Proteomics of lipid oxidation-induced oxidation of porcine and bovine oxymyoglobins

Protein Haptenation and Its Role in Allergy

Humans are exposed to numerous electrophilic chemicals either as medicines, in the workplace, in nature, or through use of many common cosmetic and household products. Covalent modification of human proteins by such chemicals, or protein haptenation, is a common occurrence in cells and may result in generation of antigenic species, leading to development of hypersensitivity reactions. Ranging in severity of symptoms from local cutaneous reactions and rhinitis to potentially life-threatening anaphylaxis and severe hypersensitivity reactions such as Stephen-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), all these reactions have the same Molecular Initiating Event (MIE), i.e. haptenation. However, not all individuals who are exposed to electrophilic chemicals develop symptoms of hypersensitivity. In the present review, we examine common chemistry behind the haptenation reactions leading to formation of neoantigens. We explore simple reactions involving single molecule additions to a nucleophilic side chain of proteins and complex reactions involving multiple electrophilic centers on a single molecule or involving more than one electrophilic molecule as well as the generation of reactive molecules from the interaction with cellular detoxification mechanisms. Besides generation of antigenic species and enabling activation of the immune system, we explore additional events which result directly from the presence of electrophilic chemicals in cells, including activation of key defense mechanisms and immediate consequences of those reactions, and explore their potential effects. We discuss the factors that work in concert with haptenation leading to the development of hypersensitivity reactions and those that may act to prevent it from developing. We also review the potential harnessing of the specificity of haptenation in the design of potent covalent therapeutic inhibitors.

Secondary Lipid Oxidation Products as Modulators of Calpain-2 Functionality In Vitro

The objective was to understand the impacts of secondary lipid oxidation products on calpain-2 activity and autolysis and, subsequently, to determine the quantity and localization of modification sites. 2-Hexenal and 4-hydroxynonenal incubation significantly decreased calpain-2 activity and slowed the progression of autolysis, while malondialdehyde had minimal impact on calpain-2 activity and autolysis. Specific modification sites were determined with LC-MS/MS, including distinct malondialdehyde modification sites on the calpain-2 catalytic and regulatory subunits. 2-Hexenal modification sites were observed on the calpain-2 catalytic subunit. Intact protein mass analysis with MALDI-MS revealed that a significant number of modifications on the calpain-2 catalytic and regulatory subunits are likely to exist. These observations confirm that specific lipid oxidation products modify calpain-2 and may affect the calpain-2 functionality. The results of these novel experiments have implications for healthy tissue metabolism, skeletal muscle growth, and post-mortem meat tenderness development.

Multispectral and molecular dynamics study on the impact of trans, trans-2,4-decadienal and 4-hydroxy-2-nonenal on myoglobin redox stability

This study investigated the interaction between myoglobin (Mb) and two lipid oxidation products, 4-hydroxy-2-nonenal (HNE) and trans, trans-2,4-decadienal (tt-DDE), at pH 5.6 and 7.4 through the combination of multispectral and molecular dynamics simulations. In this study, tt-DDE was more prone to promote Mb oxidation than HNE by loosening the Mb structure, which is associated with more destroyed secondary and tertiary structures. Furthermore, the pro-oxidation of both lipid products was stronger at pH 5.6 than at pH 7.4. The molecular docking revealed that both tt-DDE and HNE were combined closely with the heme group of Mb. And tt-DDE had hydrogen bonds, hydrophobic interactions, and van der Waals forces with Mb, but HNE only had hydrophobic interactions. In conclusion, it was firstly found that tt-DDE was also shown to have high activity in promoting Mb oxidation as another important aldehyde from lipid oxidation products.

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.

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.

Lipid Peroxidation Products Influence Calpain-1 Functionality In Vitro by Covalent Binding

The objective of the current study was to evaluate the effects of lipid peroxidation products, malondialdehyde (MDA), hexenal, and 4-hydroxynonenal (HNE), on calpain-1 function, and liquid chromatography and tandem mass spectrometry (LC-MS/MS) identification of adducts on calpain-1. Calpain-1 activity slightly increased after incubation with 100 μM MDA but not with 500 and 1000 μM MDA. However, calpain-1 activity was lowered by hexenal and HNE at 100, 500, and 1000 μM. No difference in calpain-1 autolysis was observed between the control and 1000 μM MDA. However, 1000 μM hexenal and HNE treatments slowed the calpain-1 autolysis. Adducts of MDA were detected on glutamine, arginine, lysine, histidine, and asparagine residues via Schiff base formation, while HNE adducts were detected on histidine, lysine, glutamine, and asparagine residues via Michael addition. These results are the first to demonstrate that lipid peroxidation products can impact calpain-1 activity in a concentration-dependent manner and may impact the development of meat tenderness postmortem.

Improvement of Color and Oxidative Stabilities in Nellore Bull Dark Meat in High-Oxygen Package by Lactate and Rosemary Oil Extract

This study aimed to improve the color and oxidative stabilities of dark Nellore bull steaks with greater-than-normal ultimate pH (pH_u) by the injection (8% raw wet weight basis) of a solution with L-lactate (2.5%), phosphate (0.3%) and rosemary extract (0.06%), with further packaging in high oxygen atmosphere (HiOx MAP). Longissimus lumborum muscles from pasture-fed Nellore bulls were divided into three pH_u ranges: normal (<5.80), intermediate (5.81-6.19), and high (≥6.2). Muscles were then halved, with sections were randomly assigned to non-enhanced (C, n = 6/pH_u range) or injected (E, n = 6/pH_u range) groups, at 72 h postmortem. Each section was cut into 2 cm-slices, which were HiOx-packed and then stored for 5 days (dark) and displayed for 9 days (fluorescent lighting) at 2 °C. Higher pH_u steaks exhibited greater a*, b*, h*, C* and surface oxymyoglobin and lower surface deoxymyoglobin and oxygen consumption compared to those of normal pH_u between days 0 and 5 (p < 0.05). Over the time, normal-pH_u muscles showed oxidative protection (lower TBARS and greater metmyoglobin reducing ability values, p < 0.05) in enhanced-steaks. Therefore, enhancement and HiOx MAP seem to produce greater-than-normal pH_u Nellore bull steaks with a preferable color and quality, even after display time.

Effects of multiple vitamin E levels and two fat sources in diets for swine fed to heavy slaughter weight of 150 kg: I. Growth performance, lean growth, organ size, carcass characteristics, primal cuts, and pork quality

The study objective was to evaluate the effect of two fat source and graded levels of vitamin E (VE) supplementation on growth performance, carcass characteristics, and meat quality of pigs at heavy slaughter weight (150 kg). A total of 48 individually-fed pigs (24 barrows, 24 gilts; 28.44  ± 2.69 kg) were blocked by sex and weight and randomly assigned to eight dietary treatments in a 2 × 4 factorial arrangement. Fat treatments were 5% tallow (TW) and distiller's corn-oil (DCO) in the diets. The VE treatments included four levels of α-tocopheryl-acetate (11, 40, 100, and 200 ppm). Growth performance, carcass traits, organ weight, primal cuts, and pork quality were measured. Increasing dietary VE supplementation levels linearly increased overall Average daily gain (ADG) and average daily feed intake (P < 0.05), with an interaction between fat sources and VE supplementation levels on cumulative ADG (P < 0.05) during phases 1 and 3 (28 to 100 kg) and 1 to 4 (28 to125 kg) wherein ADG in the pigs fed the DCO diet, but not the TW diet, increased with increasing dietary VE supplementation level. A similar interaction was observed in 24 h pH and picnic shoulder (P < 0.05). No notable effect of fat source was observed in growth performance. With increasing dietary VE supplementation levels, there were quadratic responses in pork pH at 45 min and 24 h postmortem with the highest value in 40 and 100 ppm of VE levels while TBARS values on day 7 postmortem decreased linearly (P < 0.05). Compared with the TW diet, the DCO diet resulted in greater TBARS values during 7 postmortem (P < 0.05; day 5, P = 0.09). These results demonstrated that increasing dietary VE supplementation level could enhance growth rate and feed intake and reduce lipid peroxidation of pork whereas the diet containing DCO as a fat source could negatively affect pork shelf-life and carcass characteristics and that increasing VE supplementation level had no notable interaction with fat sources for carcass characteristics.

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.

Quercetin as an inhibitor of hemoglobin-mediated lipid oxidation: Mechanisms of action and use of molecular docking

The antioxidant effect of quercetin on hemoglobin(Hb)-mediated lipid oxidation and the mechanisms involved were investigated. Quercetin strongly inhibited Hb-mediated lipid oxidation in washed muscle. Quercetin showed effective hydroxyl radical scavenging ability similar to butylated hydroxytoluene (BHT). Quercetin reduced metHb resulting in formation of oxyHb. Bound quercetin decreased heme dissociation from metHb. Conversion to oxyHb and decreased heme dissociation represent routes to limit Hb-mediated lipid oxidation. Electrospray ionization mass spectrometry (ESI-MS) indicated one molecule of quercetin was covalently bound to Hb α-chain. Quercetin quinone docked 3.3 Å from the thiol of αCys(H15) but not near any other Cys residues of turkey Hb. At the docking site, hydrogen bonding between quercetin quinone and amino acids of α- and β-chain was demonstrated. This represents a path by which quercetin became covalently bound to α-chain. Molecular docking of heme proteins to polyphenols provides a template to better understand antioxidant interactions in muscle foods.

Muscle protein oxidation and functionality: a global view of a once neglected phenomenon

Muscle is a highly organized apparatus with a hierarchicmicrostructure that offers the protection of cellular components againstreactive oxygen species (ROS). However, fresh meat immediately postmortem andmeat undergoing processing become susceptible to oxidation due to physicaldisruption and the influx of molecular oxygen. Upon the activation byendogenous prooxidants, oxygen species are rapidly produced, and bothmyofibrillar and sarcoplasmic proteins become their primary targets. Direct ROSattack of amino acid sidechains and peptide backbone leads to proteinconformational changes, conversion to carbonyl and thiol derivatives, andsubsequent aggregation and polymerization. Interestingly, mild radical andnonradical oxidation enables orderly protein physicochemical changes, which explainswhy gels formed by ROS-modified myofibrillar protein has improved rheologicalproperties and binding potential in comminuted meat and meat emulsions. Theincorporation of phenolic and other multi-functional compounds promotes gelnetwork formation, fat emulsification, and water immobilization; however,extensive protein modification induced by high levels of ROS impairs proteinfunctionality. Now recognized to be a natural occurrence, once-neglectedprotein oxidation has drawn much interest and is being intensively studiedwithin the international community of meat science. This review describes thehistory and evolution of muscle protein oxidation, the mechanism andfunctionality impact hereof, and innovative oxidant/antioxidant strategies tocontrol and manipulate oxidation in the context of meat processing, storage,and quality. It is hoped that the review will stimulate in-depth discussion of scientificas well as industrial relevance and importance of protein oxidation and inspirerobust international collaboration in addressing this global challenge.&nbsp;

Proteomic Technologies and their Application for Ensuring Meat Quality, Safety and Authenticity

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Proteomic tools were extensively used to understand the relationship between muscle proteome and conversion of muscle to meat, post-mortem proteolysis, meat texture, and variation in meat color. Developments in proteomic tools have also resulted in their application for addressing the safety and authenticity issues including meat species identification, detection of animal byproducts, non-meat ingredients and tissues in meat products, traceability, identification of genetically modified ingredients, chemical residues and other harmful substances. Proteomic tools are also being used in some of the potential areas like understanding the effect of animal transportation, stunning, slaughter stress, halal authentication and issues related to animal welfare. Emerging advances in proteomic and peptidomic technologies and their application in traceability, meat microbiology, safety and authentication are taking a major stride as an interesting and complementary alternative to DNA-based methods currently in use. Future research in meat science need to be linked to emerging metabolomic, lipidomic and other omic technologies for ensuring integrated meat quality and safety management. In this paper, a comprehensive overview of the use of proteomics for the assessment of quality and safety in the meat value chain and their potential application is discussed.

Prediction and Experimental Verification of a Hierarchical Transcription Factor Regulatory Network of Porcine Myoglobin (Mb)

Myoglobin is a key chemical component that determines meat's color and affects consumers' purchase intentions. In this work, we firstly identified the promoter sequence of the Mb gene from the primary assembly of high-throughput genome sequencing in pigs, and predicted its potential transcription factors by LASAGNA. Through the data mining of the mRNA expression profile of longissimus dorsi muscle of different pig breeds, we constructed a hierarchical interplay network of Mb-TFs (Myoglobin-Transcription Factors), consisting of 16 adaptive transcription factors and 23 secondary transcription factors. The verification of gene expression in longissimus dorsi muscle showed that the Mb mRNA and encoded protein were significantly (p < 0.05) more abundant in Bama pigs than Yorkshire pigs. The qRT-PCR (Real-Time Quantitative Reverse Transcription PCR) validation on genes of the Mb-TFs network showed that FOS, STAT3, STAT1, NEFL21, NFE2L2 and MAFB were significant positive regulatory core transcription factors of Mb-TFs network in Bama pigs, whereas ATF3 was the secondary transcription factor most responsible for the activation of the above transcription factors. Our study provides a new strategy to unravel the mechanism of pork color formation, based on public transcriptome and genome data analysis.

The significant influences of pH, temperature and fatty acids on meat myoglobin oxidation: a model study

Colour is one of the important quality traits affecting the meat purchasing decision by consumers, and myoglobin is the principal heme protein responsible for the meat colour. This study aimed to investigate the effects of pH (5.3, 5.8, 6.4 and 7.4) and temperature (4 and 25 °C) on oxymyoglobin (OxyMb) oxidation in model reaction mixtures containing OxyMb, fatty acids (C18:2n-6 and C18:3n-3) and vitamin E. A decrease of the OxyMb concentration with increased acidity was observed for all the reaction mixtures with/without fatty acids and vitamin E. After 48 h of storage at 4 °C, the OxyMb concentration decreased by approximately 60-70%, 61-69%, 53.7-53.9% and 40.93-41.84% in the reaction mixtures containing [OxyMb + C18:2n-6 or C18:3n-3] at pH 5.3, 5.8, 6.4 and 7.4, respectively. While, after 48 h at 25 °C, the OxyMb concentration decreased by 95-98% in all the reaction mixtures containing [OxyMb + C18:2n-6 or C18:3n-3] under all the pH conditions. The presence of vitamin E significantly inhibited the OxyMb oxidation in the reaction mixtures containing fatty acids under acidic conditions, but a higher level of vitamin E may be required for meat(s) containing high n-3 fatty acids content that are stored at high temperature.

The Relationship between Lipid Content in Ground Beef Patties with Rate of Discoloration and Lipid Oxidation during Simulated Retail Display

The relationships between the lipid content, lipid oxidation, and discoloration rate of ground beef during a simulated retail display were characterized in this study. A total of 276 batches of ground beef were manufactured with inside rounds and subcutaneous fat from 138 beef carcasses at different targeted levels of lean:fat. There was a total of four different targeted grind levels during the manufacture of the ground beef, and the lipid content for the samples used in this study ranged from 2% to 32% total lipid. Fatty acid composition was determined based on subcutaneous fat, whereas the proximate composition of moisture and total lipids, instrumental color, visual discoloration, and lipid oxidation measured as thiobarbituric acid reactive substances were evaluated on ground beef patties during 7 days of simulated retail at 4 °C display under LED lights. Analysis for the correlation and the creation of linear regression models indicated that lipid content played a more critical role in the discoloration rate compared to lipid oxidation and fatty acid composition. Lipid oxidation could be more reliably predicted by lipid content and instrumental color compared to visual discoloration. Overall, ground beef formulated with greater lipid content is expected to experience greater rates of lipid oxidation and discoloration during retail display.

Myoglobin Post-Translational Modifications Influence Color Stability of Beef Longissimus Lumborum

Post-translational modifications (PTM) of proteins play critical roles in biological processes. PTM of muscle proteins influence meat quality. Nonetheless, myoglobin (Mb) PTM and their impact on fresh beef color stability have not been characterized yet. Therefore, our objectives were to identify Mb PTM in beef longissimus lumborum muscle during postmortem aging and to characterize their influence on color stability. The longissimus lumborum muscles from 9 (n = 9) beef carcasses (24 h postmortem) were subjected to wet aging for 0, 7, 14, and 21 d. At the end of each wet-aging period, steaks were fabricated. One steak for analyses of PTM was immediately frozen at −80°C, whereas other steaks were assigned to refrigerated storage in the darkness under aerobic packaging. Instrumental color and biochemical attributes were evaluated on day 0, 3, or 6 of storage. Mb PTM were analyzed using two-dimensional electrophoresis and tandem mass spectrometry. Surface redness (a* value), color stability, and Mb concentration decreased (P &lt; 0.05) upon aging. Gel image analyses identified 6 Mb spots with similar molecular weight (17 kDa) but different isoelectric pH. Tandem mass spectrometry identified multiple PTM (phosphorylation, methylation, carboxymethylation, acetylation, and 4-hydroxynonenal alkylation) in these 6 isoforms. The amino acids susceptible to phosphorylation were serine (S), threonine (T), and tyrosine, whereas other PTM were detected in lysine (K), arginine (R), and histidine residues. Additionally, distal histidine (position 64), critical to heme stability, was found to be alkylated. Overall, Mb PTM increased with aging. The aging-induced PTM, especially those occurring close to hydrophobic heme pocket, could disrupt Mb tertiary structure, influence heme affinity, and compromise oxygen binding capacity, leading to decreased color stability of fresh beef. Furthermore, PTM at K45, K47, and K87 were unique to Mb from non-aged beef, whereas PTM at R31, T51, K96, K98, S121, R139, and K147 were unique to Mb from aged counterparts, indicating that these Mb PTM could be used as novel biomarkers for fresh beef color stability.

Principal component analysis of lipid and protein oxidation products and their impact on color stability in bison longissimus lumborum and psoas major muscles

The study aims were to compare lipid (malondialdehyde [MDA], 4-hydroxy-2-nonenal [HNE]) and protein (carbonyl content [CAR]) oxidation products between two bison muscles (longissimus lumborum [LL] and psoas major [PM]) at different aging and retail display time and determine their influence on muscle color stability. Regardless of the aging and retail display time, LL showed greater redness (a* value; P = 0.04) and lower surface discoloration (P < 0.01) than PM as well as LL exhibited lower MDA, HNE, and CAR content compared to PM (P < 0.05). In both muscles, MDA showed the highest correlation to a* (r = -0.78; P < 0.01) and discoloration (rs = 0.82; P < 0.01) scores, particularly in PM muscle compared to LL muscle. In conclusion, the principal component analysis revealed 4 distinct color deterioration clusters within steaks displayed at d 4 according to the muscle and aging time, and MDA critically influences color deterioration patterns in bison muscles.

New Insights in Muscle Biology that Alter Meat Quality

Fresh meat quality is greatly determined through biochemical changes occurring in the muscle during its conversion to meat. These changes are key to imparting a unique set of characteristics on fresh meat, including its appearance, ability to retain moisture, and texture. Skeletal muscle is an extremely heterogeneous tissue composed of different types of fibers that have distinct contractile and metabolic properties. Fiber type composition determines the overall biochemical and functional properties of the muscle tissue and, subsequently, its quality as fresh meat. Therefore, changing muscle fiber profile in living animals through genetic selection or environmental factors has the potential to modulate fresh meat quality. We provide an overview of the biochemical processes responsible for the development of meat quality attributes and an overall understanding of the strong relationship between muscle fiber profile and meat quality in different meat species.

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

Appearance is an important sensory property that significantly influences consumers' perceptions of fresh meat quality. Failure to meet consumer expectations can lead to rejection of meat products, concomitant loss in value, and potential production of organic waste. Immediately after animal harvest, skeletal muscle metabolism changes from aerobic to anaerobic. However, anoxic post-mortem muscle is biochemically active, and biomolecular interaction between myoglobin, mitochondria, metabolites, and lipid oxidation determines meat color. This review examines how metabolites and mitochondrial activity can influence myoglobin oxygenation and metmyoglobin reducing activity. Further, the review highlights recent research that has examined myoglobin redox dynamics, sarcoplasmic metabolite changes, and/or post-mortem biochemistry.

Effects of Astragalus Membranaceus supplementation on oxidative stability of Cashmere goat

Astragalus membranaceus (AM) provides a rich source of polysaccharides that can act as powerful antioxidants, but their potential as feed ingredients in the lamb industry still rarely exploited. The objective of this study was to investigate the effect of dietary astragalus membranaceus supplementation on oxidative stability of goat muscles. Longissimus dorsi (LD) muscles from two groups of Cashmere goat (basal diet, C group; basal diet supplemented with 1% astragalus membranaceus root, AM group) were evaluated for lipid oxidation, myoglobin oxidation, activity of antioxidant enzymes, and antioxidant capacity. The results showed that color parameters in Cashmere goat of two feeding conditions were no significant difference (p > .05). In AM group, myoglobin (Mb) content was higher than C, while metmyoglobin (MMb) (p < .05) and malondialdehyde (MDA) (p < .01) were lower. Additionally astragalus membranaceus supplementation had a significant effect on superoxide dismutase (SOD) and catalase (CAT) (p < .001). In whole, the AM group goats presented a relatively higher antioxidant capacity than C. Especially, RSA and CUPRAC values of AM group goats had significantly higher than C (p < .05). Consequently, the AM group goats ingested abundant astragalus membranaceus, which enhanced the antioxidant capacity. Thus, it can eliminate free radicals and effectively inhibit oxidation.

Recent Updates in Meat Color Research: Integrating Traditional and High-Throughput Approaches

Deviation from a bright cherry-red color of fresh meat results in less consumer acceptance and either discounted or discarded products in the value chain. Tissue homeostasis changes immediately after exsanguination, leading to acidification of muscle. Any alteration in pH drop can influence both muscle structure and enzymatic activity related to oxygen consumption and the redox state of myoglobin. This review focuses on both fundamental and applied approaches to under-stand the effects of pH on biochemical changes, oxygen diffusion, and its impact on meat color. Recent updates utilizing high-throughput “omics” approaches to elucidate the biochemical changes associated with high-pH meat are also dis-cussed. The fundamental aspects affecting fresh meat color are complex and highly interrelated with factors ranging from live animal production to preharvest environmental issues, muscle to meat conversion, and numerous facets along the merchandising chain of marketing meat to consumers.

Thermal Instability Induced by 4-Hydroxy-2-Nonenal in Beef Myoglobin

The secondary products of lipid oxidation, such as 4-hydroxy-2-nonenal (HNE), compromise myoglobin (Mb) redox stability and can thus impact thermal stability. Previous studies examined HNE-induced redox instability in beef Mb, whereas investigations are yet to be undertaken to evaluate the relationship between lipid oxidation and thermal stability of beef Mb. Therefore, the objective of the present study was to investigate the direct influence of HNE on thermal stability of beef Mb at meat conditions. Beef oxymyoglobin (0.15 mM) was incubated with HNE (1.0 mM) at pH 5.6 and 4°C for 21 d in the dark. Metmyoglobin formation, percentage Mb denaturation (PMD), and HNE adduction sites in Mb were examined on days 0, 7, 14, and 21. The experiment was replicated 3 times (n = 3). The data were evaluated using the MIXED procedure of SAS, and the differences among means were detected at the 5% level using the least significant difference test. The HNE-treated samples exhibited greater (P &lt; 0.05) metmyoglobin formation and PMD than the controls. Additionally, the PMD difference between HNE-treated and control samples increased (P &lt; 0.05) over time. Mass spectrometric analyses indicated that the number of HNE adduction sites increased with storage, and 6 histidines (positions 24, 36, 64, 93, 113, and 152) were adducted on day 21. HNE adduction at the distal histidine (position 64), which is critical to he me stability, was observed only on days 14 and 21. An increase in PMD on days 14 and 21 in HNE-treated samples could be partially due to the adduction at distal histidine. These findings indicated that HNE compromises thermal stability of beef Mb, possibly through altering the conformation of the heme protein by nucleophilic adduction.

Lipid protection by polyphenol-rich apple matrices is modulated by pH and pepsin in in vitro gastric digestion

Lipid oxidation takes place in the gastric tract after the ingestion of a Western diet rich in ω-6 polyunsaturated fatty acids (PUFA) and red meat (heme iron). The incorporation of oxidation products such as 4-hydroxy-2-nonenal (4-HNE) into low-density lipoproteins is further correlated to endothelial dysfunction. Gastric postprandial stress could thus be reduced by antioxidant phytomicronutrients. The aim of this study was to investigate dietary lipid oxidation and its inhibition by apple polyphenols under different matrix forms (fresh fruit, puree, extract) under in vitro gastric digestion conditions. A deep insight was given into the two factors pH and pepsin governing the metmyoglobin-initiated lipid oxidation of sunflower oil-in-water emulsions simulating the physical state of dietary lipids. Our results first showed that pepsin accelerated lipid oxidation at pH 5 through the formation of a micro-metmyoglobin form likely displaying a higher accessibility to lipids. Spectroscopic studies further highlighted the formation of a reversible unfolded metmyoglobin form at pH 3 which was shown to be more pro-oxidant in the absence of pepsin. At nutritional levels, the three apple matrices inhibited less efficiently the accumulation of lipid-derived conjugated dienes and 4-HNE at pH 5 when pepsin was present whereas at pH 3 the opposite was true. High initial bioaccessibilities of monomeric phenolic compounds were evidenced for both puree (57-74%) and the phenolic extract (79-96%) compared to fresh apple (1-14%) supporting their greater antioxidant capacity. By contrast, the bioaccessibility of dimer B2 was low for all matrices suggesting non-covalent binding to apple pectins.

Muskox myoglobin: purification, characterization and kinetics studies compared with cattle and water buffalo myoglobins

BACKGROUND

The Arctic muskox has economic potential as an alternative meat species and is becoming increasingly popular. The present study aimed to determine the primary structure and pseudoperoxidase activity of muskox myoglobin (Mb) compared to cattle and water buffalo myoglobins.

RESULTS

The primary structure of muskox Mb was determined via a matrix-assisted laser desorption ionization-time of flight mass spectrometry-based mapping approach using the sheep Mb as a reference sequence. The muskox Mb consists of 153 amino acid residues and shows 100% identity with sheep Mb, whereas 98.69% and 97.38% identity is found with cattle and water buffalo Mbs, respectively. Muskox Mb has an autoxidation rate (MetMb formation) higher than both cattle and water buffalo Mbs at pH 7.2 (37 °C). Moreover, its pseudoperoxidase activity is higher than both cattle and water buffalo Mbs at pH 7.4 (physiological pH), whereas it is slightly lower than cattle Mb and higher than water buffalo at a lower pH (5.8), corresponding to the conditions in meat.

CONCLUSION

For the first time, the present study reports the purification of myoglobin from muskoxen and, furthermore, a comparative study is conducted on autoxidation and pseudoperoxidase activity with respect to cattle and water buffalo Mbs at both physiological and acid pH. Overall, the results of the current research provide novel information for future studies useful to the meat industry when considering the importance of myoglobin as a principal pigment in meat colour stability. © 2019 Society of Chemical Industry.

Effects of Oxygen Partial Pressure on 4-Hydroxy-2-Nonenal Induced Oxymyoglobin Oxidation

4-hydroxyl-2-nonenal (HNE) is a lipid oxidation product that can increase oxymyoglobin oxidation. However, limited research has evaluated the role of oxygen partial pressure in HNE-induced metmyoglobin formation. Therefore, the objective of was to compare the effects of atmospheric and high-oxygen partial pressure on HNE-induced oxymyoglobin oxidation in vitro. Oxymyoglobin was incubated with or without HNE at atmospheric (20% O2) or high-oxygen (80% O2) partial pressure. Metmyoglobin formation was measured after 0, 48, and 96 h of incubation at 4°C, and mass spectrometry was utilized to characterize the covalent binding of HNE to myoglobin. High-oxygen condition (80% O2) increased (P < 0.05) HNE-induced oxymyoglobin oxidation compared with the atmospheric partial pressure condition (20% O2). However, HNE was bound to myoglobin at both high-oxygen and atmospheric partial pressure conditions, with no differences (P > 0.05) in the extent of adduct formation. These results suggest that high-oxygen conditions had no effect on extent of HNE-binding, but can increase oxymyoglobin oxidation.

Role of Mitochondria in Beef Color: A Review

In postmortem muscle, mitochondria remain active and can influence beef color by oxygen consumption and metmyoglobin reduction. Enzymes involved in glycolysis and the tricarboxylic acid cycle can generate reducing equivalents such as succinate or NADH. Mitochondrial activity is critical to maintain steaks that are bright cherry-red and improve color stability. This review seeks to characterize the role of mitochondria in beef color; more specifically to understand the effects of mitochondrial function on myoglobin redox stability.

The Effect of PUFA-Rich Plant Oils and Bioactive Compounds Supplementation in Pig Diet on Color Parameters and Myoglobin Status in Long-Frozen Pork Meat

The study evaluated the effect of pig diet supplementation with rapeseed or linseed oil, and vitamin E or selenium, or both vitamin E and selenium on color parameters and myoglobin content of pork Semimembranosus muscle after long-term freezing storage during nine months. The influence of the type of the bioactive compounds added to pig diet on the content of myoglobin or oxymyoglobin, metmyoglobin and deoksymyoglobin in Semimembranosus m. was also assessed. The results indicate that the presence of oils rich in polyunsaturated fatty acids (PUFA) in pig diet improves the color of pork meat. Supplementation of dietary plant oils or dietary oils with antioxidants tended to increase significantly the concentration of oxymyoglobin and decrease the concentration of metmyoglobin in meat compared to the control group. The highest content of oxymyoglobin was observed in meat obtained from pigs fed diets with linseed oil. The best color scores (highest a* parameter) was noted for rapeseed oil group (with no addition of antioxidants). In conclusion, the addition of antioxidants to pigs’ forage supplemented with PUFA-rich oils is not recommended in order to improve color of long-term frozen pork.

Exogenous and Endogenous Factors Influencing Color of Fresh Meat from Ungulates

Biochemistry of post-mortem muscle tissue is complex, and several factors affect the fresh meat color and color stability, both of which influence consumer acceptance. Therefore, improving meat color and meat color stability is of significant value to the meat industry and consumers. While extensive literature is available on the color and color stability of domestic ungulates, literature on wild ungulates is notably lacking. With an increasing global demand for meats from wild ungulates, it is critical to identify the knowledge gaps regarding their color and color stability. The objective of this paper is to overview the exogenous and endogenous factors influencing the color and color stability of fresh meats from domestic and wild ungulates. The literature highlighted that the pre- and post-harvest factors influencing meat color and meat color stability are interrelated and not mutually exclusive. Current research indicates that the effects of several of these factors are specific to species, breed, and muscle source. Novel ways to manipulate these factors using a biosystems approach should be explored to improve color attributes of fresh ungulate meats.

Factors Affecting Lipid Oxidation Due to Pig and Turkey Hemolysate

Turkey hemolysate promoted lipid oxidation in washed muscle more effectively than pig hemolysate, which was partly attributed to the greater ability of H₂O₂ that formed during auto-oxidation to oxidize the avian hemoglobin (Hb). Turkey and pig hemolysate (2.5 μM Hb) exposed to 10 μM H₂O₂ oxidized to 48% and 4% metHb, respectively. Catalase activity, which converts H₂O₂ to water, was elevated in the pig hemolysate. The larger difference in Hb oxidation when comparing turkey and pig hemolysate in washed muscle (relative to their auto-oxidation rates) suggested that lipid oxidation products facilitated formation of metHb. Turkey metHb released hemin more readily than pig metHb, which coincided with turkey metHb promoting lipid oxidation more effectively than pig metHb. Ferryl Hb was not detected during storage of turkey or pig hemolysate in washed muscle, which suggested a minor role for hypervalent forms of Hb in the oxidation of the lipids.

Species-Specificity in Myoglobin Oxygenation and Reduction Potential Properties

The objective was to compare oxygenation and reduction potential properties of bovine and porcine myoglobins in-vitro. Cyclic voltammetry and homology-based myoglobin modeling were used to determine the species-specific effects on myoglobin reduction potential and oxygenation properties at pH 5.6, 6.4, and 7.4. At all pHs, porcine myoglobin had greater (P = 0.04) oxygen affinity than bovine myoglobin. For both species, oxygen affinity was higher at pH 6.4 > pH 7.4 > 5.6 (P = 0.0002). Myoglobin reduction potential for both species was affected by pH (P < 0.0001). The redox potentials became more negative as pH increased, indicating a proton-coupled electron transfer. There were no differences (P = 0.51) between species in reduction potential properties of heme. Homology-based myoglobin modeling indicated that the porcine myoglobin has a shorter distance between the distal histidine and heme than does bovine myoglobin. The variation in amino acid composition between bovine and porcine myoglobin could be partially responsible for differences in oxygen affinity.

Proteomic based approach for characterizing 4-hydroxy-2-nonenal induced oxidation of buffalo (Bubalus bubalis) and goat (Capra hircus) meat myoglobins

BACKGROUND

Myoglobin (Mb) is a sarcoplasmic heme protein primarily responsible for meat color and its chemistry is species specific. 4-hydroxy-2-nonenal (HNE) is a cytotoxic lipid derived aldehyde detected in meat and was reported to covalently adduct with nucleophilic histidine residues of Mb and predispose it to greater oxidation. However, no literature is available on characterization of lipid oxidation induced oxidation of Indian water buffalo (Bubalus bubalis) and goat (Capra hircus) myoglobins.

METHODS

Present study characterize the Mb extracted from water buffalo and goat cardiac muscles using two-dimensional gel electrophoresis (2DE), OFFGEL electrophoresis and mass spectrometry (MS). Purified buffalo and goat bright red oxymyoglobin were reacted with HNE in-vitro at physiological pH (7.4) and temperature (37 °C) conditions and the formation of oxidised brown metmyoglobin was measured. The Mb-HNE adducts were detected using MALDI-TOF MS, whereas specific sites of adduction was determined using ESI-QTOF MS/MS.

RESULTS

Purified buffalo and goat Mb samples revealed a molecular mass of 17,043.6 and 16,899.9 Daltons, respectively. The 2DE analysis exhibited 65 (sarcoplasmic protein extract) and 6 (pure Mb) differentially expressed (P < 0.05) protein spots between buffalo and goat samples. OFFGEL electrophoresis revealed an isoelectric point of 6.77 and 7.35 respectively, for buffalo and goat Mb's. In-vitro incubation of HNE with bright red buffalo and goat oxymyoglobin's at pH 7.4 and 37 °C resulted in pronounced (P < 0.05) oxidation and formation of brown metmyoglobin. MALDI-TOF MS analysis of Mb-HNE reaction mix revealed covalent binding (via Michael addition) of 3 and 5 molecules of HNE with buffalo and goat Oxy-Mb's, respectively. ESI-QTOF MS/MS identified seven and nine histidine (HIS) residues of Mb that were readily adducted by HNE in buffalo and goat, respectively.

CONCLUSION

The study demonstrated better redox stability of buffalo Mb than goat Mb. Our findings confirm the hypothesis that relative effect of HNE was greater for Mb's with 12 ± 1 HIS residues than Mb's with 9 HIS residues and helps meat processors in developing species-specific processing strategies to reduce the color variability.

Molecular characterization of southern bluefin tuna myoglobin (Thunnus maccoyii)

The primary structure of southern bluefin tuna Thunnus maccoyii Mb has been elucidated by molecular cloning techniques. The cDNA of this tuna encoding Mb contained 776 nucleotides, with an open reading frame of 444 nucleotides encoding 147 amino acids. The nucleotide sequence of the coding region was identical to those of other bluefin tunas (T. thynnus and T. orientalis), thus giving the same amino acid sequences. Based on the deduced amino acid sequence, bioinformatic analysis was performed including phylogenic tree, hydropathy plot and homology modeling. In order to investigate the autoxidation profiles, the isolation of Mb was performed from the dark muscle. The water soluble fraction was subjected to ammonium sulfate fractionation (60-90 % saturation) followed by preparative gel electrophoresis. Autoxidation profiles of Mb were delineated at pH 5.6, 6.5 and 7.4 at temperature 37 °C. The autoxidation rate of tuna Mb was slightly higher than that of horse Mb at all pH examined. These results revealed that tuna myoglobin was unstable than that of horse Mb mainly at acidic pH.

Effects of injection of hydrolysis plasma protein solution on the antioxidant properties in porcine M. Longissimus Lumborum

BACKGROUND

Plasma protein hydrolysates have been shown to possess antioxidant activity. However, no report has yet to examine the antioxidant effects of injection of plasma protein hydrolysates on meat quality. Therefore, in this study, the effects of injection of hydrolysis plasma protein solution on meat quality and storability were investigated in porcine M. longissimus lumborum.

METHODS

Twelve pigs were randomly selected at a commercial slaughter plant and harvested. Dissected loins were injected with one of five solutions: C- control (untreated), T1- 10 mM phosphate buffer solution (PBS), T2- 10 mM PBS with 0.01 % butylated hydroxytoluene, T3- 10 mM PBS with 5 % plasma proteins, and T4- 10 mM PBS with 5 % hydrolysis plasma proteins.

RESULTS

T3 and T4 induced greater reduction in protein content of the loin muscle than other treatments. T2 resulted in the lowest pH as well as highest cooking loss. After a storage period of 3-7 days, both lightness and redness of meat were unaffected by all injection treatments. However, yellowness was significantly elevated by treatment with T4 relative to the control. T4 also resulted in the lowest shear force (a measure of meat toughness), suggesting improvement of texture or tenderness. Further, T4 resulted in the most stable TBARS values during storage, indicating that this treatment might retard rancidity in meat.

CONCLUSION

Injection of porcine M. longissimus lumborum with hydrolysis plasma protein solution could improve overall pork quality, including tenderness and storability.

Effect of MAP, vacuum skin-pack and combined packaging methods on physicochemical properties of beef steaks stored up to 12days

The physicochemical properties of M. longissimus lumborum steaks over 12days of storage at 2°C, and under three packaging conditions, were investigated: vacuum skin packaging (VSP); modified atmosphere packaging (MAP), and their combination with semi-permeable inner VSP film (VSP-MAP). Standard gas composition (80% O2/20% CO2) was used for MAP and VSP-MAP packaging. CIE L*a*b* color parameters of VSP-MAP samples were similar to those kept in MAP and significantly higher to those stored in VSP. Myoglobin oxidation was more evident in VSP-MAP and MAP samples than in VSP indicating increased oxidation processes. However, storage in MAP resulted in greater lipid oxidation compared both to VSP and VSP-MAP. No differences between treatments were observed in terms of Warner-Bratzler shear force values and drip loss. In general, these results suggest that the combination of VSP and MAP methods may be an efficient way to reduce negative quality changes typical for both systems used separately.

Proteome basis for intramuscular variation in color stability of beef semimembranosus

The objective of the present study was to characterize the proteome basis for intramuscular color stability variations in beef semimembranosus. Semimembranosus muscles from eight carcasses (n=8) were fabricated into 2.54-cm thick color-labile inside (ISM) and color-stable outside (OSM) steaks. One steak for sarcoplasmic proteome analysis was immediately frozen, whereas other steaks were allotted to retail display under aerobic packaging. Color attributes were evaluated instrumentally and biochemically on 0, 2, and 4days. Sarcoplasmic proteome was analyzed using two-dimensional electrophoresis and tandem mass spectrometry. ISM steaks demonstrated greater (P<0.01) abundance of glycolytic enzymes (fructose-bisphosphate aldolase A, phosphoglycerate mutase 2, and beta-enolase) and phosphatidylethanolamine-binding protein 1 than their OSM counterparts. Possible rapid post-mortem glycolysis in ISM, insinuated by over-abundance of glycolytic enzymes, could lead to rapid pH decline during early post-mortem, which in turn could potentially compromise its color stability. These results indicated that differential abundance of sarcoplasmic proteome contributes to intramuscular variations in beef color stability.