Bovine mitochondrial oxygen consumption effects on oxymyoglobin in the presence of lactate as a substrate for respiration

The effect of pH and aging on mitochondrial reduction of bovine myoglobin's affinity for oxygen

In skeletal muscles, mitochondria have been shown to decrease the oxygen affinity of myoglobin. In this study, we investigated whether the mitochondrial function of decreasing myoglobin affinity for oxygen persists and operates at the final pH of postmortem bovine skeletal muscle. The oxygen affinity and myoglobin consumption in the presence of mitochondria obtained from fresh and wet-aged beef were evaluated and compared at pH 5.1, 5.6, and 5.7. The results showed that mitochondria obtained from fresh beef preserved myoglobin oxygen consumption and affinity interference, whereas those obtained from wet-aged beef did not. Oxygen consumption and affinity interference were mostly absent at pH 5.1 and were higher at pH 5.7 than those at pH 5.6. Our findings suggest that mitochondria contribute both to an increase in the oxygen affinity of myoglobin in aged meat and a decrease in the oxygen affinity of myoglobin in high-pH meat, such as dark-cutting beef.

Effects of dietary resveratrol supplementation in cattle on the anti-oxidative capacity and meat quality of beef steaks under high‑oxygen packaging

The effects of dietary resveratrol supplementation on beef quality and antioxidant capacity under high‑oxygen packaging were studied. Twelve cattle were selected and fed a total mixed ration (Control, CON) or supplemented with resveratrol (5 g/cattle/day, RES) for 120 days. The antioxidant capacity and meat quality of beef under high‑oxygen modified atmosphere packaging (HiOx-MAP, 80%O2/20%CO2) and overwrap packaging (OW) were evaluated during storage. Compared to the CON, RES enhanced antioxidant enzyme activity in serum and muscle, and increased the expression of Nrf2 and its downstream target genes (P < 0.05), which decreased the lipid and protein oxidation of steaks during storage (P < 0.05). The RES resulted in a* values increasing throughout storage (P < 0.05) and lower MetMb% than CON steaks (P < 0.05) in HiOx-MAP. The water-holding capacity (WHC) was improved and Warner-Bratzler shear force (WBSF) was reduced (P < 0.05) in RES steaks during storage. Thus dietary resveratrol increased beef antioxidant capacity under HiOx-MAP and improved meat quality, and can be used as a potential method to elevate beef quality and reduce the oxidation under HiOx-MAP.

Effects of mitochondria on postmortem meat quality: characteristic, isolation, energy metabolism, apoptosis and oxygen consumption

Meat quality holds significant importance for both consumers and meat producers. Various factors influence meat quality, and among them, mitochondria play a crucial role. Recent studies have indicated that mitochondria can sustain their functions and viability for a certain duration in postmortem muscles. Consequently, mitochondria have an impact on oxygen consumption, energy metabolism, and apoptotic processes, which in turn affect myoglobin levels, oxidative stress, meat tenderness, fat oxidation, and protein oxidation. Ultimately, these factors influence the color, tenderness, and flavor of meat. However, there is a dearth of comprehensive summaries addressing the effects of mitochondria on postmortem muscle physiology and meat quality. Therefore, this review aims to describe the characteristics of muscle mitochondria and their potential influence on muscle. Additionally, a suitable method for isolating mitochondria is presented. Lastly, the review emphasizes the regulation of oxygen consumption, energy metabolism, and apoptosis by postmortem muscle mitochondria, and provides an overview of relevant research and recent advancements. The ultimate objective of this review is to elucidate the underlying mechanisms through which mitochondria impact meat quality.

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

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

Effect of dietary resveratrol supplementation on muscle fiber types and meat quality in beef cattle

In order to investigate the effect of dietary resveratrol supplementation on muscle fiber types and meat quality in beef cattle, a feeding experiment was undertaken. Longissimus lumborum, Psoas major and Semitendinosus muscles were collected 24 h post-mortem from two groups of cattle, which were fed with a total mixed ration (Control - CON) or supplemented with resveratrol (5 g/animal/day, RES) for 120 d before slaughter. The results showed that dietary resveratrol increased the gene expression of MyHC I and enhanced the proportion of type I fibers in three muscles. The cooking loss and Warner-Bratzler shear force of all muscles during aging for 21 days were decreased. However, the increased proportion of type I fibers resulted in a darker initial color, but did improve color stability, as the a* value of RES samples was lower initially but higher in the later stage of aging. This study indicates the supplementation potential of resveratrol for beef cattle for tenderness and color stability.

Concentrations of HSP27 and αβ-crystallin in Oula Tibetan sheep meat and their relationship with meat quality during postmortem aging

HSP27 and αβ-crystallin are molecular chaperones participating in multiple cellular processes. Their roles in the development of postmortem meat quality remain unclear. The current study was designed to investigate the relationship between the concentrations of HSP27 and αβ-crystallin with meat quality during postmortem aging. Specifically, cooking loss, color, pH, and the myofibril fragmentation index (MFI) of Oula Tibetan sheep meat were determined, and changes in the concentrations of HSP27 and αβ-crystallin were evaluated. The results indicated that HSP27 concentration significantly decreased in 0-3 days (p < 0.05), presenting a positive correlation with pH (p < 0.05) and a negative correlation with L*, b*, cooking loss, and MFI (p < 0.05, p < 0.05, p < 0.01, p < 0.01). Besides, αβ-crystallin concentration significantly decreased in 0-2 days (p < 0.05), exhibiting a significant positive correlation with pH (p < 0.05) and a negative correlation with L*, b*, cooking loss, and MFI (p < 0.01, p < 0.01, p < 0.01, p < 0.01). The results suggested that the HSP27 and αβ-crystallin may participate in the development of meat quality in Oula Tibetan sheep during postmortem early aging. PRACTICAL APPLICATION: Tenderness, color, and water holding capacity (WHC) are crucial quality attributes of meat. The relationship between the concentrations of HSP27 and αβ-crystallin and meat quality reveals that HSP27 and αβ-crystallin may contribute to the development of meat quality in Oula Tibetan sheep during postmortem aging. Therefore, HSP27 and αβ-crystallin are effective research objects for regulating meat quality during postmortem aging.

Evaluating the failure to bloom in dark-cutting and lactate-enhanced beef longissimus steaks

Previous studies have noted lower L* (lightness) values for both dark-cutting beef and normal-pH beef enhanced with lactate. In the current study, absorption-coefficient, scattering-coefficient, CIE L*a*b* values, refractive index of sarcoplasm, and inter-muscle bundle space were evaluated for dark-cutting beef, normal-pH beef enhanced with lactate, normal-pH beef enhanced with water, and normal-pH beef not enhanced with either water or lactate. Compared with non-enhanced loins, lactate-enhancement had lower a*, chroma, oxymyoglobin, reflectance, scattering, and inter-muscle bundle space as well as greater absorption and refractive index. Dark-cutting steaks had lower a*, chroma, oxymyoglobin values, reflectance, and scattering as well as less inter-muscle bundle space compared with lactate-enhanced steaks. Sarcoplasm refractive index values were greater in lactate-enhanced steaks than dark-cutting steaks. The results suggest that changes in muscle structure and optical properties due to either pH or lactate addition can alter muscle darkening and blooming properties.

Extended Aging and Marbling Class Effects on Color Stability of Beef Longissimus lumborum, Gluteus medius, and Biceps femoris Steaks

Postmortem aging improves palatability of various muscles, especially those from lower quality grades. This study evaluated postmortem aging and marbling class effects on the color stability of longissimus lumborum, gluteus medius, and biceps femoris steaks. Carcasses were selected at grading to have Lower Small (Small00 to Small50; n = 50) or Upper Slight (Slight50 to Slight90; n = 50) marbling scores. Strip loin and top sirloin subprimals from each carcass side were assigned to aging treatments (14, 21, 28, or 35 d) in an incomplete block arrangement. After aging, subprimals were cut into longissimus lumborum, gluteus medius, and biceps femoris steaks, respectively. Steaks were placed in a simulated retail display for 11 d. Changes in redness (a* and hue angle) were much slower and less extensive (P &lt; 0.001) in longissimus lumborum steaks than in gluteus medius steaks, which had slightly slower and less extensive (P &lt; 0.01) redness changes than biceps femoris. Increasing aging time increased (P &lt; 0.001) the rate and extent of overall color change (ΔE) during simulated retail display. Steaks from Lower Small carcasses had higher (P &lt; 0.01) L* values than steaks from Upper Slight carcasses at 14, 28, and 35 d postmortem. In steaks from Upper Slight carcasses, L* values were lower (P &lt; 0.01) in steaks aged for 28 d compared to other aging times. In steaks from Lower Small carcasses, L* values were highest (P &lt; 0.001) when aged for 14 d. Increased aging time generally decreased (P &lt; 0.05) a*, b*, and chroma values. However, within each aging time, only b* values of steaks aged for 35 d differed (P = 0.01) with regard to marbling class. Results indicate that increasing aging time decreased color life of beef muscles, and that marbling class had minimal impact on lean color stability.

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.

Changes in glycolytic and mitochondrial protein profiles regulates postmortem muscle acidification and oxygen consumption in dark-cutting beef

Dark-cutting beef is a condition in which beef fails to have a characteristic bright-red color when the cut surface is exposed to oxygen. However, the mechanistic basis for this occurrence is not clear. Protein expression profiles were compared between dark-cutting and normal-pH beef using LC-MS/MS-based proteomics. Mass spectrometry analysis identified 1162 proteins in the proteomes of dark-cutting and normal-pH beef. Of these, 92 proteins had significant changes in protein abundance between dark-cutting versus normal-pH beef. In dark-cutting beef, 25 proteins were down-regulated, including enzymes related to glycogen metabolism, glucose homeostasis, denovo synthesis of adenosine monophosphate (AMP), and glycogen phosphorylase activity. In comparison, 27 proteins were up-regulated in dark-cutting beef related to oxidation-reduction processes, muscle contraction, and oxidative phosphorylation. Down-regulation of glycogenolytic proteins suggests decreased glycogen mobilization and utilization, while the up-regulation of mitochondrial transport chain proteins indicates a greater capacity to support mitochondrial respiration in dark-cutting beef. These results showed that changes in proteins involved in glycogenolysis and mitochondrial electron transport would promote the development of high-pH and greater oxygen consumption, respectively; thus limiting myoglobin oxygenation in dark-cutting beef. SIGNIFICANCE: The current understanding indicates that defective glycolysis causes less carbon flow, leading to less postmortem lactic acid formation and elevated muscle pH in dark-cutting beef. However, to the best of our knowledge, limited research has evaluated how changes in glycolytic and mitochondrial protein abundance regulate postmortem muscle acidification and oxygen consumption in dark-cutting beef. We utilized a shotgun proteomics approach to elucidate potential differences in protein profiles between dark-cutting versus normal-pH beef that may influence differences in postmortem metabolism and muscle surface color characteristics. Our study shows that down-regulation of glycolgenolytic and IMP/AMP biosynthetic proteins results in elevated postmortem muscle pH in dark-cutting beef. In addition, the up-regulation of mitochondrial protein content coupled with the higher muscle pH are conducive factors for enhanced oxygen consumption and less myoglobin oxygenation, contributing to a dark meat color typically associated with dark-cutting beef.

Strategies to limit meat wastage: Focus on meat discoloration

Limiting meat waste is a significant factor that can help meet future needs to provide high-quality animal protein while maximizing the utilization of natural resources. Fresh meat waste occurs during production, processing, distribution, and marketing to various points of consumption. Consumers' expectation for muscle food quality is often associated with its appearance, and a bright-red color of red meat is an indicator of freshness and wholesomeness. Meat discoloration is a natural process resulting from interactions between the physical structure of meat and the oxidation of the ferrous forms of myoglobin. Understanding the biochemical processes that influence discoloration such as oxygen consumption, metmyoglobin reducing activity, lipid oxidation, and microbial growth help to develop innovative strategies to limit meat waste. The focus of this chapter is to discuss the factors involved in meat discoloration and any other color deviations that may lead to discounted pricing and/or meat loss. The impact of meat waste, economic loss, the role of packaging, and the application of high-throughput techniques to understand the biochemical basis of meat discoloration are also discussed.

Genome-wide association study identified genomic regions and putative candidate genes affecting meat color traits in Nellore cattle

Single and multiple-trait GWAS were conducted to detect genomic regions and candidate genes associated with meat color traits (L*, lightness; a*, redness; b*, yellowness) in Nellore cattle. Phenotypic records of 5000 animals, and 3794 genotypes for 614,274 SNPs were used. The BLUPF90 family programs were used through single step GWAS approach. The top 10 genomic regions from single-trait GWAS explained 13.64%, 15.12% and 13% of genetic variance of L*, a* and b*, which harbored 129, 70, and 84 candidate genes, respectively. Regarding multiple-trait GWAS, the top 10 SNP windows explained 17.46%, 18.98% and 13.74% of genetic variance of L*, a* and b*, and harbored 124, 86, and 82 candidate genes, respectively. Pleiotropic effects were evidenced by the overlapping regions detected on BTA 15 and 26 associated with L* and a* (genetic correlation of -0.53), and on BTA 18 associated with a* and b* (genetic correlation of 0.60). Similar genomic regions located on BTA 2, 5, 6, and 18 were detected through single and multi-trait GWAS. Overlapped regions harbored a total of 30 functional candidate genes involved in mitochondrial activity, structural integrity of muscles, lipid oxidation, anaerobic metabolism, and muscular pH.

Effects of quality grade and intramuscular location on beef semitendinosus muscle fiber characteristics, NADH content, and color stability

The objective of this study was to determine the impact of quality grade and steak location on color stability of semitendinosus (ST) steaks during a 9-d refrigerated study. Twenty-one ST muscles (12 Choice and 9 Select) were purchased from a commercial beef packing plant and fabricated into twelve 2.54-cm thick steaks per muscle. Steaks 1, 6, and 12 were designated for immunohistochemistry while remaining steak locations of proximal (steaks 2 to 4), middle (5 to 8), and distal (9 to 11) were randomly assigned to 0, 4, or 9 d of simulated retail display. Surface color attributes of day-9 steaks were recorded daily by a visual color panel and spectrophotometer. On days 0, 4, and 9 of display, steaks were analyzed for metmyoglobin reducing ability (MRA) and oxygen consumption (OC). Grade × day of display (DOD) interactions were detected for L*, a*, surface oxymyoglobin (OMb) and metmyoglobin (MMb) percentages, and visual panel surface redness and discoloration scores (P ≤ 0.02); however, no Grade × DOD interactions were observed for MRA or OC (P > 0.17). There were location main effect (LOC) × DOD interactions for L*, a*, surface MMb, visual panel surface redness and discoloration, and MRA (P ≤ 0.02). Distal steaks had lower L* values compared with the other locations (P < 0.01), which coincided with steaks being rated visually darker red (P < 0.01). Proximal steaks had greater a* values and had less surface discoloration than middle steaks (P < 0.05), which had an increased percentage of surface MMb (P ≤ 0.04). Distal and proximal steaks had increased MRA compared with middle steaks on days 0 and 4 (P < 0.05), and distal steaks had greater OC than the other locations throughout display (P < 0.01). There were fewer type I fibers at the proximal end with a greater percentage located at the middle and distal ends, and an increased percentage of type IIX fibers at the middle and proximal locations (P ≤ 0.01). Less type IIA fibers were detected at the middle LOC compared with the other two locations (P < 0.10). Larger type I, IIA, and IIX fibers were located at the proximal and middle locations compared with the distal LOC (P < 0.01). ST color and color-stability characteristics were influenced by DOD and LOC, which may partially be explained by differences in fiber types among locations.

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.

Colour characteristics of beef longissimus thoracis during early 72 h postmortem

This study aimed to investigate the characteristics of beef meat colour during the initial 72 h postmortem to assess the possible effects of mitochondria on meat colour development. Bovine longissimus thoracis muscles (n = 5) were collected from one side of carcasses at 0.5, 4, 8, 12, 24, and 72 h postmortem and displayed in air for 6 days to measure colour and detect mitochondrial morphology and function. The results showed that beef had higher L^⁎, a^⁎, and b^⁎ at 24 and 72 h postmortem and less colour change during 6 days of display in comparison with meat from 0.5, 4, and 8 h postmortem. Changes in mitochondrial morphology were observed at 24 and 72 h postmortem. Mitochondria presented a metabolic pattern early postmortem in that the MRA and NADH content did not change. Both the increase in beef colour stability and tissue oxygen consumption were observed within 72 h postmortem.

Impact of Up- and Downregulation of Metabolites and Mitochondrial Content on pH and Color of the Longissimus Muscle from Normal-pH and Dark-Cutting Beef

Limited knowledge is currently available on the biochemical basis for the development of dark-cutting beef. The objective of this research was to determine the metabolite profile and mitochondrial content differences between normal-pH and dark-cutting beef. A gas chromatography-mass spectrometer-based nontargeted metabolomic approach indicated downregulation of glycolytic metabolites, including glucose-1- and 6-phosphate and upregulation of tricarboxylic substrates such as malic and fumaric acids occurred in dark-cutting beef when compared to normal-pH beef. Neurotransmitters such as 4-aminobutyric acid and succinate semialdehyde were upregulated in dark-cutting beef than normal-pH beef. Immunohistochemistry indicated a more oxidative fiber type in dark-cutting beef than normal-pH beef. In support, the mitochondrial protein and DNA content were greater in dark-cutting beef. This increased mitochondrial content, in part, could influence oxygen consumption and myoglobin oxygenation/appearance of dark-cutting beef. The current results demonstrate that the more tricarboxylic metabolites and mitochondrial content in dark-cutting beef impact muscle pH and color.

Analysis of Myoglobin Stability and Bacterial Community Diversity in Mutton Chop Rolls During Cold Preservation

The nutritional value of mutton chop rolls is gradually recognized by people, but it is easy to cause microbial contamination during storage, leading to spoilage and shortening of storage time. The bacterial diversity of mutton chop rolls in different cold preservation time was analyzed to explore the main pathogens of spoilage of mutton chop rolls. At the same time, the oxidative state of myoglobin and the change of mitochondrial Metmyoglobin (MMb) Reduction Ability (MRA) in different cold preservation were studied. It lays a foundation for further study on the mechanism of meat color stabilization of mutton chop rolls during cold preservation. A total of 10,123,180 effective Tags were obtained from three samples with different cold preservation time by high throughput sequencing. The relative abundance of Pseudomonas was the highest in the samples refrigerated for 8 days, Acinetobacter, Brochothrix and Lactobacillales showed the highest relative abundance in the samples refrigerated for 4 days, which were closely related to the deterioration of mutton chop rolls and color deterioration. With the increase of cold preservation time, Oxymyoglobin (OMb) content decreased and Metmyoglobin (MMb) content increased. MRA was negatively correlated with MMb. The content of NADH was extremely significant difference with OMb and MMb. At the same time, the content of NADH was a significant difference with MRA. This study provides theoretical basis for prolonging the shelf life, maintaining meat color stability, improving the quality of mutton chop rolls. And it also plays a certain role in promoting the production and consumption of chilled meat.

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.

Changes in the colour and sensory properties of beef frozen after seven days of ageing in a modified atmosphere

The aim of the study was to evaluate the colour, sensory properties and shear force values of meat from ten young bulls produced by crossing Polish Black-and-White Holstein-Friesian cows with Belgian White Blue bulls. The quality of the longissimus lumborum (LL) muscle was determined after seven-day ageing under various modified atmosphere (MA) conditions (vacuum – group B; 40% CO2 + 60% N2 – group C; 30% CO2 + 70% Ar – group D) followed by freezing and frozen storage. The process of seven- day ageing in MA composed of 40% CO2 + 60% N2 significantly increased the colour lightness of the beef samples. Eight-month frozen storage increased colour lightness in the meat samples aged in MA composed of 30% CO2 + 70% Ar. Meat samples aged under various MA conditions had a higher contribution of redness (a*) and yellowness (b*) than non-aged beef. Meat samples frozen after ageing in MA containing Ar had less redness than the samples from other groups. After frozen storage, meat samples from all groups had less redness and yellowness. Ageing and frozen storage had no significant effect on the juiciness of the beef. The beef aged in vacuum conditions was the most tender, both before and after frozen storage. Ageing had no significant influence on the shear force of meat samples evaluated before freezing. Meat samples aged in MA composed of 30% CO2 + 70% Ar evaluated after frozen storage had lower average shear force values than beef that had not been aged prior to freezing.

Muscle-Specific Mitochondrial Functionality and Its Influence on Fresh Beef Color Stability

Fresh beef color stability is a muscle-specific trait. Mitochondria remain biochemically active in postmortem beef muscles and influence meat color. Although several intrinsic factors governing muscle-specific beef color have been studied extensively, the role of mitochondrial functionality in muscle-dependent color stability is yet to be examined. Therefore, the objective of this study was to examine mitochondrial oxygen consumption rate (OCR), mitochondrial metmyoglobin reducing activity (MMRA), and instrumental color attributes in beef Longissimus lumborum (LL) and Psoas major (PM) during retail display. Using a split-plot design, six (n = 6) beef LL and PM muscles were fabricated into 2.54-cm-thick steaks, packaged in polyvinylchloride overwrap, and randomly assigned to instrumental color measurement for six days and mitochondrial isolation for days 0, 1, 3, or 5 of display at 4 °C. Mitochondria isolated from steaks were used to assess the effects of muscle and display time on OCR and MMRA. The PM steaks were less color-stable (p < 0.05) during display compared with the LL counterparts. For both muscles, OCR decreased during display, albeit the decrease was more rapid in PM than in the LL. Similarly, MMRA decreased during display for the LL and PM. However, this decrease was less (p < 0.05) for mitochondria from LL steaks, which were more resistant to display-mediated effects on OCR and MMRA. These results indicated that the muscle-specific differences in mitochondrial activity may contribute partially to the variations in color stability of beef LL and PM muscles.

PRACTICAL APPLICATION

During retail display tenderloin steaks packaged in PVC overwrap discolor quicker than strip loin steaks. This research determines the basis for muscle-specific differences in color stability. The results indicate that mitochondria present in tenderloin lose its functionality faster than strip loin mitochondria. Developing strategies to minimize muscle-specific differences in mitochondrial changes can increase color stability and value of fresh beef.

Oxidative stability of beef from steers finished exclusively with concentrate, supplemented, or on legume-grass pasture

The objective of this study was to evaluate the effects of three finishing systems based on concentrate and legume-grass pasture on beef. Steers were finished for 91 days with an exclusively whole corn grain-based (GRAIN) diet, grazed on legume-grass pasture plus 1.4% of body weight of whole corn grain supplementation (SUPP), or grazed on legume-grass pasture (PAST) only. Lipid and myoglobin oxidation, pH, objective color, and α-tocopherol concentrations were evaluated on M. longissimus thoracis steaks. Dietary treatments did not affect pH and minimally affected protein carbonylation. Steaks from steers fed GRAIN were less red, showed higher lipid oxidation during retail display, and higher metmyoglobin formation from day 7 to 13 when compared to PAST. Levels of α-tocopherol were higher in steaks from steers fed diets containing legume and grass. Inclusion of roughage in finishing diets is essential to maintain retail color and prevent lipid and myoglobin oxidation.

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.

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.