Lipid oxidation induced by oxymyoglobin and metmyoglobin with involvement of H2O2 and superoxide anion

Impact of Washing with Antioxidant-Infused Soda-Saline Solution on Gel Functionality of Mackerel (Auxis thazard) Surimi

Mackerel (Auxis thazard), a tropical dark-fleshed fish, has the potential to be used in the production of surimi. It is necessary to identify the optimal washing method to make better use of this species since efficient washing is the most important step in surimi processing to ensure maximal gelling and high-quality surimi. The purpose of this study was to evaluate the combined effect of cold carbonated water (CW) with NaCl and antioxidants in washing media, so-called antioxidant-infused soda-saline solution, on lipid and myoglobin removal efficacy, biochemical characteristics, gelling properties, sensory features, and the oxidative stability of mackerel surimi in comparison with unwashed mince (T1) and conventional water washed surimi (T2). Mackerel mince was washed with CW in the presence of 0.6% NaCl at a medium to mince ratio of 3:1 (v/w) without antioxidant (T3) or with the addition of 1.5 mM EDTA plus 0.2% (w/v) sodium erythorbate and 0.2% sodium tripolyphosphate (T4), 100 mg/L gallic acid (T5), and 5 mM citric acid containing 8 mM calcium chloride (T6). During the first washing cycle, the antioxidants were mixed into the washing medium. The second and third washing cycles were then completed with cold water. The yields of all treatments were roughly 75-83%, based on the gross weight of the raw mince. The pH of the surimi was in a range of 5.47-6.46. All of the surimi had higher reactive sulfhydryl (SH) content and surface hydrophobicity but lower Ca2+-ATPase activity than unwashed mince (p < 0.05). After washing, lipids decreased significantly (p < 0.05), accounted for a 65-76% reduction. The T2 surimi had the highest peroxide value (PV). T1 had the lowest conjugated diene value. T1 and T4 surimi had the lowest TBARS value (p < 0.05). A lower non-heme iron level was found in all antioxidant-treated samples than in T1. Washing can increase the redox stability of myoglobin regardless of the washing media, as seen by the relatively low metmyoglobin levels. According to the dynamic viscoelastic behavior, all surimi and unwashed mince underwent the same degree of sol-gel transition following heat gelation. T1 showed the lowest breaking force, deformation, gel strength, and whiteness (p < 0.05). Surimi made from T4 or T5 had the highest gel strength when both breaking and deformation were considered, but the latter's expressible drip was noticeably higher. Surimi gel appears to be stabilized against lipid oxidation, as demonstrated by low PV and TBARS levels, when produced with T4. Because of the low level of TBARS, all 10 panelists rated rancid odor as low (~1 out of 4), with no significant variations across treatments. Only treatments with T4 and T6 tended to have a lower fishy odor score as compared to unwashed mince. Scanning electron microscope demonstrated that surimi gels washed with all washing media exhibited microstructures that were very comparable, with the exception of the T6 treatment, which had big pores and aggregates. Based on the quality features, T4 appeared to be the optimal medium to enhance the gel functionality of mackerel surimi.

Molecular Dynamics Study of the Effect of Charge and Glycosyl on Superoxide Anion Distribution near Lipid Membrane

To examine the effects of membrane charge, the electrolyte species and glycosyl on the distribution of negatively charged radical of superoxide anion (·O₂^-) around the cell membrane, different phospholipid bilayer systems containing ·O₂^- radicals, different electrolytes and phospholipid bilayers were constructed through Charmm-GUI and Amber16. These systems were equilibrated with molecular dynamics by using Gromacs 5.0.2 to analyze the statistical behaviors of ·O₂^- near the lipid membrane under different conditions. It was found that in the presence of potassium rather than sodium, the negative charge of the phospholipid membrane is more likely to rarefy the superoxide anion distribution near the membrane surface. Further, the presence of glycosyl significantly reduced the density of ·O₂^- near the phospholipid bilayer by 78.3% compared with that of the neutral lipid membrane, which may have a significant contribution to reducing the lipid peroxidation from decreasing the ·O₂^- density near the membrane.

A Novel Molecular Approach for Enhancing the Safety of Ozone in Autohemotherapy and Insights into Heme Pocket Autoxidation of Hemoglobin

Major ozone autohemotherapy (MAH) is a popular clinical practice for treating a variety of pathological conditions due to the mild and controlled oxidative stress produced by the reaction of ozone gas with other biological components. Previous studies have shown that blood ozonation leads to structural changes in hemoglobin (Hb); therefore, in the present study, the molecular effects of ozonation on Hb of a healthy individual were assessed by ozonating whole blood samples with single doses of ozone at 40, 60, and 80 μg/mL or double doses of ozone at 20 + 20, 30 + 30, and 40 + 40 μg/mL ozone to investigate whether ozonating once versus twice (but with the same final ozone concentration) would have varying effects on Hb. Additionally, our study aimed to verify whether using a very high ozone concentration (80 + 80 μg/mL), despite mixing it with blood in two steps, would result in Hb autoxidation. The pH, oxygen partial pressure, and saturation percentage of the whole blood samples were measured through a venous blood gas test, and the purified Hb samples were analyzed using several techniques including intrinsic fluorescence, circular dichroism and UV-vis absorption spectroscopies, SDS-polyacrylamide gel electrophoresis, dynamic light scattering, and a zeta potential analyzer. Structural and sequence analyses were also used to study the Hb heme pocket autoxidation sites and the residues involved. The results showed that the oligomerization and instability of Hb can be reduced if the ozone concentration to be used in MAH is divided into two doses. Indeed, our study demonstrated that two-step ozonation with 20, 30, and 40 μg/mL of ozone instead of single-dose ozonation with 40, 60, and 80 μg/mL of ozone reduced the potential adverse effects of ozone on Hb including protein instability and oligomerization. Moreover, it was found that for certain residues, their orientation or displacement leads to the entry of excess water molecules into the heme moiety, which can contribute to Hb autoxidation. Additionally, the autoxidation rate was found to be higher in alpha globins compared to beta globins.

The Effect of Reduced Crude Protein on Growth Performance, Nutrient Digestibility, and Meat Quality in Weaning to Finishing Pigs

This study aimed to evaluate optimal crude protein (CP) levels based on the National Research Council guidelines from 1998 and 2012 and their impacts on growth performance, fecal score, blood profiles, nutrient digestibility, and carcass characteristics of weaning to finishing pigs. Four diets were established in this experiment: high-protein (HP), medium-high-protein (MHP), medium-low-protein (MLP), and low-protein (LP). The HP diet followed the NRC (1998) guidelines, while the MHP diet reduced the CP content by 1%. The MLP diet had 1.5% lower CP content than the HP diet. The LP diet followed the NRC guideline of 2012, which suggests less protein than the NRC guideline of 1998. There were no significant differences in body weight, average daily feed intake, or nutrient digestibility. However, the average daily gain (ADG) of pigs fed the LP diet at 7-10 weeks was lower than in the other treatments, whereas the ADG of the pigs fed the LP diet was higher compared with that of pigs fed the other diets, showing compensatory growth in finishing periods (p < 0.05). The blood urea nitrogen of pigs fed the LP diet showed the lowest value, whereas the highest value was found in pigs fed the HP diet, and the other two diets were similar to the HP diet or positioned between the HP and LP diets (p < 0.05). Water holding capacity, cooking loss, shear force, and pH in the longissimus muscle were not influenced by varying dietary CP levels (p > 0.05), but the hunter values L and b were increased in pigs fed the LP diet (p < 0.05). Conclusively, a low-protein diet did not negatively affect growth performance, nutrient digestibility, or meat quality.

Effects of a Novel Lin Seed Polysaccharide on Beef Sausage Properties

Functional ingredients are substances that offer health benefits beyond their nutritional value. A novel heteropolysaccharide, named Linum water soluble polysaccharide (LWSP) was purified from Linum usitatissimum L. seeds powder and identified, via TLC and NMR, as a polymer composite of α1-2-L-arabinose, β1-2-D-xylose, β1-2-D-mannose and α1-2-D-glucose. The effect of incorporating LWSP on the quality of beef sausages, stuffed into collagen casings after 15 days of storage at 4 °C, was evaluated for texture profile analysis, color, sensory analysis and oxidation attributes. The new sausages formulated with LWSP recorded good textural attributes via reduction of cohesiveness, hardness and chewiness and improved the sensory features, especially texture, color and general acceptability. In addition, substituting ascorbic acid, a synthetic antioxidant, via the biological ingredient LWSP, retarded lipid oxidation and improved the oxymyoglobin rate until 15 days of storage. LWSP was proved to be a good natural substituent to synthetic antioxidants that definitely improves the oxidation stability and quality of sausages.

Myoglobin-Pyruvate Interactions: Binding Thermodynamics, Structure-Function Relationships, and Impact on Oxygen Release Kinetics

Myoglobin (Mb), besides its roles as an oxygen (O₂) carrier/storage protein and nitric oxide NO scavenger/producer, may participate in lipid trafficking and metabolite binding. Our recent findings have shown that O₂ is released from oxy-Mb upon interaction with lactate (LAC, anerobic glycolysis end-product). Since pyruvate (PYR) is structurally similar and metabolically related to LAC, we investigated the effects of PYR (aerobic glycolysis end-product) on Mb using isothermal titration calorimetry, circular dichroism, and O₂-kinetic studies to evaluate PYR affinity toward Mb and to compare the effects of PYR and LAC on O₂ release kinetics of oxy-Mb. Similar to LAC, PYR interacts with both oxy- and deoxy-Mb with a 1:1 stoichiometry. Time-resolved circular dichroism spectra revealed that there are no major conformational changes in the secondary structures of oxy- or deoxy-Mb during interactions with PYR or LAC. However, we found contrasting results with respect to binding affinities and substrate preference, where PYR has higher affinity toward deoxy-Mb when compared with LAC (which prefers oxy-Mb). Furthermore, PYR interaction with oxy-Mb releases a significantly lower amount of O₂ than LAC. Taken together, our findings support the hypothesis that glycolytic end-products play a distinctive role in the Mb-rich tissues by serving as novel regulators of O₂ availability, and/or by impacting other activities related to oxy-/deoxy-Mb toggling in resting vs. exercised or metabolically activated conditions.

Model systems for studying lipid oxidation associated with muscle foods: Methods, challenges, and prospects

Lipid oxidation is a complex process in muscle-based foods (red meat, poultry and fish) causing severe quality deterioration, e.g., off-odors, discoloration, texture defects and nutritional loss. The complexity of muscle tissue -both composition and structure- poses as a formidable challenge in directly clarifying the mechanisms of lipid oxidation in muscle-based foods. Therefore, different in vitro model systems simulating different aspects of muscle have been used to study the pathways of lipid oxidation. In this review, we discuss the principle, preparation, implementation as well as advantages and disadvantages of seven commonly-studied model systems that mimic either compositional or structural aspects of actual meat: emulsions, fatty acid micelles, liposomes, microsomes, erythrocytes, washed muscle mince, and muscle homogenates. Furthermore, we evaluate the prospects of stem cells, tissue cultures and three-dimensional printing for future model system development. Based on this reviewing of oxidation models, tailoring correct model to different study aims could be facilitated, and readers are becoming acquainted with advantages and shortcomings. In addition, insight into recent technology developments, e.g., stem cell- and tissue-cultures as well as three-dimensional printing could provide new opportunities to overcome the current bottlenecks of lipid oxidation studies in muscle.

Myoglobin Interaction with Lactate Rapidly Releases Oxygen: Studies on Binding Thermodynamics, Spectroscopy, and Oxygen Kinetics

Myoglobin (Mb)-mediated oxygen (O₂) delivery and dissolved O₂ in the cytosol are two major sources that support oxidative phosphorylation. During intense exercise, lactate (LAC) production is elevated in skeletal muscles as a consequence of insufficient intracellular O₂ supply. The latter results in diminished mitochondrial oxidative metabolism and an increased reliance on nonoxidative pathways to generate ATP. Whether or not metabolites from these pathways impact Mb-O₂ associations remains to be established. In the present study, we employed isothermal titration calorimetry, O₂ kinetic studies, and UV-Vis spectroscopy to evaluate the LAC affinity toward Mb (oxy- and deoxy-Mb) and the effect of LAC on O₂ release from oxy-Mb in varying pH conditions (pH 6.0–7.0). Our results show that LAC avidly binds to both oxy- and deoxy-Mb (only at acidic pH for the latter). Similarly, in the presence of LAC, increased release of O₂ from oxy-Mb was detected. This suggests that with LAC binding to Mb, the structural conformation of the protein (near the heme center) might be altered, which concomitantly triggers the release of O₂. Taken together, these novel findings support a mechanism where LAC acts as a regulator of O₂ management in Mb-rich tissues and/or influences the putative signaling roles for oxy- and deoxy-Mb, especially under conditions of LAC accumulation and lactic acidosis.

Effect of the exposure to oxidation and malondialdehyde on turkey and rabbit meat protein oxidative stability

The present study aimed at evaluating the effect of the exposure to a strong oxidative environment (100 mM NaClO) and the concurrent incubation with different malondialdehyde (MDA) concentrations (0 to 5 mM) on protein carbonylation, free thiol groups, total heme pigments, and on the relative concentration of the different myoglobin (Mb) derivatives in turkey thigh and rabbit hind leg meat to elucidate their eventual role in inducing oxidative modifications on the protein fraction. With regard to turkey meat, the addition of a strong oxidant resulted in remarkably higher (P < 0.001) carbonyls along with a reduction in free thiol groups (which become undetectable). The relative concentration of MbO₂ and MetMb was significantly affected (P < 0.001) and total heme pigment was reduced by 62% when fresh meat is compared to its oxidized counterpart. The addition of MDA 2.5 mM (or greater) resulted in a 1.4-fold increase in carbonyls and a tendency (P = 0.07) has been observed for free thiol groups whose content decreased as the MDA level increased. Overall, the aforementioned results are in agreement with those obtained on rabbit hind leg meat in which a three-fold increase (P < 0.001) in carbonyls and a remarkably higher (P < 0.001) MetMb content coupled with a 53% reduction in free thiol groups were found. No significant differences ascribable to MDA addition were found. In conclusion, exposing turkey and rabbit meat to the same environment resulted in distinctive oxidative changes that might be related to the compositional traits and a species-specific susceptibility of the meat toward oxidation. PRACTICAL APPLICATION: Protein and lipid oxidation have been investigated in different meat types; nevertheless, the knowledge concerning the interaction between these two phenomena is limited. According to their compositional traits (high Polyunsaturated fatty acids (PUFA) and heme pigment content), turkey and rabbit leg meats are particularly susceptible to oxidation. Providing information concerning the oxidative stability of turkey thigh and rabbit hind leg meat exposed to strong oxidative conditions and to a concurrent increasing content of a secondary product of lipid oxidation, the findings of the present study can be useful when proper processing strategies and storage conditions have to be implemented for manufacturing processed products.

Kimchi extracts as inhibitors of colour deterioration and lipid oxidation in raw ground pork meat during refrigerated storage

BACKGROUND

Kimchi is a Korean, traditional fermented food made from Korean cabbage, radish, fermented jeotgal, ginger, garlic, and red pepper powder. It is a good source of natural antioxidants such as phenolic compounds, flavonoids, vitamins, and carotenoids. In this study, the antioxidant effects of various kimchi extracts on raw ground pork during refrigerated storage were investigated. Raw ground pork samples were treated with ascorbic acid, butylated hydroxyl toluene, baechu kimchi extract (BKE), gat kimchi extract (GKE), puchu kimchi extract (PKE), and white kimchi extract (WKE) and compared with raw ground pork without antioxidant treatment (NC).

RESULTS

Increased metmyoglobin (MetMb), thiobarbituric acid reacting substance (TBARS), and total bacterial counts (TBC) were observed in all meat samples after storage, whereas pH, lightness, and redness values tended to decrease with increased storage time. All treated samples had lower TBARS and MetMb values and TBC compared to the control samples. Various kimchi ethanol extracts protected raw ground pork from lipid oxidation. The most potent antioxidant was GKE, whereas WKE was the weakest.

CONCLUSIONS

This study suggests that the tested extracts, especially kimchi, have potential as natural preservatives to reduce colour degradation, lipid oxidation, and bacterial count in raw ground pork meat. © 2018 Society of Chemical Industry.

Novel X-ray sequences and crystal structures of Persian and Starry sturgeon methemoglobins: Highlighting the role of heme pocket waters in causing autoxidation

Although there is a high sequence similarity between mammalian and fish hemoglobin (Hb), the oxidation and heme loss rates can vary greatly between them such that fish Hbs oxidise much more rapidly than mammalian Hbs. There is to date no sequence or structural data for any sturgeon Hb to reveal the level of autoxidation in these fish. In this study, novel high resolution X-ray sequences and crystal structures of methemoglobin (Met-Hb) from two sturgeon fish including Persian sturgeon (Acipenser percisus) and Starry sturgeon (Acipenser stellatus) belonging to the Caspian sea has been determined. A comprehensive sequence and structure comparison between these sturgeon Met-Hbs and a number of non-sturgeon and normal and sickle cell anaemia human Hb in varying heme states has been carried out highlighting (i) the structural variability in the heme propionate groups; (ii) the existence of certain residues or their displacement and shift in the heme pocket allowing entry of water molecules into the heme pocket; (iii) the importance of the number of water molecules in the heme pocket; (iv) the hydrogen bonding between oxygens of A and D propionate groups and that of waters in the heme pocket; and (v) the role of heme binding waters causing oxidative stress and heme autoxidation.

Optimization of low-fat meat hamburger formulation containing quince seed gum using response surface methodology

In the present study, feasibility of low-fat hamburger production by partial replacement with quince seed gum (QSG) was investigated. The effects of different QSG levels (1.2, 2.4, 3.6, and 4.8 wt%) on cooking loss, water holding capacity, lipid oxidation, antioxidant activity, and hardness of hamburger were investigated during a period of 9 days. The optimization was carried out based on minimum cooking loss, lipid oxidation, and maximum water holding capacity, antioxidant activity, and tissue hardness. Optimum conditions were achieved as 3.26% oil, 4.73% QSG, and 8.25th day of storagability. According to the optimum conditions, values for cooking loss, water holding capacity, lipid oxidation, free radical scavenging, raw hamburger hardness, and fried hamburger hardness were as 13.80%, 55.61%, 0.59 mg MDA/Kg, 48.12%, 2.99 N, and 8.66 N, respectively. Overall acceptability of optimized hamburgers was better and more acceptable than control ones.

Effect of slaughter age on the antioxidant enzyme activity, color, and oxidative stability of Korean Hanwoo (Bos taurus coreanae) cow beef

This study investigated the effect of slaughter age on the antioxidant enzyme activity, lipid and protein oxidation, and color stability in striploins (M. longissimus lumborum) from Korean Hanwoo (Bos taurus coreanae) cows of different age groups (1.9 to 3.7, 4.0 to 4.8, 5.0 to 5.7, 6.0 to 6.9, and 7.5 to 11.5yr). Myoglobin content and the activities of catalase, superoxide dismutase, and glutathione peroxidase were significantly (P<0.05) increased in older cow beef. During refrigerated storage, 2-thiobarbituric acid reactive substances and protein carbonyls were significantly (P<0.05) increased in the meat from the older cows. The beef from older cows was darker and had lower color stability. These findings suggest that slaughter age has a negative effect on the color and lipid stability of Hanwoo cow beef.

Interrelationship between myoglobin and lipid oxidations in oxeye scad (Selar boops) muscle during iced storage

The interrelationship between myoglobin oxidation, lipid oxidation and discolouration in oxeye scad fish during iced storage were investigated. The myoglobin autoxidation rate increased with increasing storage time up to 12 days (p < 0.05) and remained constant thereafter (p > 0.05). Increase in metmyoglobin correlated well with a blue shift from 410 to 408 nm for myoglobin. The soret band of myoglobin decreased with a concomitant decrease in the redness index (p < 0.05). During storage, the extractable haem iron decreased (p < 0.05), while the non-haem iron increased (p < 0.05). Hydrogen peroxide and ferrylmyoglobin concentrations had increased at the end of storage (p < 0.05). The conjugated diene (CD) and peroxide value (PV) of oxeye scad lipids tended to stabilise during the initial phase of storage, increased in the differentiation phase and had declined at the end of storage. However, thiobarbituric acid reactive substances (TBARS) increased markedly (p < 0.05). Overall, lipid and myoglobin oxidations in oxeye scad occurred in a concurrent manner and each process appeared to enhance the other.

Relationship between histochemical, structural characteristics and oxidative stability of rhea limb muscles

Histochemical and structural characteristics were investigated in Gastrocnemius pars interna (GN) and Iliofiburalis (IF) limb muscles of Rhea americana. The average myofibre area cross-section was greater in GN than IF muscle (p<0.001), whereas the fibre density per section was higher in IF than GN muscle. The only type of myofibre found in both the rhea limb muscles analysed in this study was fast-twitch oxidative-glycolytic fibres (FOG). Immunolabelling analysis and ultrastructural observation of myofibres confirmed the contractile and metabolic characteristics of rhea myofibres, revealing the absolute fast isoform of myosin heavy chain and the abundance of glycogen and mitochondria inside the cells, mainly in IF muscle. These findings converged with previous results on the biochemical and physicochemical characteristics of rhea meat to provide further evidence that myofibre composition substantially influences the oxidative reactions of the muscle and therefore the meat quality, but more in-depth examination is needed to establish the links between myofibre characteristics, myofibre glycogen concentration and meat stability during storage.

Interactions between hemoglobin and cod muscle constituents following treatment at extreme pH values

Acid and/or alkaline solubilization is a recent method developed to separate proteins from muscle foods with good functional properties. However, exposure of the muscle and its components to low pH values has been shown to promote lipid oxidation, limiting therefore the applications of this novel method. This research aimed primarily to study the physicochemical changes of the fish membranes brought about during acid or alkali solubilization processes. The effect on lipid oxidation and the possible role of the water soluble fraction of the muscle (press juice) as a potent antioxidant were also investigated. Model systems comprising minced cod muscle or cod microsomal suspensions were used. Results showed that acid or alkaline treatment (pH < 3.5 or pH > 10.5) of cod membranes significantly delayed lipid oxidation. Added triacylglycerols to washed cod system treated at low pH did not enhance hemoglobin-mediated lipid oxidation. Decreased precipitation of hemoglobin was observed with the alkali-treated membranes at all protein concentrations compared to the acid-treated and the untreated membranes. Finally, the addition of press juice to washed cod muscle tissue or to the membrane model system, significantly delayed hemoglobin lipid oxidation.

PRACTICAL APPLICATION

The results of this study can be used to improve pH-shifting technologies to avoid or decrease lipid oxidation problems. Also, the use of press-juice from cod muscle as means of protecting the muscle against lipid oxidation is suggested.

Reducing lipid peroxidation for improving colour stability of beef and lamb: on-farm considerations

Meat colour and lipid stability are important sensory properties. Myoglobin oxidation is correlated with lipid oxidation, and one can exacerbate the occurrence of the other. Approaches to reduce both oxidative processes could focus on minimising oxidising agents in meat. In on-farm practices, dietary supplementation of antioxidants is a useful approach for improving lipid stability and then meat colour stability, and further improvement could be a combination of using hydrophobic and hydrophilic antioxidants. Genetic variations in the endogenous antioxidant systems could be identified for the development of a breeding strategy to bring a long-term benefit to the meat industry. To have a better understanding of oxidative stress and oxidation of long chain unsaturated fatty acids in live animals, the isoprostanes could be measured as an effective marker in vivo.

Species-specific myoglobin oxidation

The effect of the lipid oxidation product, 4-hydroxy-2-nonenal (HNE), on oxidation of oxymyoglobin (OxyMb) from seven different meat-producing species was investigated. Relative to controls, HNE increased OxyMb oxidation within all species (p < 0.05) at both 25 and 4 °C, pH 5.6. The relative effect of HNE was greater for myoglobins (Mbs) that contained 12 ± 1 histidine (His) residues than for those that contained 9 His residues (p < 0.05); HNE efficacy in all species except chicken and turkey decreased with time. Mono-HNE adducts were detected in all species except chicken and turkey. In general, HNE alkylation increased the Mbs' ability to accelerate lipid oxidation in a microsome model. However, neither an HNE nor a Mb species dependent effect was observed. Results suggested that microsome model system associated lipid oxidation overshadowed HNE and species effects on OxyMb oxidation observed in lipid-free systems.

Effect of frozen storage duration and cooking on physical and oxidative changes in M. Gastrocnemius pars interna and M. Iliofiburalis of Rhea americana

This study was conducted to evaluate the effect of frozen storage time (30, 60, 90 or 180 days) and cooking (100 °C, 30 min) on the physical characteristics and oxidative stability of M. Gastrocnemius pars interna (GN) and M. Iliofiburalis (IF) of rhea americana. Physical parameters measured included thawing and cooking loss, colour parameters (L*a*b*), while oxidation was assessed by determining the TBA-RS, carbonyl and aromatic amino acid content. Prolonged frozen storage of rhea meat decreased lightness (L*), yellowness (b*), and increased the discoloration parameter hue angle and redness a*. During storage, muscle IF was more prone to lipid and myoglobin oxidation than muscle GN. Cooking loss declined with the increase of storage time and was higher in GN than in IF muscle. With cooking, TBA-RS, carbonyl content, and aromatic amino acids (phenylalanine, tyrosine, and tryptophan) were highly affected, but the extent of oxidation ranged according to muscle and duration of frozen storage.

Effects of salt and ammonium hydroxide on the quality of ground buffalo meat

The objective of this study was to evaluate the effects of ammonium hydroxide (AH) and sodium chloride on the quality of ground buffalo meat patties. Ground buffalo meat was treated with distilled water (control), 0.5% v/w AH, 1.0% v/w AH, 2.0% v/w AH and 1.0% w/w sodium chloride was added for all the samples. Treatment with AH increased (P<0.05) the pH and water holding capacity (WHC) of ground buffalo meat patties during storage relative to their controls. Hunterlab a* (redness) and chroma values increased (P<0.05) and hue decreased (P<0.05) in all AH treated samples in comparison to controls during storage. Ammonium hydroxide significantly (P<0.05) inhibited metmyoglobin formation compared to control after 3rd day of storage. There was a significant (P<0.05) reduction in thiobarbituric acid reactive substances (TBARS) values in all AH treated samples compared to control throughout storage. These results indicate the potential antioxidant and myoglobin redox stabilizing effect of AH in ground buffalo meat patties.

Structural analysis of fish versus mammalian hemoglobins: effect of the heme pocket environment on autooxidation and hemin loss

The underlying stereochemical mechanisms for the dramatic differences in autooxidation and hemin loss rates of fish versus mammalian hemoglobins (Hb) have been examined by determining the crystal structures of perch, trout IV, and bovine Hb at high and low pH. The fish Hbs autooxidize and release hemin approximately 50- to 100-fold more rapidly than bovine Hb. Five specific amino acid replacements in the CD corner and along the E helix appear to cause the increased susceptibility of fish Hbs to oxidative degradation compared with mammalian Hbs. Ile is present at the E11 helical position in most fish Hb chains whereas a smaller Val residue is present in all mammalian alpha and beta chains. The larger IleE11 side chain sterically hinders bound O(2) and facilitates dissociation of the neutral superoxide radical, enhancing autooxidation. Lys(E10) is found in most mammalian Hb and forms favorable electrostatic and hydrogen bonding interactions with the heme-7-propionate. In contrast, Thr(E10) is present in most fish Hbs and is too short to stabilize bound heme, and causes increased rates of hemin dissociation. Especially high rates of hemin loss in perch Hb are also due to a lack of electrostatic interaction between His(CE3) and the heme-6 propionate in alpha subunits whereas this interaction does occur in trout IV and bovine Hb. There is also a larger gap for solvent entry into the heme crevice near beta CD3 in the perch Hb (approximately 8 A) compared with trout IV Hb (approximately 6 A) which in turn is significantly higher than that in bovine Hb (approximately 4 A) at low pH. The amino acids at CD4 and E14 differ between bovine and the fish Hbs and have the potential to modulate oxidative degradation by altering the orientation of the distal histidine and the stability of the E-helix. Generally rapid rates of lipid oxidation in fish muscle can be partly attributed to the fact that fish Hbs are highly susceptible to oxidative degradation.

Effect of heating oxymyoglobin and metmyoglobin on the oxidation of muscle microsomes

Myoglobin (Mb) and its iron have been proposed to be major prooxidants in cooked meats. To understand the mechanisms and differentiate between the prooxidant and antioxidant potential of oxymyoglobin (OxyMb) and metmyoglobin (MetMb), their prooxidant activity, iron content, solubility, free radical scavenging activity, and iron binding capacity were determined as a function of thermal processing. The ability of native and heat denatured OxyMb and MetMb to promote the oxidation of muscle microsomes was different. MetMb promoted lipid oxidation in both its native and denatured states. Conversely, OxyMb became antioxidative when the protein was heated to temperatures >or=75 degrees C. The increased antioxidant activity of heat denatured OxyMb was likely due to a decrease in its prooxidative activity due to its loss of solubility. These data show that the impact on oxidative reactions of Mb is the result of the balance between its antioxidant and prooxidant activities.