Biomolecular Interactions Governing Fresh Meat Color in Post-mortem Skeletal Muscle: A Review

Lipidome and metabolome profiling of longissimus lumborum beef with different ultimate pH and postmortem aging

The objective of this exploratory study was to assess the changes on lipidome and metabolome profiling of Longissimus lumborum bull muscle with different ultimate pH (pHu) and aging periods. The bull muscles classified as normal, intermediate, or high pHu were collected from a Brazilian commercial slaughterhouse, cut into steaks, individually vacuum-packaged, and aged for 3 days (3-d) or 21 days (21-d) at 2 °C. Muscle extracts were analyzed for the profiles of both lipids, by mass spectrometry (via direct flow-injection), and metabolites, by nuclear magnetic resonance, with downstream multivariate data analysis. As major results, pairwise comparisons identified C12:0 and C14:0 acylcarnitines as potential biomarkers of the intermediate pHu-muscle, which are related to lipid catabolism for alternative energy metabolism and indicate less protein breakage postmortem. Interestingly, the concentration of arginine at early postmortem aging (3-d) may influence the previously reported improved tenderness in normal and high pHu-muscles. Moreover, upregulation of fumarate, formate, and acetate with increased pHu muscle at 21-d aging indicate more intense tricarboxylic acid cycle, amino acid degradation, and pyruvate oxidation by reactive oxygen species, respectively. These three compounds (fumarate, formate, and acetate) discriminated statistically the muscle with high pHu at 21-d aging. The normal pHu-muscle showed higher concentrations of glycogenolysis and glycolysis metabolites, including glucose, mannose, and pyruvate. Hence, our results enhance knowledge of postmortem biochemical changes of beef within different pHu groups aged up to 21 days, which is essential to understand the mechanisms underpinning bull meat quality changes.

Combination of contact ultrasound and infrared radiation for improving the quality and flavor of air-dried beef during hot air drying

Air-dried beef, a traditional dry fermented meat product in China, whose quality is largely influenced by processing conditions. In this study, contact ultrasound (CU) and infrared radiation (IR) were employed to enhance hot air drying (HAD), with an investigation into the mechanisms underlying improvements in quality and flavor. Samples subjected to CU and IR treatments during HAD (CU-IRD) demonstrated superior color (L* = 42.68, a* = 5.05, b* = -3.86) and tenderness (140.59 N) than HAD group, primarily attributed to reduced drying times and alterations in ultrastructure. Analyses utilizing SDS-PAGE and total volatile basic nitrogen (TVB-N) revealed that HAD and CU-HAD resulted in significant protein oxidation (197.85 mg TVB-N/kg and 202.23 mg TVB-N/kg, respectively), while IR treatments were associated with increased thermal degradation of proteins, producing lower molecular weight peptides. Compared with HAD group, the activities of certain lipases and proteases were enhanced by ultrasound and infrared treatments, leading to the release of greater amounts of free fatty acids and flavor amino acids. Furthermore, the thermal effects of infrared and the cavitation effects of ultrasound contributed to increased fat oxidation, amino acid Strecker degradation, and esterification reactions, thereby augmenting the diversity and concentration of volatile flavor compounds, including alkanes, ketones, aldehydes, and esters. These findings indicate that the synergistic application of CU and IR represents a promising strategy for enhancing the quality of air-dried beef.

Effects of sodium lactate injection on meat quality and lactate content in broiler chickens: emphasis on injection method and dosage

This study aims to develop an experimental model of high lactate levels in broilers to mimic the condition of birds under stress or diseases and evaluate its consequent effects on meat quality. The injection sites and dosage effects were compared separately in 2 experiments. Experiment 1 includes 3 injection sites: intraperitoneal injection, intramuscular injection, and subcutaneous injection. Experiment 2 was a dosage experiment based on the results of Experiment 1: sodium lactate intraperitoneal injection group with 1.5, 3, 6 mM concentration. The results showed that injecting sodium lactate intraperitoneally, intramuscularly, or subcutaneously all significantly decreased body weight and breast muscle weight while elevating lactic acid levels in both the blood and breast muscle of broilers. Moreover, all 3 injection methods caused a significant reduction in pH24h and an increase in the shear force value of breast muscle. In addition, dose-response experiments of intraperitoneal injection showed that a concentration of 3 mM and 6 mM were significantly decreased body weight and breast muscle weight in broiler chickens, accompanied by a notable increase in breast muscle lactate content. Compared to the control group, intraperitoneal injections of 1.5 mM, 3 mM, and 6 mM sodium lactate treatments significantly reduced the yellowness values of the breast muscle. As the dose of sodium lactate increased, the shear force value of the breast meat exhibited linear and quadratic increments, while the drip loss decreased linearly. Intraperitoneal injection of 3 mM sodium lactate also significantly reduced the pH24h of broiler breast muscle. In addition, an increased dose of lactate injections up-regulated the glycolytic pathway responsible for endogenous lactate production in the breast muscle by upregulating the expression of phosphofructokinase, pyruvate kinase and lactate dehydrogenase A. In conclusion, intraperitoneal injection of sodium lactate at 3 mM directly increased breast muscle lactate levels, providing a valuable method for establishing a high-level lactate model in poultry.

Investigation of oxygen packaging to maintain beef color stability and microbiology safety after periods of long-term superchilled storage

This study aimed to develop an appropriate modified atmosphere packaging (MAP) system for displayed beef steaks following long-term superchilled (-1 °C) storage. After superchilled storage for 0, 2, 8, or 16 weeks, beef loins were fabricated into steaks and displayed with 20%, 50%, or 80% O2-MAP under chilled conditions. At each storage point, after display for 0, 3, 7, or 10 days, instrumental color, myoglobin redox forms percentage, lipid oxidation, total viable count (TVC), and total volatile basic nitrogen (TVB-N) were evaluated. Meat color stability decreased, with prolonged storage period and display time. When the storage period was within 8 weeks, under all the above MAP conditions, the display time for the beef steaks was up to 10 days. Considering 80% O2-MAP promoted lipid oxidation, 50% and 80% O2-MAP were not recommended for displaying steaks for more than 10 and 7 days respectively after 16 weeks of storage. However, 20%, 50%, or 80% O2-MAP could maintain 3 days of microbial shelf-life according to TVC and TVB-N results. Additionally, after long-term superchilled storage for 16 weeks, the various O2 concentrations had minimal impact on microbiota succession during the MAP display period. Furthermore, beef steaks packaged under various MAP systems exhibited similar microbial compositions, with the dominant bacteria alternating between Lactobacillus and Carnobacterium. This study provided practical guidance for improving beef color stability after long-term superchilled storage.

Changes in meat quality, metabolites and microorganisms of mutton during cold chain storage

During the cold chain storage process, changes in metabolites and microorganisms are highly likely to lead to changes in meat quality. To elucidate the changes in the composition of metabolites and microbiota during cold chain storage of mutton, this study utilized untargeted metabolome and 5R 16S rRNA sequencing analyses to investigate the changes in the longissimus dorsi under different cold chain temperatures (4 °C and -20 °C). With the extension of cold chain storage time, the meat color darkened and the content of C18:2n-6, C20:3n-6, and C23:0 were significantly increased in mutton. In this study, nine metabolites, including 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine, alanylphenylala-nine, indole-3-acrylic acid and the others, were significantly altered during cold chain storage. The abundance of the dominant microorganisms, including Brachymonas, Aeromonas, Corynebacterium and Steroidobacter, was significantly altered. Furthermore, a high correlation was observed between the different metabolites and microorganisms. These findings provide an in-depth understanding of the effects of different cold chain storage temperatures and times on the quality of mutton.

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.

Meat quality and sensory traits in rabbits fed with two different percentages of bovine colostrum

The nutritional, antimicrobial, and antioxidant properties of bovine colostrum (BC) have encouraged its use in animal nutrition as a functional food in recent years. Nonetheless, the potential implications of BC supplementation on meat quality remain to be thoroughly assessed. To address this, thirty-nine New Zealand White rabbits (n = 13/group) were fed different dietary regimens until slaughter.: commercial standard diet for the control group (C) and C with 2.5% and 5% w/w of BC for BC-2.5 and BC-5 groups, respectively. Rabbits were slaughtered at 91 days of age and meat quality, and sensory characteristics were evaluated at days 2 (48 h after slaughter), 5, and 10 of refrigerated storage at 4 °C. The addition of colostrum in the diet resulted in a reduction of the total viable count, albeit only at the highest concentration and at the final detection, whereas for Lactobacillus spp. and Pseudomonas spp., there was little or no effect. The colour coordinates showed no differences between the groups, but they varied over time according to diet. Some differences between groups emerged in the definition of sensory attributes but did not affect the overall liking and overall scores of individual descriptors. These results indicate that the use of colostrum in rabbit feeding does not significantly impart meat quality and sensory attributes, but the potential of this valuable by-product for the food industry needs further investigation.

Unveiling the Genetic Mechanism of Meat Color in Pigs through GWAS, Multi-Tissue, and Single-Cell Transcriptome Signatures Exploration

Meat color traits directly influence consumer acceptability and purchasing decisions. Nevertheless, there is a paucity of comprehensive investigation into the genetic mechanisms underlying meat color traits in pigs. Utilizing genome-wide association studies (GWAS) on five meat color traits and the detection of selection signatures in pig breeds exhibiting distinct meat color characteristics, we identified a promising candidate SNP, 6_69103754, exhibiting varying allele frequencies among pigs with different meat color characteristics. This SNP has the potential to affect the redness and chroma index values of pork. Moreover, transcriptome-wide association studies (TWAS) analysis revealed the expression of candidate genes associated with meat color traits in specific tissues. Notably, the largest number of candidate genes were observed from transcripts derived from adipose, liver, lung, spleen tissues, and macrophage cell type, indicating their crucial role in meat color development. Several shared genes associated with redness, yellowness, and chroma indices traits were identified, including RINL in adipose tissue, ENSSSCG00000034844 and ITIH1 in liver tissue, TPX2 and MFAP2 in lung tissue, and ZBTB17, FAM131C, KIFC3, NTPCR, and ENGSSSCG00000045605 in spleen tissue. Furthermore, single-cell enrichment analysis revealed a significant association between the immune system and meat color. This finding underscores the significance of the immune system associated with meat color. Overall, our study provides a comprehensive analysis of the genetic mechanisms underlying meat color traits, offering valuable insights for future breeding efforts aimed at improving meat quality.

Comparison of muscle fiber characteristics and meat quality between newborn and adult Haimen goats

Goat meat is popular with consumers for its rich nutritional content. Muscle fiber characteristics have been shown to play a crucial role in determining the quantity and quality of meat. However, little is known about the temporal changes in muscle fiber characteristics and meat quality during growth in goats. In this study, muscle fiber type, fiber diameter, fiber cross-sectional area (CSA), glycolytic potential (GP), meat pH, and meat color were analyzed in the gastrocnemius (GAS), gluteus medius (GM), biceps brachii (BB), longissimus lumborum (LL) muscles from newborn (NHMG) and adult (AHMG) Haimen goats. The distribution of type I and type Π fiber in goats is not consistent across the four muscles and undergoes alterations with age. The diameter and CSA of the muscle fibers were similar among the four NHMG muscles. However, in AHMG, the LL muscle had the largest fiber in terms of both diameter and CSA, followed by BB, GM, and GAS muscles. Moreover, the CSA of type Π fibers was higher than that of type I fibers in both NHMG and AHMG. GP values ranged from 90 to 140 umol/g across the muscle and no significant differences were observed. AHMG had a higher pH level and a* value, but lower L* and b* values than NHMG. Overall, our findings enhance our understanding of the changes in muscle fiber type and meat quality during the growth in Haimen goats and provide a basis for future research on the development and transformation of muscle fibers in goats.

The color of fresh pork: Consumers expectations, underlying farm-to-fork factors, myoglobin chemistry and contribution of proteomics to decipher the biochemical mechanisms

The color of fresh pork is a crucial quality attribute that significantly influences consumer perception and purchase decisions. This review first explores consumer expectations and discrimination regarding pork color, as well as an overview of the underlying factors that, from farm-to-fork, contribute to its variation. Understanding the husbandry factors, peri- and post-mortem factors and consumer preferences is essential for the pork industry to meet market demands effectively. This review then delves into current knowledge of pork myoglobin chemistry, its modifications and pork discoloration. Pork myoglobin, which has certain peculiarities comparted to other meat species, plays a weak role in determining pork color, and a thorough understanding of the biochemical changes it undergoes is crucial to understand and improve color stability. Furthermore, the growing role of proteomics as a high-throughput approach and its application as a powerful research tool in meat research, mainly to decipher the biochemical mechanisms involved in pork color determination and identify protein biomarkers, are highlighted. Based on an integrative muscle biology approach, the available proteomics studies on pork color have enabled us to provide the first repertoire of pork color biomarkers, to shortlist and propose a list of proteins for evaluation, and to provide valuable insights into the interconnected biochemical processes implicated in pork color determination. By highlighting the contributions of proteomics in elucidating the biochemical mechanisms underlying pork color determination, the knowledge gained hold significant potential for the pork industry to effectively meet market demands, enhance product quality, and ensure consistent and appealing pork color.

Changes in physical architecture and lipids compounds in skeletal muscle from Pekin duck and Liancheng white duck

As a complex food, meat displays various biochemical properties that are determined to a great extent by physical architecture and lipid metabolites. Pekin duck and Liancheng white duck are elite breeds with distinct characteristics. Here, we explored the development of the muscle fibers from embryonic stage to 10-wk after birth, and muscle fibers grow slowly after 8-wk. We investigated the meat quality, ultrastructure, lipidomics profiling, and lipids spatial distribution of skeletal muscle at 8 wk. Pekin duck has lower Warner-Bratzler shear force (WBSF) (P < 0.05), high intramuscular fat (IMF) (P < 0.01), longer and wider sarcomere, and higher mitochondrial density (P < 0.001). Liancheng white duck with tighter collagen architecture. A total of 950 lipids from 6 lipid classes identified with lipidomics were analyzed, the levels of GP, GL, and PR were significantly higher in Pekin duck (P < 0.05), SL and ST were significantly higher in Liancheng white duck (P < 0.05). There were 333 significantly different lipids (|log2(Fold Change)| ≥ 1 and FDR < 0.05) screened, most lipids distributed in the muscle tissue were uniform, but some specifically distributed in connective tissue. To some extent, the results demonstrate the high lipid deposition capacity of Pekin duck and the high medicinal function of Liancheng white duck. Our study provides new insights into the relationship between skeletal muscle architecture and meat toughness, which increased the knowledge of lipidomic characteristics and provide a basis for duck meat authentication.

Dissociation of ferriheme from oxidized heme proteins and re-reduction of ferriheme to ferroheme are crucial for the formation of zinc protoporphyrin IX in nitrite/nitrate-free dry-cured meat products

Zinc protoporphyrin IX (ZnPP) is the dominant red pigment in nitrate/nitrite-free dry-cured meat products such as Parma ham, and it is considered to be a potential alternative to nitrite/nitrate for reddening dry-cured meat products. Ferroheme and ferriheme dissociated from heme proteins in meat were proposed as substrates to form ZnPP. To elucidate their specific formation mechanism, nitric oxide, carbon monoxide, and azide were used to stable heme in heme proteins. The exogenous hemoglobin derivatives bound with these ligands showed lower heme dissociation compared with exogenous oxyhemoglobin and did not contribute to ZnPP formation. Meanwhile, azide inhibited almost all ZnPP formation by binding to ferriheme, indicating ferriheme dissociation from oxidized heme proteins, predominantly for ZnPP formation. Free ferriheme could not be converted to ZnPP unless it was reduced to ferroheme. Overall, ferriheme dissociated from oxidized heme proteins was the dominant substrate for conversion to ZnPP after re-reduction to ferroheme.

Forensic Proteomics for the Discovery of New post mortem Interval Biomarkers: A Preliminary Study

Estimating the time since death (post mortem interval, PMI) represents one of the most important tasks in daily forensic casework. For decades, forensic scientists have investigated changes in post mortem body composition, focusing on different physical, chemical, or biological aspects, to discover a reliable method for estimating PMI; nevertheless, all of these attempts remain unsuccessful considering the currently available methodical spectrum characterized by great inaccuracies and limitations. However, recent promising approaches focus on the post mortem decomposition of biomolecules. In particular, significant advances have been made in research on the post mortem degradation of proteins. In the present study, we investigated early post mortem changes (during the first 24 h) in the proteome profile of the pig skeletal muscle looking for new PMI specific biomarkers. By mass spectrometry (MS)-based proteomics, we were able to identify a total of nine potential PMI biomarkers, whose quantity changed constantly and progressively over time, directly or inversely proportional to the advancement of post mortem hours. Our preliminary study underlines the importance of the proteomic approach in the search for a reliable method for PMI determination and highlights the need to characterize a large number of reliable marker proteins useful in forensic practice for PMI estimation.

In-depth characterization of the sarcoplasmic muscle proteome changes in lambs fed with hazelnut skin by-products: Relationships with meat color

This study investigated the effect of agro-industrial hazelnut skin by-products supplementation on lamb meat color variation and the changes in the sarcoplasmic muscle proteome during post-mortem storage (0, 4 and 7 days). Gel-based proteomics and bioinformatics approaches were applied to better understand the potential role of feeding strategies in modulating the mechanisms underpinning meat discoloration and post-mortem changes during storage. Therefore, twenty-two Valle del Belice male lambs were randomly assigned to two dietary treatments: control (C), lambs fed with maize-barley diet, and hazelnut skin (H), lambs fed hazelnut skin by-product as maize partial replacer in the concentrate diet. Hazelnut dietary treatment led to better lamb meat color stability as evidenced by the lowest decrease in redness and saturation index values. Proteomics and bioinformatics results revealed changes in the abundance of 41 proteoforms, which were mainly involved in glycolytic processes, responses to oxidative stress, and immune and endocrine system. The proteins allowed revealing interconnected pathways to be behind meat color variation as a consequence of using hazelnut skin by-products to sustainable feed lamb. The proteins can be used as potential predictors of lamb meat color variation. Accordingly, the regression equations developed in this paper revealed triosephosphate isomerase (TPI1) as a reliable candidate biomarker of color stability in lamb meat. SIGNIFICANCE: The use of agro-industrial by-products in animal feeding can be a potential sustainable strategy to reduce the environmental impacts of the food production chain and consequently improve animal welfare and product quality. The inclusion of hazelnut skin by-products in the animal's diet, due to the high concentration of polyphenols, represents an effective strategy to improve the oxidative stability of meat, with significant implications on color. The use of proteomics combined with bioinformatics on the sarcoplasmic proteome is a powerful approach to decipher the underlying mechanism. Accordingly, this approach allowed in this trial a deeper understanding of the molecular mechanisms involved in the post-mortem processes through the discovery of several biological pathways linked with lamb meat color variation. Glycolysis, followed by responses to oxidative stress, and other proteins involved in the immune and endocrine system were found as the major interconnected pathways that could act as potential predictors of lamb meat color stability. Candidate proteins biomarkers were further revealed in this study to be related with multiple meat color traits.

Effects of dietary L-Citrulline supplementation on growth performance, meat quality, and fecal microbial composition in finishing pigs

Gut microbiota play an important role in the gut ecology and development of pigs, which is always regulated by nutrients. This study investigated the effect of L-Citrulline on growth performance, carcass characteristics, and its potential regulatory mechanism. The results showed that 1% dietary L-Citrulline supplementation for 52 days significantly increased final weight, liveweight gain, carcass weight, and average backfat and markedly decreased drip loss (p < 0.05) of finishing pigs compared with the control group. Microbial analysis of fecal samples revealed a marked increase in α-diversity and significantly altered composition of gut microbiota in finishing pigs in response to L-Citrulline. In particular, these altered gut microbiota at the phylum and genus level may be mainly involved in the metabolic process of carbohydrate, energy, and amino acid, and exhibited a significant association with final weight, carcass weight, and backfat thickness. Taken together, our data revealed the potential role of L-Citrulline in the modulation of growth performance, carcass characteristics, and the meat quality of finishing pigs, which is most likely associated with gut microbiota.

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.

Meat color and iridescence: Origin, analysis, and approaches to modulation

Meat color is an important aspect for the meat industry since it strongly determines the consumers' perception of product quality and thereby significantly influences the purchase decision. Emergence of new vegan meat analogs has renewed interest in the fundamental aspects of meat color in order to replicate it. The appearance of meat is based on a complex interplay between the pigment-based meat color from myoglobin and its chemical forms and light scattering from the muscle's microstructure. While myoglobin biochemistry and pigment-based meat color have been extensively studied, research on the physicochemical contribution of light scattering to meat color and the special case of structural colors causing meat iridescence has received only little attention. Former review articles focused mostly on the biochemical or physical mechanisms rather than the interplay between them, in particular the role that structural colors play. While from an economic point of view, meat iridescence might be considered negligible, an enhanced understanding of the underlying mechanisms and the interactions of light with meat microstructures can improve our overall understanding of meat color. Therefore, this review discusses both biochemical and physicochemical aspects of meat color including the origin of structural colors, highlights new color measurement methodologies suitable to investigate color phenomena such as meat iridescence, and finally presents approaches to modulate meat color in terms of base composition, additives, and processing.

Age-Related Changes in Post-Translational Modifications of Proteins from Whole Male and Female Skeletal Elements

One of the key questions in forensic cases relates to some form of age inference, whether this is how old a crime scene is, when in time a particular crime was committed, or how old the victim was at the time of the crime. These age-related estimations are currently achieved through morphological methods with varying degrees of accuracy. As a result, biomolecular approaches are considered of great interest, with the relative abundances of several protein markers already recognized for their potential forensic significance; however, one of the greatest advantages of proteomic investigations over genomics ones is the wide range of post-translational modifications (PTMs) that make for a complex but highly dynamic resource of information. Here, we explore the abundance of several PTMs including the glycosylation, deamidation, and oxidation of several key proteins (collagen, fetuin A, biglycan, serum albumin, fibronectin and osteopontin) as being of potential value to the development of an age estimation tool worthy of further evaluation in forensic contexts. We find that glycosylations lowered into adulthood but deamidation and oxidation increased in the same age range.

Metabolome-Based Genome-Wide Association Study of Duck Meat Leads to Novel Genetic and Biochemical Insights

Meat is among the most consumed foods worldwide and has a unique flavor and high nutrient density in the human diet. However, the genetic and biochemical bases of meat nutrition and flavor are poorly understood. Here, 3431 metabolites and 702 volatiles in 423 skeletal muscle samples are profiled from a gradient consanguinity segregating population generated by Pekin duck × Liancheng duck crosses using metabolomic approaches. The authors identified 2862 metabolome-based genome-wide association studies (mGWAS) signals and 48 candidate genes potentially modulating metabolite and volatile levels, 79.2% of which are regulated by cis-regulatory elements. The level of plasmalogen is significantly associated with TMEM189 encoding plasmanylethanolamine desaturase 1. The levels of 2-pyrrolidone and glycerophospholipids are regulated by the gene expression of AOX1 and ACBD5, which further affects the levels of volatiles, 2-pyrrolidone and decanal, respectively. Genetic variations in GADL1 and CARNMT2 determine the levels of 49 metabolites including L-carnosine and anserine. This study provides novel insights into the genetic and biochemical basis of skeletal muscle metabolism and constitutes a valuable resource for the precise improvement of meat nutrition and flavor.

Antioxidant Properties of Cranberry Leaves and Walnut Meal and Their Effect on Nutritional Quality and Oxidative Stability of Broiler Breast Meat

Dietary sources of bioactive compounds in animal diets, are the natural way to produce animal food products with improved nutritional quality. The present study aimed to test the hypothesis of a synergistic effect of bioactive compounds of cranberry leaf powder and walnut meal on the nutritional quality and antioxidant compounds of broiler meat. An experiment was conducted on 160 COBB 500 broiler chickens, housed in an experimental hall with permanent wood shave litter in boxes of 3 m². The six dietary treatments were based on corn and soybean meal; three experimental groups were fed diets supplemented with cranberry leaves (CLs) with three inclusion rates (0% in the control group and CL 1% and CL 2%); two experimental groups were fed diets supplemented with walnut meal (WM) with two inclusion rates (0% and WM 6%); and two groups were fed diets with a combination of the selected supplements (CL 1% WM 6% and CL 2% WM 6%). The results show that the experimental groups registered higher concentrations of copper and iron compared with the control group. An antagonist effect was noticed on lipophilic compounds, and the lutein and zeaxanthin concentrations presented a dose-dependent increasing effect under CL influence, while vitamin E concentrations decreased in the same manner. The dietary WM positively influenced vitamin E deposits on breast tissue. The dietary supplements did not produce any effect on the primary oxidation products, but the secondary products were influenced, and the maximum effect on the TBARS values were recorded for the dietary combination of CL 1% and WM 6%.

Chitosan Coating Functionalized with Flaxseed Oil and Green Tea Extract as a Bio-Based Solution for Beef Preservation

Ecological and safe packaging solutions arise as pivotal points in the development of an integrated system for sustainable meat production. The aim of this study was to assess the effect of a combined chitosan (Ch) + green tea extract (GTE) + essential oil (thyme oil, TO; flaxseed oil, FO; or oregano oil, OO) coating on the safety and quality of vacuum-packaged beef during storage at 4 °C. An optimized bio-based coating formulation was selected (2% Ch + 2% GTE + 0.1% FO) to be applied to three fresh beef cuts (shoulder, Sh; knuckle, Kn; Striploin, St) based on its pH (5.8 ± 0.1), contact angle (22.3 ± 0.4°) and rheological parameters (viscosity = 0.05 Pa.s at shear rate > 20 s^-1). Shelf-life analysis showed that the Ch-GTE-FO coating delayed lipid oxidation and reduced total viable counts (TVC) and Enterobacteriaceae growth compared with uncoated beef samples over five days. In addition, Ch-GTE-FO coating decreased total color changes of beef samples (e.g., ∆E* = 9.84 and 3.94, for non-coated and coated Kn samples, respectively) for up to five days. The original textural parameters (hardness, adhesiveness and springiness) of beef cuts were maintained during storage when Ch-GTE-FO coating was applied. Based on the physicochemical and microbial characterization results, the combination of the Ch-GTE-FO coating developed was effective in preserving the quality of fresh beef cuts during refrigerated storage along with vacuum packaging.

Molecular Changes of Meat Proteins During Processing and Their Impact on Quality and Nutritional Values

Meats are rich in lipids and proteins, exposing them to rapid oxidative changes. Proteins are essential to the human diet, and changes in the structure and functional attributes can greatly influence the quality and nutritional value of meats. In this article, we review the molecular changes of proteins during processing, their impact on the nutritional value of fresh and processed meat, the digestibility and bioavailability of meat proteins, the risks associated with high meat intake, and the preventive strategies employed to mitigate these risks. This information provides new research directions to reduce or prevent oxidative processes that influence the quality and nutritional values of meat.

Novel insights from protein degradation: deciphering the dynamic evolution of biogenic amines as a quality indicator in pork during storage

Biogenic amines (BAs) have drawn great attention as important markers for monitoring food quality. However, the BAs content in protein degradation profiles during pork storage was inadequately investigated. In this work, the Longissimus lumborum and Breast and flank of pork were collected, and their peptides contents, free amino acids (FAAs) contents, BAs contents, and several characteristic physicochemical indexes were monitored during storage at 4 °C. As a result, the differences of nutritional components in the Longissimus lumborum and Breast and flank could not affect the shelf life of refrigerated pork. There are 161 small peptides in the Longissimus lumborum of pork identified by LC-MS. As verified, arginine, glutamic acid, valine, and alanine could serve as four indicative amino acids during protein degradation in pork, and the arginine degradation pathway is more complex. Redundancy analysis confirmed that putrescine and cadaverine were significantly related to the precursor FAAs content, and their sum value could be used as a novel quality indicator instead of the biogenic amine index (BAI). Finally, the above prediction was also verified by the other species (beef, mutton and chicken) to improve the index system of meat quality evaluation in cold chain logistics.

Melatonin supplementation promotes muscle fiber hypertrophy and regulates lipid metabolism of skeletal muscle in weaned piglets

Melatonin has been reported to play crucial roles in regulating meat quality, improving reproductive properties, and maintaining intestinal health in animal production, but whether it regulates skeletal muscle development in weaned piglet is rarely studied. This study was conducted to investigate the effects of melatonin on growth performance, skeletal muscle development, and lipid metabolism in animals by intragastric administration of melatonin solution. Twelve 28-d-old DLY (Duroc × Landrace × Yorkshire) weaned piglets with similar body weight were randomly divided into two groups: control group and melatonin group. The results showed that melatonin supplementation for 23 d had no effect on growth performance, but significantly reduced serum glucose content (P < 0.05). Remarkably, melatonin increased longissimus dorsi muscle (LDM) weight, eye muscle area and decreased the liver weight in weaned piglets (P < 0.05). In addition, the cross-sectional area of muscle fibers was increased (P < 0.05), while triglyceride levels were decreased in LDM and psoas major muscle by melatonin treatment (P < 0.05). Transcriptome sequencing showed melatonin induced the expression of genes related to skeletal muscle hypertrophy and fatty acid oxidation. Enrichment analysis indicated that melatonin regulated cholesterol metabolism, protein digestion and absorption, and mitophagy signaling pathways in muscle. Gene set enrichment analysis also confirmed the effects of melatonin on skeletal muscle development and mitochondrial structure and function. Moreover, quantitative real-time polymerase chain reaction analysis revealed that melatonin supplementation elevated the gene expression of cell differentiation and muscle fiber development, including paired box 7 (PAX7), myogenin (MYOG), myosin heavy chain (MYHC) IIA and MYHC IIB (P < 0.05), which was accompanied by increased insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 5 (IGFBP5) expression in LDM (P < 0.05). Additionally, melatonin regulated lipid metabolism and activated mitochondrial function in muscle by increasing the mRNA abundance of cytochrome c oxidase subunit 6A (COX6A), COX5B, and carnitine palmitoyltransferase 2 (CPT2) and decreasing the mRNA expression of peroxisome proliferator-activated receptor gamma (PPARG), acetyl-CoA carboxylase (ACC) and fatty acid-binding protein 4 (FABP4) (P < 0.05). Together, our results suggest that melatonin could promote skeletal muscle growth and muscle fiber hypertrophy, improve mitochondrial function and decrease fat deposition in muscle.

Integrative proteomics and metabolomics profiling to understand the biochemical basis of beef muscle darkening at a slightly elevated pH

Previous studies investigated the biochemical basis of dark-cutting conditions at elevated muscle pH (above 6), but the molecular basis at slightly above normal pH (between 5.6 and 5.8) is still unclear. The objective was to determine protein and metabolite profiles to elucidate postmortem muscle darkening at slightly elevated pH. Loins were selected based on the criteria established in our laboratory before sample collections, such as pH less than 5.8, L* values (muscle lightness) less than 38, and not discounted by the grader (high-pH beef with dark color are discounted and not sold in retail stores). Six bright red loins (longissimus lumborum) at normal-pH (average pH = 5.57) and six dark-colored strip loins at slightly elevated pH (average pH = 5.70) from A maturity carcasses were obtained within 72-h postmortem from a commercial beef purveyor. Surface color, oxygen consumption, metmyoglobin reducing activity, protein, and metabolite profiles were determined on normal-pH and dark-colored steaks at slightly elevated pH. Enzymes related to glycogen metabolism and glycolytic pathways were more differently abundant than metabolites associated with these pathways. The results indicated that oxygen consumption and metmyoglobin reducing activity were greater (P < 0.05) in darker steaks than normal-pH steaks. Enzymes involved with glycogen catabolic pathways and glycogen storage disease showed lower abundance in dark beef. The tricarboxylic acid metabolite, aconitic acid, was overabundant in darker-colored beef than normal-pH beef, but glucose derivative metabolites were less abundant. The majority of glycogenolytic proteins and metabolites reported as overabundant in the previous dark-cutting studies at high pH (>6.4) also did not show significant differences in the current study. Therefore, our data suggest enzymes involved in glycogen metabolism, in part, create a threshold for muscle darkening than metabolites.

Metabolomics and bioinformatic analyses to determine the effects of oxygen exposure within longissimus lumborum steak on beef discoloration

Meat discoloration starts from the interior and spreads to oxymyoglobin layer on the surface. The effects of oxygen exposure within a steak on the metabolome have not been evaluated. Therefore, the objective of this study was to evaluate the impact of oxygen exposure on the metabolome of the longissimus lumborum muscle. Six United States Department of Agriculture (USDA) Low Choice beef strip loins were sliced into steaks (1.91-cm) and packaged in polyvinyl chloride overwrap trays for 3 or 6 d of retail display. The oxygen exposed (OE) surface was the display surface during retail, and the non-oxygen exposed (NOE) surface was the intact interior muscle. The instrumental color was evaluated using a HunterLab MiniScan spectrophotometer. To analyze the NOE surface on days 3 and 6, steaks were sliced parallel to the OE surface to expose the NOE surface. Metmyoglobin reducing ability (MRA) was determined by nitrite-induced metmyoglobin reduction. A gas chromatography-mass spectrometry was used to identify metabolites. The a* values of steaks decreased (P < 0.05) with display time. MRA was greater (P < 0.05) in the NOE surface compared with the OE surface on days 3 and 6. The KEGG pathway analysis indicated the tricarboxylic acid (TCA) cycle, pentose and glucuronate interconversions, phenylalanine, tyrosine, and tryptophan metabolism were influenced by the oxygen exposure. The decrease in abundance of succinate from days 0 to 6 during retail display aligned with a decline in redness during display. Furthermore, citric acid and gluconic acid were indicated as important metabolites affected by oxygen exposure and retail display based on the variable importance in the projection in the PLS-DA plot. Citric acid was lower in the NOE surface than the OE surface on day 6 of retail display, which could relate to the formation of succinate for extended oxidative stability. Greater alpha-tocopherol (P < 0.05) in the NOE surface supported less oxidative changes compared to the OE surface during retail display. These results indicate the presence of oxygen can influence metabolite profile and promote migration of the metmyoglobin layer from interior to surface.

Effects of altitude on meat quality difference and its relationship with HIF-1α during postmortem maturation of beef

This study investigated the differences in meat quality during postmortem aging of yak meat from different altitudes as well as the relationship between the release of hypoxic factor HIF-1α and meat quality. The results showed that the HIF-1α increased with altitude but during aging process, there was an initial increase before a subsequent decrease (p < .05). Moreover, significant increases were showed in glycolytic potential, a* value, pH, HIF-1α mRNA expression, HIF-1α protein expression and shear force with altitude (p < .05). Additionally, the b* value, L* value, water holding power and MFI decreased significantly (p < .05). HIF-1α was shown, by PLS-DA method analysis, to be the main protein marker for differences in the quality during aging time of meat from three altitude groups. HIF-1α protein expression was high correlated with glycolytic potential, pH value, meat color, tenderness and water holding capacity during postmortem aging. The results demonstrated that HIF-1α is a novel marker protein that influences meat quality in yak from different altitudes and that HIF-1α-mediated glycolytic pathway was key to the meat quality during postmortem aging. PRACTICAL APPLICATIONS: Yak meat has the advantages of high protein, low fat, good amino acid and fatty acid composition, so the nutritional value of yak meat is in line with the current best-selling beef with less fat in domestic and foreign markets. But consumers often think that the meat tenderness of yak meat is worse than that of beef and improving the quality of yak meat was worthy of attention specifically. This study investigated the differences in meat quality during postmortem aging of yak meat at different altitudes and the relationship between hypoxic factor HIF-1α release and meat quality.

Exploratory lipidome and metabolome profiling contributes to understanding differences in high and normal ultimate pH beef

The aim of this work was to compare the lipidome and metabolome profiling in the Longissimus thoracis muscle early and late postmortem from high and normal ultimate pH (pHu) beef. Lipid profiling discriminated between high and normal pHu beef based on fatty acid metabolism and mitochondrial beta-oxidation of long chain saturated fatty acids at 30 min postmortem, and phospholipid biosynthesis at 44 h postmortem. Metabolite profiling also discriminated between high and normal pHu beef, mainly through glutathione, purine, arginine and proline, and glycine, serine and threonine metabolisms at 30 min postmortem, and glycolysis, TCA cycle, glutathione, tyrosine, and pyruvate metabolisms at 44 h postmortem. Lipid and metabolite profiles showed reduced glycolysis and increased use of alternative energy metabolic processes that were central to differentiating high and normal pHu beef. Phospholipid biosynthesis modification suggested high pHu beef experienced greater oxidative stress.

New horizons for selenium in animal nutrition and functional foods

Selenium (Se), one of the indispensable nutrients for both human health and animal growth, participates in various physiological functions, such as antioxidant and immune responses and metabolism. The role of dietary Se, in its organic and inorganic forms, has been well documented in domestic animals. Furthermore, many feeding strategies for different animals have been developed to increase the Se concentration in animal products to address Se deficiency and even as a potential nutritional strategy to treat free radical-associated diseases. Nevertheless, studies on investigating the optimum addition of Se in feed, the long-term consequences of Se usage in food for animal nutrition, the mechanism of metallic Se nanoparticle (SeNP) transformation in vivo, and the nutritional effects of SeNPs on feed workers and the environment are urgently needed. Starting from the absorption and metabolism mechanism of Se, this review discusses the antioxidant role of Se in detail. Based on this characteristic, we further investigated the application of Se in animal health and described some unresolved issues and unanswered questions warranting further investigation. This review is expected to provide a theoretical reference for improving the quality of food animal meat as well as for the development of Se-based biological nutrition enhancement technology.

Inhibitory mechanisms of polyphenols on heme protein-mediated lipid oxidation in muscle food: New insights and advances

Lipid oxidation is a major cause of quality deterioration that decreases the shelf-life of muscle-based foods (red meat, poultry, and fish), in which heme proteins, particularly hemoglobin and myoglobin, are the primary pro-oxidants. Due to increasing consumer concerns over synthetic chemicals, extensive research has been carried out on natural antioxidants, especially plant polyphenols. The conventional opinion suggests that polyphenols inhibit lipid oxidation of muscle foods primarily owing to their strong hydrogen-donating and transition metal-chelating activities. Recent developments in analytical techniques (e.g., protein crystallography, nuclear magnetic resonance spectroscopy, fluorescence anisotropy, and molecular docking simulation) allow deeper understanding of the molecular interaction of polyphenols with heme proteins, phospholipid membrane, reactive oxygen species, and reactive carbonyl species; hence, novel hypotheses regarding their antioxidant mechanisms have been formulated. In this review, we summarize five direct and three indirect pathways by which polyphenols inhibit heme protein-mediated lipid oxidation in muscle foods. We also discuss the relation between chemical structures and functions of polyphenols as antioxidants.

Effects of Dietary L-malic Acid Supplementation on Meat Quality, Antioxidant Capacity and Muscle Fiber Characteristics of Finishing Pigs

L-malic acid is a vital intermediate in the citric acid cycle and has been reported to improve the antioxidant capacity and aerobic oxidation of weaned piglets; however, its application in finishing pigs is limited at present. This study explored the effects of dietary L-malic acid supplementation on the carcass traits and meat quality of finishing pigs. In a 45-day experiment, 192 Duroc × Landrace × Yorkshire pigs (75.01 ± 0.51 kg) were divided into four treatments, i.e., a basal diet supplemented with 0, 0.5%, 1%, and 2% L-malic acid complex. The results showed that L-malic acid supplementation had no effects on the growth performance of finishing pigs. Importantly, L-malic acid significantly increased redness (a*) value at 24-h postmortem (quadratic, p < 0.05) and tended to increase the proportion of oxymyoglobin (OMb) (quadratic, p = 0.10), as well as the total antioxidant capacity (T-AOC) activity (quadratic, p = 0.08) in the longissimus dorsi (LD) muscle. Further, dietary supplementation of 1% L-malic acid markedly increased the protein expression level of slow skeletal myosin heavy chain (MyHC) in the LD muscle (p < 0.05). Moreover, 0.5% and 2% L-malic acid supplementation significantly increased carcass length and loin eye area (p < 0.05). In conclusion, dietary L-malic acid could effectively improve the meat color and carcass traits of finishing pigs.

Supranutritional Supplementation of Vitamin E Influences Myoglobin Post-Translational Modifications in Postmortem Beef Longissimus Lumborum Muscle

Post-translational modifications (PTM) in myoglobin (Mb) can influence fresh meat color stability. Dietary supplementation of vitamin E improves beef color stability by delaying lipid oxidation–induced Mb oxidation and influences proteome profile of postmortem beef skeletal muscles. Nonetheless, the influence of vitamin E on Mb PTM in postmortem beef skeletal muscles has yet to be investigated. Therefore, the objective of the current study was to examine the effect of dietary vitamin E on Mb PTM in postmortem beef longissimus lumborum muscle. Beef longissimus lumborum muscle samples (24 h postmortem) were obtained from the carcasses of 9 vitamin E–supplemented (VITE; 1,000 IU vitamin E diet/heifer·d−1for 89 d) and 9 control (CONT; no supplemental vitamin E) heifers. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to separate Mb from other sarcoplasmic proteins of beef longissimus lumborum muscle. Tandem mass spectrometry identified multiple PTM (phosphorylation, acetylation, 4-hydroxynonenalalkylation, methylation, dimethylation, trimethylation, and carboxymethylation) in the protein bands (17 kDa) representing Mb. The amino acids susceptible to phosphorylation were threonine (T) and tyrosine (Y), whereas lysine (K) residues were prone to other PTM. The same sites of phosphorylation (T34, T67, Y103), carboxymethylation (K77, K78), and 4-hydroxynonenal alkylation (K77, K78, K79) were identified in Mb from CONT and VITE samples, indicating that these PTM were not influenced by the vitamin E supplementation in cattle. Nonetheless, differential occurrence of acetylation, methylation, dimethylation, and trimethylation were identified in Mb from CONT and VITE samples. Overall, a greater number of amino acids were modified in CONT than VITE, suggesting that the supplementation of vitamin E decreased thenumbers of post-translationally modified residues in Mb. Additionally, PTM at K87, K96, K98, and K102 were unique to CONT, whereas PTM at K118 were unique to VITE. These findings suggested that dietary supplementation of vitamin E in beef cattle might protect amino acid residues in Mb—especially those located spatially close to proximal histidine—from undergoing PTM, thereby improving Mb redox stability.

Dietary α-lipoic acid supplementation improves postmortem color stability of the lamb muscles through changing muscle fiber types and antioxidative status

This study investigated the effect of dietary α-lipoic acid (600 mg/kg) supplementation on the postmortem color stability of the biceps femoris from lambs. The results showed that dietary α-lipoic acid supplementation increased a* and decreased b* and metmyoglobin (MMb) percentage of the biceps femoris with the time of storage (P < 0.05). The content of malondialdehyde (MDA) reduced with the time of storage after treatment with α-lipoic acid (P < 0.05). α-lipoic acid increased the myoglobin (Mb) content, and myosin heavy chain I (MyHC I) gene expression but decreased glycogen content, lactate dehydrogenase (LDH) activity, and MyHC IIb gene expression (P < 0.05). The T-AOC value, catalase (CAT) activity, and expression of SOD and CAT gene expression increased after α-lipoic acid treatment (P < 0.05). Therefore, dietary α-lipoic acid supplementation improved the meat color by regulating muscle fiber types and inhibited glycolysis. Moreover, α-lipoic acid maintained meat color stability by effectively inhibiting muscle oxidation via enhancing the antioxidant capacity.

Evidence of the mechanism underlying zinc protoporphyrin IX formation in nitrite/nitrate-free dry-cured Parma ham

A large amount of zinc protoporphyrin IX (ZnPP) is found in nitrite/nitrate-free dry-cured meat products, such as Parma ham, and is known to contribute to the favorable bright red color of the latter. ZnPP is a metalloporphyrin, in which zinc is coordinated, instead of iron, in the porphyrin ring. ZnPP proved to be more stable than heme, and its formation should be favored in dried meat products to improve color without the addition of nitrites or nitrates. Toward that, understanding the mechanisms of formation of ZnPP in nitrite/nitrate-free dry-cured ham would be important. In this lecture, I introduce some of our research group's findings regarding the endogenous and exogenous factors contributing to the formation and distribution of ZnPP in Parma ham and why ZnPP formation is suppressed in common cured meat products.

Myoglobin from Atlantic and Tinker mackerels: Purification, characterization and its possible use as a molecular marker

Here, we report the characterization (purification, autoxidation rate, pseudoperoxidase activity) and amino acid sequence determination of S. scombrus (Atlantic mackerel) and S. colias (Tinker mackerel) mioglobins (Mbs), considering the increasing consumption of fresh and canned mackerel meat and Mb implication in meat storage (e.g.: browning and lipid oxidation). We found that Atlantic mackerel Mb has major autoxidation rate (0.204 ± 0.013 h^-1) compared to Tinker mackerel Mb (0.140 ± 0.009 h^-1), while the pseudoperoxidase activity is major for Tinker mackerel (K_m: 87.71 ± 7.19 μM; k_cat: 0.32 s^-1) Mb with respect to Atlantic mackerel (K_m: 96.08 ± 6.91 μM; k_cat: 0.50 s^-1). These functional differences are confirmed by primary structure determination, in which six amino acid substitutions are found, with the first N-terminal amino acid residue acetylated. Furthermore, we predicted by AphaFold 3D model both fish Mbs and used them to investigate the possible structural differences. In addition, phylogenetic analysis using Mb sequences from Scombridae family confirms that Atlantic and Tinker mackerels are two distinct species. Finally, an analytic qualitative RP-HPLC method to distinguish S. scombrus and S. colias specimens was developed considering the different retention times of the two mackerel apoMbs.

Sequential Membrane Filtration to Recover Polyphenols and Organic Acids from Red Wine Lees: The Antioxidant Properties of the Spray-Dried Concentrate

The vinification process produces a considerable amount of waste. Wine lees are the second most generated byproduct, representing around 14% of total vinification wastes. They are a valuable source of natural antioxidants, mainly polyphenols, as well as organic acids, such as tartaric acid. This paper deals with the application of an integrated, environment friendly membrane separation process to recover polyphenols and organic acids. A two-step membrane process is described, consisting of an ultra- and a nano-filtration process. The physicochemical and antioxidant properties of all the process streams were determined. High Pressure Liquid Chromatography (HPLC) was employed for identifying certain individual organic acids and polyphenols, while the antioxidant potential was determined by the 2,2′-diphenyl-1-picrylhydrazyl radical) (DPPH) radical scavenging ability and ferric reducing ability. A liquid concentrate stream containing 1351 ppm of polyphenols was produced and then spray dried. The resulting powder retained most of the polyphenols and antioxidant properties and was successfully applied to a real food system to retard lipid oxidation, followed by Thiobarbituric Acid Reactive Substances (TBARS) and the determination of oxymyoglobin content. The results show that membrane separation technology is an attractive alternative process for recovering value-added ingredients from wine lees.

Housekeeping Proteins in Meat Quality Research: Are They Reliable Markers for Internal Controls in Western Blot? A Mini Review

Advancements in technology and analytical methods enable researchers to explore the biochemical events that cause variation in meat quality. Among those, western blot techniques have been successfully used in identifying and quantifying the key proteins that have critical functions in the development of meat quality. Housekeeping proteins, like β-actin, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and tubulins are often used as internal controls in western blots to normalize the abundance of the protein of interest. However, there are increasing concerns about using housekeeping proteins for western blot normalization, as these proteins do not demonstrate any loading differences above the relatively small total protein loading amounts of 10μg. In addition, the interaction between these housekeeping proteins and programmed cell death processes highlights the concerns about using the housekeeping protein as the internal control in meat quality research. Moreover, recent proteomic research has indicated that the abundance of some housekeeping proteins, like β-actin, GAPDH, and tubulin, can be altered by preslaughter stress, dietary supplementation, sex, slaughter method, genotype, breed, aging period, muscle type, and muscle portion. Furthermore, these housekeeping proteins could have differential expression in meat with differing color stability, tenderness, and water holding capacity. Therefore, this review aims to examine the realities of using housekeeping proteins as the loading control in meat quality research and introduce some alternative methods that can be used for western blot normalization.

Lipid oxidation and antioxidant delivery systems in muscle food

Lipid oxidation accelerates quality deterioration in muscle-based foods (fish, red meat, and poultry), resulting in off-odors/flavors, color problems, texture defects, and safety concerns. Adding antioxidants is one approach to control lipid oxidation, and several delivery strategies have been applied, such as supplementing antioxidants to the feed, direct mixing into minces, or, for whole muscle pieces; spraying, glazing, and injection. However, some issues linked to these technologies hinder their wide utilization, such as low effectiveness, noncompatibility with clean label, and off-flavor. These shortcomings have promoted the development of new antioxidant delivery technologies. In this review, the main focus is on the principles, characteristics, and implementation of five novel antioxidant delivery methods in different types of muscle food products. Their advantages and drawbacks are also summarized, plus comments about future trends in this area. Among novel routes to deliver antioxidants to muscle foods are, for whole tissues, recyclable dipping solutions; for minces, encapsulation; and, for both minces and whole tissues, cross-processing with nonmuscle antioxidant-containing raw materials as well as applications of edible films/coatings and active packaging. Advantages of these technologies comprise, for example, low price, the possibility to control the antioxidant release rate, overcoming strong aromas from natural antioxidants, and allowing antioxidant-containing raw materials from the food industry to be valorized, providing an opportunity for more circular food production.

Pulmonary arterial pressure in fattened Angus steers at moderate altitude influences early postmortem mitochondria functionality and meat color during retail display

Pulmonary hypertension is a noninfectious disease of cattle at altitudes > 1524 m (5,000 ft). Mean pulmonary arterial pressures (PAP) are used as an indicator for pulmonary hypertension in cattle. High PAP cattle (≥50 mmHg) entering the feedlot at moderate elevations have lower feed efficiency as compared to low PAP cattle (< 50 mmHg). The impact of pulmonary arterial pressure on mitochondrial function, oxidative phosphorylation (OXPHOS) protein abundance, and meat color was examined using longissimus lumborum (LL) from high (98 ± 13 mmHg; n = 5) and low (41 ± 3 mmHg; n = 6) PAP fattened Angus steers (live weight of 588 ± 38 kg) during early postmortem period (2 and 48 h) and retail display (days 1 to 9), respectively. High PAP muscle had greater (P = 0.013) OXPHOS-linked respiration and proton leak-associated respiration than low PAP muscles at 2 h postmortem but rapidly declined to be similar (P = 0.145) to low PAP muscle by 48 h postmortem. OXPHOS protein expression was higher (P = 0.045) in low PAP than high PAP muscle. During retail display, redness, chroma, hue, ratio of reflectance at 630 and 580 nm, and metmyoglobin reducing activity decreased faster (P < 0.05) in high PAP steaks than low PAP. Lipid oxidation significantly increased (P < 0.05) in high PAP steaks but not (P > 0.05) in low PAP. The results indicated that high PAP caused a lower OXPHOS efficiency and greater fuel oxidation rates under conditions of low ATP demand in premortem beef LL muscle; this could explain the lower feed efficiency in high PAP feedlot cattle compared to low PAP counterparts. Mitochondrial integral function (membrane integrity or/and protein function) declined faster in high PAP than low PAP muscle at early postmortem. LL steaks from high PAP animals had lower color stability than those from the low PAP animals during simulated retail display, which could be partially attributed to the loss of muscle mitochondrial function at early postmortem by ROS damage in high PAP muscle.

Tandem Mass Tag Labeling-Based Analysis to Characterize Muscle-Specific Proteome Changes during Postmortem Aging of Bison Longissimus Lumborum and Psoas Major Muscles

The objective of the study was to examine the variations in sarcoplasmic proteomes of bison longissimus lumborum (LL) and psoas major (PM) muscles during postmortem aging utilizing tandem mass tag (TMT) isobaric labeling coupled with liquid chromatography mass-spectrometry (LC-MS/MS) for the categorization of muscles with muscle-specific inherent color stability. A total of 576 proteins were identified (P < 0.05) in both bison LL and PM muscles, where 97 proteins were identified as differentially abundant (fold change > 1.5, P < 0.05) from the three comparisons between muscles during postmortem aging periods (PM vs LL at 2 d, 7 d and 14 d). Among those proteins, the most important protein groups based on functions are related to electron transport chain (ETC) or oxidative phosphorylation, tricarboxylic acid cycle (TCA), ATP transport, carbohydrate metabolism, fatty acid oxidation, chaperones, oxygen transport, muscle contraction, calcium signaling, and protein synthesis. In PM, most of the proteins from ETC, TCA cycle, fatty acid oxidation, ATP and oxygen transport, and muscle contraction were more abundant or exhibited increased expression during aging compared to LL. On the other hand, the proteins involved in carbohydrate metabolism, chaperone function and protein synthesis mostly exhibited decreased expression in PM muscle relative to LL. These results clearly demonstrate that the proteins associated with oxidative metabolism showed increased expression in PM muscles. This indicates that oxidative damage or subsequent color deterioration resulted in bison PM muscles being attacked by the reactive oxygen species produced during those metabolic process. In contrast, proteins involved in glycolysis and chaperone activity exhibited a decrease in expression in bison PM muscles, resulting decline in color stability compared with LL. Because glycolytic enzymes and chaperones maintain oxidative and/or color stability by producing reducing equivalents in glycolytic pathway and with the protein folding ability of chaperones, respectively in LL muscles.

Proteomic Changes in Sarcoplasmic and Myofibrillar Proteins Associated with Color Stability of Ovine Muscle during Post-Mortem Storage

The objective of this study was to investigate the proteomic characteristics for the sarcoplasmic and myofibrillar proteomes of M. longissimus lumborum (LL) and M. psoasmajor (PM) from Small-tailed Han Sheep. During post-mortem storage periods (1, 3, and 5 days), proteome analysis was applied to elucidate sarcoplasmic and myofibrillar protein changes in skeletal muscles with different color stability. Proteomic results revealed that the identified differentially abundant proteins were glycolytic enzymes, energy metabolism enzymes, chaperone proteins, and structural proteins. Through Pearson’s correlation analysis, a few of those identified proteins (Pyruvate kinase, Adenylate kinase isoenzyme 1, Creatine kinase M-type, and Carbonic anhydrase 3) were closely correlated to representative meat color parameters. Besides, bioinformatics analysis of differentially abundant proteins revealed that the proteins mainly participated in glycolysis and energy metabolism pathways. Some of these proteins may have the potential probability to be predictors of meat discoloration during post-mortem storage. Within the insight of proteomics, these results accumulated some basic theoretical understanding of the molecular mechanisms of meat discoloration.