Characteristics of myoglobin and haemoglobin-mediated lipid oxidation in washed mince from bighead carp (Hypophthalmichthys nobilis)

L-lysine enhances pork color through antioxidant activity and myoglobin conformational changes

This study aimed to investigate the effect of L-lysine (Lys) on the color of pork and reveal the possible mechanism. The results showed that the L* and a* values increased from 53.69 to 56.32, 56.39, and 56.47, and from 12.93 to 13.21, 13.24, and 13.52 with the addition of 0.1 %, 0.15 % and 0.2 % Lys, respectively. Meanwhile, the oxymyoglobin (Fe2+) levels increased from 21.14 % to 22.63 %, 23.83 %, and 23.53 %, while the metmyoglobin (Fe3+) levels decreased from 44.69 % to 40.28 %, 41.21 %, and 41.63 % with the addition of 0.1 %, 0.15 % and 0.2 % Lys, respectively. Additionally, the addition of Lys increased total sulfhydryl and active sulfhydryl contents, and decreased the levels of reactive oxygen species (ROS) (P<0.05). The particle size and the absolute value of the ζ-potential increased with the addition of Lys, reaching maximum values of 534.39 nm and -13.73 mV, respectively. The molecular dynamics results suggested that Lys can bind to myoglobin (Mb) through hydrophobic interactions and hydrogen bonds, forming a stable Lys-Mb complex, acting as a protective shield to prevent the entry of ROS and other oxidizing agents. Finally, the addition of 0.15 % Lys resulted in the highest surface hydrophobicity, which was 5.79 μg. The multispectral results indicated that Lys primarily induces changes in the secondary and tertiary structures of Mb through interactions with tyrosine residues. These changes stabilized the free-moving rings within the amino acid residues of Mb, thereby improving the structural stability of Mb and ultimately enhancing the color stability of pork. In summary, Lys improved meat color stability through a dual mechanism of antioxidation and interaction with Mb to alter its conformational stability.

Market Status of Meat Analogs and Their Impact on Livestock Industries

The alternative meat industry, which aims to replace traditional livestock products, is experiencing growth. However, information regarding this industry remains limited, and plant-based meat analogs that have already entered the market are not growing as rapidly as initially anticipated. Moreover, the traditional livestock industry has significant concerns that the growth of meat analogs will encroach upon the livestock market and strongly opposes the approval of cultured meat and other meat analogs. In this study, we investigated the latest research on the production of plant-based meat analogs and examined the current market status of these products. We also predicted the impact of the growth of meat analogs on the livestock industry. Our findings indicate that the meat analog market has secured a substantial presence in the United States and European markets and is gradually expanding in major Asian countries, such as South Korea, China, and Japan. Additionally, while the meat analog market is growing slowly, the traditional livestock industry continues to expand. Furthermore, our analysis shows that the growth of the meat analog market, including plant-based meat analogs, has had a minimal impact on the traditional livestock market so far. Nevertheless, it is essential to continuously monitor potential market changes resulting from future advancements in meat analog technologies.

Tumor-Targeted CO Nanodelivery System Design and Therapy for Hepatocellular Carcinoma

In recent years, carbon monoxide (CO) has garnered increased attention as a novel green therapy for hepatocellular carcinoma (HCC) treatment. However, the CO donor is still limited in clinical application due to its lack of targeted ability and unstable release rate. Here, self-assembled amphiphilic nanomicelles glucose-polyethylene glycol (PEG)-lipoic acid (LA)-Fe2(CO)6 (Glu-Fe2(CO)6) are first designed as a CO donor and synthesized via a chemical method, combining glucose with Fe2(CO)6 through PEG-LA. Some advantages of this tumor-targeted Glu-Fe2(CO)6 delivery system include (I) good water-solubility, (II) the glutathione responsive CO slow release, (III) the active tumor-targeted ability of glucose as targeted ligands, and (IV) outstanding efficacy of antitumor and safety of CO therapy of HCC both in vitro and in vivo. These findings suggest that Glu-Fe2(CO)6 nanomicelles hold promise for enhancing antitumor therapeutic capabilities, presenting a novel tumor-targeted delivery strategy in gas therapy for HCC treatment.

Effect of heme proteins on the lipid molecule profile and aroma formation during hot air drying of non-smoked bacon

Heme proteins and their derivatives play important roles in inducing lipid oxidation to produce volatile compounds during bacon drying. This study investigated the effects of heme proteins and their derivatives (hemoglobin, myoglobin, nitrosylmyoglobin, hemin, Fe2+, and Fe3+) on lipid and volatiles profiles in the washed pig muscle (WPM) model. The results of the study indicated that the inducers primarily caused the oxidation of glycerophospholipids. Furthermore, hemoglobin and myoglobin had the most significant impact, and their potential substrates may include PE (O-18:2/20:4), PE (O-18:1/20:4), PC (16:0/18:1), and PE (O-18:2/18:2). Nitrosomyoglobin has limited ability to promote lipid oxidation and may protect ether phospholipids from oxidation. The analysis of the volatiles in the model revealed that heme proteins and their derivatives have the ability to induce the production of key aroma compounds. The descending order of effectiveness in inducing the production of aroma compounds is as follows: hemoglobin, myoglobin, hemin, and nitrosylmyoglobin. The effectiveness of Fe2+ and Fe3+ is similar to that of nitrosylmyoglobin.

Oxidized myoglobin: Revealing new perspectives and insights on factors affecting the water retention of myofibrillar proteins

The impact of oxidized myoglobin (Mb) on myofibrillar protein (MP) oxidation and water retention was investigated. Results showed that the oxidation of Mb increased with increasing concentration of oxidized linoleic acid (OLA). In the presence of 100 mmol/L OLA, hemin iron decreased by 62.07 % compared to the control group. Further investigation showed that mild oxidation of Mb (≤10 mmol/L OLA) increased the water retention and the absolute value of the zeta potential of MP, whereas excessive oxidation (>10 mmol/L OLA) decreased these properties. With the increase of Mb oxidation, the carbonyl content in MP increased, and α-helices changed to random helix. And the tertiary structure changed. Pearson correlation analysis suggested that oxidized Mb affected the water retention of MP, which was closely related to hemin iron and non-hemin iron. In conclusion, OLA induced Mb oxidation, further promoted MP oxidation and affected its water retention.

Effects of Different Phenolic Compounds on the Redox State of Myoglobin and Prevention of Discoloration, Lipid and Protein Oxidation of Refrigerated Longtail Tuna (Thunnus tonggol) Slices

Effects of different phenolic compounds on the redox state of myoglobin and their potential for preserving the color and chemical quality of refrigerated longtail tuna (Thunnus tonggol) slices were studied. Purified myoglobin from dark muscle (15.83 kDa) was prepared. Catechin, EGCG, quercetin, and hyperoside affected the absorption spectra and redox state of metmyoglobin (metMb) at 4 °C for up to 72 h differently. Reduction of metMb to oxymyoglobin (oxyMb) was notably observed for two flavonols (EGCG and quercetin) at 50 and 100 ppm. Based on the reducing ability of metMb, EGCG and quercetin were selected for further study. Longtail tuna slices were treated with EGCG and quercetin at 200 and 400 mg/kg. Color (a* and a*/b*), proportion of myoglobin content, and quality changes were monitored over 72 h at 4 °C. Tuna slices treated with 200 mg/kg EGCG showed better maintenance of oxyMb and color as well as lower lipid oxidation (PV and TBARS) and protein oxidation (carbonyl content) than the remaining samples. Nevertheless, EGCG at 400 mg/kg exhibited lower efficacy in retaining the quality of tuna slices. Thus, EGCG at 200 mg/kg could be used to maintain the color and prolong the shelf life of refrigerated longtail tuna slices.

Lipid oxidation and antioxidant delivery systems in muscle food

Lipid oxidation accelerates quality deterioration in muscle-based foods (fish, red meat, and poultry), resulting in off-odors/flavors, color problems, texture defects, and safety concerns. Adding antioxidants is one approach to control lipid oxidation, and several delivery strategies have been applied, such as supplementing antioxidants to the feed, direct mixing into minces, or, for whole muscle pieces; spraying, glazing, and injection. However, some issues linked to these technologies hinder their wide utilization, such as low effectiveness, noncompatibility with clean label, and off-flavor. These shortcomings have promoted the development of new antioxidant delivery technologies. In this review, the main focus is on the principles, characteristics, and implementation of five novel antioxidant delivery methods in different types of muscle food products. Their advantages and drawbacks are also summarized, plus comments about future trends in this area. Among novel routes to deliver antioxidants to muscle foods are, for whole tissues, recyclable dipping solutions; for minces, encapsulation; and, for both minces and whole tissues, cross-processing with nonmuscle antioxidant-containing raw materials as well as applications of edible films/coatings and active packaging. Advantages of these technologies comprise, for example, low price, the possibility to control the antioxidant release rate, overcoming strong aromas from natural antioxidants, and allowing antioxidant-containing raw materials from the food industry to be valorized, providing an opportunity for more circular food production.

Effect of squid pen chitooligosaccharide and epigallocatechin gallate on discoloration and shelf-life of yellowfin tuna slices during refrigerated storage

This study evaluated the effects of treatments of squid pen chitooligosaccharide (COS) or epigallocatechin gallate (EGCG) or COS/EGCG mixture (1:1, w/w) at different concentrations (0, 200, and 400 mg/kg) on the discoloration and quality changes in yellowfin tuna slices stored at 4 °C for 12 days. Tuna slices added with 200 and 400 mg/kg of COS (C2 and C4, respectively) showed the lowest reduction in oxymyoglobin and a* value (redness) ascertained by the lower metmyoglobin formation than other samples. Additionally, C2 and C4 samples showed a lower total viable count and TBARS value than the remaining samples. EGCG alone and its mixture with COS exhibited lower efficacy in retaining the quality loss than COS alone. COS at both levels effectively reduced the metMb formation. It maintained the redness with sensory acceptability of slices up to 9 days, and C4 sample prolonged shelf-life for 12 days based on the microbiological limit.

Hemolysis, tocopherol, and lipid oxidation in erythrocytes and muscle tissue in chickens, ducks, and turkeys

Muscle from turkeys is more sensitive to lipid oxidation during post mortem storage compared with that of chicken and duck which may involve increased lysis of turkey erythrocytes that releases hemoglobin oxidant. Three separate experiments were conducted to study characteristics of chicken, duck, and turkey erythrocytes in which dietary tocopherols were standardized. In Experiment I, tocopherol, fatty acid composition, and lipid oxidation capacity were measured in erythrocytes from chickens, ducks, and turkeys. Tocopherol content was greater in chicken erythrocytes compared with that of duck and turkey (P < 0.05). Oleic and linoleic acid content was higher in chicken erythrocytes compared with that of turkey (P < 0.05). Lipid oxidation capacity of erythrocytes in washed turkey muscle (WTM) at pH 5.8 ranked chicken > duck > turkey (P < 0.05). In Experiment II, hemolysis was measured in erythrocytes from turkeys and chickens. Detergent-induced hemolysis (pH 7.4) was on average 12-fold greater for turkey erythrocytes compared with that of chicken (P < 0.05). In Experiment III, the ability of lysed and non-lysed erythrocytes to promote lipid oxidation was examined. Lysed erythrocytes promoted lipid oxidation in WTM more effectively than intact erythrocytes (P < 0.05). Reasons that turkey erythrocytes were more labile to detergent-induced hemolysis whereas chicken erythrocytes more effectively promoted lipid oxidation in the WTM model system are discussed. These studies describe variation in chemical and physical properties of erythrocytes from chickens, ducks, and turkeys that can influence progression of lipid oxidation in poultry muscle.

Factors Affecting Lipid Oxidation Due to Pig and Turkey Hemolysate

Turkey hemolysate promoted lipid oxidation in washed muscle more effectively than pig hemolysate, which was partly attributed to the greater ability of H₂O₂ that formed during auto-oxidation to oxidize the avian hemoglobin (Hb). Turkey and pig hemolysate (2.5 μM Hb) exposed to 10 μM H₂O₂ oxidized to 48% and 4% metHb, respectively. Catalase activity, which converts H₂O₂ to water, was elevated in the pig hemolysate. The larger difference in Hb oxidation when comparing turkey and pig hemolysate in washed muscle (relative to their auto-oxidation rates) suggested that lipid oxidation products facilitated formation of metHb. Turkey metHb released hemin more readily than pig metHb, which coincided with turkey metHb promoting lipid oxidation more effectively than pig metHb. Ferryl Hb was not detected during storage of turkey or pig hemolysate in washed muscle, which suggested a minor role for hypervalent forms of Hb in the oxidation of the lipids.

Myoglobin and haemoglobin-mediated lipid oxidation in washed muscle: observations on crosslinking, ferryl formation, porphyrin degradation, and haemin loss rate

Reduced trout haemoglobin (Hb) is a mixture of oxy- and deoxy-Hb at pH 6.3. Addition of oxy/deoxyHb to washed muscle resulted in detectable ferryl Hb while adding bovine oxyHb, trout metHb, or bovine metHb did not. Trout metHb promoted lipid oxidation more rapidly than bovine metHb, attributable to lower haemin affinity in fish Hbs. Protoporphyrin IX degradation was prevalent during trout and bovine Hb-mediated lipid oxidation. Caffeic acid prevented porphyrin degradation and lipid oxidation. Crosslinked myoglobin (Mb) promoted lipid oxidation more effectively than metMb. Fish metMb released haemin more readily than mammalian metMb at pH 5.5. These studies suggest haemin dissociation from metHb causes formation of free radicals that degrade protoporphyrin and cause lipid oxidation, and appreciable quantities of deoxyHb are needed to generate ferryl Hb oxidant. Crosslinking appears to facilitate Mb-mediated lipid oxidation in washed muscle yet haemin release can occur from fish metMb at low pH.

Bleeding Efficiency and Meat Oxidative Stability and Microbiological Quality of New Zealand White Rabbits Subjected to Halal Slaughter without Stunning and Gas Stun-killing

A study was conducted to compare the effect of halal slaughter without stunning and gas stun killing followed by bleeding on residual blood content and storage stability of rabbit meat. Eighty male New Zealand white rabbits were divided into two groups of 40 animals each and subjected to either halal slaughter without stunning (HS) or gas stun-kill (GK). The volume of blood lost during exsanguination was measured. Residual blood was further quantified by determination of haemoglobin content in Longissimus lumborum (LL) muscle. Storage stability of the meat was evaluated by microbiological analysis and measuring lipid oxidation in terms of thiobarbituric acid reactive substances (TBARS). HS resulted in significantly higher blood loss than GK. HS had significantly lower residual haemoglobin in LL muscle compared to GK. Slaughter method had no effect on rabbit meat lipid oxidation at 0, 1, and 3 d postmortem. However, at 5 and 8 days of storage at 4°C, significant differences (p<0.05) were found, with meat from the GK group exhibiting significantly higher levels of MDA than that from HS. At day 3, greater growth of Pseudomonas aeroginosa and E. coli were observed in the GK group (p<0.05) with B. thermosphacta and total aerobic counts remained unaffected by slaughter method. At days 5 and 7 postmortem, bacterial counts for all tested microbes were affected by slaughter method, with GK exhibiting significantly higher growth than HS. It can be concluded that slaughter method can affect keeping quality of rabbit meat, and HS may be a favourable option compared to GK due to high bleed out.

Lipid oxidation and fishy odour in protein hydrolysate derived from Nile tilapia (Oreochromis niloticus) protein isolate as influenced by haemoglobin

BACKGROUND

Although protein isolates have been proven as a potent raw material for protein hydrolysate preparation, the fishy odour associated with lipid oxidation is still detected. The remaining haemoglobin (Hb) in protein isolates can effectively induce lipid oxidation, leading to the formation of fishy odour in the resulting hydrolysate. The aim of this study was to elucidate the impact of Hb with different forms, oxyhaemoglobin (oxy-Hb) and methaemoglobin (met-Hb), on lipid oxidation and the development of fishy odour during hydrolysis of protein isolates.

RESULTS

During hydrolysis of protein isolate up to 120 min, non-haem iron content, peroxide value and thiobarbituric acid reactive substances slightly increased (P < 0.05). When oxy-Hb or met-Hb was incorporated, the marked increases in all parameters were observed, especially within the first 60 min of hydrolysis. The higher increases were obtained with the latter, suggesting that met-Hb was more pro-oxidative than oxy-Hb. However, no differences in degree of hydrolysis of all samples were observed (P > 0.05). The marked increases in the b*, ΔE*, ΔC* values, fishy odour/flavour and volatile compounds were also found in the resulting hydrolysate containing either oxy-Hb or met-Hb.

CONCLUSION

Hb, particularly met-Hb, induced lipid oxidation and the development of a fishy odour/flavour in fish protein hydrolysate.

Redox reactions of myoglobin

SIGNIFICANCE

Failure to maintain myoglobin (Mb) in the reduced state causes the formation of metMb, ferryl Mb species, and cross-linked Mb. Dissociation of ferriprotoporphyrin IX from the globin and release of iron atoms can also occur as oxidized Mb accumulates. These modifications may contribute to various oxidative pathologies in muscle and muscle foods.

RECENT ADVANCES

The mechanism of ferryl Mb-mediated oxidative damage to nearby structures has been partially elucidated. Dissociation of ferriprotoporphyrin IX from metMb occurs more readily at acidic pH values. The dissociated ferriprotoporphyrin IX (also called hemin) readily decomposes preformed lipid hydroperoxides to reactive oxygen species. Heme oxygenase as well as lipophilic free radicals can degrade the protoporphyrin IX moiety, which results in the formation of free iron.

CRITICAL ISSUES

The multiple pathways by which Mb can incur toxicity create difficulties in determining the major cause of oxidative damage in a particular system. Peroxides and low pH activate each of the oxidative Mb forms, ferriprotoporphyrin IX, and released iron. Determining the relative concentration of these species is technically difficult, but essential to a complete understanding of oxidative pathology in muscle tissue.

FUTURE DIRECTIONS

Improved methods to assess the different pathways of Mb toxicity are needed. Although significant advances have been made in the understanding of Mb interactions with other biomolecules, further investigation is needed to understand the physical and chemical nature of these interactions.

Lipid oxidation in trout muscle is strongly inhibited by a protein that specifically binds hemin released from hemoglobin

The recombinant streptococcal protein apoShp can be used as a probe for hemoglobin (Hb) reactivity in fish muscle due to its specific affinity for hemin that is released from Hb at post-mortem pH values. Hemin affinity measurements indicated that apoShp binds hemin released from Hb but not myoglobin (Mb). Hemin affinity of holoShp was higher at pH 5.7 compared to pH 8.0. This may be attributed to enhanced electrostatic interaction of His58 with the heme-7-propionate at lower pH. ApoShp readily acquired hemin that was released from trout IV metHb in the presence of washed cod muscle during 2 °C storage at pH 6.3. This was based on increases in redness in the washed cod matrix, which occurs when apoShp binds hemin that is released from metHb. ApoShp prevented Hb-mediated lipid oxidation in washed cod muscle during 2 °C storage. The prevention of Hb-mediated lipid oxidation by apoShp was likely due to bis-methionyl coordination of hemin that dissociated from metHb. This hexacoordination of hemin appears to prevent peroxide-mediated redox reactions, and there is no component in the matrix capable of dissociating hemin from Shp. ApoShp was also added to minced muscle from rainbow trout ( Oncorhynchus mykiss ) to examine the degree to which Hb contributes to lipid oxidation in trout muscle. Addition of apoShp inhibited approximately 90% of the lipid oxidation that occurred in minced trout muscle during 9 days of 2 °C storage on the basis of lipid peroxide, hexanal, and thiobarituric acid reactive substances (TBARS) values. These results strongly suggest that Hb is the primary promoter of lipid oxidation in trout muscle.

Site E14 in hemoglobins and myoglobins: a key residue that affects hemin loss and lipid oxidation capacity

Fish hemoglobins (Hbs) frequently contain glycine at site E14 while mammalian Hbs contain larger residues (e.g., alanine and serine). These differences were examined by creating structural variants at E14 using recombinant bovine myoglobin (Mb) as a model heme protein that contains alanine at E14. The Ala(E14)Gly mutation increased k(ox) and hemin loss 3-fold and 45-fold, respectively. Glycine at E14 creates a channel for solvent to enter the heme crevice, which enhances autoxidation and hemin loss rates. Hydration of the proximal heme pocket facilitates hemin loss because protonation of the proximal histidine weakens the linkage of the imidazole group to the iron atom of the hemin moiety. Ala(E14)Gly promoted lipid oxidation in washed fish muscle more rapidly during iced storage compared to wild type Mb at pH 5.7. This suggested that the rapid hemin loss from Ala(E14)Gly accelerated lipid oxidation. Ala(E14)Ser and Ala(E14)Val had little effect on k(ox) but somewhat accelerated net hemin loss. These studies suggest that enhanced access of solvent to the heme crevice of many fish Hbs at site E14 facilitates rapid hemin loss and moderately accelerates autoxidation. This likely is part of the reason fish Hbs promote lipid oxidation much more effectively compared to mammalian Hbs.