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Background: Limited knowledge is currently available on the effects of modified atmospheric packaging (MAP) on the metabolite profiles of cooked beef. The objective was to evaluate the impact of packaging on the cooked color and cooked metabolite profile of normal-pH (normal bright-red color) and atypical-dark-cutting beef (inherently slightly dark-colored) longissimus lumborum muscle. Methods: Normal-pH (pH 5.56) and atypical dark-cutting (pH 5.63) loins (n = 6) were procured from a commercial meat processor. Steaks were randomly assigned to one of three different packaging methods: vacuum packaging, carbon monoxide (CO-MAP), and high oxygen (HiOx-MAP). Following 5 d of retail display, steaks were cooked to 71 °C on a clamshell-style grill, and samples were collected for untargeted metabolites using gas-chromatography mass spectrometry. Results: Raw atypical dark-cutting steaks were less red (p < 0.05) than raw normal-pH steaks. However, there were no differences in internal cooked color between normal-pH and atypical dark-cutting steaks. Steaks packaged in HiOx-MAP steaks had a lower (p < 0.05) cooked redness than vacuum and CO-MAP steaks. A total of 129 metabolite features were identified in the study. Serine and tryptophan were over-abundant in cooked atypical dark-cutting beef compared to raw atypical samples. Citric acid levels were greater in HiOx-MAP packaged beef compared with VP both in normal and atypical dark-cutting beef after cooking, while no differentially abundant metabolites were shared between vacuum and CO-MAP steaks after cooking. Discussion: A slight increase in pH did not influence metabolite profiles in different packaging. However, there were packaging effects within normal and atypical dark-cutting beef. Conclusions: This study suggests that packaging conditions change metabolite profiles, which can influence cooked metabolites. Therefore, the metabolomics approach can be used to better understand cooked color defects such as premature browning. [ABSTRACT FROM AUTHOR]

Meat colour is one of the primary factors affecting the acceptability of retail meat cuts. Therefore, displaying the natural bright-red colour of meat is a major goal of the meat industry. Consumers frequently reject to retail meat cuts with discolouration even at low levels of surface browning and/or darkening, which in turn results in significant food waste and economic loss. Thus, understanding the factors that influence meat colour deviations such as discolouration or darkening is crucial in developing effective strategies to minimise the display colour-related quality issues. Numerous factors influence series of biochemical reactions of post-mortem muscles and the chemical state of myoglobin, which ultimately affects meat colour and colour stability. Recent studies have demonstrated the incidence of dark-cutting beef post-mortem can be attributed to the combination of lower glycolytic potential, less glycolytic metabolites, enzymes and dysregulated energy metabolism. This review will focus on the role of post-mortem bioenergetics and mitochondria dynamics that affect beef colour chemistry. [ABSTRACT FROM AUTHOR]

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

Meat color is an important sensory property influencing purchasing decisions and the value of the product during grading. Any deviation from a bright red color, especially in beef, leads to economic losses. Darkcutting beef is a color deviation in which beef fails to have a bright red color. The dark-cutting condition has a worldwide occurrence. The dark-cutting condition in the US results in $210 million annually. The current talk will focus on recent advances in basic and applied research in dark-cutting beef color. The proteomics and metabolomics research showed that glycolytic proteins and metabolites are less abundant in dark-cutting beef than normal-pH beef. Interestingly, dark-cutting beef has greater mitochondrial protein content than normal-pH beef. Although the mechanistic basis for increased mitochondrial content is unclear, we speculate that higher energy demand pre-slaughter contributes to increased mitochondrial biogenesis. This metabolic alteration plays a critical role in detriments of substrate metabolism in dark-cutting beef muscles, contributing to aberrant postmortem pH decline. In recent research, we compared metabolomic and lipidomic profiles using different shades of dark-cutting beef, such as mild, moderate, and severe, demonstrating that metabolite and lipid profiles vary significantly between normal and severe dark-cutting samples. However, there were not many differences between mild and moderate. Applied research to improve dark-cutting beef has utilized various post-harvest practices such as modified atmospheric packaging, enhancement, nitrite-embedded film, and high-pressure processing. The use of modified atmospheric packaging and antioxidant enhancement reversed the dark color of steaks. Recently, we have demonstrated that high-pressure processing (HPP) of strip loin steaks can reverse dark color when packaged in PVC overwrap. Dark-cutting steaks processed with 300 MPa (megapascal pressure) for 90 sec using chilled water (6 to 10 °C) immediately improved redness and had similar redness as USDA Choice steak on d 3 of retail storage. In addition, dark-cutters maintained a brighter red color than normal-pH USDA Choice during retail display (hence, less loss due to meat discoloration). The trained panelists also noticed no taste, flavor, or tenderness differences between USDAChoice and dark-cutters applied with 300 MPa. The application of HPP allows aerobic overwrap polyvinyl chloride (PVC) packaging with no use of modified atmosphere packaging (MAP) trays. In summary, understanding the fundamental basis helps to elucidate the etiology of dark-cutting beef occurrence, while applied research helps to improve the value of dark-cutting beef. [ABSTRACT FROM AUTHOR]

A dark red to coffee bean color present within the ribeye between the 12th and 13th rib of a beef carcass at the time of grading is the hallmarking characteristic of dark-cutting (DC) beef. However, the degree of darkness within the ribeye can vary. Limited studies have evaluated DC beef of varying visual severity throughout aging and retail display. Therefore, the objective was to evaluate the impact of varying degrees of dark-cutting severity on the bloom and retail color of beef longissimus lumborum subjected to 0, 21, or 39 d of aging. Beef strip loins (IMPS #180; n = 8/ treatment) were collected from commercial beef processors based on the visual degree of SC at the time of grading. Strip loins represented one-half dark, twothirds dark, full dark, and a normal, cherry-red colored control. At 48 to 60 h postmortem, loins were fabricated by slicing two 2.54 cm steaks from the anterior end of each loin for retail display (unaged) or biochemical analysis. The remaining portion of the strip loin was segmented into two sections and assigned to 21 or 39 d of wet aging. Following aging, one 2.54 cm steak from the anterior end of each loin was cut for retail display. All steaks designated for retail display were placed into Styrofoam trays and overwrapped with polyvinyl chloride film and placed into retail display following aging. Bloom, metmyoglobin reducing activity, and pH were evaluated for biochemical analysis. Color measurements were taken each day of display using a HunterLab MiniScan EZ spectrophotometer. The data were analyzed using the Glimmix procedure of SAS. One-half and normal steaks had a lower (P < 0.05) initial pH than two-thirds and full steaks. Unaged full steaks had greater (P < 0.05) metmyoglobin reducing activity than unaged normal and half steaks. Steaks aged for 21 and 39 d were more (P < 0.05) red initially following bloom than unaged steaks. Full and two-thirds steaks aged for 0 d had a decreased (P < 0.05) a* value on d 0 of display than normal and half steaks aged for 0 d. Similarly, following 21 and 39 d of aging full and two-thirds dark steaks had a lower (P < 0.05) a* value and were less red in color than normal and half steaks on the initial day of retail display. By d 4 of display, normal and one-half steaks aged for 21 d had a greater (P < 0.05) a* value than two-thirds steaks aged for 21 d. When aged for 39 d, all treatments were similar (P < 0.05) in redness by the end of display. Results from this study indicate that the visual severity of dark-cutting can impact color throughout aging and retail display. [ABSTRACT FROM AUTHOR]

Dark-cutting beef is hallmarked by a dark red to almost purple color present within the interface of the ribeye between the 12th and 13th rib of the beef carcass. Yet, the shade or degree of darkness present within the ribeye can vary widely and have a substantial impact on the color and biochemical traits of the steaks. However, limited studies have compared color characteristics of different degrees of dark-cutting during retail display. Therefore, the objective of this study was to evaluate the impact of the visual degree of dark cutting at the time of grading on the retail color and color stability attributes of beef longissimus lumborum steaks. Beef strip loins (IMPS #180) were collected from two different Midwestern beef processors over the course of two collections. Strip loins (n = 8/treatment) were identified based on the degree of dark-cutting present within the ribeye to represent one-half dark, two-thirds dark, full dark, and a control of USDA Choice. At 48 to 60 h postmortem, loins were fabricated from the anterior end into 2.54 cm steaks and randomly assigned to retail display or d 0 lab analysis. Steaks designated for retail display were placed into Styrofoam trays and overwrapped with polyvinyl chloride film, and placed into retail display in coffin style display cases under continuous lighting for 5 d. Steaks designated for d 0 analysis were evaluated for pH, bloom, oxygen consumption, and metmyoglobin reducing activity. All color measurements were taken using a HunterLab MiniScan EZ spectrophotometer. The data were analyzed using the PROC GLIMMIX procedure of SAS at an a < 0.05. Two-thirds and full dark-cutter steaks had a greater (P < 0.05) pH than half and normal steaks on d 0. Moreover, full dark-cutter steaks had a decreased (P < 0.05) bloomed L* value and were darker in color on d 0 than normal and half steaks. Full dark-cutter steaks had a greater (P < 0.05) oxygen consumption and metmyoglobin reducing activity on d 0 than normal and half steaks. Full and two-third steaks had a decreased (P < 0.05) a* value and were less red in color on d 0 of retail display than normal and half steaks. All degrees of dark-cutters had a reduced change in redness than USDA Choice steaks. These results indicate color stability activity can be dependent on the degree of dark-cutting, with full and two-thirds dark-cutters being similar in biochemical activity. [ABSTRACT FROM AUTHOR]

The frequency and severity of injection-site lesions in the outside round muscles of both beef and dairy cattle were evaluated through a series of audits. Audits were conducted in 2017 on 1,300 rounds from dairy and beef cows from seven locations throughout the United States. Outside round muscles were butterfly cut into 1.25-cm slices and, if present, lesions were counted, measured, and categorized. Rounds from beef (7%) and dairy cattle (15%) had at least one injection-site lesion present. The most common location of injection-site lesions was quadrant 2 and 3, which contained both the biceps femoris and semitendinosus muscles. Injection-site lesions were more frequent (P < 0.05) in the biceps femoris for both beef and dairy rounds. Clear lesions accounted for 57% of injection-sites in both beef and dairy rounds, whereas metallic lesions made up 23% of the total in beef and 25% in dairy. Overall, there was a dramatic decline in the frequency (P < 0.05) of injection-site lesions since the 1998 (24 and 45 percentage units greater in beef and dairy rounds, respectively) and 2000 audits (13 and 20 percentage units greater in beef and dairy rounds, respectively). Educational programs, such as Beef Quality Assurance (BQA) and requirements for BQA training, have resulted in substantial improvements in beef management practices for both the beef and dairy industries. [ABSTRACT FROM AUTHOR]

Interrelationship between mitochondria and myoglobin function influence beef color. NADH level in postmortem muscle is an important determinant of mitochondrial activity and metmyoglobin reduction. Increased aging time promotes discoloration of steaks; however, the mechanism of this effect is not clear. The objective was to characterize the role of wet‐aging in beef longissimus lumborum muscle mitochondrial function and to characterize the global metabolome to determine the mechanism of that can regenerate NADH. Beef longissimus lumborum muscles were randomly assigned to 3, 7, 14, 21, and 28 days aging periods. Surface color, biochemical, mitochondrial, and metabolite profiles were determined at each aging period and at the end of 6‐day display. During 6‐day display, sections aged for 28 days had 30.4% decrease in redness than sections aged for 3 days. Aging time decreased (P <0.05) muscle oxygen consumption, mitochondrial protein content, and antioxidant capacity. Metabolites such as fumaric acid, creatinine, and fructose, that can take part in glycolytic/TCA cycle and regenerate NADH decreased (P <0.05) with aging and display time. In support, NADH levels also decreased (P <0.05) with aging time, but aging time had no effect (P = 0.44) on NADH‐dependent reductase activity. The results suggest that decreased color stability in aged beef can be attributed to increased mitochondrial damage, depletion of metabolites that can regenerate NADH, and increased oxidative stress. Practical Application: Beef aging time results in increased discoloration of steaks under retail display. The current research determines the fundamental basis of lower color stability in aged beef. The results indicate that mitochondrial degeneration, depletion of metabolites that produce NADH, and increased oxidative stress can limit shelf‐life of aged steaks. Hence, application of post‐harvest strategies to minimize mitochondrial damage and oxidative changes may have the potential to increase shelf‐life of aged beef. [ABSTRACT FROM AUTHOR]

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Meat discoloration starts from the interior and rises to the surface of steaks. Recently developed near-infrared single-fiber probe (SFP) in our laboratory allows characterizing interior color changes. The objective was to determine how changes in surface and interior metmyoglobin correlate with color changes in psoas major muscle during retail display. Seven USDA Select tenderloins were collected from a commercial processing facility. Steaks were cut from each muscle and placed in polyvinyl chloride overwrap trays for retail display. The SFP was a 400-µm fiber in a 5-gauge needle and inserted into the muscle at five positions with each position increasing in depth by mm. A mathematical model developed in MATLAB determined the percent metmyoglobin at each depth and day. Surface color was analyzed using a HunterLab MiniScan spectrophotometer each day and percent metmyoglobin was determined. Steaks were randomly assigned to analysis of oxygen consumption (OC) and metmyoglobin reducing activity (MRA) of the interior and retail surfaces on d 0, d 3, and d 5 of display. Pearson's correlation coefficients were used to evaluate the relationship between calculated percentages, color stability parameters, and retail color with significance considered at a P < 0.05. Metmyoglobin determined by the SFP increased at all depths during display with greater metmyoglobin at shallower depths. Metmyoglobin calculated by the SFP at mm and by HunterLab spectrophotometer were strongly negatively (P < 0.05) correlated with a* values during retail display. The MRA determined using the retail surface was strongly negatively (P < 0.05) correlated with HunterLab surface metmyoglobin and SFP metmyoglobin at mm depth. The OC of the retail surface was moderately negatively correlated (P < 0.05) with HunterLab surface metmyoglobin and SFP metmyoglobin at all depths. The development of internal metmyoglobin demonstrated a strong relationship with retail color and negatively impacted color stability attributes. [ABSTRACT FROM AUTHOR]

Consumers often use meat color to determine doneness. A greater than normal pH of dark-cutting (DC) beef leads to less myoglobin denaturation, resulting in a persistent pink color that negatively impacts the perception of consumers of the cooked beef degree of doneness. High-Pressure Processing (HPP) is a non-thermal pasteurization technology to extend shelf-life. High pressure leads to denaturation of proteins and structural changes. There has been limited research and application utilizing HPP on fresh meat due to the pale color caused by HPP. The objective of the study was to evaluate different HPP levels on cooked steak color and sensory attributes of dark-cutting beef. Eight USDA Choice (mean pH = 5.5) and twelve DC (mean pH = 6.3) strip loins were obtained from a commercial packing plant within 1 d of harvest. Loins were cut into equal sections, vacuum packaged, and assigned HPP levels of 0 (no HPP), 300, 450, and 600 MPa with a holding time of 90 s. Following 48 hours of dark storage, loin sections were cut into 1.9 cm thick steaks, vacuum packaged, and randomly assigned to external cooked color, Warner-Braztler shear force (WBSF), and trained sensory panel. Steaks were cooked and then tempered to 71°C. A trained sensory panel (n = 6) evaluated initial juiciness, sustained juiciness, tenderness, beef flavor intensity, and overall acceptability. The data were analyzed using the Glimmix Procedure of SAS. HPP treatment did not (P > 0.05) affect initial juiciness, sustained juiciness, beef flavor intensity, or overall acceptability. However, 600 MPa made DC steaks tougher and lighter in appearance (P < 0.05) than all other treatments. HPP treatments did not affect the a* and chroma of the external cooked color. In conclusion, low (300 MPa) and moderate (450 MPa) pressure levels did not have a negative impact on cooked steaks. [ABSTRACT FROM AUTHOR]

The effects of oxygen exposure on the metabolites present in beef longissimus lumborum have not been evaluated. Therefore, the objective of this study was to evaluate the impact of oxygen exposure on the color attributes and metabolites present in longissimus lumborum muscle. USDA Low Choice beef strip loins were sliced into steaks (1.91 cm) and packaged in polyvinyl chloride overwrap trays for 3 or 6 days of retail display. The oxygen exposed (OE) surface was considered the display surface during retail, and the non-oxygen exposed (NOE) surface was the intact interior muscle. Instrumental color was evaluated using a HunterLab Miniscan EZ spectrophotometer. To analyze the NOE surface on day 3 and 6, steaks were sliced parallel to the OE surface to expose the NOE surface. Metmyoglobin reducing ability (MRA) was determined by submerging samples in nitrite to induce metmyoglobin reduction. A gas chromatography-mass spectrometry was used to identify metabolites. The least square means were determined using the GLIMMIX procedure of SAS with significance at a P < 0.05. Metabolites were analyzed using the MetaboAnalyst 5.0. Redness (a* values) of steaks decreased (P < 0.05) with greater display time. MRA was greater (P < 0.05) in the NOE surface compared with the OE surface on days 3 and 6. Upregulation of glucose-1-phosphate and down regulation of gluconic acid, ribose, sedoheptulose-7-phosphate in the NOE surface on day 0 compared with NOE on day 6 indicates a shift from glycolysis to the pentose phosphate pathway. On day 6 of display, the OE surface was upregulated in xanthine and gluconic acid, indicating an increase in purine and pentose phosphate metabolisms, while there was a down regulation of mannitol and malic acid compared with the NOE surface. These results indicate the presence of oxygen can influence metabolite profile and negatively influence MRA and color. [ABSTRACT FROM AUTHOR]

Limited studies have compared the effects of oxygen within a steak on biochemical properties. The objective was to evaluate the effects of oxygen exposure on the biochemical attributes of longissimus lumborum muscle. Steaks were (1.91 cm) sliced from USDA Low Choice beef strip loins (n = 7), packaged in polyvinyl chloride overwrap trays, and randomly assigned to day 3 or day 6 in retail display. During display, instrumental color was evaluated daily using a HunterLab MiniScan spectrophotometer. The display surface was considered as oxygen exposed (OE), while the interior of the steak was denoted as not exposed to oxygen (NOE). NOE was obtained by slicing the steak in half parallel to the previously OE surface. The NOE pieces were evaluated for bloom, while NOE and OE surfaces were used oxygen consumption (OC) and metmyoglobin reducing ability (MRA). Nitrite-induced metmyoglobin reduction was used to measure MRA, while changes in deoxymyoglobin level with vacuum were used as an indicator of OC. The data were analyzed using the GLIMMIX Procedure of SAS (n = 7 replications) and considered significance at P < 0.05. With increased display time, the a* values (redness) decreased (P < 0.05) for instrumental color. NOE steak surface had greater (P < 0.05) MRA compared with OE surfaces. Oxygen exposure affected the OC of the steaks, with the OE surfaces having lower (P < 0.05) OC compared to NOE surfaces on day 6 of display. The exposure of oxygen to the muscle resulted in a decrease in activity, paralleling in decline in retail color and color stability. In conclusion, the presence of oxygen can result in negative impacts on the shelf life of steaks; however, the non-exposed interior of muscle remains more biochemically active. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to determine the effects of dietary inclusion of lasalocid in combination with zeranol implants on the performance and carcass characteristics of hair sheep. Thirty wether hair lambs (BW = 25.8 + 4.6 kg) were stratified by BW and BCS and randomly assigned to 1 of 2 experimental treatments in a randomized complete block design. The treatments included no implant or ionophore (CON); and the experimental treatment, receiving the ionophore lasalocid (Bovatec® 91; Zoetis, Kalamazoo, MI) and anabolic zeranol implants (Ralgro®; MSD Animal Health, Spartan, RSA; LZ). Lambs on the LZ treatment received 12 mg of zeranol on d 0, 56, and 112, unless lambs were harvested prior to day 112, and consumed an average of 35 mg per day of lasalocid. Lambs had ad libitum access to feed and water throughout the experiment and were housed in individual, slatted floor pens. Performance data were collected on d 0, 14, 28, 56, 84, and at harvest. After d 84, harvest dates were selected and lambs were harvested by block based on proximity to ideal harvest weight and fat thickness. Lasalocid in the diet combined with zeranol implants increased final BW by 14.2% in comparison to CON (P < 0.01). Overall ADG was increased by 36.2% (P < 0.01), and overall G:F was improved by 24.4% for LZ when compared to CON (P = 0.01). There was no difference in overall DMI between treatments (P = 0.13). Hot carcass weight (HCW; P < 0.01), and loin eye area (LEA; P < 0.01) were also greater for the LZ treatment. Dietary inclusion of lasalocid in combination with zeranol implants improved overall BW, ADG, and feed efficiency as well as HCW and LEA in hair sheep. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to determine the effects of dietary inclusion of lasalocid in combination with zeranol implants on the performance and carcass characteristics of hair sheep. Thirty wether hair lambs (BW = 25.8 + 4.6 kg) were stratified by BW and BCS and randomly assigned to 1 of 2 experimental treatments in a randomized complete block design. The treatments included no implant or ionophore (CON); and the experimental treatment, receiving the ionophore lasalocid (Bovatec® 91; Zoetis, Kalamazoo, MI) and anabolic zeranol implants (Ralgro®; MSD Animal Health, Spartan, RSA; LZ). Lambs on the LZ treatment received 12 mg of zeranol on d 0, 56, and 112, unless lambs were harvested prior to day 112, and consumed an average of 35 mg per day of lasalocid. Lambs had ad libitum access to feed and water throughout the experiment and were housed in individual, slatted floor pens. Performance data were collected on d 0, 14, 28, 56, 84, and at harvest. After d 84, harvest dates were selected and lambs were harvested by block based on proximity to ideal harvest weight and fat thickness. Lasalocid in the diet combined with zeranol implants increased final BW by 14.2% in comparison to CON (P < 0.01). Overall ADG was increased by 36.2% (P < 0.01), and overall G:F was improved by 24.4% for LZ when compared to CON (P = 0.01). There was no difference in overall DMI between treatments (P = 0.13). Hot carcass weight (HCW; P < 0.01), and loin eye area (LEA; P < 0.01) were also greater for the LZ treatment. Dietary inclusion of lasalocid in combination with zeranol implants improved overall BW, ADG, and feed efficiency as well as HCW and LEA in hair sheep. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate nitriteembedded packaging (NEP) and enhancement effects on the color of dark-cutting beef after repackaging into polyvinyl chloride (PVC) for display. From a commercial packing plant, dark-cutting beef strip loins (n = 8; pH = 6.39) and USDA Low Choice beef strip loins (normal-pH, n = 6) were collected. Bisected darkcutting loins were randomly assigned to nonenhanced dark-cutting (DCN) and enhanced dark-cutting (DCE) with glucono delta-lactone and rosemary. Steaks (1.91 cm) sliced from nonenhanced normal-pH, DCN, and DCE loins were randomly assigned to 3, 6, or 9 d in dark storage, and DCE steaks were packaged in nitrite-embedded packaging (NEP) while normal-pH and DCN steaks packaged in vacuum packaging. At dark storage d of 3, 6, or 9, steaks were repackaged in PVC and displayed for 6 d. The instrumental color was evaluated every 12 h, and metmyoglobin formation was calculated using the ratio of reflectance of 572 nm and 525 nm. Delta E was calculated to determine the change in color over time using the change in L*, a*, and b* values from h 0 to h 12 of display. Data were analyzed using the Mixed Procedure of SAS, and least squares means were considered significant at P < 0.05 and separated using the PDIFF option. Metmyoglobin formation increased (P < 0.05) within 12 h of repackaging DCE steaks held for 3 d and 6 d of dark storage. At h 12 of display, DCE steaks had significantly more metmyoglobin formation than DCN and normal-pH steaks. The DE of DCE steaks was negative, indicating a decline in color after 12 h of display, while the normal-pH and DCN steaks had a positive DE value indicative of improved surface color. Therefore, repackaging DCE steaks resulted in decreased color stability and increased metmyoglobin formation. [ABSTRACT FROM AUTHOR]

The color of meat is an important deciding factor in consumers' assessment of meat quality. To meat buyers, the bright cherry-red color of meat indicates freshness and wholesomeness. However, atypical dark-cutting beef represents dark-colored meat with a muscle pH between 5.6 and 5.8. Although previous studies have indicated that the ultimate pH of atypical dark-cutting beef is greater than normal, the mechanistic basis for the occurrence is not clear. Therefore, the objective of this study was to identify protein and metabolite profiles of normal and atypical dark-cutting beef. Longissimus thoracic (LT) muscles from 12 different animals (6 atypical dark-cutters and 6 normal-pH beef) were analyzed by comparing changes in metabolites and protein profiles using GC-MS non-targeted metabolomics and LC-MS/MS-based proteomics, respectively. Metabolomics analysis showed down-regulation of glycolytic metabolites such as glucose-6-phosphate, lactose, and glucose, indicating a reduced capacity to accumulate lactate postmortem in atypical dark-cutters compared with normal-pH beef. Mass spectrometry analysis identified 66 proteins with significant changes in protein expression profiles (P < 0.05) between atypical and normal-pH beef. Of these, 22 proteins were up-regulated while 14 were down-regulated in atypical dark-cutting beef. Functional annotation and protein-protein interaction network analyses revealed that up-regulated proteins such as NADH ubiquinone oxidoreductase subunit A7, ATPase Na+/K+ transporting subunit alpha 2, 3-oxoacid CoA-transferase 1, cytochrome b5 reductase 3, actinin alpha 4, tropomyosin 2, heat shock protein beta-7, and DnaJ heat shock protein family (Hsp40) member B4 are involved in energy synthesis, muscle contraction and stress responses. By contrast, down-regulated proteins, including phosphofructokinase, glycogen phosphorylase, amyloalpha-1,6-glucosidase, phosphorylase kinase regulatory subunit alpha and gamma are involved in glycogen metabolism. In summary, lower glycolytic metabolites and glycogen degradation enzymes are associated with differences in muscle pH and color of atypical darkcutting beef. [ABSTRACT FROM AUTHOR]

Quality variation within the pork industry is commonly associated with intramuscular fat and muscle color. The objective of this study was to determine the effects of packaging, pork quality types, and cooking temperature on color and shear force. Normal, non-enhanced (N, n = 10), Enhanced with salt and phosphate (E, n = 10) and Highly Marbled (H, n = 10) pork loins from a local food distributor. Loins were cut into 2.54-cm-thick chops and assigned to retail display or tenderness evaluation. Retail display chops were assigned to 1 of 3 packaging treatments: polyvinyl chloride overwrap (PVC), carbon monoxide modified atmosphere packaging (CO-MAP) and high-oxygen modified atmospheric packaging (HiOx-MAP). Visual color measurement for muscle color (MC), fat color (FC), surface discoloration (SD), and surface color uniformity (SCU) was recorded on d 0, 2, and 4 of retail display. Pork tenderness was evaluated at 3 different degrees of doneness (63, 68, & 74°C) using Warner-Bratzler shear (WBS) force. There were significant treatment and packaging interactions for muscle color. For muscle color score, E pork loins had a significantly lower (P < 0.05) muscle color score compared with N and H loins indicative of a brighter, more pale pink color. In addition, CO- and HiOx-MAP packaged chops were significantly brighter (P < 0.05) compared to PVC chops. There were treatment and degree of doneness main effects (P < 0.05) for WBS force values. Enhanced pork loins were more tender (P < 0.05) than N pork loins. Furthermore, pork chops cooked to 63 °C were more tender than chops cooked to 68 and 73°C. In conclusion, enhanced chops packaged in CO- or HiOx-MAP result in a brighter color of lean compared non-enhanced and high-quality. Additionally, the results suggest that enhanced, non-enhanced, and high-quality pork products available in market have different quality parameters. [ABSTRACT FROM AUTHOR]

Deviation from characteristic bright-red color during grading leads to discounted carcass price and value. Dark-cutting carcasses are examples of color deviation due to high-pH. However, atypical dark-cutters are not discounted at grading but have a dark color compared to normal-pH beef. Limited knowledge is currently available on the biochemical properties of atypical dark cutting beef compared with normal-pH beef. Therefore, the objective of the study was to determine metmyoglobin reducing activity and oxygen consumption of atypical dark-cutting beef. Strip loins from atypical dark-cutting (ADC; selected based on HunterLab L* values and pH less than 5.8 and not discounted by grader) and USDA Low Choice (C) carcasses were selected from a commercial beef processing plant and transported to the Food and Agricultural Products Center in Stillwater, Oklahoma. pH, color, oxygen consumption, and metmyoglobin reducing activity of atypical dark cutters and normal pH loins were determined on d3 postmortem. The surface color was determined using a HunterLab Miniscan spectrophotometer. Reflectance-based methods using K/S ratios were utilized to determine oxygen consumption and metmyoglobin reducing activity. The data were analyzed using the Mixed Procedure of SAS and the experiment was replicated 10 times (n = 10). There were no differences in initial pH (C = 5.46 and ADC = 5.6 atypical dark-cutter; P = 0.05) between normal-pH and atypical dark cutters. However, atypical dark cutters had lower lightness (L* values; C = 44.2 and ADC = 38.4), redness (a* values; C = 28.6 and ADC = 25.2), and red intensity (chroma; C = 40.2 and ADC = 36.4) compared with normal-pH. Further, atypical dark cutters had greater (P < 0.05) oxygen consumption and metmyoglobin reducing activity than normal-pH. The results suggest that atypical dark cutters and normal-pH beef have different biochemical properties. [ABSTRACT FROM AUTHOR]