• Animal Bioscience
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• v.36 no.2_spc
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• pp.374-384
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• 2023

Skeletal muscle metabolism regulates homeostatic balance in animals. The metabolic impact persists even after farm animal skeletal muscle is converted to edible meat through postmortem rigor mortis and aging. Muscle metabolites resulting from animal growth and postmortem storage have a significant impact on meat quality, including flavor and color. Metabolomics studies of postmortem muscle aging have identified metabolisms that contain signatures inherent to muscle properties and the altered metabolites by physiological adaptation, with glycolysis as the pivotal metabolism in postmortem aging. Metabolomics has also played a role in mining relevant postmortem metabolisms and pathways, such as the citrate cycle and mitochondrial metabolism. This leads to a deeper understanding of the mechanisms underlying the generation of key compounds that are associated with meat quality. Genetic background, feeding strategy, and muscle type primarily determine skeletal muscle properties in live animals and affect post-mortem muscle metabolism. With comprehensive metabolite detection, metabolomics is also beneficial for exploring biomarker candidates that could be useful to monitor meat production and predict the quality traits. The present review focuses on advances in farm animal muscle metabolomics, especially postmortem muscle metabolism associated with genetic factors and muscle type.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.8
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• pp.1172-1185
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• 2019

Objective: Meat quality attributes in postmortem muscle tissues depend on skeletal muscle metabolites. The objective of this study was to determine the key metabolic compounds and pathways that are associated with postmortem aging and beef quality in Japanese Black cattle (JB; a Japanese Wagyu breed with highly marbled beef). Methods: Lean portions of Longissimus thoracis (LT: loin) muscle in 3 JB steers were collected at 0, 1, and 14 days after slaughter. The metabolomic profiles of the samples were analyzed by capillary electrophoresis time-of-flight mass spectrometry, followed by statistical and multivariate analyses with bioinformatics resources. Results: Among the total 171 annotated compounds, the contents of gluconic acid, gluconolactone, spermidine, and the nutritionally vital substances (choline, thiamine, and nicotinamide) were elevated through the course of postmortem aging. The contents of glycolytic compounds increased along with the generation of lactic acid as the beef aging progressed. Moreover, the contents of several dipeptides and 16 amino acids, including glutamate and aromatic and branched-chain amino acids, were elevated over time, suggesting postmortem protein degradation in the muscle. Adenosine triphosphate degradation also progressed, resulting in the generation of inosine, xanthine, and hypoxanthine via the temporal increase in inosine 5'-monophosphate. Cysteine-glutathione disulfide, thiamine, and choline increased over time during the postmortem muscle aging. In the Kyoto encyclopedia of genes and genomes database, a bioinformatics resource, the postmortem metabolomic changes in LT muscle were characterized as pathways mainly related to protein digestion, glycolysis, citric acid cycle, pyruvate metabolism, pentose phosphate metabolism, nicotinamide metabolism, glycerophospholipid metabolism, purine metabolism, and glutathione metabolism. Conclusion: The compounds accumulating in aged beef were shown to be nutritionally vital substances and flavor components, as well as potential useful biomarkers of aging. The present metabolomic data during postmortem aging contribute to further understanding of the beef quality of JB and other breeds.

• Journal of Animal Science and Technology
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• v.65 no.6
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• pp.1151-1168
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• 2023

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.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.2
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• pp.254-261
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• 2017

Objective: The effects of aging and freezing/thawing sequence on color, physicochemical, and enzymatic characteristics of two beef muscles (Mm. gluteus medius, GM and biceps femoris, BF) were evaluated. Methods: Beef muscles at 3 d postmortem were assigned to four different combinations of aging and freezing/thawing sequence as follows; aging at $2^{\circ}C$ for 3 wk (A3, never-frozen control), freezing at $-28^{\circ}C$ for 2 wk then thawing (F2, frozen/thawed-only), aging at $2^{\circ}C$ for 3 wk, freezing at $-28^{\circ}C$ for 2 wk then thawing (A3F2), and freezing at $-28^{\circ}C$ for 2 wk, thawing then further aging at $2^{\circ}C$ for 3 wk (F2A3). Results: No significant interactions between different aging/freezing/thawing treatments and muscle type on all measurements were found. Postmortem aging, regardless of aging/freezing/thawing sequence, had no impact on color stability of frozen/thawed beef muscles (p<0.05). F2A3 resulted in higher purge loss than F2 and A3F2 treatments (p<0.05). A3F2 and F2A3 treatments resulted in lower shear force of beef muscles compared to F2 (p<0.05). Although there was no significant difference in glutathione peroxidase (GSH-Px) activity, F2A3 had the highest ${\beta}-N-acetyl$ glucominidase (BNAG) activity in purge, but the lowest BNAG activity in muscle (p<0.05). GM muscle exhibited higher total color changes and purge loss, and lower GSH-Px activity than BF muscle. Conclusion: The results from this present study indicate that different combinations of aging/freezing/thawing sequence would result in considerable impacts on meat quality attributes, particularly thaw/purge loss and tenderness. Developing a novel freezing strategy combined with postmortem aging will be beneficial for the food/meat industry to maximize its positive impacts on tenderness, while minimizing thaw/purge loss of frozen/thawed meat.

• Animal Bioscience
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• v.36 no.3
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• pp.506-520
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• 2023

Objective: Japanese Brown (JBR) cattle, especially the Kochi (Tosa) pedigree (JBRT), is a local breed of moderately marbled beef. Despite the increasing demand, the interbreed differences in muscle metabolites from the highly marbled Japanese Black (JBL) beef remain poorly understood. We aimed to determine flavor-related metabolites and postmortem metabolisms characteristic to JBRT beef in comparison with JBL beef. Methods: Lean portions of the longissimus thoracis (loin) muscle from four JBRT cattle were collected at 0, 1, and 14 d postmortem. The muscle metabolomic profiles were analyzed using capillary electrophoresis time-of-flight mass spectrometry. The difference in post-mortem metabolisms and aged muscle metabolites were analyzed by statistical and bioinformatic analyses between JBRT (n = 12) and JBL cattle (n = 6). Results: A total of 240 metabolite annotations were obtained from the detected signals of the JBRT muscle samples. Principal component analysis separated the beef samples into three different aging point groups. According to metabolite set enrichment analysis, post-mortem metabolic changes were associated with the metabolism of pyrimidine, nicotinate and nicotinamide, purine, pyruvate, thiamine, amino sugar, and fatty acid; citric acid cycle; and pentose phosphate pathway as well as various amino acids and mitochondrial fatty acid metabolism. The aged JBRT beef showed higher ultimate pH and lower lactate content than aged JBL beef, suggesting the lower glycolytic activity in postmortem JBRT muscle. JBRT beef was distinguished from JBL beef by significantly different compounds, including choline, amino acids, uridine monophosphate, inosine 5'-monophosphate, fructose 1,6-diphosphate, and betaine, suggesting interbreed differences in the accumulation of nucleotide monophosphate, glutathione metabolism, and phospholipid metabolism. Conclusion: Glycolysis, purine metabolism, fatty acid catabolism, and protein degradation were the most common pathways in beef during postmortem aging. The differentially expressed metabolites and the relevant metabolisms in JBRT beef may contribute to the development of a characteristic flavor.

• Food Science of Animal Resources
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• v.40 no.1
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• pp.34-43
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• 2020

The objectives of this study was to compare palatability changes of the longissimus thoracis (LT) and vastus lateralis (VL) muscles of Hanwoo steers from different beef quality grades (1⁺ and 1) during 28 d of wet-aging in order to improve the utilization of the VL muscle as a steak. The VL muscle showed a higher collagen content and a lower intramuscular fat content than the LT muscle (p<0.05). As expected, the Warner-Bratzler shear force value was greater in the LT 1 grade (LT-1) muscle than the LT-1⁺ muscle (p<0.05); whereas no difference was observed between the grades in the VL muscle at 24 h postmortem. Compared to 0 d of aging, tenderness scores significantly increased after 14 and 21 d of aging in the LT and VL muscles, respectively (p<0.05). Additionally, there was no difference in tenderness score between the VL-1⁺ aged for 21 d and the LT-1 at 24 h postmortem, although tenderness score was greater in the LT than the VL at each period (p<0.05). Moreover, the VL-1⁺ steak exhibited a higher tenderness score than the VL-1 steak at 21 and 28 d of aging (p<0.05). On the other hand, the effect of aging time on juiciness and flavor in the VL muscle was somewhat limited unlike the LT muscle. Taken together, the VL muscle requires a longer aging time than the LT muscle to improve consumer preference. Considering the tenderness, using a higher quality grade for aging is more useful in the VL muscle.

• Animal Bioscience
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• v.37 no.2
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• pp.284-294
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• 2024

Objective: Pork is an important source of animal protein in many countries. Subtle physiochemical changes occur during pork postmortem aging. The changes of apoptosis and autophagy in pork at 6 h to 72 h after slaughter were studied to provide evidence for pork quality. Methods: In this article, morphological changes of postmortem pork was observed through Hematoxylin-eosin staining, apoptotic nuclei were observed by TdT-mediated dUTP nick end labeling assay, protein related to apoptosis and autophagy expressions were tested by western blot and LC3 level were expressed according to immunofluorescence assay. Results: In this study, we found the occurrence of apoptosis in postmortem pork, and the process was characterized by nucleus condensation and fragmentation, formation of apoptotic bodies, increase in apoptosis-related Bax/Bcl-2 levels, and activation of caspases. Autophagy reached its peak between 24 and 48 h after slaughter, accompanied by the formation of autophagosomes on the cell membrane and expression of autophagy-related proteins beclin-1, P62, LC3-I, LC3-II, and ATG5. Conclusion: Obvious apoptosis was observed at 12 h and autophagy reached its peak at 48 h. The present work provides the evidence for the occurrence of apoptosis and autophagy during postmortem aging of pork. In conclusion, the apoptosis and autophagy of muscle cells discovered in this study have important implications for pork in the meat industry.

• Food Science of Animal Resources
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• v.36 no.2
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• pp.159-169
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• 2016

Animal muscles are stored for specific period (aging) at refrigerated temperatures, during and after which the living muscles start to convert into meat and thus, attain certain superior properties in the final product. Proteolysis, lipolysis, and oxidation are the major biochemical processes involved during the postmortem aging of meat that affect the tenderness, juiciness, and flavor, as well as sometimes may introduce certain undesirable traits. This review analyzes the role of pre- and post-mortem factors that are important for aging and their effect on the chemical and physical changes in the “dry- and wet-aged meat.” Thus, if the meat processing manufacturers optimize the effects of aging for specific muscles, the palatability, color, and the shelf life of the aged meat products could be significantly enhanced.

• Food Science of Animal Resources
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• v.42 no.5
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• pp.723-743
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• 2022

Beef muscles from mature cows and bulls, especially those originating from the extremities of the carcass, are considered as underutilized due to unsatisfactory palatability. However, beef from culled animals comprises a substantial proportion of the total slaughter in the US and globally. Modern consumers typically favor cuts suitable for fast, dry-heat cookery, thereby creating challenges for the industry to market inherently tough muscles. In general, cull cow beef would be categorized as having a lower extent of postmortem proteolysis compared to youthful carcasses, coupled with a high amount of background toughness. The extent of cross-linking and resulting insolubility of intramuscular connective tissues typically serves as the limiting factor for tenderness development of mature beef. Thus, numerous post-harvest strategies have been developed to improve the quality and palatability attributes, often aimed at overcoming deficiencies in tenderness through enhancing the degradation of myofibrillar and stromal proteins or physically disrupting the tissue structure. The aim of this review is to highlight existing and recent innovations in the field that have been demonstrated as effective to enhance the tenderness and palatability traits of mature beef during the chilling and postmortem aging processes, as well as the use of physical interventions and enhancement.

• Food Science of Animal Resources
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• v.18 no.4
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• pp.292-300
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• 1998

This study was undertaken to determine the influence in the Z-disk domain of titin on the tenderization of meat by the structure change of myofibrillar Z-disks during post-mortem aging. After weakening the structure of Z-disks, the Z-disk region was splitted. As the results, myofibrils were fragmented by mechanical strength. Using indirect immunofluorescence microscopy, we show that the Z-disk domain of titin was disappeared from myofibrils in this period. There phenomenon were also shown by treating myofibrils with a solution containing 0.1mM $Ca^{2+}$. We conclude that change in Z-disk domain of titin is directly effected on the tenderization of meat during post-mortem aging and these change is due to manily calcium ions.