrosylation levels of LT group were higher than HT group, while myocyte apoptosis levels were lower in LT group (p < 0.05). Additionally, LT group possessed a lower caspase-3 activity while a higher abundance of intact caspase-3 and greater S-nitrosylation levels of cleaved caspase-3 (p < 0.05). However, none of the above differences were found in caspase-9 (p > 0.05). The lower tenderness in LT group might be associated with reduced caspase-3 activity resulted from increased S-nitrosylation levels of its active subunits, which delayed myocyte apoptosis and lowed the degradation of desmin and troponin T.

TMT-based quantitative proteomics reveals the effects of electromagnetic field and freezing preservation techniques on mutton quality

This study investigated the effects of electromagnetic field preservation (EP) and freezing storage (FS) on the quality of northern Qianbei Ma mutton. Using tandem mass tagging (TMT)-labeled quantitative proteomics and bioinformatics, it was observed that EP more effectively inhibited pH increase and maintained a* and b* values compared to FS. Furthermore, the EP group was able to better maintain the water-holding capacity and tenderness of the mutton under prolonged storage. Proteomics analysis identified 397 differentially expressed proteins (DEPs) between the two storage methods at the same storage duration. GO and KEGG enrichment analyses indicated that proteins such as A0A452DSW4, A0A452E8M7, and D3JYV6 were involved in energy metabolism and redox processes, while A0A452EJ66, A0A452DSW4, and A0A452FJE8 played significant roles in protein binding. Overall, EP technology demonstrated superior benefits for maintaining mutton quality, suggesting a novel approach for mutton preservation.

Unveils key proteins in Xinjiang goat muscle linked to post-mortem meat quality: A TMT-based proteomic analysis

An extensive proteomic analysis utilizing the tandem mass tag (TMT) method was conducted to investigate the changes in protein expression in the longissimus dorsi muscle of Xinjiang goats over various post-mortem intervals: immediately after death within 0 h, 12 h, 24 h and 48 h. The investigation carefully identified around 108 proteins that showed significant changes in expression during these intervals. Among these proteins, six were highlighted for their crucial roles in muscle growth and differentiation of muscle fibers post-mortem. These proteins, namely COL12A1, MRPL46, CTNNB1, MYH1, CAPZA1, and MYL9, have a direct effect on the meat's quality attributes, such as tenderness and color. Further discuss observed a progressive increase in the expression of proteins linked with oxidative metabolism (MSRB2, ENOX1, LOC102170282, GSTM1, and AOC3) as the post-mortem aging period extended, particularly between 24 h to 48 h. These proteins are instrumental in defining the color and flavor profiles of goat meat, underscoring the importance of precise processing and storage conditions to preserve meat quality during the critical aging phase. This enhanced understanding of protein expression dynamics offers significant implications for optimizing meat quality and provides a scientific basis for post-mortem handling practices in the goat meat industry.

Role of the intestines on the muscle quality of Pacific white shrimp (Litopenaeus vannamei) during chilled storage: Physicochemical and label-free-based peptidomics analyses

The effect of shrimp deveining on the quality of Pacific white shrimp muscle was investigated by analyzing the protein degradation during chilled storage via physicochemical and label-free peptidomics analyses. In this study, shrimp with intact intestines were in the control group (CS), while deveined shrimp (DS) were in the treatment group. The total viability count (TVC), total volatile base nitrogen (TVB-N) content, and trichloroacetic acid (TCA)-soluble peptide content in all of the shrimp groups gradually increased with prolonged chilled storage. However, in the later stages of chilled storage, the DS samples exhibited significantly lower TVB-N, total bacterial, and TCA-soluble peptide contents than the CS samples, indicating that deveining treatment effectively prolonged shrimp quality. The peptidomics analysis revealed varying degrees of protein hydrolysis in the DS and CS samples during chilled storage. A total of 396 differentially abundant peptides (DAPs) were identified in the DS compared with the CS, comprising 98 upregulated and 298 downregulated segments. This suggests that the removal of the intestine effectively inhibits protein hydrolysis. Gene ontology (GO) analysis suggested that the DAPs were mainly involved in catalytic activity, binding, and metabolic processes. The cluster of orthologous groups of protein (COG) analysis showed that the cytoskeleton dynamics of the muscle proteins underwent considerable alterations influenced by the shrimp's intestines during chilled storage.

Importance of proteins and mitochondrial changes as freshness indicators in fish muscle post-mortem

Evaluating protein and mitochondrial alterations post-mortem can contribute to determining correlations between fish-processing parameters and ultimate fish muscle quality. The myofibrillar protein alteration during rigor mortis directly affects the texture of fish muscle. To identify the mechanisms behind post-mortem softness and quality deterioration, it is crucial to understand the conditions linked to the breakdown of myofibrillar proteins in fish skeletal muscle. Therefore, monitoring protein breakdown at the molecular level and finding target proteins would be considered a marker for fish freshness. Mitochondria play an important role in executing and regulating cell death processes, including apoptosis and necrosis. The mitochondria are the seat of cellular respiration and experience significant alterations in post-mortem tissues. Processes used to reduce protein degradation, such as optimizing chilling and handling practices, would also minimize mitochondrial changes in fillet quality. Moreover, pH fluctuations are considered a critical point that influences both protein and mitochondrial changes. This review considered the implications of protein and mitochondrial alteration during post-mortem storage in fish fillets and the possible pathways of their interaction on fillet quality. Mitochondrial characteristics, such as membrane integrity, pH, and ATP levels, are important for post-mortem muscle cell changes, serving as an early indicator of fish freshness. Understanding the mechanisms behind protein degradation in fish muscle led to maintaining fillet quality and requires further experiments. Label-free proteomics combined with bioinformatics is crucial for comprehending protein degradation mechanisms to provide customers with safe and fresh fish products while minimizing economic losses associated with fillet deterioration. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Recent Applications and Prospects of Enzymes in Quality and Safety Control of Fermented Foods

Fermented foods have gained global attention for their unique flavor and immense health benefits. These flavor compounds and nutrients result from the metabolic activities of microorganism during fermentation. However, some unpleasant sensory characteristics and biohazard substances could also be generated in fermentation process. These quality and safety issues in fermented foods could be addressed by endogenous enzymes. In this review, the applications of enzymes in quality control of fermented foods, including texture improvement, appearance stability, aroma enhancement, and debittering, are discussed. Furthermore, the enzymes employed in eliminating biohazard compounds such as ethyl carbamate, biogenic amines, and nitrites, formed during fermentation, are reviewed. Advanced biological methods used for enhancing the enzymatic activity and stability are also summarized. This review focused on the applications and future prospects of enzymes in the improvement quality and safety qualities of fermented foods.

Growth Performance, Carcass Quality, and Lipid Metabolism in Krškopolje Pigs and Modern Hybrid Pigs: Comparison of Genotypes and Evaluation of Dietary Protein Reduction

This study compared the performance, meat quality and adipose tissue characteristics of Krškopolje pigs and modern hybrid pigs under identical rearing conditions, besides examining the effects of dietary protein reduction in both genotypes. A total of 29 pigs (14 Krškopolje and 15 hybrids) were assigned to litter into two dietary groups (high and low protein). The low-protein diet for hybrid pigs corresponded to the high-protein diet for Krškopolje pigs. All diets were iso-energetic. Dietary protein reduction decreased growth rate and muscle development in modern hybrids but had no significant impact on performance, quality or metabolic traits in Krškopolje pigs. Genotype differences revealed that Krškopolje pigs had lower growth rates, less lean and more fat deposition, as reflected in thicker subcutaneous and higher intramuscular fat compared to modern hybrids. Krškopolje pigs also exhibited higher myoglobin concentration and fatty acid saturation. Lipogenic enzyme activity and histo-morphological traits behaved in a tissue-specific manner but still indicated a greater lipogenic potential in Krškopolje pigs. This study provides valuable insights into breed-specific responses to dietary changes and highlights the unique characteristics of Krškopolje pigs.

Discovery of a temperature-dependent protease spoiling meat from Pseudomonas fragi: Target to myofibrillar and sarcoplasmic proteins rather than collagen

Chilled meat frequently suffered microbial spoilage because bacteria can secrete various proteases that break down the proteins. In this study, Pseudomonas fragi NMC 206 exhibited a temperature-dependent secretion pattern, with the ability to release the specific protease only below 25 °C. It was identified as alkaline protease AprA by LC-MS/MS, with the molecular weight of 50.4 kDa, belonging to the Serralysin family metalloprotease. Its significant potential for meat spoilage in situ resulted in alterations in meat color and sensory evaluation, as well as elevated pH, total volatile basic nitrogen (TVB-N) and the formation of volatile organic compounds (VOCs). The hydrolysis of meat proteins in vitro showed that AprA possessed a considerable proteolysis activity and degradation preferences on meat proteins, especially its ability to degrade myofibrillar and sarcoplasmic proteins, rather than collagen. These observations demonstrated temperatures regulated the secretion of AprA, which was closely related to chilled chicken spoilage caused by bacteria. These will provide a new basis for the preservation of meat products at low temperatures.

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.

Metabolome and Transcriptome Profiling Reveals Age-Associated Variations in Meat Quality and Molecular Mechanisms of Taihe Black-Bone Silky Fowls

To explore the changes in meat quality and molecular mechanisms during the growth and development of Taihe black-bone silky fowl, this study employed liquid chromatography-mass spectrometry (LC-MS/MS) metabolomics to elucidate the dynamic changes of key differential metabolites (DMs) affecting meat quality, indicating that chicken at D120 had higher levels of ω-3 polyunsaturated fatty acids (PUFAs), creatine, anserine, and homocarnosine, while D150 had the most stachydrine and D210 had the most acylcarnitines. Additionally, D120 and D180 had more umami and sweet compounds. Furthermore, key metabolic pathways influenced by age included purine metabolism, the pentose phosphate pathway, nicotinate and nicotinamide metabolism, and taurine and hypotaurine metabolism. Transcriptomic identified differential expression genes (DEGs) are predominantly enriched in focal adhesion, the TGF-β signaling pathway, and the MAPK signaling pathway. Integrated metabolomics and transcriptomics revealed complex regulatory networks of DEGs and DMs in key metabolic pathways. This research enhanced our understanding of the biology of Taihe black-bone silky fowl meat quality, revealing possible biomarkers.

S-nitrosoproteomics profiling elucidates the regulatory mechanism of S-nitrosylation on beef quality

This study aimed to quantitively profile the S-nitrosylation in beef semimembranosus (SM) with different treatments (nitric oxide donor or nitric oxide synthase inhibitor) by applying iodoTMT-based nitrosoproteomics. Results showed that 2096 S-nitrosylated cysteine sites in 368 proteins were detected in beef SM. Besides, differential SNO-modified proteins were screened, some of which were involved in crucial biochemical pathways, including calcium-releasing-related proteins, energy metabolic enzymes, myofibrils, and cytoskeletal proteins. GO analysis indicated that differential proteins were localized in a wide range of cellular compartments, such as cytoplasm, organelle, and mitochondrion, providing a prerequisite for S-nitrosylation exerting broad roles in post-mortem muscles. Furthermore, KEGG analysis validated that these proteins participated in the regulation of diverse post-mortem metabolic processes, especially glycolysis. To conclude, changes of S-nitrosylation levels in post-mortem muscles could impact the structure and function of crucial muscle proteins, which lead to different levels of muscle metabolism and ultimately affect beef quality.

Effects of oyster mushroom (Pleurotus ostreatus) stem residue supplementation on growth performance, meat quality and health status of broilers

Oyster mushroom stem residue, a by-product with medicinal and nutritive values, might be a prospective feed supplement in poultry nutrition. The study focused on evaluating the impact of oyster mushroom (Pleurotus ostreatus) stem residue (OMSR) powder supplementation on growth performance, carcass traits, meat quality, blood characteristics, and the cecal bacterial count in Arbor Acres broilers raised 35 d. A total of 144 day-old chicks, with an average weight of 40.27± 2.45 g, were divided into 3 groups: control (received a standard basal diet), antibiotic (basal diet + 75 mg/kg chlortetracycline), and OMSR (fed a basal diet with 300 mg/kg OMSR), where each group comprises 8 replications of 6 chicks. Supplementation of 300 mg/kg of OMSR powder in the broiler diet significantly (P < 0.05) enhanced the average daily gain (ADG) and final body weight as opposed to the control and antibiotic treatments, though the average daily feed intake was not influenced by OMSR supplementation during the whole experimental period. However, in comparison to the control and antibiotic groups, OMSR significantly reduced the postmortem breast meat drip loss percentage (P < 0.05) at 24 hours and on the seventh d. Furthermore, the OMSR group reported significantly elevated levels of Hb and RBC counts (P < 0.05), and decreased levels of serum triglyceride (TG) and total cholesterol (TC) concentrations (P < 0.05) on d 35 in comparison to broilers in the control and antibiotic groups. Additionally, the OMSR group exhibited an improved Heterophil/Lymphocytes (H/L) ratio (P < 0.05) relative to the broilers of the control and antibiotic groups. In contrast, the inclusion of OMSR in the broiler diet did not significantly (P > 0.05) influence other serum biochemical and hematological values tested. Broilers in OMSR group had reduced number (P < 0.05) of E. coli and Salmonella spp., but higher presence of Lactobacillus spp. (P < 0.05) in contrast to the control broilers. To summarize, the study's findings revealed that 300 mg of OMSR powder supplementation per kg of basal diet could be act as a natural growth promoter, and confer favorable effects on health and meat quality of broilers.

Effects and mechanism of sub-freezing storage on water holding capacity and tenderness of beef

In order to explore the effect of sub-freezing storage on water holding capacity and tenderness of beef, four treatments were compared in this study: sub-freezing (-7 °C) fast sub-freezing (-38 °C until the core temperature achieved to -7 °C), superchilling (-1 °C) and fast frozen (-38 °C until the core temperature achieved to -18 °C) with the latter two treatments serving as the controls. The differences in muscle fiber structure, water distribution, protein oxidation and cytoskeletal protein degradation were studied. The results demonstrated that compared with other treatments, the fast sub-freezing treatment resulted in less structural damage to the muscle fibers and had better water holding capacity. Both sub-freezing and fast sub-freezing treatments inhibited protein oxidation compared with superchilling, but the former treatment's level of protein oxidation was higher than that in fast sub-freezing treatment during long-term storage (42 weeks). In addition, the structural proteins in the sub-freezing and fast sub-freezing treatments underwent faster degradation during long-term storage and therefore the meat was more tender compared with the fast frozen treatment. The results indicate that the fast sub-freezing treatment can be potentially applied in beef storage.

Comparative Study on the Postmortem Proteolysis and Shear Force during Aging of Pork and Beef Semitendinosus Muscles

The differences in the proteolytic patterns and shear force of pork and beef during aging were evaluated. Pork and beef semitendinosus muscles were obtained at 24 and 48 h postmortem, respectively, and aged at 4°C for 0 (Day 0), 7 (Day 7), and 14 days (Day 14). Changes in the electrical conductivity were observed in pork on Day 7 and beef on Day 14. The calpain activity increased in pork (p<0.05) after 14 days of aging, whereas that of beef decreased on Day 7 (p<0.05). The cathepsin B activity in pork and beef increased between Day 7 and 14 (p<0.05). The content of α-amino group in the 10% trichloroacetic acid-soluble fraction increased between Day 7 and 14 in pork (p<0.05), but increased steadily in beef throughout aging (p<0.05). The electrophoretogram of the myofibrillar proteins revealed a 30 kDa protein band only in the beef lane on Day 14. The cooked pork had no significant changes in the shear force during aging periods (p>0.05), while the gradual decrease in the shear force with the increasing aging periods was shown in the cooked beef (p<0.05). Circular dichroism analysis of myosin extracts from pork and beef revealed thermal denaturation temperatures of 55°C and 58°C, respectively. This study highlights the different post-mortem proteolytic patterns and thermal denaturation temperatures of myosin in pork and beef semitendinosus muscles, which contribute to distinct changes in the shear force during aging between pork and beef.

Impact of lipid droplet characteristics on the rheology of plant protein emulsion gels: Droplet size, concentration, and interfacial properties

Plant-based meat analogs are being developed to address environmental, sustainability, health, and animal welfare concerns associated with real meat products. However, it is challenging to mimic the desirable physicochemical, functional, and sensory properties of real meat products using plant-based ingredients. Emulsion gels consisting of lipid droplets embedded in biopolymer matrices are commonly used to create products with appearances, textures, and sensory attributes like meat products. In this study, the impact of soybean oil droplet characteristics (concentration, size, and charge) on the physicochemical properties of potato protein gels was studied. The oil droplets were either coated by a non-ionic surfactant (Tween 20) or a plant protein (patatin) to obtain different surface properties. The introduction of the oil droplets caused the protein gels to change from mauve to off-white, which was attributed to increased light scattering. Increasing the oil droplet concentration in the emulsion gels decreased their shear modulus and Young's modulus, which was mainly attributed to the fact that the oil droplets were less rigid than the surrounding protein network. Moreover, increasing the oil droplet size made this effect more pronounced, which was attributed to their greater deformability. Competitive adsorption of proteins and surfactants at the oi-water interface in the Tween emulsion promoted emulsion instability. This research highlights the complexity of the interactions between oil droplets and protein networks in emulsion gels. These insights are important for the utilization of emulsion gels in the formulation of plant-based foods with improved quality attributes.

Hydroxyl Radical-Induced Oxidation on the Properties of Cathepsin H and Its Influence in Myofibrillar Proteins Degradation of Coregonus peled In Vitro

The most frequently occurring protein modification in fish postmortem is oxidization, which further affects meat quality through multiple biochemical pathways. To investigate how hydroxyl radicals affect the structure of cathepsin H and its ability to break down myofibrillar proteins in Coregonus peled, cathepsin H was oxidized with 0, 0.1, 0.5, 1, 5, and 10 mM H2O2 and subsequently incubated with isolated myofibrillar proteins. The results showed that as the H2O2 concentration increased, the carbonyl and sulfhydryl contents of cathepsin H significantly increased and decreased, respectively. There were noticeable changes in the α-helix structures and a gradual reduction in UV absorbance and fluorescence intensity, indicating that oxidation can induce the cross-linking and aggregation of cathepsin H. These structural changes further reduced the activity of cathepsin H, reaching its lowest at 10 mM H2O2, which was 53.63% of the activity at 0 mM H2O2. Moreover, desmin and troponin-T all degraded at faster rates when cathepsin H and myofibrillar proteins were oxidized concurrently as opposed to when cathepsin H was oxidized alone. These findings provide vital insights into the interaction mechanism between oxidation, cathepsin H, as well as myofibrillar protein degradation, laying a groundwork for understanding the molecular mechanisms underlying changes in fish meat quality after slaughter and during processing.

Effect of verjuice (Vitis vinifera L.) on physicochemical and textural properties of beef M. biceps femoris

The objective of this study was to investigate the effect of verjuice on beef M. biceps femoris (BF). BF blocks were marinated with 30%, 70%, and 100% verjuice solutions containing 2% NaCl, for different marination times (12, 24, 48, and 72 h). Verjuice marination reduced the pH values of BF samples from 6.77 in control sample to 3.66 in 100% of verjuice for 72 h. The decreased values of water holding capacity (from 54.06% to 47.46%) with increasing verjuice concentration (from 30% to 100% for 72 h) confirmed the drop of proteins isoelectric point of the muscle due to salt presence preventing fibers swelling. Less cookout was observed with increasing acid concentration. Marination time had no significant effect on L* and a* coordinates of uncooked samples while acidification made the samples lighter and less red. Enzymatic proteolysis of myosin and troponin-T concomitant with increase in myofibrillar fragmentation index contributed to the decrease of shear force in a way dependent on verjuice concentration and marination time. Sensory panelists gave the highest score to cooked samples marinated with 70% verjuice solution.

l-arginine and l-lysine supplementation to NaCl tenderizes porcine meat by promoting myosin extraction and actomyosin dissociation

This study investigated the individual and combined effects of l-arginine, l-lysine, and NaCl on the ultrastructure of porcine myofibrils to uncover the mechanism underlying meat tenderization. Arg or Lys alone shortened A-bands and damaged M-lines, while NaCl alone destroyed M- and Z-lines. Overall, Arg and Lys cooperated with NaCl to destroy the myofibrillar ultrastructure. Moreover, these two amino acids conjoined with NaCl to increase myosin solubility, actin band intensity, and the protein concentration of the actomyosin supernatant. However, they decreased the turbidity and particle size of both myosin and actomyosin solutions, and the remaining activities of Ca2+- and Mg2+-ATPase. The current results revealed that Arg/Lys combined with NaCl to extract myosin and dissociate actomyosin, thereby aggravating the destruction of the myofibrillar ultrastructure. The present results provide a good explanation for the previous phenomenon that Arg and Lys cooperated with NaCl to improve meat tenderness.

Difference in muscle metabolism caused by metabolism disorder of rainbow trout liver exposed to ammonia stress

Ammonia pollution is an important environmental stress factors in water eutrophication. The intrinsic effects of ammonia stress on liver toxicity and muscle quality of rainbow trout were still unclear. In this study, we focused on investigating difference in muscle metabolism caused by metabolism disorder of rainbow trout liver at exposure times of 0, 3, 6, 9 h at 30 mg/L concentrations. Liver transcriptomic analysis revealed that short-term (3 h) ammonia stress inhibited carbohydrate metabolism and glycerophospholipid production but long-term (9 h) ammonia stress inhibited the biosynthesis and degradation of fatty acids, activated pyrimidine metabolism and mismatch repair, lead to DNA strand breakage and cell death, and ultimately caused liver damage. Metabolomic analysis of muscle revealed that ammonia stress promoted the reaction of glutamic acid and ammonia to synthesize glutamine to alleviate ammonia toxicity, and long-term (9 h) ammonia stress inhibited urea cycle, hindering the alleviation of ammonia toxicity. Moreover, it accelerated the consumption of flavor amino acids such as arginine and aspartic acid, and increased the accumulation of bitter substances (xanthine) and odorous substances (histamine). These findings provide valuable insights into the potential risks and hazards of ammonia in eutrophic water bodies subject to rainbow trout.

Determining muscle plasticity and meat quality development of low-input extended fed market-ready steers

In March 2020, the World Health Organization declared COVID-19 a pandemic, which ultimately led to many meat processors temporarily shutting down or reducing processing capacity. This backlog in processing capacity forced many feedlots to retain cattle for longer periods of time and assume the risk of major market fluctuations. The aim of this study was to understand how a dietary insult affects meat quality and muscle metabolism in market-ready steers (590 kg). Sixteen market-ready (590 kg) commercial Angus crossbred steers were subjected to a maintenance diet of either forage or grain for 60 d. Longissimus lumborum (LL) muscle samples were collected immediately postmortem and processed for characteristics reflecting the underlying muscle fiber type and energy state of the tissue. Despite cattle being subjected to a 60-d feeding period, there were no detectable differences (P > 0.05) in carcass characteristics, color of lean, or ultimate pH (pHu). Moreover, our data show that muscle plasticity is rather resilient, as reflected by lack of significance (P > 0.05) in oxidative and glycolytic enzymes, myosin heavy chain isoforms (MyHC), myoglobin, and mitochondrial DNA (mtDNA) contents. These data show that market-ready steers are capable of withstanding a low-input feeding strategy up to 60 d without dramatically impacting underlying muscle characteristics and meat quality development.

Depth of Interbreed Difference in Postmortem Bovine Muscle Determined by CE-FT/MS and LC-FT/MS Metabolomics

Japanese Brown (JBR) cattle have moderately marbled beef compared to the highly marbled beef of Japanese Black (JBL) cattle; however, their skeletal muscle properties remain poorly characterized. To unveil interbreed metabolic differences over the previous results, we explored the metabolome network changes before and after postmortem 7-day aging in the trapezius muscle of the two cattle breeds by employing a deep and high-coverage metabolomics approach. Using both capillary electrophoresis (CE) and ultra-high-performance liquid chromatography (UHPLC)-Fourier transform mass spectrometry (FT/MS), we detected 522 and 384 annotated peaks, respectively, across all muscle samples. The CE-based results showed that the cattle were clearly separated by breed and postmortem age in multivariate analyses. The metabolism related to glutathione, glycolysis, vitamin K, taurine, and arachidonic acid was enriched with differentially abundant metabolites in aged muscles, in addition to amino acid (AA) metabolisms. The LC-based results showed that the levels of bile-acid-related metabolites, such as tauroursodeoxycholic acid (TUDCA), were high in fresh JBR muscle and that acylcarnitines were enriched in aged JBR muscle, compared to JBL muscle. Postmortem aging resulted in an increase in fatty acids and a decrease in acylcarnitine in the muscles of both cattle breeds. In addition, metabolite set enrichment analysis revealed that JBR muscle was distinctive in metabolisms related to pyruvate, glycerolipid, cardiolipin, and mitochondrial energy production, whereas the metabolisms related to phosphatidylethanolamine, nucleotide triphosphate, and AAs were characteristic of JBL. This suggests that the interbreed differences in postmortem trapezius muscle are associated with carnitine/acylcarnitine transport, β-oxidation, tricarboxylic acid cycle, and mitochondrial membrane stability, in addition to energy substrate and AA metabolisms. These interbreed differences may characterize beef quality traits such as the flavor intensity and oxidative stability.

Physicochemical properties and sensory profile of some breeds of rabbits in Algeria

The objective of this study was to compare physicochemical traits and sensory profile of meat from rabbits of both sexes belonging to two genotypes, local population and new line (ITELV 2006) which exhibited better characteristics due to its genetic potential. A total of 60 rabbits at 90 days of age were used in the experiment. At slaughter, meat physicochemical and sensory characteristics were measured on Longissimus lumborum muscle. Differences related to genotype were found in most of the physicochemical characteristics studied like Cooking Losses (P < 0.001), Percentage of Released Water (P < 0.001), Myofibril Fragmentation Index (P < 0.001) and a* value (P < 0.001). However, in some of the traits, the differences were related to interaction of sex and genotype (S*G) as in the case of Cooking Losses (P < 0.001) and b* value (P < 0.01). Regarding SDS-PAGE analysis results, the comparison between two breeds has not shown any particular distinction in the myofibrillar and sarcoplasmic protein profiles in relation to the number and the intensity of bands. No significant differences in the sensory characteristics of the meat were noted (P > 0.05). Interestingly, no relevant differences were found between meat from male and female rabbits in all the variables studied (P > 0.05). It was concluded that meat quality was mainly affected by genotype. Thus, the new line exhibited good physicochemical characteristics compared to the local one. This study is the first to analyse and compare the physicochemical and sensory properties of Algerian rabbit meat.

Effect of beef long-storage under different temperatures and vacuum-packaging conditions on meat quality, oxidation processes and microbial growth

BACKGROUND

The global beef market demands the meat industry to ensure product quality and safety in markets that are often very distant. The present study aimed to evaluate the effects of chilled (CH, 120 d) and chilled-then-frozen (CHF, 28 d + 92 d) storage conditions of beef vacuum packaged (VP) and vacuum packaged with antimicrobial (VPAM) on meat quality, oxidative status and microbial loads. Treatments resulted from the combination of storage condition and packaging type: VP + CH, VP + CHF, VPAM + CH and VPAM + CHF.

RESULTS

Warner-Bratzler shear force values decreased in all treatments after 28 d of chilling. Except for VP + CH, L* values (lightness) of meat color did not differ in each treatment as the storage time increased. Meat from VP + CH had greater a* values than CHF treatments on day 120 of storage. A consumer panel did not detect differences in tenderness, flavor and overall liking between VP and VPAM beef, but they preferred CHF steaks rather than CH beef. TBARS values did not differ between VP and VPAM and between CH and CHF at any time during the storage period. At the end of storage time, all treatments except VP + CHF presented a greater concentration of thiols than at 48 h post-mortem. On day 120 of storage, VP + CH had greater catalase enzyme activity than CHF treatments while VP + CH and VP + CHF showed a greater superoxide dismutase activity than VPAM + CHF. Storage condition (CH or CHF) had a greater impact on microbial counts than the type of packaging.

CONCLUSION

Freezing meat after an ageing period represents a suitable strategy to extend beef storage life without a detrimental impact on its quality. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Early postmortem beef muscle proteome and metabolome variations due to supranutritional zinc and ractopamine hydrochloride supplementation

It was hypothesized that the longissimus thoracis (LT) muscle proteome, phosphoproteome, and metabolome could explain postmortem metabolism and tenderness differences in muscle from cattle supplemented zinc (Zn) and/or ractopamine hydrochloride (RH). High percentage Angus steers (N = 20) were fed in a 2 × 2 factorial assigned to Zn and RH treatments: control (CON; n = 10; analyzed 36 mg Zn/kg dry matter [DM]) or supranutritional Zn supplementation (SUPZN; n = 10; control diet + 60 mg Zn/kg DM [from ZnSO4] + 60 mg Zn/kg DM [from Zn-amino acid complex]) for the entire 89-d trial. During the 28 d before harvest, steers were blocked by body weight within Zn treatments to RH treatments of 0 (NO; n = 10) or 300 mg (RAC; n = 10) per steer per day. Steers were harvested at the Iowa State Meat Laboratory, where pH decline (1, 3, 6, and 24 h postmortem) was measured. At 24 h postmortem, LT muscle sections were removed from carcasses, and steaks were analyzed for Warner-Bratzler shear force (WBSF) values at 1, 3, 7, and 14 d postmortem. Muscle samples were taken at 1 h, 1, 3, 7, and 14 d postmortem for the following analysis: troponin-T degradation (1, 3, 7, and 14 d postmortem), myosin heavy chain analysis (1 h postmortem), sarcoplasmic proteome analysis through tandem mass tagging analysis (1 h and 1 d postmortem), metabolome analysis (1 h and 1 d postmortem), and phosphoproteome analysis (1 h postmortem). SUPZN-NO tended to have a lower (P = 0.06) pH at 6 h postmortem and a lower WBSF value (P = 0.06) at 1 d postmortem. CON-RAC had a higher (P = 0.04) pH at 6 h postmortem and WBSF value (P < 0.01) at 1 d postmortem. A lower pH at 6 h postmortem and lower WBSF value at 1 d postmortem in the SUPZN-NO treatment was accompanied by more sorbitol and fructose at 1 d postmortem, and less myosin regulatory light chain 2 at 1 h postmortem, and less adenosine monophosphate deaminase 1 (AMPD1) at 1 d postmortem than all other treatments. A higher pH at 6 h postmortem and higher WBSF value at 1 d postmortem in CON-RAC and SUPZN-RAC was accompanied by more soluble structural proteins (troponin-T and myosin-7) at 1 h postmortem than CON-NO. At 1 h postmortem, CON-RAC had more glyceraldehyde-3-phosphate dehydrogenase than CON-NO or SUPZN-RAC. Differences in energy metabolism enzymes, metabolites, and structural proteins may affect ATP production, rigor development, and lactate buildup which may explain the differences in postmortem metabolism and tenderness development at 1 d postmortem.

Relationship between peptides and the change in quality characteristics of beef strip loin (M. longissimus lumborum) and tenderloin (M. psoas major)

Peptides in fresh and aged beef strip loin (M. longissimus lumborum) and tenderloin (M. psoas major) were quantified to investigate the relationship between proteolysis-induced peptides and beef quality characteristics. A total of 409 and 450 peptides were quantified from strip loin and tenderloin, respectively, and found to be significantly correlated to beef quality characteristics. Changes in redness and yellowness were significantly correlated to the peptides derived from G3P, ENOB, and KCRM in both muscles during 14 days of storage. The peptides produced from MYG, ENOB, HBA, PGK1, and TPIS were strongly associated with improved tenderness, while those derived from major myofibrillar proteins, such as MYH1, MYH2, ACTS, and DESM, were associated with changes in tenderloin color. These results improve our understanding of the association between peptides and changes in meat quality during cold storage, indicating that proteolysis-induced peptides can be indicators of the quality characteristics of fresh and aged meat.

Challenges and opportunities of using Bos indicus cattle to meet consumers' demand for quality beef

Beef consumption is expected to increase worldwide, which necessitates the use of Bos indicus cattle that are well-adapted to harsher climates, like the tropics. Yet, beef from these cattle is considered inferior to that of Bos taurus breeds, primarily due to lowered tenderness values and reduced intramuscular fat content. However, the benefits of using Bos indicus genetics are numerous and undeniable. Herein, we explore how decreases in meat quality in these cattle may be offset by increases in livability. Further, we review the knowledge surrounding beef tenderness and explore the processes occurring during the early events of the transformation of muscle to meat that are different in this biological type and may be altered by stress. Growth rate, calpastatin activity and mitochondrial function will be discussed as they relate to tenderness. The opportunities of using Bos indicus cattle are of great interest to the beef industry worldwide, especially given the pressures for enhancing the overall sustainability and carbon footprint of this sector. Delivering a consistently high-quality product for consumers by exploiting Bos indicus genetics in a more sustainable manner will be proposed. Information on novel factors that influence the conversion of muscle to meat is explored to provide insights into opportunities for maximizing beef tenderization and maturation across all cattle. Exploring the use of Bos indicus cattle in modern production schemes, while addressing the mechanisms undergirding meat tenderness should provide the industry with a path forward for building greater demand through producing higher quality beef.

Optimal conditions for beef tenderization through radiofrequency heating with cold air

High-temperature (15-37°C) aging can shorten the tenderizing time of beef; however, the use of constant temperature heating can lead to microbial spoilage. This study tested radiofrequency (RF) tenderization (RF-T) to find the appropriate conditions for the aging-like effect of beef without microbial spoilage. After subjecting beef to 22 h RF-T with four different cooling temperatures (15, 5, -10, and -20°C), the proliferated aerobic bacteria on the surface showed a concentration of 6-6.2 log CFU/g at -10 and -20°C, lower than 7-7.5 log CFU/g at 15 and 5°C. When beef was treated with 25 W/kg RF heating power for 48 h RF-T, the estimated reduction rate of the sliced shear force (SSF) and the increase rate of glutamic acid based on the weight before RF-T were 22.6% and 1.51-fold, which were greater than 19.6% and 1.37-fold with 20 W/kg, and 11.0% and 1.11-fold with 15 W/kg. The optimal specific RF heating power was calculated as 30 W/kg from the results' extrapolation. When processed for 48 h under optimal conditions (30 W/kg specific RF heating power, -20°C cooling air), the tenderization rate and the increased rates of free amino acids based on the weight before RF-T of beef reached over 20% and 1.5-fold with 5.22 log CFU/g aerobic bacteria, which was lesser than the Korean regulation value of 6.7 log CFU/g (5 × 106  CFU/g). Therefore, RF-T could be proposed as a promising high-temperature tenderization method with lowered risk of microbial spoilage. PRACTICAL APPLICATION: We showed that lowering the chamber temperature during RF-T was effective in surface drying and inhibiting aerobic bacteria. RF-T for 24-48 h with 30 W/kg specific RF heating power had an aging-like effect given tenderization and increase in FAAs. Moreover, by providing the matching circuit and impedance during RF-T, this method could be industrially reproducible.

Modification-Specific Proteomic Analysis Reveals Cysteine S-Nitrosylation Mediated the Effect of Preslaughter Transport Stress on Pork Quality Development

This study aimed to explore the effects of preslaughter transport stress on protein S-nitrosylation levels and S-nitrosylated proteome in post-mortem pork longissimus thoracis (LT) muscle. Pigs (N= 16) were randomly divided into 3 h transport (high-stress group, HS) and 3 h transport followed by 3 h resting treatments (low-stress control group, LS). Results demonstrated that high transport stress levels induced nitric oxide (NO) overproduction by promoting NO synthase (NOS) activity and neuronal NOS (nNOS) expression, which thereby notably increased protein S-nitrosylation levels in post-mortem muscle (p < 0.05). Proteomic analysis indicated that 133 S-nitrosylation-modified cysteines belonging to 85 proteins were significantly differential, of which 101 cysteines of 63 proteins were higher in the HS group (p < 0.05). Differential proteins including cytoskeletal and calcium-handling proteins, glycolytic enzymes, and oxidoreductase were mainly involved in the regulation of muscle contraction and energy metabolism that might together mediate meat quality development. Overall, this study provided direct evidence for changes in S-nitrosylation levels and proteome in post-mortem muscle in response to preslaughter transport stress and revealed the potential impact of S-nitrosylated proteins on meat quality.

Integrated Analysis of Transcriptome and Metabolome Profiles in the Longissimus Dorsi Muscle of Buffalo and Cattle

Buffalo meat is gaining popularity for its nutritional properties, such as its low fat and cholesterol content. However, it is often unsatisfactory to consumers due to its dark color and low tenderness. There is currently limited research on the regulatory mechanisms of buffalo meat quality. Xinglong buffalo are raised in the tropical Hainan region and are undergoing genetic improvement from draught to meat production. For the first time, we evaluated the meat quality traits of Xinglong buffalo using the longissimus dorsi muscle and compared them to Hainan cattle. Furthermore, we utilized a multi-omics approach combining transcriptomics and metabolomics to explore the underlying molecular mechanism regulating meat quality traits. We found that the Xinglong buffalo had significantly higher meat color redness but lower amino acid content and higher shear force compared to Hainan cattle. Differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) were identified, with them being significantly enriched in nicotinic acid and nicotinamide metabolic and glycine, serine, and threonine metabolic pathways. The correlation analysis revealed that those genes and metabolites (such as: GAMT, GCSH, PNP, L-aspartic acid, NADP+, and glutathione) are significantly associated with meat color, tenderness, and amino acid content, indicating their potential as candidate genes and biological indicators associated with meat quality. This study contributes to the breed genetic improvement and enhancement of buffalo meat quality.

Effects of different protein phosphorylation levels on the tenderness of different ultimate pH beef

This study investigated the relationship between tenderness and protein phosphorylation levels of normal ultimate pH (pHu, 5.4-5.8, NpHu), intermediate pHu (5.8-6.2, IpHu) and high pHu (≥6.2, HpHu) Longissimus lumborum from beef. During 21 d of ageing, the HpHu group had the lowest Warner-Bratzler shear force (WBSF) values, while the IpHu group showed the highest and even after 21 days of ageing still had high levels. In the late stage of the 24 h post-mortem period the faster degradation rate of troponin T and earlier activation of caspase 9 in the HpHu group were the key reasons for the lower WBSF compared with the NpHu and IpHu groups. The activity of caspase 3 cannot explain the tenderness differences between IpHu and HpHu groups, since their activities did not show any difference. At 24 h post-mortem, 17 common differential phosphorylated peptides were detected among pHu groups, of which nine were associated with pHu and WBSF. The higher phosphorylation level of glycogen synthase may have caused the delay of meat tenderization in the IpHu group.

Supplementation of chestnut tannins in diets can improve meat quality and antioxidative capability in Hu lambs

Chestnut tannins (CNT), as a source of hydrolyzable tannins, positively affect the antioxidant status of livestock. In the current study, 90 male Hu lambs were used to investigate the effect of dietary CNT intake on growth performance, nutrient digestibility, meat quality and oxidative stability, rumen microbial, and the transcriptomes of muscle and liver. A completely randomized design with three CNT intake levels (0, 0.3%, and 0.6%) was used. Rumen microbial and nutrient digestibility were not significantly altered by CNT intake. Diets with 0.3% CNT intake significantly reduced the shear force, yellowness at 24 h, and C20:2 polyunsaturated fatty acids of lamb meat and malondialdehyde in serum and longissimus thoracis (LT) muscle. Meanwhile, the 0.3% CNT diet significantly increased average daily gain during the 1- 21 days and 64- 90 days, dry matter intake during the 1- 21 days, the slaughter weight, and liver index of lambs. The 0.3% CNT diet significantly increased C26:0 saturated fatty acids, total antioxidant capacity, glutathione peroxidase, superoxide dismutase, and catalase in LT muscle. The meat shelf life of 0.3% CNT and 0.6% CNT groups was prolonged by 8.7 h and 5.4 h, respectively. Transcriptomic analysis revealed that CNT supplementation can induce the expression of antioxidant enzyme gene (CAT, SOD1), and the differentially expressed genes were mainly involved in antioxidant activity, transferase activity, and adenosine triphosphate binding. These results suggest that 0.3% CNT intake can relieve the oxidative stress of lambs, and improve the stability of meat color and meat tenderness, due to the enhanced antioxidative capacity.

Matrix metalloproteinase- 9 may contribute to collagen structure modification during postmortem aging of beef

Matrix metalloproteinases (MMPs) are responsible for the turnover of intramuscular connective tissue in live animals. We hypothesize that MMPs may play a role in postmortem aging of beef muscles for the degradation of connective tissues. Four different experiments were performed to: 1) characterize MMP activity during postmortem aging of beef; 2) determine if the native beef MMP can contribute to connective tissue degradation in a simulated standard industry postmortem aging condition; 3) explore approaches to improve the native beef MMP activity and 4) characterize MMP activity in beef from cattle supplemented with supranutritional level of Zn. In experiment 1, MMP was active throughout the entire aging periods (3, 21, 42 and 63 d) for beef muscles Longissimus lumborum, Gluteus medius and Gastrocnemius, and the unknown MMP responsible for the collagen degradation was identified as MMP-9 by Western Blot. In experiment 2 and 3, MMP-9 activity was noticeable in the gels after 42 d of storage in the cooler. Moreover, the addition of ZnCl2 in the model system significantly increased MMP-9 activity when compared to the control (P < 0.01). In experiment 4, Longissimus thoracis from animals supplemented with a supranutritional Zn level had increased Zn availability and MMP-9 activity than those from animals fed with a control diet (P < 0.05). Further research is needed better understand MMP-9 mechanism during postmortem aging of meat. With a better understanding of MMP-9 in the aging process, the beef industry can provide better connective tissue management strategies for lower-quality beef cuts.

Challenges and processing strategies to produce high quality frozen meat

Freezing is an effective means to extend the shelf-life of meat products. However, freezing and thawing processes lead to physical (e.g., ice crystals formation and freezer burn) and biochemical changes (e.g., protein denaturation and lipid oxidation) in meat resulting in loss of quality. Over the last two decades, several attempts have been made to produce thawed meat with qualities similar to that of fresh meat to no avail. This is due to the fact that no single technique exists to date that can mitigate all the quality challenges caused by freezing and thawing. This is further confounded by the consumer perception of frozen meat as lower quality compared to equivalent fresh-never-frozen meat cuts. Therefore, it remains challenging for the meat industry to produce high quality frozen meat and increase consumer acceptability of frozen products. This review aimed to provide an overview of the applications of novel freezing and thawing technologies that could improve the quality of thawed meat including deep freezing, high pressure, radiofrequency, electro-magnetic resonance, electrostatic field, immersion solution, microwave, ohmic heating, and ultrasound. This review will also discuss the development in processing strategies such as optimising the ageing of meat pre- or post-freezing, and the integration of freezing and thawing in one process/regime to collapse the difference in quality between thawed meat and fresh-never-frozen equivalents.

Aging mechanism for improving the tenderness and taste characteristics of meat

Tenderness and taste characteristics of meat are the key determinants of the meat choices of consumers. This review summarizes the contemporary research on the molecular mechanisms by which postmortem aging of meat improves the tenderness and taste characteristics. The fundamental mechanism by which postmortem aging improves the tenderness of meat involves the operation of the calpain system due to apoptosis, resulting in proteolytic enzyme-induced degradation of cytoskeletal myofibrillar proteins. The improvement of taste characteristics by postmortem aging is mainly explained by the increase in the content of taste-related peptides, free amino acids, and nucleotides produced by increased hydrolysis activity. This review improves our understanding of the published research on tenderness and taste characteristics of meat and provides insights to improve these attributes of meat through postmortem aging.

Impact of sampling location and aging on the Longissimus thoracis et lumborum muscle proteome of dry-aged beef

This study aimed to explore the differences in the proteome and molecular pathways between two sampling locations (external, internal) of bovine Longissimus thoracis et lumborum (LTL) muscles at 0, 21, and 28 days of dry-aging (i.e. 3, 24, and 31 days post-mortem). It further assessed the impact of post-mortem aging on the meat proteome changes and the biological processes at interplay. Proteins related to defence response to bacterium and regulation of viral entry into host cell were identified to be more abundant on the external location before dry-aging, which may be associated to the oxidative conditions and microbial activity to which post-mortem muscle is exposed during dressing, chilling, and/or quartering of the carcasses. This highlights the relevance of sampling from interior tissues when searching for meat quality biomarkers. As dry-aging progressed, the meat proteome and related biological processes changed differently between sampling locations; proteins related to cell-cell adhesion and ATP metabolic processes pathways were revealed in the external location at 21 and 28 days, respectively. On the other hand, the impact of aging on the proteome of the interior meat samples, evidenced that muscle contraction and structure together with energy metabolism were the major pathways driving dry-aging. Additionally, aging impacted other pathways in the interior tissues, such as regulation of calcium import, neutrophil activation, and regeneration. Overall, the differences in the proteome allowed discriminating the three dry-aging times, regardless of the sampling location. Several proteins were proposed for validation as robust biomarkers to monitor the aging process (tenderization) of dry-aged beef: TTN, GRM4, EEF1A1, LDB3, CILP2, TNNT3, GAPDH, SERPINI1, and OMD.

Effects of dietary methionine supplementation from different sources on growth performance and meat quality of barrows and gilts

Methionine is indispensable for growth and meat formation in pigs. However, it is still unclear that increasing dietary sulphur-containing amino acid (SAA) levels using different methionine sources affects the growth performance and meat quality of barrows and gilts. To investigate this, 144 pigs (half barrows and half gilts) were fed the control (100% SAA, CON), DL-Methionine (125% SAA, DL-Met)-supplemented, or OH-Methionine (125% SAA, OH-Met)-supplemented diets during the 11-110 kg period. The results showed that plasma methionine levels varied among treatments during the experimental phase, with increased plasma methionine levels observed following increased SAA consumption during the 25-45 kg period. In contrast, pigs fed the DL-Met diet had lower plasma methionine levels than those fed the CON diet (95-110 kg). Additionally, gilts fed the DL-Met or OH-Met diets showed decreased drip loss in longissimus lumborum muscle (LM) compared to CON-fed gilts. OH-Met-fed gilts had higher pH45min values than those fed the CON or DL-Met diets, whereas OH-Met-fed barrows had higher L45min values than those fed the CON or DL-Met diets. Moreover, increased consumption of SAA, regardless of the methionine source, tended to decrease the shear force of the LM in pigs. In conclusion, this study indicates that increasing dietary levels of SAA (+25%) appeared to improve the meat quality of gilts by decreasing drip loss and increasing meat tenderness.

Different nutritional systems influence the tenderness and lipid oxidation of ewe lamb meat without altering gene expression

Feeding is a determining factor in the various characteristics of sheep meat and animal performance, the objectives were to evaluate the effect of supplementation of ewe lambs finished in different nutritional planes on the gene expression of CASP3, CAPN1, CAPN2 and CAST and its possible association with meat quality. Samples of the Longissimus lumborum muscle of 24 ewe lambs were used, distributed in 3 groups (n=8): P (pasture), PS (pasture and supplement) and F (feedlot). Physicochemical analyses were performed for centesimal analysis, pH, lipid oxidation, Warner-Bratzler shear force and RT-qPCR for the analysis of relative gene expression of the following genes: CASP3, CAPN1, CAPN2 and CAST. There is an increase in daily weight gain and ethereal extract values in the meat of confined animals, due to the greater energy intake in the nutrition of these animals. Animals kept only on pasture have lower lipid oxidation in meat than other treatments because of the lower percentage of lipids. The Warner-Bratzler shear force is considerably higher in the meat of animals kept only on pasture but is still considered tender. The different nutritional systems do not interfere with the gene expression of CASP3, CAPN1, CAPN2 and CAST in ewe lambs.

Distribution and Degradation of Pork Filamin during Postmortem Aging

The filamin C (FLNC) was hypothesized to be colocalized with its certain binding partners in pork tissues and calpain as well as caspase was assumed responsible for the postmortem degradation of FLNC. Therefore, the specific distribution of pork FLNC and its degradation pattern during postmortem aging were investigated in this study. The longissimus thoracis muscles from 12 pigs were removed from the carcasses and then aged at 4 °C for 1, 6, 12, 24, 72, and 168 h, respectively. The FLNC signals appeared to localize in subsarcolemmal areas by cross-sectional images, while the localization was found surrounding the myofibrils at the level of the Z-discs in longitudinal sections. FLNC displayed a highly overlapped spatial colocalization with actin or integrin. Western blot results showed that the intact 290 kDa FLNC was rapidly degraded to produce an approximately 280 kDa band. An almost overlapped distribution pattern was observed between FLNC and μ-calpain or caspase-3 in porcine skeletal muscle cells. Moreover, both the μ-calpain inhibitor and the caspase-3 inhibitor could inhibit the degradation of FLNC in porcine LT muscles during postmortem aging.

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.

Effect of Marinating in Dairy-Fermented Products and Sous-Vide Cooking on the Protein Profile and Sensory Quality of Pork Longissimus Muscle

The aim of the study was to evaluate the effect of marinating (3 or 6 days) in kefir (KE), yogurt (YO) and buttermilk (BM) and sous-vide cooking (SV) at 60 or 80 °C on changes in the protein profile of pork in relation to its sensory quality. In the marinated raw meat, an increased share of some fractions of myofibrillar and cytoskeletal proteins and calpains were found. The greatest degradation of proteins, regardless of time, was caused by marinating in YO and KE and cooking SV at 80 °C. The lowest processing losses were in samples marinated in KE and YO and cooked SV at 60 °C, with marinating time having no significant effect. The odor, flavor, tenderness and juiciness of meat marinated in BM was better than in KE and YO. Meat marinated and cooked SV at 60 °C was rated better by the panelists. Changes in proteins significantly affect the formation of meat texture, tenderness and juiciness, which confirms the correlations. This is also reflected in the sensory evaluation. During the process of marinating and cooking meat, protein degradation should be taken into account, which can be a good tool for shaping the sensory quality of cooked pork.

Unlocking the potential of stem cells: Their crucial role in the production of cultivated meat

Cellular agriculture is an emerging research field of agribiotechnology that aims to produce agricultural products using stem cells, without sacrificing animals or cultivating crops. Cultivated meat, as a representative cellular product of cellular agriculture, is being actively researched due to global food insecurity, environmental, and ethical concerns. This review focuses on the application of stem cells, which are the seeds of cellular agriculture, for the production of cultivated meat, with emphasis on deriving and culturing muscle and adipose stem cells for imitating fresh meat. Establishing standards and safety regulations for culturing stem cells is crucial for the market entry of cultured muscle tissue-based biomaterials. Understanding stem cells is a prerequisite for creating reliable cultivated meat and other cellular agricultural biomaterials. The techniques and regulations from the cultivated meat industry could pave the way for new cellular agriculture industries in the future.

Effects of mitochondria on postmortem meat quality: characteristic, isolation, energy metabolism, apoptosis and oxygen consumption

Meat quality holds significant importance for both consumers and meat producers. Various factors influence meat quality, and among them, mitochondria play a crucial role. Recent studies have indicated that mitochondria can sustain their functions and viability for a certain duration in postmortem muscles. Consequently, mitochondria have an impact on oxygen consumption, energy metabolism, and apoptotic processes, which in turn affect myoglobin levels, oxidative stress, meat tenderness, fat oxidation, and protein oxidation. Ultimately, these factors influence the color, tenderness, and flavor of meat. However, there is a dearth of comprehensive summaries addressing the effects of mitochondria on postmortem muscle physiology and meat quality. Therefore, this review aims to describe the characteristics of muscle mitochondria and their potential influence on muscle. Additionally, a suitable method for isolating mitochondria is presented. Lastly, the review emphasizes the regulation of oxygen consumption, energy metabolism, and apoptosis by postmortem muscle mitochondria, and provides an overview of relevant research and recent advancements. The ultimate objective of this review is to elucidate the underlying mechanisms through which mitochondria impact meat quality.

Flavor evolution of normal- and low-fat Chinese sausage during natural fermentation

This work compared the flavor evolution of normal-fat (NF) with that of low-fat (LF) Chinese sausage during natural fermentation. Higher degree of lipid oxidation occurred in NF sausages, resulting in its faster formation of stable volatile profiles. Faster formation of esters occurred in NF sausage in the initial 10 days, whereas prolonged fermentation reduced the level of ethyl lactate-M, ethyl heptanoate, ethyl hexanoate-D and ethyl pentanoate-D. Gradual reduction of alcohols was observed in both groups, and surge in aldehydes occurred in LF samples during day 20-30 period. Faster formation of taste characteristics and larger amount of 2-methylfuran as well as 2,3-dimethylpyrazine were found in LF sausages, since more free amino acids were liberated in LF sausages. Umami and aftertaste tastes formed in the first 20 days, whereas prolonged fermentation reduced these favorable taste. These results highlight that the choice of proper fermentation duration should largely depend on the fat content in Chinese sausages.

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.

Effects of apoptotic factor levels on palatability variation during postmortem aging of Holstein longissimus thoracis muscles classified as Warner-Bratzler shear force change value

This study compared the caspase levels and myofibrillar protein degradation of longissimus thoracis muscles between the two groups with varying extents of tenderization during postmortem aging to investigate the cause of tenderness variation between aged beef from Holstein-Friesian steers. The change value (CV) of Warner-Bratzler shear force (WBS) was determined as the difference in WBS between 0 and 14 d of aging. The higher change (HC) value group exhibited lower WBS and higher initial tenderness values than the lower change (LC) value group aged 14 and 28 d (P < 0.05), even though there was no difference between the CV groups aged 0 d (P > 0.05). The higher tenderness improvement in the HC group at 14 d might be related to the lower cytochrome C and caspase values and higher degradation of desmin and troponin T compared to the LC group (P < 0.05).