Metmyoglobin Reducing Research Articles

Light Source Influences Color Stability and Lipid Oxidation in Steaks from Low Color Stability Beef Triceps brachii Muscle

AbstractColor of retail fresh meat is one of the most important quality attributes affecting purchasing decisions for consumers. The objective of this study was to evaluate the impact of different light sources on surface color and lipid oxidation during retail display of fresh steaks from beef Triceps brachii (TB), a muscle with low color and lipid oxidative stabilities. Steaks (n = 12) from 20 TB muscles were overwrapped with oxygen-permeable polyvinyl chloride, and assigned to one of three lighting treatments, i.e., high UV fluorescent (HFLO), low UV fluorescent (FLO), and light emitting diode (LED), in temperature-controlled deli cases. Steaks were removed on retail display d 1, 3, 5, and 7 for evaluating instrumental color (L*, a*, and b* values), surface myoglobin redox forms, metmyoglobin reducing ability, and lipid oxidation. Surface redness (a* values) of TB steaks decreased (P < 0.05) during retail display. Light source influenced a* values, with HFLO-displayed steaks having higher (P < 0.05) a* values than steaks exposed to both FLO and LED light sources. Oxymyoglobin levels were higher (P < 0.05) for TB steaks displayed under HFLO lights than those displayed under FLO (on d 3 and 7) or LED (on d 5 and 7) lights. Steaks displayed under HFLO lights had lower (P < 0.05) metmyoglobin levels than those exposed to both FLO and LED lights on d 5 and 7. Lipid oxidation increased over retail display time, and on d 7 of retail display, steaks exposed to HFLO had less (P < 0.05) lipid oxidation than those displayed in FLO or LED. The results of the present study indicated that color stability and lipid oxidation in TB steaks during retail display are impacted by light source. The HFLO lighting may help to minimize surface discoloration and lipid oxidation in low color stability beef muscles.

In Vitro Zinc Protoporphyrin IX Formation in Different Meat Sources Related to Potentially Important Intrinsic Parameters

For several years, researchers have studied the formation of zinc protoporphyrin IX in meat, as it is considered to be an important natural colouring agent in dry cured or fermented meat products in the absence of nitrite and/ or nitrate. Until now, however, mainly pork meat is used for these investigations. The goal of this research was to relate in vitro zinc protoporphyrin IX and protoporphyrin IX formation in eight meat sources (chicken, turkey, pork, lamb, beef, veal, horse and porcine liver) to eight intrinsic parameters using partial least squares regression (PLS) analysis. Significant differences in pH, initial metmyoglobin formation, metmyoglobin reduction ability, total heme, zinc chelatase activity, and total iron and zinc concentration between meat sources were found. Water activity, however, was not significantly different between meat sources. Liver tissue and horse meat showed the best ability to form zinc protoporphyrin IX. Formation of protoporphyrin IX was limited in all meat sources. PLS analysis revealed that mainly zinc chelatase activity, followed by total heme, total iron and zinc content, were predominant intrinsic parameters to explain variations in zinc protoporphyrin IX formation. These findings could be important for meat industry in order to establish the production of red coloured nitrite-free meat products.

Myofibrillar Protein, Lipid and Myoglobin Oxidation, Antioxidant Profile, Physicochemical and Sensory Properties ofCaprine longissimus thoracisduringPostmortemConditioning

The study examined the impact of refrigerated storage on antioxidant profile, oxidative changes in myoglobin, lipids and myofibrillar proteins and quality attributes of longissimus thoracis (LT) muscle from goats. Analyses were conducted on LT obtained from carcasses of sixteen Boer bucks on 0, 1, 5 and 10 days postmortem. Ageing had no effect on antioxidant enzyme activities. Concentration of tocopherols and total carotenoids decreased over storage. Myoglobin, metmyoglobin reducing activity, redness and shear force decreased while metmyoglobin content and drip loss increased over storage. Free thiol decreased while carbonyls and TBARS increased over storage. The relative density of myosin heavy chain, actin and troponin T and the concentration of n−6 and n−3 fatty acids were stable until day 5 but declined afterward. Tocopherol and carotenoid were correlated (P < 0.05) with oxidative changes. Ageing did not affect consumer preference for juiciness, flavor and overall acceptability. However, preference for tenderness increased over storage. Practical Applications Information on the impact of postmortem ageing on the antioxidant status of chevon in relation to its oxidative changes, physicochemical properties and shelf life is limited. This study demonstrates that although tenderness improved, quality loss during ageing of chevon is inexorable. The tocopherols and carotenoids are the primary drivers of postmortem oxidative stability of chevon. Antioxidant enzymes do not seem to play a significant role in the postmortem oxidative stability of chevon. The oxidative stability of longissimus thoracis in goats could be maintained for 5 days during chill storage. The current findings would provide useful information to consumers, retailers and meat industries on the merits and demerits of postmortem ageing of chevon and the factors to consider when longer ageing periods are desired or necessitated.

Effects of aging on the fundamental color chemistry of dark-cutting beef.

The objective of the current study was to evaluate the effects of aging on myoglobin chemistry of dark-cutting beef. Ten USDA Choice (mean pH = 5.6; normal pH beef) and 10 no-roll dark cutter (mean pH = 6.4) strip loins were obtained from a commercial packing plant within 3 d of harvest. Loins were cut into 4 sections, vacuum packaged, randomly assigned to 0-, 21-, 42-, and 62-d aging at 2°C in the dark. Following aging, loin sections were cut into 2.5-cm-thick steaks and were used to determine bloom development, oxygen consumption (OC), metmyoglobin reducing activity (MRA), and lipid oxidation. Surface color readings were measured using a HunterLab Miniscan XE Plus spectrophotometer. A significant muscle type × aging time interaction resulted for OC ( < 0.001). Normal pH steaks declined more ( < 0.001) in OC during aging than dark-cutting beef. On d 0, dark-cutting beef had a greater OC ( < 0.001) than normal pH beef. There was a significant muscle type × oxygenation time × aging period interaction for L* values, deoxymyoglobin (DeoxyMb), and oxymyoglobin (OxyMb). When dark-cutting sections were aged for 62 d, both 0 and 60 min bloom development L* values were greater ( < 0.0001) than 0 min dark-cutting sections aged for 21 or 42 d. At all aging periods, normal pH beef had greater OxyMb content and lower DeoxyMb ( < 0.0001) during bloom development than dark-cutting beef. An aging period × muscle type interaction was significant for % overall reflectance ( = 0.0017) and absorbance ( = 0.0038). Dark cutting and normal pH beef loin sections aged for 62 d had greater reflectance ( < 0.0001) than 21 d. On d 0, dark-cutting beef had greater ( < 0.0001) MRA than normal pH beef. There were no significant ( = 0.14) differences in MRA between 42 and 62 d between dark-cutting and normal pH beef. Dark cutting steaks had lower thiobarbituric acid reactive substances values ( < 0.0001) than normal pH steaks. The results indicate that characterizing the myoglobin chemistry during aging will help to design strategies to improve appearance of high pH beef.

Comparison of myofibrillar protein degradation, antioxidant profile, fatty acids, metmyoglobin reducing activity, physicochemical properties and sensory attributes of gluteus medius and infraspinatus muscles in goats

BackgroundThe functionality of myofibrillar proteins is a major factor influencing the quality attributes of muscle foods. Nonetheless, the relationships between muscle type and oxidative changes in chevon during ageing are meagrely elucidated. Postmortem changes in antioxidant status and physicochemical properties of glycolytic gluteus medius (GM) and oxidative infraspinatus (IS) muscles in goats were compared.MethodsTwenty Boer bucks (9–10 months old, body weight of 36.9 ± 0.725 kg) were slaughtered and the carcasses were subjected to chill storage (4 ± 0.5 °C). Analyses were conducted on GM and IS muscles sampled on 0, 1, 4 and 7 d postmortem.ResultsChill storage did not affect the antioxidant enzyme activities in both muscles. The IS had greater (P < 0.05) superoxide dismutase and catalase activities than GM. Carotenoid and tocopherol contents did not differ between muscles but decreased (P < 0.05) over storage. The IS had higher (P < 0.05) glycogen and ultimate pH and lower (P < 0.05) shear force and cooking loss than GM. The carbonyl content, % metmyoglobin, drip loss and TBARS increased (P < 0.05) while free thiol, metmyoglobin reducing activity (MRA), shear force and myoglobin decreased (P < 0.05) over storage. Muscle type had no effect (P > 0.05) on free thiol, MRA and TBARS. The GM had lower (P < 0.05) redness on d 0 and 1 than IS while the IS had greater carbonyl, % metmyoglobin and drip loss than GM on d 7. The reflective density of slow myosin heavy chain (MHC) was higher (P < 0.05) while the density of fast MHC and actin was lower (P < 0.05) in IS than GM. Regardless of muscle type, the density of MHC decreased (P < 0.05) while that of actin was stable over storage. Nonetheless, the degradation of fast and slow MHC was greater (P < 0.05) in IS than GM. Muscle type had no effect (P > 0.05) on consumer preference for flavour, juiciness and overall acceptability. However, IS had higher (P < 0.05) tenderness score than GM on d 1 and 4 postmortem. Intramuscular fat was higher (P < 0.05) in IS compared with GM. Fatty acid composition did not differ between the muscles. However, GM had lower (P < 0.05) n-6/n-3 ratio than IS. The n-3 and n-6 PUFA declined (P < 0.05) while the SFA increased (P < 0.05) over storage.ConclusionThe changes in myofibrillar proteins and physicochemical properties of goat meat during postmortem chill storage are muscle-dependent.

Fatty acids, lipid and protein oxidation, metmyoglobin reducing activity and sensory attributes of &lt;i&gt;biceps femoris&lt;/i&gt; muscle in goats fed a canola and palm oil blend

The link between the consumption of saturated fatty acids of ruminant meat and the incidence of chronic diseases in humans substantiates efforts to modify its lipid profile. However, altering the lipid profile of ruminant meat could affect its quality attributes and shelf life. This study investigated the effect of a blend of 80% canola oil and 20% palm oil (BCPO) and post mortem ageing on lipid composition, antioxidant status, colour, metmyoglobin reducing activity (MRA) and lipid and protein oxidation in biceps femoris muscle in goats. Twenty-four bucks were randomly assigned to diets containing on a dry matter basis, 0%, 4% or 8% BCPO, fed for 100 d, and slaughtered. The biceps femoris was subjected to 7 d post mortem ageing (4 oC). Neither diet nor post mortem ageing altered catalase, superoxide dismutase and glutathione peroxidase activities or sensory attributes of the biceps femoris . Dietary BCPO improved α- and γ-tocopherol, but did not affect total carotenoids and δ-tocopherol, colour, metmyoglobin content, MRA, TBARS, carbonyl content and free thiol content. Goats fed 4% BCPO had higher cis-9 trans -11 CLA, while those fed 8% BCPO had higher C18:3n-3 and C20:5n-3 compared with other treatments. The 4% and 8% BCPO meat had lower C14:0, but higher C18:1n-9 and C22:5n-3 than the control goats. Post mortem ageing decreased muscle polyunsaturated fatty acids (PUFA), antioxidant compounds, redness, MRA and oxidative stability of lipid and proteins, but increased metmyoglobin content. Dietary BCPO enhanced beneficial muscle lipids without compromising the sensory quality, and lipid and protein stability of the goat meat. Keywords: Antioxidants, carbonyl, fatty acids, metmyoglobin, thiol

Color attributes and oxidative stability of longissimus lumborum and psoas major muscles from Nellore bulls

The influence of muscle source on color stability of fresh beef from purebred Bos indicus cattle was investigated. Longissimus lumborum (LL) and psoas major (PM) muscles obtained from twelve (n=12) Nellore bull carcasses (24h post-mortem) were fabricated into 2.54-cm steaks, aerobically packaged, and stored at 4°C for nine days. Steaks were analyzed on day 0 for proximate composition and myoglobin concentration, whereas pH, instrumental color, metmyoglobin reducing activity (MRA), lipid oxidation, and protein oxidation were evaluated on days 0, 3, 6, and 9. LL steaks exhibited greater (P<0.05) redness, color stability, and MRA than PM counterparts. On the other hand, PM steaks demonstrated greater (P<0.05) myoglobin content, lipid oxidation, and protein oxidation than LL steaks. These results indicated the critical influence of muscle source on discoloration of fresh beef from Bos indicus animals and suggested the necessity to engineer muscle-specific strategies to improve color stability and marketability of beef from Bos indicus cattle.

Influence of Diet and Postmortem Ageing on Oxidative Stability of Lipids, Myoglobin and Myofibrillar Proteins and Quality Attributes of Gluteus Medius Muscle in Goats.

This study appraised the effects of dietary blend of 80% canola oil and 20% palm oil and postmortem ageing on oxidative stability, fatty acids and quality attributes of gluteus medius (GM) muscle in goats. Twenty-four Boer bucks were randomly allotted to diet supplemented with 0, 4 and 8% oil blend, fed for 100 days and slaughtered, and the GM muscle was subjected to a 7 d chill storage (4±1°C). Diet had no effect (P> 0.05) on the colour, drip loss, thiobarbituric acid-reactive substances (TBARS) value, free thiol, carbonyl, myoglobin and metmyoglobin contents, metmyoglobin reducing activity (MRA), antioxidant enzyme activities and abundance of myosin heavy chain (MHC) and actin in the GM muscle in goats. The meat from goats fed 4 and 8% oil blend had higher (P< 0.05) concentration of α and γ-tocopherol and abundance of troponin T compared with that from the control goats. The GM muscle from the oil-supplemented goats had lower (P< 0.05) concentration of C16:0 and greater (P< 0.05) concentration of C18:1n-9, C18:3n-3 and C20:5n-3 compared with that from the control goats. Nonetheless, diet did not affect (P< 0.05) the total fatty acid in the GM muscle in goats. Regardless of the diet, the free thiol and myoglobin contents, concentration of tocopherol and total carotenoids, MHC and MRA in the GM muscle decreased (P< 0.05) while carbonyl content, TBARS, drip loss and metmyoglobin content increased over storage. Dietary blend of 80% canola oil and 20% palm oil beneficially altered tissue lipids without hampering the oxidative stability of chevon.

Effects of extended aging and modified atmospheric packaging on beef top loin steak color.

The objective of this study was to evaluate the effects of extended aging and modified atmospheric packaging on beef LM color. Using a randomized complete block design, each beef longissimus lumborum muscle ( = 10; USDA Choice, 3 d postmortem) was equally divided into 3 sections and randomly assigned to 1 of 3 aging periods (21, 42, or 62 d at 2°C). After respective aging, each loin section was cut into four 2.5-cm-thick steaks and randomly assigned to 1 of 3 packaging types (PVC, HiOx-MAP [80% oxygen and 20% carbon dioxide], or CO-MAP [0.4% carbon monoxide, 69.6% nitrogen, and 30% carbon dioxide]). The steaks were displayed under continuous fluorescent lighting for 6 d, and surface color was determined daily using a HunterLab Miniscan XE Plus spectrophotometer and a visual panel. The fourth steak was used to characterize oxygen consumption (OC), lipid oxidation, and metmyoglobin reducing activity (MRA) on 21, 42, and 62 d (before display). On d 6 display, MRA, OC, and lipid oxidation also were measured. An increase in aging time decreased ( < 0.0001) muscle pH. Loin sections aged for 42 and 62 d had a lower ( < 0.0002) pH compared with loin sections aged for 21 d. An aging period × packaging × display time interaction ( < 0.0001) resulted for a* values (redness), chroma, and visual color (muscle color and surface discoloration). As aging time increased, HiOx-MAP had the most discoloration ( < 0.0001) compared with other packaging types on d 6. At all aging periods, steaks packaged in CO-MAP had greater ( < 0.0001) MRA on d 6 than PVC and HiOx-MAP, whereas steaks packaged in HiOx-MAP had the least MRA ( < 0.0001). There were no differences ( = 0.34) in thiobarbituric acid reactive substances values between steaks aged for 21 and 42 d when steaks were packaged in CO-MAP and displayed for 6 d. However, steaks packaged in HiOx-MAP and displayed 6 d had greater ( < 0.0001) lipid oxidation than CO-MAP. Steaks packaged in HiOx-MAP had a lower ( < 0.0001) OC compared with PVC and CO-MAP when aged for 42 and 62 d. There were no differences ( = 0.49) in OC between steaks packaged in PVC and HiOx-MAP when aged for 21 d and displayed 6 d. The results indicate that extended aging is detrimental to color stability when packaged in PVC and HiOx-MAP. However, steaks in CO-MAP had stable red color during display. Decreased color stability in PVC and HiOx-MAP could be associated, in part, with decreased MRA and OC.

Rapid Myoglobin Aggregation through Glucosamine-Induced α-Dicarbonyl Formation.

The extent of glycation and conformational changes of horse myoglobin (Mb) upon glycation with N-acetyl-glucosamine (GlcNAc), glucose (Glc) and glucosamine (GlcN) were investigated. Among tested sugars, the rate of glycation with GlcN was the most rapid as shown by MALDI and ESI mass spectrometries. Protein oxidation, as evaluated by the amount of carbonyl groups present on Mb, was found to increase exponentially in Mb-Glc conjugates over time, whereas in Mb-GlcN mixtures the carbonyl groups decreased significantly after maximum at 3 days of the reaction. The reaction between GlcN and Mb resulted in a significantly higher amount of α-dicarbonyl compounds, mostly glucosone and 3-deoxyglucosone, ranging from and 27 to 332 mg/L and from 14 to 304 mg/L, respectively. Already at 0.5 days, tertiary structural changes of Mb-GlcN conjugate were observed by altered tryptophan fluorescence. A reduction of metmyoglobin to deoxy-and oxymyoglobin forms was observed on the first day of reaction, coinciding with the greatest amount of glucosone produced. In contrast to native α-helical myoglobin, 41% of the glycated protein sequence was transformed into a β-sheet conformation, as determined by circular dichroism spectropolarimetry. Transmission electron microscopy demonstrated that Mb glycation with GlcN causes the formation of amorphous or fibrous aggregates, started already at 3 reaction days. These aggregates bind to an amyloid-specific dye thioflavin T. With the aid of α-dicarbonyl compounds and advanced products of reaction, this study suggests that the Mb glycation with GlcN induces the unfolding of an initially globular protein structure into amyloid fibrils comprised of a β-sheet structure.

Effects of natural antioxidants on colour stability, lipid oxidation and metmyoglobin reducing activity in raw beef patties.

Minced meats undergo oxidative changes and develop rancidity more quickly than intact muscle since grinding exposes more of the muscle surface to air and microbial contamination. Due to concerns about toxicological safety of synthetic antioxidants, recent studies have put more focus on natural antioxidant compounds derived from food components. The effects of four natural antioxidants (vitamin E, carnosine, grape seed extract and tea catechins) on oxidative processes and metmyoglobin reducing activity in raw beef patties during refrigerated (4°C) storage were investigated and the results were compared with butylated hydroxyanisole treatment patties. The correlation of lipid oxidation, colour and metmyoglobin reducing activity of beef patties were also studied. Samples treated with carnosine had the highest redness values on the eighth day. Tea catechins, vitamin E and grape seed extract showed higher protective effect against lipid oxidation than carnosine. Metmyoglobin reducing activity increased greatly in all samples during the storage. Significant correlation between redness value and lipid oxidation was demonstrated, while a weak correlation between metmyoglobin reducing activity and any other parameters was shown.

Species-specific effects on non-enzymatic metmyoglobin reduction in vitro

Our objectives were to determine the non-enzymatic metmyoglobin reduction properties of bovine, porcine, and equine myoglobins and to characterize the effects of pre-incubation of 4-hydroxy-2-nonenal (HNE) with myoglobins on non-enzymatic metmyoglobin reduction in vitro. Purified bovine, porcine, and equine metmyoglobins (0.05mM) were reduced at pH5.6 and 7.4 in the presence or absence of HNE. Rates of metmyoglobin reduction were monitored by spectrophotometry, and myoglobin adducts were characterized by high-resolution mass-spectrometry. Results showed that the species origins of individual myoglobins determined rates of non-enzymatic reduction (beef>equine>pork; P<0.05). Irrespective of species, pre-incubation of HNE myoglobin decreased non-enzymatic metmyoglobin reduction compared with control at both pH5.6 and 7.4 (P<0.05). Mass spectrometric analysis revealed adducts of HNE with bovine, porcine, and equine myoglobins. The results indicate that the amino acid composition and the covalent binding of HNE with myoglobin can significantly decrease the ability of heme to accept electrons.

Reverse electron transport effects on NADH formation and metmyoglobin reduction

The objective was to determine if NADH generated via reverse electron flow in beef mitochondria can be used for electron transport-mediated reduction and metmyoglobin reductase pathways. Beef mitochondria were isolated from bovine hearts (n=5) and reacted with combinations of succinate, NAD, and mitochondrial inhibitors to measure oxygen consumption and NADH formation. Mitochondria and metmyoglobin were reacted with succinate, NAD, and mitochondrial inhibitors to measure electron transport-mediated metmyoglobin reduction and metmyoglobin reductase activity. Addition of succinate and NAD increased oxygen consumption, NADH formation, electron transport-mediated metmyoglobin reduction, and reductase activity (p<0.05). Addition of antimycin A prevented electron flow beyond complex III, therefore, decreasing oxygen consumption and electron transport-mediated metmyoglobin reduction. Addition of rotenone prevented reverse electron flow, increased oxygen consumption, increased electron transport-mediated metmyoglobin reduction, and decreased NADH formation. Succinate and NAD can generate NADH in bovine tissue postmortem via reverse electron flow and this NADH can be used by both electron transport-mediated and metmyoglobin reductase pathways.

Species specific effects on non-enzymatic metmyoglobin reduction

Species specific effects on non-enzymatic metmyoglobin reduction

Effects of water- and oil-based rosemary on ground beef metmyoglobin reducing activity

Effects of water- and oil-based rosemary on ground beef metmyoglobin reducing activity

Understanding the Meat Color Attributes by Direct Electrochemistry of Myoglobin Films on Electrodes

Protein film electrochemistry (PFE) is a unique method with high simplicity to obtain mechanistic information about complex biological electron transfer and catalytic processes. The emerging applications of PFE are in the development of selective biosensors, biofuel production, renewable energy processes, green biocatalytic systems, and biomedical tools.[i],[ii],[iii] Along this line, we are exploring the novel utilization of heme-protein electrochemistry to understand the meat color qualities. Myoglobin (Mb) is a muscle protein predominantly responsible for meat color. Mb can exist in three different forms namely deoxy-, oxy-, and metmyoglobin. The extent of oxymyoglobin (Mb-FeII-O2) state mainly influences the characteristic red color of meat. On the other hand, the oxidation of oxy- or deoxymyoglobin leads to discoloration of meat or metmyoglobin (Mb-FeIII) accumulation.Our objective was to investigate the kinetics of metmyoglobin reduction and oxymyoglobin formation using myoglobin model and examine its relevance to meat color properties. For our initial electrochemical analysis, we have chosen three meat related pH conditions such as pH 7.4 (physiological muscle), pH 6.4 (stress-out animal muscle), and pH 5.6 (typical postmortem muscle) and investigated the rates of Mb-FeIII reduction and Mb-FeII-O2 formation using Mb-films adsorbed on graphite electrodes. We observed that under the physiological muscle pH condition, the rates of Mb-FeIII reduction and the subsequent formation of Mb-FeII-O2 were highly favored in comparison to the low acidic pH conditions. Our electrochemical results correlated well with the prior biochemical and redox-titration studies that reported the faster discoloration of meat with lowering pH conditions.[iv],[v] Our investigation suggests that myoglobin-PFE is simple, inexpensive, rapid, and powerful in probing atomic level redox-properties, and thus a valuable tool to predict meat color. Acknowledgements. This work was supported by the Oklahoma State University.[i]. (a) M. Meredith and S.D. Minteer, Annu. Rev. Anal. Chem., 2012, 5, 157-179; (b) S. Xu and S.D. Minteer, ACS Catalysis, 2013, 3, 1756-1763.[ii]. L. Halamkova, J. Halamek, V. Bocharova, A. Szczupak, L. Alfonta and E. Katz, J . Am . Chem . Soc ., 2012,4 , 5040.[iii]. (a) S. Krishnan and F. A. Armstrong, Chem . Sci ., 2012, 3, 1015-1023; (b) S. Krishnan and J. F. Rusling, Thin Iron Heme Enzyme Films on Electrodes and Nanoparticles for Biocatalysis, Chapter 5, p.125, in New and Future Developments in Catalysis, S. Suib (Ed.), Elsevier Publishers, 2013; (c) C. Walgama and S. Krishnan,J. Electrochem. Soc., 2014, 161, H1-H6; (d) S. Krishnan and C. Walgama, Anal. Chem., 2013, 85, 11420−11426.[iv]. A. L. Alderton, C. Faustman, D. C. Liebler, D. W. Hill, Biochemistry 2003 , 42, 4398.[v]. R. Ramanathan, R. A. Mancini, G. A. Dady, C. B. Van Buiten, Meat Science 2013, 93, 888.

Comparsion of the Effects of Succinate and NADH on Postmortem Metmyoglobin Redcutase Activity and Beef Colour Stability

In two experiments, the effects of succinate and NADH (reduced nicotinamide adenine dinucleotide) on metmyoglobin reductase activity and electron transport chain-linked metmyoglobin reduction were investigated and compared. In experiment 1, metmyoglobin (MetMb), substrate and inhibitors were incubated with mitochondria. Comparsion of the effects of succinate and NADH on MetMb reduction was investigated. The MetMb percentage in sample treated with 8 mol L−1 succinate decreased by about 69% after 3 h incubation, and the effect was inhibited by the addition of 10 mol L−1 electron transfer chain complex II inhibitor malonic acid; the MetMb percentage in samples treated with 2 mol L−1 NADH decreased by 56% and the effect was inhibited by the addition of 0.02 mol L−1 electron transport chain complex I inhibitor rotenone. These results indicated that electron transport chain played an important role in MetMb reduction. Both complex II and complex I take part in the MetMb reduction in mitochondria through different pathways. NADH-MetMb reduction system was less stable than succinate-MetMb system. In experiment 2, the beef longissimus dorsi muscle was blended with different concentrations of succinate or NADH. Enhancing patties with higher concentration of succinate or NADH improved colour stability in vacuum packaged samples (P<0.05). These results verified that mitochondria electron transport chain is related to the MetMb reduction in meat system.

Effect of dietary zinc and ractopamine hydrochloride on pork chop muscle fiber type distribution, tenderness, and color characteristics1,2

A total of 320 finishing pigs (PIC 327 × 1050; initially 98 kg) were used to determine the effects of adding Zn to diets containing ractopamine HCl (RAC) on muscle fiber type distribution, fresh chop color, and cooked meat characteristics. Dietary treatments were fed for approximately 35 d and consisted of a corn-soybean meal-based negative control (CON), a positive control diet with 10 mg/kg of RAC (RAC+), and the RAC+ diet plus 75, 150, or 225 mg/kg added Zn from either ZnO or Availa-Zn. Loins randomly selected from each treatment (n = 20) were evaluated using contrasts: CON vs. RAC+, interaction of Zn level × source, Zn level linear and quadratic polynomials, and Zn source. There were no Zn source effects or Zn source × level interactions throughout the study (P > 0.10). Pigs fed RAC+ had increased (P < 0.02) percentage type IIX and a tendency for increased (P = 0.10) percent type IIB muscle fibers. Increasing added Zn decreased (linear, P = 0.01) percentage type IIA and tended to increase (P = 0.09) IIX muscle fibers. On d 1, 2, 3, 4, and 5 of display, pork chops from pigs fed the RAC+ treatment had greater (P < 0.03) L* values compared to the CON. On d 0 and 3 of display, increasing added Zn tended to decrease (quadratic, P = 0.10) L* values and decreased (quadratic, P < 0.03) L* values on d 1, 2, 4, and 5. Pigs fed RAC+ had decreased (P < 0.05) a* values on d 1 and 4 of display and tended to have decreased (P < 0.10) a* values on d 0 and 2 compared to CON pork chops. Pork chops from the RAC+ treatment had a tendency for increased (P < 0.08) oxymyoglobin percentage compared to CON pork chops on d 1, 2, 4, and 5. On d 0, as dietary Zn increased in RAC+ diets, there was a decrease (linear, P < 0.01) in the formation of pork chop surface oxymyoglobin percentage. Metmyoglobin reducing ability (MRA) of pork chops on d 5 was decreased in the RAC+ group. Chops from pigs fed added Zn had increased (quadratic, P < 0.03) MRA on d 3 and 5 of the display period. There was a trend for increased (linear, P = 0.07) cooking loss with increasing Zn in RAC diets and treatments did not affect tenderness as measured by Warner-Bratzler shear force (P > 0.07). In conclusion, RAC+ diets produced chops that were lighter and less red but maintained a greater percentage of surface oxymyoglobin throughout a 5-d simulated retail display. Ractopamine reduced MRA at the end of the display period, but supplementing Zn to RAC diets restored MRA to near CON treatment levels at the end of the display period.

Correlating the Electrochemical Kinetics of Myoglobin‐Films to pH Dependent Meat Color

AbstractWe report here for the first time application of electrochemical kinetics to understand the myoglobin redox‐properties at three relevant meat pH conditions. We investigated the kinetics of oxymyoglobin formation electrochemically using films of myoglobin coated on high‐purity graphite electrodes. Three pH conditions corresponding to the physiological state (pH 7.4), stressed animal muscle (pH 6.4), and post‐mortem meat (pH 5.6) were examined in this study. Our findings show that slower metmyoglobin reduction rate and diminished oxygen‐affinity cause the discoloration of red‐meat at low acidic pH‐conditions in comparison to the physiological pH 7.4.

Covalent Binding of 4-Hydroxy-2-nonenal to Lactate Dehydrogenase Decreases NADH Formation and Metmyoglobin Reducing Activity

Lactate dehydrogenase (LDH) activity can regenerate NADH, which is a critical component in metmyoglobin reduction. However, limited research has determined the effects of lipid oxidation products on LDH activity. The overall objective of this study was to determine the effects of 4-hydroxy-2-nonenal (HNE) on LDH activity. LDH was reacted with HNE at pH 5.6 and 7.4, and LDH activity was measured as NADH formation following the addition of lactate and NAD. The effects of HNE on NADH-dependent metmyoglobin reduction also were analyzed. Mass spectrometric examination revealed that HNE adducts to LDH at both pH 5.6 and 7.4. More specifically, HNE binds with cysteine and histidine residues of LDH at pH 5.6 and 7.4. Covalent binding of HNE decreased NADH formation and metmyoglobin reduction (P < 0.05). These results indicate that secondary lipid oxidation products can inactivate enzymes involved in metmyoglobin reduction and have the potential to increase beef discoloration.