Contribution of mitochondria to postmortem muscle tenderization: a review

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.

Identifying the Potential Apoptotic Metabolites in Postmortem Beef Muscle by Targeted Metabolomics

Apoptotic cells may release specific metabolites to act as messengers during the apoptotic process. This study represents the first attempt to identify potential apoptotic metabolites in postmortem muscle. Ninety potential apoptotic metabolites in beef were selected and analyzed through targeted metabolomics, with 84 of them exhibiting significant differences over the postmortem time. Following the addition of the mitochondria-targeted antiapoptotic agent mitoquinone to postmortem muscle, metabolomic analysis revealed that 73 apoptotic metabolites still underwent significant changes, even against the backdrop of altered apoptosis. Of these 73 apoptotic metabolites, 54 exhibited similar trends at various treatment times with adding mitoquinone, including lipids (6), amino acids (27), nucleosides (11), and carbohydrate and energy metabolism (10). Mitoquinone significantly reduced the levels of most apoptotic metabolites, and inhibition of apoptosis resulted in a significant decrease in the levels of numerous apoptotic metabolites. Consequently, these apoptotic metabolites are considered complementary to apoptosis in postmortem muscle, with their increased levels potentially promoting apoptosis. Noteworthy apoptotic metabolites, such as glycerol 3-phosphate, serine, AMP, ATP, GMP, and creatine, were identified as active signaling molecules that attract and recruit phagocytes during apoptosis, assisting in recognizing apoptotic cells by phagocytes. This study provides, for the first time, insights into potential apoptotic metabolites in postmortem muscle, contributing to a better understanding of meat biochemistry.

New Implications of Metabolites and Free Fatty Acids in Quality Control of Crossbred Wagyu Beef during Wet Aging Cold Storage

Efficient cold-chain delivery is essential for maintaining a sustainable global food supply. This study used metabolomic analysis to examine meat quality changes during the "wet aging" of crossbred Wagyu beef during cold storage. The longissimus thoracic (Loin) and adductor muscles (Round) of hybrid Wagyu beef, a cross between the Japanese Black and Holstein-Friesian breeds, were packaged in vacuum film and refrigerated for up to 40 days. Sensory evaluation indicated an increase in the umami and kokumi taste owing to wet aging. Comprehensive analysis using gas chromatography-mass spectrometry identified metabolite changes during wet aging. In the Loin, 94 metabolites increased, and 24 decreased; in the Round, 91 increased and 18 decreased. Metabolites contributing to the umami taste of the meat showed different profiles during wet aging. Glutamic acid increased in a cold storage-dependent manner, whereas creatinine and inosinic acid degraded rapidly even during cold storage. In terms of lipids, wet aging led to an increase in free fatty acids. In particular, linoleic acid, a polyunsaturated fatty acid, increased significantly among the free fatty acids. These results provide new insight into the effects of wet aging on Wagyu-type beef, emphasizing the role of free amino acids, organic acids, and free fatty acids generated during cold storage.