Effects of tartrate on color stability and myoglobin affinity for oxygen in beef

The effects of the affinity of myoglobin for oxygen on meat discoloration were investigated. First, we showed that 10 mmol/L tartrate significantly decreased the deoxygenation rate in vacuum-packed beef, although it did not reduce mitochondrial oxygen consumption activity. Second, the myoglobin affinity was evaluated with or without 1 mg/mL mitochondria and/or 10 mmol/L tartrate. The oxygen concentration that gives 50 % of the deoxygenation ratio was evaluated as myoglobin affinity. The affinity in the "with mitochondria" condition (0.370 ± 0.006 %) was significantly lower than that of "myoglobin" (0.312 ± 0.019 %), "with tartrate" (0.292 ± 0.009 %), and "with mitochondria and tartrate" (0.287 ± 0.022 %). Furthermore, the effect of 10 mmol/L tartrate on the myoglobin oxidation rate in beef was observed at 0.18-4.2 % oxygen. The addition of tartrate inhibited oxidation at lower concentrations but promoted oxidation at higher concentrations, with 1 % being the divergent concentration. Using tartrate, we demonstrated that myoglobin affinity is a determining factor for the oxygen concentrations that promote beef discoloration.

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.

Characterization of Pork Loin Chop Color Stability Using Loin Quality Traits and Instrumental Discoloration Measures

The objective of this study was to characterize the color stability of pork loin chops using fresh quality traits and instrumental measures of discoloration. Boneless pork loins (N=484) were evaluated for quality traits at 11 or 14 d post-mortem. One chop was cut from each loin near the 10th rib for retail display, overwrapped, and displayed under constant fluorescent lighting for 7 d. Objective color, myoglobin redox forms, and subjective visual discoloration traits were evaluated daily. After retail display, chops were categorized based on final visual discoloration (Day 7) as Very Color Stable (VCS; 0% to 5% discoloration), Color Stable (CS; 5% to 10% discoloration), Neutral (10% to 25% discoloration), Color Labile (CL; 25% to 30% discoloration), or Very Color Labile (VCL; >30% discoloration). Quality and color traits were analyzed using the GLIMMIX (visual discoloration) or MIXED (all other measures) procedure of SAS. Retail display data were analyzed as repeated measures. Chops ultimately classified as CS or VCS were darker, redder, and had lesser surface metmyoglobin (P<0.01) than CL and VCL chops at both Day 1 of retail display and throughout display. Stable chops also had generally increased R630/580 values as well as decreased visual discoloration scores and yellowness during display. A group×day interaction was observed for all traits measured during retail display (P<0.0001). No differences in aged loin ventral surface redness were observed between color stability groups (P≥0.16). Overall, chops ultimately classified as CS came from aged loins that were generally darker, redder, and less yellow, with greater pH values, greater marbling scores,and decreased purge loss.

Effects of Modified Atmospheric Packaging on Ground Chicken Color and Lipid Oxidation

The objective of the current study was to evaluate the color changes and lipid oxidation of ground chicken patties packaged in polyvinyl chloride (PVC) film, high-oxygen (HiOx)–modified atmospheric packaging (MAP; 80% oxygen + 20% carbon dioxide [CO2]), and carbon monoxide (CO)-MAP (0.4% CO + 19.6% CO2 + 80% nitrogen) and stored at 2°C. Surface color was measured using a HunterLab MiniScan spectrophotometer on days 0, 1, 2, and 4. Lipid oxidation, pH, and aerobic plate count were determined on days 0 and 4 of storage. Fatty acid profiles were determined on day 0 to characterize saturated and unsaturated fatty acids. Patties packaged in PVC had greater (P < 0.05) pH than HiOx-MAP and CO-MAP. Gas chromatography analysis indicated that ground chicken has 72.8% unsaturated fatty acids and 27.2% saturated fatty acids (based on total lipids and fatty acid methyl ester). The formation of carboxymyoglobin on ground chicken patty surface was confirmed by peaks at 420 and 570 nm, whereas oxymyoglobin had peaks at 410 and 580 nm. Instrumental color analysis indicated both HiOx-MAP and CO-MAP had greater (P < 0.05) redness (a* values) than PVC on day 4 of storage. Patties packaged in HiOx-MAP had greater (P < 0.05) chroma values than CO-MAP and PVC on day 4 of storage. Visual panelists noted less (P < 0.05) surface discoloration in CO-MAP than PVC and HiOx-MAP on day 4 of storage. Lipid oxidation was greater (P < 0.05) in PVC and HiOx-MAP than CO-MAP. CO inclusion at 0.4% level effectively inhibited lipid oxidation and stabilized surface redness during refrigerated storage of ground chicken.

Hemoglobin catalyzes ATP-synthesis in human erythrocytes: a murburn model

Blood hemoglobin (Hb), known to transport oxygen, is the most abundant globular protein in humans. Erythrocytes have ∼10^-3 M concentration of ATP in steady-state and we estimate that this high amounts cannot be formed from 10^-4 - 10^-7 M levels of precursors via substrate-level phosphorylation of glycolysis. To account for this discrepancy, we propose that Hb serves as a 'murzyme' (a redox enzyme working along the principles of murburn concept), catalyzing the synthesis of the major amounts of ATP found in erythrocytes. This proposal is along the lines of our earlier works demonstrating DROS (diffusible reactive oxygen species) mediated ATP-synthesis as a thermodynamically and kinetically viable mechanism for physiological oxidative phosphorylation. We support the new hypothesis for Hb with theoretical arguments, experimental findings of reputed peers and in silico explorations. Using in silico methods, we demonstrate that adenosine nucleotide and 2,3-bisphosphoglycerate (2,3-BPG) binding sites are located suitably on the monomer/tetramer, thereby availing facile access to the superoxide emanating from the heme center. Our proposal explains earlier reported in situ experimental findings/suggestions of 2,3-BPG and ADP binding at the same locus on Hb. The binding energy is in the order of 2,3-BPG > NADH > ATP > ADP > AMP and agrees with earlier reports, potentially explaining the bioenergetic physiology of erythrocytes. Also, the newly discovered site for 2,3-BPG shows lower affinity in fetal Hb (as compared to adults) explaining oxygen transfer from mother to embryo. The findings pose significant implications in routine physiology and pathologies like sickle cell anemia and thalassemia.Communicated by Ramaswamy H. Sarma.

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.

Characterization of the Cofactors Involved in Non-enzymatic Metmyoglobin/Methemoglobin Reduction In Vitro

Previous research reported the role of nonenzymatic metmyoglobin (MetMb) and methemoglobin (MetHb) reduction in meat color; however, limited studies have characterized the cofactors involved in nonenzymatic reduction. The objective of this study was to characterize electron donors and carriers in nonenzymatic MetMb and MetHb reduction at various temperatures and postmortem muscle pHs in vitro. Methylene blue and cytochrome c (cyt-c) were evaluated as electron carriers and nicotinamide adenine dinucleotide, reduced form (NADH) and ascorbate were considered as electron donors. All combinations of electron donors and carriers were evaluated in the following order: NADH plus methylene blue, ascorbate plus methylene blue, NADH plus cyt-c, and ascorbate plus cyt-c. Spectrophotometry was utilized to monitor the rates of reduction. The results indicated that methylene blue was an effective electron carrier than cyt-c in the presence of NADH. Temperature and pH had cofactor-specific effects on nonenzymatic MetMb and MetHb reduction. Lower temperature resulted in an increased nonenzymatic MetMb reduction for methylene blue regardless of electron donor (ascorbate, P = 0.03, NADH, P = 0.04). As pH increased, MetHb reduction was enhanced in the presence of ascorbate plus cyt-c. Nonenzymatic MetHb reduction was numerically lower than nonenzymatic MetMb reduction in the presence of NADH plus methylene blue. In summary, in addition to NADH, the current in vitro research demonstrated that ascorbate plus cyt-c could contribute to nonenzymatic MetMb and MetHb reduction at meat-pH and storage temperature.

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 Aging, Modified Atmospheric Packaging, and Display Time on Metmyoglobin Reducing Activity and Oxygen Consumption of High-pH Beef

The objective of current research was to determine the effects of extended aging, modified atmospheric packaging (MAP), and display time on metmyoglobin reducing activity (MRA) and oxygen consumption (OC) of high-pH beef using pH sensitive methodology for MRA and OC. Ten normal-pH (mean pH = 5.6) and 10 high-pH loins (mean pH = 6.4) were vacuum packaged on d 3 postmortem and aged for 0, 21, 42, and 62 d at 2°C. Following aging, 2.0-cm-thick steaks were cut from each of the normal- and high-pH loin sections and packaged in either PVC film, high-oxygen (HiOx-MAP), or carbon monoxide modified atmospheric (CO-MAP) packaging. Surface color, OC, and MRA were measured on d 0 and 6 of the respective aging periods. Steaks in HiOx-MAP and CO-MAP had similar (P > 0.05) L* values, which were greater (P < 0.05) than high-pH steaks packaged in PVC film. On 21-d of aging, steaks with at both pHs in CO-MAP and HiOx-MAP had greater (P < 0.05) a* values than steaks packaged in PVC. As aging time increased, MRA decreased (P < 0.05) for steaks with normal- and high-pH when packaged in PVC and HiOx-MAP. Steaks with a high-pH in CO-MAP had greater (P < 0.05) MRA than steaks with a normal-pH in CO-MAP at all aging periods. Steaks with a high-pH had greater (P < 0.05) OC on d 0 and 6 than normal-pH steaks. Steaks with a normal-pH aged for 21 d and packaged in PVC and HiOx-MAP had greater (P < 0.05) lipid oxidation than high-pH steaks aged for 21 d and packaged in PVC and HiOx-MAP. After 62 d of aging and 6 d of display, the greatest color stability chemistry (based on MRA and OC for all package types) were: high-pH meat > normal-pH meat; thus the MRA and OC methodology was useful in relative comparison of packaged meat color stability differences due to pH.

Growth Performance and Meat Quality Evaluations in Three-Way Cross Cattle Developed for the Tibetan Plateau and their Molecular Understanding by Integrative Omics Analysis

Despite of favorable characteristics of high protein, low fat, and free-pollution, yak meat has intrinsically poor performance in tenderness and color, which is ever challenging yak sector. To this end, a three-way cross system was first developed for high quality beef of the Tibetan Plateau using Angus cattle ( Bos taurus) as terminal sire to mate with 1/2 yak (F1) generated from♂Qaidam cattle ( Bos taurus) × ♀yak ( Bos grunniens). The withers height, chest girth, and body weight of 1/4 yak (F2) were all great higher than that of yak and 1/2 yak ( P < 0.01), especially at later period, suggesting the faster growth rate of 1/4 yak. Also the dressing percentage was much better in 1/4 yak ( P < 0.01). Tenderness and meat color were both significantly improved in 1/4 yak with some unpleasant sacrifice of PUFAs, such as EPA and DHA, and meat protein, given the significantly lower shear force and higher L* ( P < 0.01). A total of 769 genes, including SREBF1, GHR, and FASN, the widely recognized causal genes of meat quality, were identified from 11947 differently expressed genes by the data integration of transcriptome, GWAS and QTL. These genes were significantly enriched for important pathway and GO terms, such as insulin signaling pathway, fatty acid biosynthesis, calcium signaling pathway, metabolic pathway, and cellular response to stress ( P < 0.01). And 12 promising candidates were exemplified with annotation of H3K4me3 data from divergent meat quality, such as OSTF1, NRAS1, and KCNJ11. Interestingly, 75 high-altitude adaptive candidate genes were also detected in the list. This study is a first step toward high quality beef of the Tibetan Plateau and provides useful information for their molecular understanding.

Modified Atmosphere Packaging Improves Surface Color of Dark-Cutting Beef

The objective was to determine the effects of modified atmosphere packaging (MAP) on the surface color of dark-cutting beef that had been aged for 21 d. The USDA Choice (normal-pH; IMPS #180) strip loins (n = 10) and no-roll dark-cutter strip loins (n = 10) were obtained from a commercial packing plant within 72 h of harvest. Both normal-pH and dark-cutting beef were vacuum packaged and aged for 21 d. Steaks were cut from both normal and dark-cutting loins, assigned to 1 of 3 packaging treatments; PVC, HiOx-MAP, and CO-MAP, and stored in a simulated retail display under continuous fluorescent lighting at 2°C for 6 d. Instrumental and visual color were measured every 24 h. Thiobarbituric acid assay was used as an indicator for lipid oxidation. There was a packaging × muscle type × display time interaction (P < 0.0001) for instrumental and visual color. On d 1 of display, dark-cutting steaks packaged in HiOx-MAP had greater (P < 0.001) a* values and chroma than dark-cutting PVC steaks. On d 6 of the display, dark-cutting steaks packaged in CO-MAP had 10 units greater a* values than dark-cutting steaks packaged in PVC. The visual panel also noted less muscle darkening (P < 0.002) in HiOx-MAP and CO-MAP compared with steaks packaged in PVC on d 6 of the display. There was less surface discoloration (P < 0.001) in HiOx-MAP and CO-MAP dark-cutting steaks compared with PVC dark-cutting steaks by the end of the display. There was a packaging × muscle type interaction for instrumental L* values and lipid oxidation. Dark-cutting steaks packaged in HiOx-MAP and CO-MAP had greater (P < 0.05) L* values compared with dark-cutting steaks in PVC packaging. In conclusion, HiOx-MAP improved redness of dark-cutting beef during the initial phase of display, while CO-MAP resulted in a stable red color.

Contribution of nitric oxide synthase from coagulase-negative staphylococci to the development of red myoglobin derivatives

As part of the microbial community of meat or as starter cultures, coagulase-negative staphylococci (CNS) serve several essential technological purposes in meat products, such as color development through the reduction of nitrate to nitrite. As the safety of nitrite as an additive has been questioned, we explored the potential of CNS to develop red myoglobin derivatives such as oxymyoglobin and nitrosomyoglobin. Nitrosoheme was extracted to evaluate NO production. This production could be due to a nitric oxide synthase (NOS) activity. In all CNS strains, a nos gene was identified. The NOS sequences deduced were highly conserved within CNS. A phylogenetic tree based on the NOS sequences revealed that the strains within species were clustered. Ninety-one percent of the strains, whatever the species, were able to form red myoglobin derivatives in aerobic conditions, but a high variability was observed between strains within species. However, NO production was low as nitrosomyoglobin represented 8% to 16% of the red pigments according to the species. Formation of oxymyoglobin, especially under aerobic conditions, was substantial, but varied greatly within species. The mechanism involved in the formation of oxymyoglobin could rely on staphylococcal reductases and remains to be explored.