Effects of protein oxidation on the texture and water-holding of meat: a review

Uncovering quality changes in oysters (Crassostrea hongkongensis) during frozen storage based on lipidomics and proteomics

This study investigated quality changes in oysters during frozen storage through physicochemical analysis, quantitative lipidomics, and quantitative proteomics. Results showed that the quality of oysters progressively deteriorated with increasing freezing time and temperature, as evidenced by color darkening, texture softening, reduced water-holding capacity, and increased TVB-N levels. Simultaneously, protein oxidation and lipid oxidation were observed, resulting in increased carbonyl, disulfide bonds, dityrosine, TBARS, and Schiff base content, and decreased free sulfhydryl groups. Lipidomics analysis revealed oxidation and hydrolysis of polyunsaturated lipids in oysters during storage, with PC being preferentially oxidized. Proteomics analysis revealed extensive oxidation and degradation of structural proteins, particularly MHC and filamin-C. Correlation analysis further highlighted oxidative degradation of polyunsaturated lipids and structural proteins as major contributors to the quality decline of oysters during frozen storage. This study sheds light on the mechanisms of quality deterioration in frozen oysters and provides valuable guidance for enhancing their preservation quality.

Synergistic effects of polymethoxyflavonoids from citrus peel extracts on harmful compound formation and flavor quality in grilled beef patties

Three polymethoxyflavonoids (PMFs) from citrus peel: tangeretin (TG), isosinensetin (ISN), and 3',4',5,7-tetramethoxyflavone (TMHF) and their combination significantly inhibited heterocyclic amines (HAs) and advanced glycation-end products (AGEs) formation. In particular, ISN with five methoxyl structure and B-ring distribution was significantly effective reduce HAs to 50.1 %-77.9 %. The PMF mixture was effective reduce both HAs and AGEs at rates of 52.2 %-77.3 % and 16.4 %-66.8 %, respectively. For ISN, the radical scavenging activity and inhibitory effects of HAs and AGEs were highly correlated. However, the inhibitory action of mixed PMFs against harmful substances was related to free radical scavenging activity and their impact on water distribution. Furthermore, GC-IMS analysis revealed the PMF mixture did not significantly change the key aldehyde and ketone compounds in grilled meat. This study provides insights into the effect of PMF mixtures, which appear to synergistically regulate the formation of aromatic and harmful compounds in grilled meat products.

Effects of freeze-thaw cycles on texture and protein digestive properties of scallop adductor muscles: Role of protein oxidative changes

This study investigated the effects of freeze-thaw cycles (F-T cycles) on texture and protein digestive properties of scallop adductor muscles and the underlying mechanisms involved. Results showed that F-T cycles significantly increased free radical intensity of scallop adductor muscles and oxidation level of scallop protein. Simultaneously, the protein oxidative degradation occurred, as evidenced by increased levels of TCA-soluble peptides and water-soluble Hyp, which led to myofiber breakage and decreased textural properties. Nile Red staining showed that F-T cycles-induced oxidation promoted protein aggregation, which in turn reduced protein digestibility. Peptidomics analysis further showed that F-T cycles-induced oxidation altered the enzymatic cleavage sites in scallop protein, resulting in an increased abundance of macromolecular peptides (>2500 Da) and decreased release of bioactive peptides. These results highlight the role of protein oxidation in the deterioration of texture and protein digestibility of scallops during frozen storage, providing a basis for improving quality preservation strategies.

Preparation of whey protein-chitosan edible coating modulated by cold plasma and its effect on quality and metabolites of chilled beef

The stability, safety, and sustainability of food preservation coatings have garnered increasing attention, with cold plasma modification emerging as an environmentally friendly alternative. This study developed a cold plasma (CP)-treated 1 % (w/v) whey protein isolate (WPI)/carboxymethyl chitosan (CMCS) coating (mass ratio 1:1) (CPW). The effects of CP treatment were investigated through particle size and zeta potential analyses. Further characterization using intrinsic fluorescence, confocal laser microscopy, and Fourier-transform infrared spectroscopy revealed the impact of CP treatment on WPI-CMCS polymer binding and stability within pH 4-6. Applied to beef preservation, CPW significantly inhibited color deterioration, delayed increases in TVB-N and TBARS levels, reduced total microbial counts, and maintained favorable texture properties during 4 °C storage (p < 0.05). Combined LC/MS and GC/MS analyses demonstrated that CPW treatment effectively reduced critical deterioration markers: lipid peroxidation products (13-L-hydroperoxylinoleic acid, 9(S)-HPODE, 9,10-DHOME) and protein degradation products (L-glutamic acid, L-arginine, L-phenylalanine), while regulating energy metabolism metabolites (citric acid, lactic acid). These findings indicate that CPW maintains beef quality by modulating energy metabolism, lipid peroxidation, and protein degradation pathways. This study demonstrates that CP modification enhances WPI-CMCS composites binding and stability, positioning CPW as a safe, green, and effective preservation coating with promising application prospects for chilled beef preservation, which has the potential to replace traditional chemical synthetic preservatives and mitigate the environmental pollution caused by non-biodegradable packaging.

Riboflavin-mediated ultraviolet photosensitive oxidation of beef myofibrillar proteins with different storage times

The study was designed to investigate the mechanism of Riboflavin (RF)-mediated UVA photosensitive oxidation on beef myofibrillar proteins (MP) oxidized at different storage times. To elucidate the direct relationship between RF and protein oxidation, the mechanism of action was analyzed in terms of amino acid and side chain residues, protein structure, and protein oxidative metabolism. Oxidation of MP resulted in significant changes in the levels of carbonyls, sulfhydryls, Lysine, Arginine, Threonin, and Histidine. The oxidized MP secondary structure was changed, fluorescence intensity decreased, and surface hydrophobicity increased. Metabolomics results revealed that RF-mediated UVA photosensitized oxidation is primarily mediated by Riboflavin metabolism and co-regulated with Phenylalanine metabolism. Moreover, with the increase of frozen storage time, Arginine and proline metabolism was inhibited, and the contents of creatine were significantly reduced, which exacerbated MP oxidative damage. The results provide a theoretical basis for unraveling the mechanism of RF-mediated UVA photosensitive oxidation of MP.

Protein oxidation and its effect on functional properties of livestock products during the processing and storage: A review

Protein oxidation is a complex chemical process that pervades the entirety of the food domain. It is governed by two primary mechanisms: the direct oxidation by active entities and the indirect oxidation by secondary oxidation byproducts like lipid oxidation, influenced by many factors. The oxidation of proteins in livestock products readily occurs post-processing and storage through techniques such as freezing, cooking, ultrasonication, among others, leading to protein carbonylation and subsequent alterations in structure. Consequently, the purpose of this manuscript is to scrutinize the impacts of conventional processing and storage methodologies on protein oxidation in livestock products, delineating potential mechanisms, action sites, and influential factors implicated in this progression. Additionally, we delve into the ramifications of protein oxidation on the processing attributes of livestock products, while venturing into forthcoming trends and obstacles to set a groundwork for ensuring and regulating the caliber of these commodities.

Extrusion of plant proteins: A review of lipid and protein oxidation and their impact on functional properties

Extrusion processing can improve the functional and nutritional value of plant proteins, making them a sustainable source for various applications. During both low- and high-moisture extrusion, raw materials are subjected to harsh process conditions, leading to lipid and protein oxidation. In general, oxidation products are associated with adverse effects on product properties and human health. The oxidation rates are influenced by a number of factors, including temperature, water, oil content, and protein source, with lipid-protein interactions playing a significant role in oxidation dynamics and measurement accuracy. Higher extrusion temperatures and water content promote oxidation, yet are also necessary for fiber formation. Mild protein oxidation can improve functional properties and digestibility, while extensive oxidation tends to reduce both. Therefore, adjusting extrusion parameters is critical for controlling oxidation. In addition, natural antioxidants may reduce oxidation during extrusion, but their impact on functional properties requires further investigation.

Protein degradation mechanisms during refrigerated storage of gazami crab (Portunus trituberculatus) at endogenous and microbial-derived enzyme levels

During storage, the proteins of gazami crab (Portunus trituberculatus) are prone to hydrolysis into amino acids and biogenic amines, in which enzymes play a critical role. However, studies exploring spoilage mechanisms from the perspective of enzymes are limited. This study identified 84 endogenous and 52 microbial-derived proteolytic enzymes and peptidases by proteomics and metagenomics. There are 7 endogenous amino acid deaminases, primarily degrade glutamate and aspartate. Additionally, 25 amino acid deaminases of microbial origin were identified, which mainly degrade serine. The formation of biogenic amines involved 14 enzymes, all of which were microbial in origin, primarily synthesizing putrescine from arginine. The main microbial contributors to these enzymes were Photobacterium, Vibrio, and Aliivibrio, accounting for 63.87 %, 15.51 %, and 8.69 % at the end of refrigeration, respectively. This study provides insights into the mechanisms of quality deterioration in gazami crab during refrigeration, from the perspectives of metabolic enzymes and microbial activity.

Oxidative stress-induced changes in wooden breast and mitigation strategies: A review

Wooden breast (WB) is a multifactorial muscular abnormality resulting from the interplay between genetic predispositions for rapid growth, physiological stress, and anatomical impairments. This myopathy has been a persistent challenge in the poultry industry since its initial identification a decade ago. WB negatively impacts meat quality, leading to increased toughness and reduced nutritional value. Building on foundational research utilizing multiomics technologies, hypoxia-induced oxidative stress has been identified as a key early event driving the pathological processes of WB. This review provides a comprehensive overview and the state-of-the-art evidence on the pivotal role of oxidative stress in WB myopathy. It begins by examining the generation of reactive intermediates that induce oxidative damage and the host's defense mechanisms aimed at mitigating these threats. The discussion then focuses on the consequences of oxidative damage for mitochondria, protein and lipid oxidation, connective tissue remodeling, and inflammation-pathological hallmarks of WB-affected muscles. Additionally, the review highlights how oxidative stress influences satellite cell behavior, impairing the repair and regeneration of muscle tissues, a process implicated in WB. Finally, efforts to prevent or mitigate WB myopathy are summarized, with particular attention to potential intervention strategies targeting oxidative stress. These include innovative feed formulations and gut microbiota modulation, which show promise in alleviating the severity of the condition.

Physicochemical and conformational changes of krill myofibrillar protein induced by two-stage thermal treatment and their relationship with muscle texture

To preserve the juiciness of Krill muscle, a simple but robust strategy of two-stage thermal treatment (40-70 °C followed by 90 °C) was explored while the alterations in muscles, physicochemical and conformational changes of myofibrillar proteins were investigated. Conventional one-stage boiling treatment was considered as the control. The results revealed that the actomyosin dissociation was most pronounced preheated by 50 °C, supported by higher content of actin and increased surface hydrophobicity with a substantial drop in α-helix. The disulfide bonding for the control and 70 °C group was significantly higher, indicating a pronounced oxidation. The most robust affinity for water of krill was observed when subjected to preheating at 50 °C, exhibiting the wildest separations between muscle bundles and well-preserved fibers, while severe contraction of muscle bundles was observed with fracturing and minor gaps. The findings provide direct proof to support the feasibility of implementing a preheating thermal processing method for krill.

Effect of flaxseed oil cyclolinopeptides on lipid oxidation, protein oxidation, and lipid profile during in vitro digestion of high-fat beef

This study investigated the influence of flaxseed oil cyclolinopeptides (CLs) on lipid and protein oxidation during high-fat meat digestion. Fourteen CLs were identified in flaxseed oil through UHPLC-ESI-QTOF-MS/MS, with dominant CLA, CLB, CLE, and CLM. During in vitro digestion, CLs inhibited lipid oxidation products (lipid hydroperoxide, Malondialdehyde, and 4-hydroxynonenal) and protein carbonylation. Compared to other groups, the lipid (16.28 ± 0.35) and protein (17.5 ± 0.6) oxidation was significantly inhibited, and antioxidant activity was remarkably increased when the CLs content reached 200 mg/kg. Through untargeted lipidomic analysis using Q-Exactive, it was observed that CLs mitigated the formation of oxidized triglycerides (OxTG) products and enhanced the hydrolysis of lipids to generate sphingolipid and polyunsaturated fatty-acids enriched glycerophospholipids imparting nutritional value to meat. Electron spin-resonance and fluorescence quenching showed that primary radicals such as alkyl and alkoxy radicals during high-fat meat digestion with flaxseed oil CLs significantly mitigate their formation. These findings collectively indicate that consuming CLs enriched flaxseed oil could reduce lipid oxidation and enhance the nutritional value of high-fat meat during digestion.

Plant-based protein emulsions with soy protein isolate and gluten improve freeze-thaw stability and shelf life of pork meatballs

This study investigated the effects of oil-in-water emulsions used as fat substitutes on the physicochemical properties of meatballs during frozen storage. Different formulations of fat replacers were prepared, including pork fat as the control (C), oil and water (OW), oil-in-water emulsion (E), emulsion with soy protein isolate (SE), emulsion with gluten (GE), and emulsion with soy protein isolate and gluten (SG). These fat substitutes were applied to a meatball paste. The samples were stored at -18 °C for 30 and 60 days, and their physicochemical properties were analyzed after thawing at 4 °C for 12 h. The SE formulation had the highest values for both water content and liquid holding capacity during frozen storage (P < 0.05). SE, GE, and SG showed significantly higher hardness, cohesiveness, springiness, gumminess, and chewiness than those of E during storage (P < 0.05). The vegetable protein addition treatments maintained a compact structure throughout storage. SE, GE, and SG prevented lipid and protein oxidation during frozen storage. These results demonstrated that SE, GE, and SG offer significant advantages in improving the freeze-thaw stability, liquid holding capacity, and oxidation stability of pork meatballs during long-term frozen storage. Therefore, our study suggest that plant-based protein emulsions can effectively replace animal fats while maintaining product quality, offering valuable implications for the meat processing industry.

Elucidating the degradation mechanism of beef myofibrillar proteins under hydroxyl radical oxidation through the lens of cysteine oxidation modifications

The study aimed to assess the oxidative modification behavior of bovine myofibrillar proteins (MPs) cysteines (Cys) by hydroxyl radical (·OH) through the construction of an in vitr Fenton reaction system. The ·OH generated by the Fenton reaction induced large-scale oxidative modification of Cys, and redox proteomics identified a total of 1192 differential oxidation sites (Dos), 59 Dos were located in the MPs structure. The Cys of actin (17 Dos), myosin/myomesin (16 Dos), tenascin (12 Dos) and sarcomere (10 Dos) in the MPs structure showed active oxidative modification behavior towards ·OH, especially with the "-C-X-X-X-X-W-" structure amino acid sequence showed high sensitivity. Notably, the oxidative modification of Cys by ·OH was an irreversible process, as evidenced mainly by a significant decrease (p < 0.05) in protein sulfhydryl groups and unfolding of protein secondary and tertiary structures. While the intermolecular forces of MPs were altered, with the most direct result being the degradation of MPs, which had a positive effect on beef tenderness and a negative effect on water-holding capacity.

Evaluation of the water state and protein characteristics of Tibetan pork under the storage conditions of modified atmosphere packaging: Effect of oxygen concentration

To explore the changes in water status and protein characteristics of Tibetan pork (TP) under modified atmosphere packaging (MAP) with different oxygen concentrations compared to Duroc×Landrace×Yorkshire pork (DLY), the water holding capacity (WHC), water distribution, protein oxidation, and conformation of both types were determined. Results indicate that under MAP, TP pork and DLY pork exhibited higher water retention and lower protein oxidation compared to air packaging. However, with increased oxygen concentration in the MAP, protein oxidation intensified, leading to reduced WHC in the pork. Compared to DLY pork, TP pork in different packaging conditions maintained the integrity of protein secondary and tertiary structures, reducing protein cross-linking aggregation. The lower content of P 3 in the two-dimensional relaxation spectra, shorter T 1 and T 2 relaxation times, and higher proton density suggest better water retention properties in Tibetan pork. These findings support the development of long-distance preservation and transportation technologies for TP pork.

Effect of Boiling Treatment on Linoleic Acid-Induced Oxidation of Myofibrillar Protein in Grass Carp

The aim of this study was to investigate the promotion of linoleic acid (OLA)-induced myofibrillar protein (MP) oxidation by boiling treatment. The effect of the boiling treatment on grass carp MP oxidation induced by OLA was investigated. The total sulfhydryl content, fluorescence intensity, and amino acid content were reduced with the increasing OLA concentration after the boiling treatment, while the boiled oxidized MP's carbonyl content (4.76 ± 0.14 nmol/mg) was 2.14 times higher than that of the native MP (2.22 ± 0.02 nmol/mg) at an OLA concentration of 10 mM. Additionally, the secondary structure of MP became more disordered, shifting from an α-helix to random coils and β-turns. When the concentration of OLA was higher than 5 mM, both the surface hydrophobicity and water holding capacity (WHC) decreased with the increasing OLA concentration. Furthermore, the boiling treatment led to a reduction in immobile water and an increase in free water content in the MP gel. These findings establish a theoretical basis for regulating MP oxidation to improve fish quality during boiling.

A comprehensive review of intelligent packaging materials based on biopolymers: Role of anthocyanins, type and properties of materials, and their application in monitoring meat freshness

The demands of consumers for meat safety and quality have promoted the rapid development of clear, intuitive, low-cost, and real-time monitoring technologies for meat freshness. Anthocyanins-based materials can be used to monitor meat freshness by providing intuitive information of meat freshness, thus effectively avoiding the supply and consumption of spoiled meat. The complex physical and chemical changes inside the package are transformed into intuitive and recognizable color signals by anthocyanins-based materials. Therefore, this review comprehensively examined the recent advances on four materials based on anthocyanins and biopolymers including film, hydrogel, aerogel, and colorimetric sensor array for monitoring meat freshness. The etiology of meat spoilage and effects of anthocyanins addition on the performance of four materials were also investigated. Furthermore, the limitations existing in the production and application of anthocyanins-based materials are discussed and the corresponding countermeasures are proposed. The findings indicated that anthocyanins-based materials had great potential as indicative packaging of meat freshness, but their sensitivity and stability still need to be further improved. Furthermore, the combination of anthocyanins-based materials, smartphone, machine learning, computer vision, and novel chemometrics methods are crucial for the progress of anthocyanins-based materials.

Effect of pre-acidification induction on the physicochemical features, myofibrillar protein microstructure, and headspace volatiles of ready-to-cook goose meat

This study examined the impact of pre-acidification induction on the quality attributes and flavor retention of ready-to-cook (RTC) goose meat products. The results demonstrated that pre-acidification could influence the eating qualities of RTC goose meat by effectively regulating the physicochemical properties of goose myofibrillar proteins (MP) including solubility and water-holding capacity. Elevated carbonyl contents indicated an enhanced gel-forming capacity in RTC goose meat during storage, accompanied with reduced total sulfhydryl contents from enhanced protonation pretreatment and augmented lipid oxidation. Structural characterization of MP via sodium dodecyl sulfate-polyacrylamide gel electrophoresis, circular dichroism spectroscopy, and intrinsic fluorescence revealed the formation of a dense protein matrix under highly acidic conditions. Furthermore, the headspace concentration of aldehydes increased by 3.23 times upon enhancing the pre-acidification intensity, resulting in the production of esters and acidic flavor compounds with favorable aromas. Correlation analysis demonstrated the dependence of headspace concentrations of volatile constituents on the acidification-enhanced surface hydrophobicity of MP, attributed to the modified binding sites of proteins after pre-acidification. Current results have indicated both the positive and negative influence of pre-acidulation induction on the eating quality of goose meat products, suggesting the necessity of introducing extra processes to modulate the quality of prefabricated products.

Antioxidative Status and Meat Quality Traits as Affected by Dietary Supplementation of Finishing Pigs with Natural Phenolics

This work investigated the effect of a plant-based phenolic supplement on the color, myoglobin forms, lipid oxidation, and antioxidative status of fresh and stored (10 days at 4 °C) meat (Longissimus thoracis et lumborum), as well as the antioxidative status of the blood and liver. The sensory quality of the meat was also evaluated for color, aroma, texture, juiciness, and palatability. Twenty-four finishing pigs, divided into two groups, were fed a basal diet and a diet with a phenolic supplement (0.1%). The supplementation increased the redness of the meat (+36% for a* and +28% for redness index), the myoglobin (Mb) content (+7%), the antioxidant activity, and the juiciness. The treatment increased the antioxidant status of meat, reflected by superoxide dismutase (SOD) activity and total glutathione (GSH + GSSG). The catalase and SOD activities and GSH + GSSG of the blood and liver were also elevated in the supplemented samples when compared to the control group. A significant effect of time was observed for all tested parameters (pH, color attributes, Mb forms, the antioxidant activity, lipid oxidation) except for the Mb content. For the stored samples, only TBARSs (thiobarbituric acid reagent substances) were affected by the diet. The slope of the plot for TBARS changes with time was significantly different between the control and treated groups (p = 0.017), which indicated a significant effect of dietary supplementation. A higher rate of lipid oxidation was observed in the control samples.

Improvement on gel properties of chicken myofibrillar protein with electron beam irradiation: Based on protein structure, gel quality, water state

This study aimed to investigate the effects of electron beam (E-beam) irradiation at different doses (0-15 kGy) on the solubility, rheological properties, emulsification characteristics, and moisture distribution of chicken myofibrillar proteins (MPs). Irradiation treatment notably increased the solubility, surface hydrophobicity, emulsification properties, and apparent viscosity of MPs, based on conformational changes caused by irradiation-induced oxidative denaturation of proteins. However, high doses of irradiation (15 kGy) induced in excessive cross-linking and aggregation of proteins, reducing the solubility, emulsification properties, and shear stress. Degradation of myosin heavy and light chains in irradiated MPs increased the content of β-turns and random coils. Additionally, the initial relaxation times of T21 and T22 in irradiated protein gels were reduced, and the peak value of P21 was increased, which improved the water-capturing ability of protein gels. Altogether, these results findings suggest that electron beam irradiation can be applied as a potential technique for modifying muscle proteins.

Impact of Packaging Methods Coupled with High Barrier Packaging Loaded with TiO2 on the Preservation of Chilled Pork

This study investigated the impact of packaging methods coupled with high barrier packaging loaded with titanium dioxide (TiO2) on the quality of chilled pork. The experiment consisted of three treatment groups: air packaging (AP), vacuum packaging (VP), and vacuum antibacterial packaging (VAP). Changes in total viable count (TVC), pH value, total volatile basic nitrogen (TVB-N) value, sensory attributes, and water holding capacity of pork were analyzed at 0, 3, 6, 9, and 12 d. TVC of the VAP group was 5.85 Log CFU/g at 12 d, which was lower than that of AP (6.95 Log CFU/g) and VP (5.93 Log CFU/g). The antibacterial film incorporating TiO2 effectively inhibited microorganism growth. The VAP group exhibited the lowest pH value and TVB-N value among all the treatment groups at this time. The findings demonstrated that the application of VAP effectively preserved the sensory attributes of pork, the hardness, cohesiveness and adhesiveness of pork in VAP group were significantly superior than those in AP group (p<0.05), but not significantly compared with VP group. On the 12 d, the CIE a* value of pork in VAP group was significantly higher (p<0.05). This exhibited that VAP could effectively maintain the freshness of chilled pork and extend the shelf life for 3 d compared to the AP group. These findings provide empirical evidence to support the practical implementation of TiO2-loaded packaging film in the food industry.

Effects and mechanism of sub-freezing storage on water holding capacity and tenderness of beef

In order to explore the effect of sub-freezing storage on water holding capacity and tenderness of beef, four treatments were compared in this study: sub-freezing (-7 °C) fast sub-freezing (-38 °C until the core temperature achieved to -7 °C), superchilling (-1 °C) and fast frozen (-38 °C until the core temperature achieved to -18 °C) with the latter two treatments serving as the controls. The differences in muscle fiber structure, water distribution, protein oxidation and cytoskeletal protein degradation were studied. The results demonstrated that compared with other treatments, the fast sub-freezing treatment resulted in less structural damage to the muscle fibers and had better water holding capacity. Both sub-freezing and fast sub-freezing treatments inhibited protein oxidation compared with superchilling, but the former treatment's level of protein oxidation was higher than that in fast sub-freezing treatment during long-term storage (42 weeks). In addition, the structural proteins in the sub-freezing and fast sub-freezing treatments underwent faster degradation during long-term storage and therefore the meat was more tender compared with the fast frozen treatment. The results indicate that the fast sub-freezing treatment can be potentially applied in beef storage.

Influence of 7-day subfreezing storage on physicochemical, nutritional, and microstructural attributes of porcine longissimus thoracis et lumborum muscle

The effect of 7-day subfreezing storage on the physicochemical properties, nutritional composition, and microstructure of pork was investigated. After 7 days of chilling at 4°C, the meat exhibited color deterioration and the development of off-flavors. In contrast, the -12°C treatment significantly reduced the deterioration in water-holding capacity and color of samples (p < 0.05) and prevented changes in pH value. Similarly, the treatments at -12 and -18°C effectively preserved the meat's tenderness, thiobarbituric acid-reactive substances, protein solubility, and textural properties, maintaining these qualities close to those of fresh meat (p > 0.05). The nutrient content of samples stored at -12°C was comparable to those stored at -18°C (p > 0.05). Furthermore, subfreezing at -12°C was found to protect muscle integrity, promoting the formation of an elastic gel network and a homogenous muscle fiber structure. Therefore, the study concludes that 7-day subfreezing storage at -12°C can reduce protein denaturation and maintain thequality of pork, a result that is typically achieved under more extreme freezing conditions at -18°C.

Hydroxyl Radical-Induced Oxidation on the Properties of Cathepsin H and Its Influence in Myofibrillar Proteins Degradation of Coregonus peled In Vitro

The most frequently occurring protein modification in fish postmortem is oxidization, which further affects meat quality through multiple biochemical pathways. To investigate how hydroxyl radicals affect the structure of cathepsin H and its ability to break down myofibrillar proteins in Coregonus peled, cathepsin H was oxidized with 0, 0.1, 0.5, 1, 5, and 10 mM H2O2 and subsequently incubated with isolated myofibrillar proteins. The results showed that as the H2O2 concentration increased, the carbonyl and sulfhydryl contents of cathepsin H significantly increased and decreased, respectively. There were noticeable changes in the α-helix structures and a gradual reduction in UV absorbance and fluorescence intensity, indicating that oxidation can induce the cross-linking and aggregation of cathepsin H. These structural changes further reduced the activity of cathepsin H, reaching its lowest at 10 mM H2O2, which was 53.63% of the activity at 0 mM H2O2. Moreover, desmin and troponin-T all degraded at faster rates when cathepsin H and myofibrillar proteins were oxidized concurrently as opposed to when cathepsin H was oxidized alone. These findings provide vital insights into the interaction mechanism between oxidation, cathepsin H, as well as myofibrillar protein degradation, laying a groundwork for understanding the molecular mechanisms underlying changes in fish meat quality after slaughter and during processing.

Antioxidation Activity Enhancement by Intramolecular Hydrogen Bond and Non-Browning Mechanism of Active Ingredients in Rosemary: Carnosic Acid and Carnosol

Rosemary is one of the most promising, versatile, and studied natural preservatives. Carnosic acid (CA) and carnosol (CARN), as the primary active ingredients of rosemary extracts, have little difference in structure, but their antioxidant activities vary significantly, depending on the system studied. The underlying molecular mechanisms remain unclear. By means of optical spectroscopies, stopped-flow, laser photolysis, and density functional theory (DFT) calculations, we have compared CA and CARN between their reaction dynamics of radical scavenging, metal ion chelation, and oxidation inhibition in lipid emulsion and beef, as well as between their interactions with β-carotene (β-Car). For reference, 3-isopropyl catechol (IC), which is structurally similar to the active groups of CA and CARN, was studied in parallel. It is found for CA that the intramolecular hydrogen bond can boost the acidity of its phenol hydroxyl and that the synergistic effect with β-Car can substantially enhance its antioxidation activity in the model systems of lipid and meat via the CA-to-β-Car electron transfer reaction. The substitution of A and B rings on the catechol group in both CA and CARN limits browning caused by their formation of oxidative products as antioxidants.

Preservation effects of photodynamic inactivation-mediated antibacterial film on storage quality of salmon fillets: Insights into protein quality

The preservation effects of a photodynamic inactivation (PDI)-mediated polylactic acid/5-aminolevulinic acid (PLA/ALA) film on the storage quality of salmon fillets were investigated. Results showed that the PDI-mediated PLA/ALA film could continuously generate reactive oxygen species by consuming oxygen to inactivate native pathogens and spoilage bacteria on salmon fillets. Meanwhile, the film maintained the content of muscle proteins and their secondary and tertiary structures, as well as the integrity of myosin by keeping the activity of Ca2+-ATPase, all of which protected the muscle proteins from degradation. Furthermore, the film retained the activity of total superoxide dismutase (T-SOD), suppressed the accumulation of lipid peroxides (e.g., MDA), which greatly inhibited four main types of protein oxidations. As a result, the content of flavor amino acids and essential amino acids in salmon fillets was preserved. Therefore, the PDI-mediated antimicrobial packaging film greatly preserves the storage quality of aquatic products by preserving the protein quality.

Quantitative Proteomics Reveals the Relationship between Protein Changes and Volatile Flavor Formation in Hunan Bacon during Low-Temperature Smoking

This study aimed to investigate the changes in proteins and volatile flavor compounds that occur in bacon during low-temperature smoking (LTS) and identify potential correlations between these changes. To achieve this, a combination of gas chromatography-mass spectrometry and proteomics was employed. A total of 42 volatile flavor compounds were identified in the bacon samples, and, during LTS, 11 key volatile flavor compounds with variable importance were found at a projection value of >1, including 2',4'-dihydroxyacetophenone, 4-methyl-2H-furan-5-one, Nonanal, etc. In total, 2017 proteins were quantified at different stages of LTS; correlation coefficients and KEGG analyses identified 27 down-regulated flavor-related proteins. Of these, seven were involved in the tricarboxylic acid (TCA) cycle, metabolic pathways, or amino acid metabolism, and they may be associated with the process of flavor formation. Furthermore, correlation coefficient analysis indicated that certain chemical parameters, such as the contents of free amino acids, carbonyl compounds, and TCA cycle components, were closely and positively correlated with the formation of key volatile flavor compounds. Combined with bioinformatic analysis, the results of this study provide insights into the proteins present in bacon at various stages of LTS. This study demonstrates the changes in proteins and the formation of volatile flavor compounds in bacon during LTS, along with their potential correlations, providing a theoretical basis for the development of green processing methods for Hunan bacon.

The Effects of Four Different Thawing Methods on Quality Indicators of Amphioctopus neglectus

Amphioctopus neglectus is a species of octopus that is favored by consumers due to its rich nutrient profile. To investigate the influence of different thawing methods on the quality of octopus meat, we employed four distinct thawing methods: air thawing (AT), hydrostatic thawing (HT), flowing water thawing (FWT), and microwave thawing (MT). We then explored the differences in texture, color, water retention, pH, total volatile basic nitrogen (TVB-N), total sulfhydryl content, Ca2+-ATPase activity, and myofibrillar protein, among other quality indicators in response to these methods, and used a low-field nuclear magnetic resonance analyzer to assess the water migration that occurred during the thawing process. The results revealed that AT had the longest thawing time, leading to oxidation-induced protein denaturation, myofibrillar protein damage, and a significant decrease in water retention. Additionally, when this method was utilized, the content of TVB-N was significantly higher than in the other three groups. HT, to a certain extent, isolated the oxygen in the meat and thus alleviated protein oxidation, allowing higher levels of Ca2+-ATPase activity, sulfhydryl content, and springiness to be maintained. However, HT had a longer duration: 2.95 times that of FWT, resulting in a 9.84% higher cooking loss and a 28.21% higher TVB-N content compared to FWT. MT had the shortest thawing time, yielding the lowest content of TVB-N. However, uneven heating and in some cases overcooking occurred, severely damaging the protein structure, with a concurrent increase in thawing loss, W value, hardness, and shear force. Meanwhile, FWT improved the L*, W* and b* values of octopus meat, enhancing its color and water retention. The myofibrillar protein (MP) concentration was also the highest after FWT, with clearer subunit bands in SDS-PAGE electrophoresis, indicating that less degradation occurred and allowing greater springiness, increased Ca2+-ATPase activity, and a higher sulfhydryl content to be maintained. This suggests that FWT has an inhibitory effect on oxidation, alleviating protein oxidation degradation and preserving the quality of the meat. In conclusion, FWT outperformed the other three thawing methods, effectively minimizing adverse changes during thawing and successfully maintaining the quality of octopus meat.

Impacts of acute ammonia-N exposure on the muscle quality of whiteleg shrimp (Penaeus vannamei): Novel insights into lipid and protein oxidation

This study explored the effect of ammonia-N exposure on the muscle quality of Penaeus vannamei and the underlying mechanisms based on the oxidation of lipids and proteins. Acute ammonia-N exposure reduced the hardness but increased the centrifugal loss and drip loss of the shrimp muscle. Meanwhile, reactive oxygen species and reactive nitrogen species were overproduced, thereby increasing the free fatty acid (FFA) content, fluorescent compound content, peroxide value (PV), and thiobarbituric acid reactive substance (TBAR) value. In addition, lipid peroxidation byproducts and free radicals could reduce sulfhydryl (SH) content and intrinsic fluorescence intensity. They may also increase carbonyl concentration, disulfide bond (SS) content, and surface hydrophobicity, and degrade myofibrillar protein, leading to the unfolding and conformational alterations in proteins in shrimp muscle. This study provided significant insights into the mechanisms underlying the impacts of ammonia toxicity on the quality of shrimp muscle.

Emerging challenges and efficacy of polyphenols-proteins interaction in maintaining the meat safety during thermal processing

Polyphenols are well documented against the inhibition of foodborne toxicants in meat, such as heterocyclic amines, Maillard's reaction products, and protein oxidation, by means of their radical scavenging ability, metal chelation, antioxidant properties, and ability to form protein-polyphenol complexes (PPCs). However, their thermal stability, low polarity, degree of dispersion and polymerization, reactivity, solubility, gel forming properties, low bioaccessibility index during digestion, and negative impact on sensory properties are all questionable at oil-in-water interface. This paper aims to review the possibility and efficacy of polyphenols against the inhibition of mutagenic and carcinogenic oxidative products in thermally processed meat. The major findings revealed that structure of polyphenols, for example, molecular size, no of substituted carbons, hydroxyl groups and their position, sufficient size to occupy reacting sites, and ability to form quinones, are the main technical points that affect their reactivity in order to form PPCs. Following a discussion of the future of polyphenols in meat-based products, this paper offers intervention strategies, such as the combined use of food additives and hydrocolloids, processing techniques, precursors, and structure-binding relationships, which can react synergistically with polyphenols to improve their effectiveness during intensive thermal processing. This comprehensive review serves as a valuable source for food scientists, providing insights and recommendations for the appropriate use of polyphenols in meat-based products.

Carcass characteristics, meat quality, sensory palatability and chemical composition of Thai native cattle grazing in lowland and Phu Phan mountain forest

OBJECTIVE

The aim of this study was to assess the effect of Thai native cattle grazing in the lowland or mountain forest on carcass characteristics, meat quality, sensory palatability, and chemical composition.

METHODS

Twelve male Thai native cattle with an average weight of 110±10 kg are allowed to be grazing in the lowland or Phu Phan mountain forest during the rainy season in northeastern Thailand.

RESULTS

The carcass characteristics, meat pH, and meat color were unaffected by treatment (p>0.05). The boiling loss was lower in the cattle grazing on the mountain forest (p = 0.027). The cattle grazing in the mountain forest had increased shear force (p = 0.039), tenderness (p = 0.011), and flavor intensity (p = 0.003). The protein and fat were higher (p<0.001 and p = 0.035, respectively) in cattle grazing in the mountain forest. The different grazing systems of the cattle had no effect (p>0.05) fatty acids in meat, except for capric acid (C10:0) and lauric acid (C12:0), which were higher (p = 0.046 and p = 0.049, respectively) when the cattle were grazing in the mountain forest. The different grazing systems did not influence (p>0.05) the unsaturated fatty acids in meat.

CONCLUSION

Thai native cattle grazing in the Phu Phan mountain forest in the rainy season improves meat quality, sensory evaluation, and chemical composition.

Catalytic Antioxidant Activity of Two Diterpenoid Polyphenols of Rosemary, Carnosol, and Isorosmanol, against Lipid Oxidation in the Presence of Cysteine Thiol

Lamiaceae herbs such as rosemary have excellent antioxidant properties, and lipidic diterpenoid constituents, such as carnosol, are known as characteristic components to exhibit strong antioxidant activity. This study investigates the effect of thiol compounds on the antioxidant properties of diterpenoid polyphenols. The results concerning the antioxidant activity of polyphenols in the presence of thiol showed that two polyphenols, namely, carnosol and isorosmanol, enhanced antioxidant capacity against the radical-induced oxidation of lipids. Further examination of the mechanism revealed that both polyphenols exhibit excellent catalytic antioxidant activity by using the thiol group as a reduction source. Using density functional theory calculations, we attempted to explain why only these two polyphenols exhibit catalytic antioxidant properties. The calculation results and the assumed reaction mechanism suggested that the orthoquinones produced in the antioxidant reactions of carnosol and isorosmanol are more unstable than the others and that the regioselectivity of their reactions with thiols contributes to their catalytic antioxidant properties.

Changes in Meat of Hu Sheep during Postmortem Aging Based on ACQUITY UPLC I-Class Plus/VION IMS QTof

Meat and meat products have a critical role in the human diet as important high-nutrient foods that are widely consumed worldwide. This study evaluated the effects of postmortem aging on Hu sheep's meat quality in the longissimus dorsi (LD) muscle during postmortem aging. The samples were stored at 4 ± 1 °C; the meat quality was measured at 6 h, 12 h, 24 h, 36 h, 48 h, 72 h, 96 h, 120 h, 144 h, and 168 h of postmortem aging. The results showed that, during the postmortem aging process, the pH of the muscles first decreased and then increased, and the shear force first increased and then decreased. The muscle fiber skeleton began to degrade, and the overall meat quality was improved to some extent. In addition, through ACQUITY UPLC I-Class Plus IMS Qtof identification of the muscle samples at different time points during the postmortem maturation process of the meat of Hu sheep, a total of 2168 metabolites were identified, and 470 metabolites were screened based on the VIP, P, and FC values, of which 79 were involved in KEGG pathways. In addition, pathways such as sphingolipid metabolism, glycerophospholipid metabolism, phenylalanine metabolism, and fatty acid elongation and degradation play an important role in the metabolic product changes in the meat of Hu sheep throughout the entire maturation process. These findings provide some insights into the changes in meat quality during the post-slaughter maturation process of lake lamb.

Optimizing UVC-LED application to improve the shelf life of vacuum-packed refrigerated stored Nile tilapia (Oreochromis niloticus) fillets

Although ultraviolet-C light-emitting diode (UVC-LED) has proven antimicrobial effectiveness doses needed to reach it cause adverse effects on the physicochemical quality of fish, and thus, optimization studies are crucial to boost its industrial application. This study aimed to identify optimal UVC-LED conditions for maximum shelf life extension with the least possible quality changes of refrigerated stored tilapia fillets from a central composite rotatable design (CCRD). UVC-LED powers (1, 1.38, and 1.58 mW/cm2 ) and times (500, 1800, and 2700 s) were set on the CCRD, which generated 11 treatments, including three replicate experiments. Treatments were analyzed for total aerobic psychrotrophic count, lipid oxidation, instrumental color, and texture parameters on days 0, 2, 4, 7, 11, and 14. The UVC-LED affected shelf life and physicochemical parameters in a nonlinear fashion. UVC-LED-treated fish had increased shelf life by 2.80-4.76 days and increase or decrease in lipid oxidation (0.025-0.276 mg of malondialdehyde [MDA]/kg), total color change (∆E = 3.47-9.06), and hardness (1.31-8.51 N) over the refrigerated storage depending on specific UVC-LED conditions applied. The optimal UVC-LED condition was 0.97 mW/cm2 with 2503.6 s (2428.50 mJ/cm2 ), which increased the fillet's shelf life by 2.5-fold (2 days) while maintaining quality closer to the original throughout refrigerated storage, resulting in ∆E < 5, an increase of only 0.05 mg of MDA/kg, and preservation of the decrease in hardness by 3.38 N compared to its control counterparts. Therefore, it represents an eco-friendly technology that can easily scaled industrially to enhance the sustainable fish production chain. PRACTICAL APPLICATION: The high fish perishability is a global concern due to food safety risks and waste generation impacting the environment adversely, especially nowadays, where fish production and consumption have increased, and there are more evident efforts to sustainable production. UVC-LED is an eco-friendly technology with proven antimicrobial effectiveness but doses needed to reach this effect enhance oxidative degradation. Despite that, optimization studies concerning the maximum shelf life extension while retaining the physicochemical quality of refrigerated stored fish are a gap in the literature and a barrier to its industrial application. Our findings are helpful in sustainably enhancing the fish production chain.

LF-NMR determination of water distribution and its relationship with protein- related properties of yak and cattle during postmortem aging

The water distribution have a profound influence on meat quality, and proteins play a critical role in water distribution. The water distribution detected with proton NMR and its relationship with protein related properties were investigated. Three populations of water were detected: bound water (T21, P21), immobilized water (T22, P22), and free water (T23, P23). The decreased T22 and T23 indicated an increase in water-holding capacity in both muscles from 3 days of aging. The P22 in cattle was higher than that in yak and the P23 in cattle was lower than that in yak, suggesting that cattle exhibited a greater water-holding capacity compared to yak. Moreover, postmortem aging affected muscle protein oxidation, denaturation, and degradation. Correlation analysis suggested that protein oxidation and denaturation caused muscle water loss and protein degradation could allow the muscle to retain water. It provides a basis for the optimization of quality of meat and products.

Effects of electron beam irradiation on protein oxidation and textural properties of shrimp (Litopenaeus vannamei) during refrigerated storage

Protein oxidation leads to changes in shrimp texture, which affects sensory profile and consumer acceptability. This study aimed to evaluate the impact of electron beam irradiation (EBI) on protein oxidation and textural properties of Litopenaeus vannamei during refrigerated storage. Results revealed that EBI treatment and storage increased the protein oxidation level of shrimps. Shrimps irradiated with ≥ 7 kGy exhibited remarkably higher (P < 0.05) reactive oxygen species, turbidity, and carbonyl contents, and remarkably lower (P < 0.05) Ca2+-ATPase activity, surface hydrophobicity, solubility, and total sulfhydryl contents compared to the control group (0 kGy) on the 7th day of storage. Shrimps irradiated with 3 and 5 kGy exhibited remarkably higher (P < 0.05) hardness, springiness, and chewiness compared to the control group (14.99 N, 1.26 mm, and 3.19 mJ). Collectively, suitable EBI doses of 3-5 kGy were recommended in shrimp preservation to inhibit texture softening by inducing moderate protein oxidation.

Paprika extract as a natural antioxidant in cold-stored pork patties: Effect on oxidative stability and heterocyclic amines inhibition

In this study, we compared the degree of oxidation of pork patties refrigerated at 7 °C for 0, 7, and 14 days and the content of 10 types of heterocyclic amines (HCAs) after heating. The pork patties used in the study were added with 0.7 mg sodium nitrite (SN) and 5 mg paprika extract (PE), respectively. IQx (2-Amino-3-methyl-imidazo[4,5-f]-quinoxaline), MeIQx (2-Amino-3, 8-dimethyl-imidazo[4,5-f]-quinoxaline), PhIP (2-Amino-1-methyl-6-phenyl-imidazo[4,5-b]-pyridine), and Harman (1-Methyl-9H-pyrido[4,3-b]-indole) contents increased with increasing storage periods of treatment. On the other hand, HCAs production in SN and PE treatments were suppressed over the storage period, with IQ (2-Amino-3-methyl-imidazo[4,5-f]-quinoline) and Aαc (2-Amino-9H-dipyrido[2,3-b]-indole) being suppressed significantly (P < 0.05). The control's pH, cooking loss, lipid, and protein oxidation were higher than SN and PE-treated patties at 14 d (P < 0.05). These differences affect the formation of HCAs. PLS-DA showed a strong correlation between protein oxidation and IQx, Harman, 4,8-DiMelQx (2-Amino-3, 4, 8-trimethyl-imidazo[4,5-f]-quinoxaline), PhIP, and MeIQx, while lipid oxidation correlated with IQx, Harman, and PhIP. Both SN and PE showed HCAs inhibitory activity and exhibited oxidative stability during storage.

Protein oxidation-mediated changes in digestion profile and nutritional properties of myofibrillar proteins from bighead carp (Hypophthalmichthys nobilis)

Digestibility is an important factor in accessing the nutritional quality and potential health benefits of protein. In this study, exudates were utilized to incubate myofibrillar proteins (MPs) for simulating the oxidation of MPs in frozen-thawed fish fillets. An in vitro gastrointestinal system was used to investigate the effect of protein oxidation on the digestion profile and nutritional properties of MPs. Results showed that exudates treatment caused the moderate oxidation of MPs and its digestibility thus increased, hydroxyl radical generation system treatment reduced the digestibility significantly. The analysis of SDS-PAGE, tricine-SDS-PAGE, amino acid composition, and peptidomics of digestion products indicates that protein oxidation decreases digestibility by causing protein cross-linking, degradation, and amino acid residues conversion. Additionally, protein oxidation reduces nutritional value of MPs via several ways including loss of essential amino acids, the proportion increase of macromolecular peptides (>2 kDa) in digests, and the percentage decrease of potential bioactive peptides in digests. The present study provides an intuitive insight into the impact of protein oxidation in frozen/thawed fillets on the digestibility of MPs, emphasizing the importance of mitigating protein oxidation to preserve their nutritional quality.

The impact of ice slurry as a medium on oxidation status and flesh quality of shrimp (Litopenaeus vannamei) during refrigeration storage

Oxidation of lipid and protein is a major reason of flesh quality deterioration during storage. In this work, cold storage (CS) and flake ice (FI) storage, as traditional strategies for live shrimp (Litopenaeus vannamei) sedation and refrigerated storage, showed remarkable oxidation damage of lipid and protein in shrimp flesh during storage. In contrast, ice slurry (IS), with good heat exchange capacity and contactability, stunned shrimp in a sudden and thus relieved antemortem stress, which resulted in reducing the reactive oxygen species and reactive nitrogen species accumulation, and the oxidation damage risk in flesh. Additionally, IS, as a storage medium acted an oxygen barrier, further inhibited the oxidation of lipid and myofibrillar protein (MP), as revealed by the lower thiobarbituric acid reactive substances level, carbonyl (CO) derives content, total disulfide bond (S-S) content, and the higher total sulfhydryl (SH) content in shrimp flesh during storage, compared with CS and FI. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis electrophoretogram pattern of MP also suggested better preservation of myosin heavy chain, myosin light chain, actin, and tropomyosin in IS, whereas these proteins degraded in CS and FI. Consequently, IS prevented the formation of cross-linking caused by oxidation in MP, leading to improved shrimp flesh quality during refrigerated storage, as demonstrated by the better maintained hardness, springiness, and water-holding capacity compared to CS and FI.

Effect of Capsaicin and Dihydrocapsaicin in Capsicum on Myofibrillar Protein in Duck Meat

Spice and its extracts have gained widespread utilization as natural and eco-friendly additives, imparting enhancements in flavor, color, and antioxidative attributes to meat-based products. This work aims to study the effect mechanism of capsaicin (CA) and dihydrocapsaicin (DI) in capsicum (chili pepper) on the structure and function of myofibrillar proteins (MPs) in duck meat during thermal treatment. The results showed that at a CA-DI to MP ratio of 1:500 (g/g) following a 12 min heat treatment, the carbonyl content of MPs in duck meat decreased by 48.30%, and the sulfhydryl content increased by 53.42%. When the concentration was 1:500 (CA-DI, g/g) after 24 min of heat treatment, the •OH and DPPH radical scavenging rates were highest at 59.5% and 94.0%, respectively. And the initial denaturation temperature of MPs was the highest at 96.62 °C, and the thermal absorption was lowest at 200.24 J g-1. At the parameter, the smallest particle size and size distribution range of MP were 190 nm (9.51%). Furthermore, the interplay between CA-DI and MPs contributed to a reduction in the protein particle size and intrinsic fluorescence. In summary, the combination of CA-DI and MPs played a crucial role in inducing protein unfolding and disintegration.

Effects of 2,2'-Azobis(2-methylpropionamidine) Dihydrochloride Stress on the Gel Properties of Duck Myofibrillar Protein Isolate

The aim of this study was to investigate the biochemical properties and gel-forming capacity of duck myofibrillar proteins under the effects of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH)-mediated oxidation. Duck myofibrillar proteins were extracted and treated with different concentrations of AAPH solutions (0, 1, 3, 5, 10 mmol/L) and then analysed for carbonyl content, dynamic rheology, protein profiles and gel-forming properties (colour, water holding capacity, gel strength and microstructure). The results showed that with increasing AAPH concentration, the carbonyl content of the proteins exhibited an increasing trend (p < 0.05); SDS-PAGE pattern changes indicated that moderate oxidation (3 mmol/L AAPH) induced myosin aggregation via covalent bonds including disulfide, enhanced protein-protein interactions, and thus affected the gel strength of the DMPs' heat-induced gels. However, high oxidation (5 and 10 mmol/L AAPH) led to the partial degradation of the myosin heavy chain (MHC) isoforms, as evidenced by lower storage modulus and irregular microstructures, which significantly reduced gelation ability. These results suggest that the internal relationship between alkylperoxyl radical-induced oxidation should be taken into account in the processing of duck meat, as mild protein oxidation is conducive to improving gel quality.

Effect of boiling on texture of scallop adductor muscles and its mechanism based on label-free quantitative proteomic technique

The mechanism behind textural changes in scallop adductor muscle during boiling was investigated through proteomic analysis, determination of water holding capacity (WHC) and oxidative indices, as well as observation with scanning electron microscopy and multiphoton nonlinear optical microscopy. The hardness and shear force showed the trend of first rising and then falling in 45 min-boiling time. The results suggested that short-time boiling caused the oxidation, denaturation and aggregation of proteins, resulting in the transverse contraction of myofibers and lateral cross-linked aggregation of muscle fibers and a rise in WHC, which led to the increase in hardness and shear force. While long-time boiling caused the progressive degradation of structural proteins such as fibrillin-1, collagen alpha-2(I) chain, myosin heavy chain, basement membrane-specific heparan sulfate proteoglycan core protein, and paramyosin, resulting in a loose myofibril network and the decrease in WHC, which led to the decrease in hardness and shear force.

Preparation of Complementary Food for Infants and Young Children with Beef Liver: Process Optimization and Storage Quality

In this study, fuzzy mathematics and response surface modeling were applied to optimize the preparation process of beef liver paste and characterize the proximate composition, sensory and physicochemical qualities, and in vitro simulated digestive properties while refrigerated at 0-4 °C (0, 3, 7, 15, 30, 45, and 60 days). The results showed that the optimal preparation process was 4.8% potato starch, 99.4% water, 10.2% olive oil, and a 3:2 ratio of chicken breast and beef liver. The beef liver paste prepared contained essential amino acids for infants and children, with a protein content of 10.29 g/100 g. During storage, the pH of the beef liver paste decreased significantly (p < 0.05) on day 7, texture and rheological properties decreased significantly after 30 days, a* values increased, L* and b* values gradually decreased, and TVB-N and TBARS values increased significantly (p < 0.05) on day 7 but were below the limit values during the storage period (TVB-N value ≤ 15 mg/100 g, TBARS value ≤ 1 mg/Kg). In vitro simulated digestion tests showed better digestibility and digestive characteristics in the first 15 days. The results of this study provide a reference for the development of beef liver products for infant and child supplementation.

Physicochemical and structural changes of myofibrillar proteins in muscle foods during thawing: Occurrence, consequences, evidence, and implications

Myofibrillar protein (MP) endows muscle foods with texture and important functional properties, such as water-holding capacity (WHC) and emulsifying and gel-forming abilities. However, thawing deteriorates the physicochemical and structural properties of MPs, significantly affecting the WHC, texture, flavor, and nutritional value of muscle foods. Thawing-induced physicochemical and structural changes in MPs need further investigation and consideration in the scientific development of muscle foods. In this study, we reviewed the literature for the thawing effects on the physicochemical and structural characters of MPs to identify potential associations between MPs and the quality of muscle-based foods. Physicochemical and structural changes of MPs in muscle foods occur because of physical changes during thawing and microenvironmental changes, including heat transfer and phase transformation, moisture activation and migration, microbial activation, and alterations in pH and ionic strength. These changes are not only essential inducements for changes in spatial conformation, surface hydrophobicity, solubility, Ca2+ -ATPase activity, intermolecular interaction, gel properties, and emulsifying properties of MPs but also factors causing MP oxidation, characterized by thiols, carbonyl compounds, free amino groups, dityrosine content, cross-linking, and MP aggregates. Additionally, the WHC, texture, flavor, and nutritional value of muscle foods are closely related to MPs. This review encourages additional work to explore the potential of tempering techniques, as well as the synergistic effects of traditional and innovative thawing technologies, in reducing the oxidation and denaturation of MPs and maintaining the quality of muscle foods.

Insight into the microorganisms, quality, and protein structure of golden pompano (Trachinotus ovatus) treated with cold plasma at different voltages

Cold plasma (CP) is a non-thermal novel technology for the processing of heat-sensitive food products, but there is concern regarding its impact on food quality. Voltage is one of the most direct factors affecting the bacteriostatic effect of CP. Golden pompano (Trachinotus ovatus) was treated with CP at different voltages (10, 20, and 30 kV). The total viable count decreased as the CP voltage increased, reaching a maximum reduction of 1.54 lg CFU/g on golden pompano treated at 30 kV. No effects on water-holding capacity, pH, total volatile base nitrogen, and T_2b relaxation time were observed, indicating that all CP treatments retained the freshness and bound water of the samples. However, as the CP voltage increased, peroxide value and thiobarbituric acid-reactive substances of golden pompano gradually increased, the protein tertiary structure unfolded, and α-helices converted to β-sheets, indicating inevitable lipid and protein oxidation caused by excessive CP voltage. Therefore, a suitable voltage of CP should be selected to inhibits the growth of microorganisms, which avoids deterioration of sea-foods quality.

Oxidation of Cathepsin D by Hydroxy Radical: Its Effect on Enzyme Structure and Activity against Myofibrillar Proteins Extracted from Coregonus peled

In this study, cathepsin D was oxidized in vitro with different concentrations of H₂O₂, and the activity, structure, and extent of myofibrillar protein degradation by oxidized cathepsin D were evaluated. The sulfhydryl content of cathepsin D decreased to 9.20% after oxidation, while the carbonyl content increased to 100.06%. The β-sheet in the secondary structure altered due to oxidation as well. The changes in the intrinsic fluorescence and UV absorption spectra indicated that oxidation could cause swelling and aggregation of cathepsin D molecules. The structure of cathepsin D could change its activity, and the activity was highest under 1 mM H₂O₂. Cathepsin D could degrade myofibrillar proteins in different treatment groups, and the degree of degradation is various. Therefore, this study could provide a scientific basis for the mechanism of interaction among hydroxyl radical oxidation, cathepsin D, and MP degradation.

Insight into the protein oxidation impact on the surface properties of myofibrillar proteins from bighead carp

The objective of this study was to elucidate the influence of oxidative modifications of myofibrillar proteins (MPs) on their surface properties. Oxidative modifications (deamination, formation of disulfide bonds and Schiff bases), particle size, net surface charge, and binding ability of volatiles (2-enthylfuran, 1-octen-3-ol, hexanal, and octanal) of oxidized MPs was measured. Molecular docking of volatiles with actomyosin was performed using Qvina-W program and the specific oxidative modifications (monoxidation and deamination) of MPs were determined using LC-MS/MS. Results showed that oxidation of Cys (forming sulfinic, sulfonic, sulfenic acid, and disulfide bonds), monoxidation of Ala, Lys, Glu, and Asn, and deamination of Lys changed the surface properties of oxidized MPs including enhanced surface hydrophobicity and decreased affinity to volatile compounds and water. Overall, this study gives evidence of how protein oxidation affects the properties of MPs and therefore deteriorates fish meat quality.

Role of the endoplasmic reticulum in the search for early biomarkers of meat quality

Defects in meat quality such as dark, firm and dry (DFD) beef have been related to high levels of oxidative stress that produce cellular alterations that may affect to the process of meat quality acquisition. Despite the important role of endoplasmic reticulum (ER) in the cellular response to oxidative stress, its function in the muscle-to-meat conversion process has not yet been studied. In this study, differences in muscular antioxidant defense and the unfolded protein response (UPR) of the ER in CONTROL (normal pH₂₄) and dark, firm, and dry (DFD, pH₂₄ ≥ 6.2) beef at 24 h post-mortem were analyzed to understand the changes in the muscle-to-meat conversion process related to meat quality defects. DFD meat showed poor quality, lower antioxidant activity (P < 0.05) and higher UPR activation (P < 0.05), which indicates higher oxidative stress what could partly explain the occurrence of meat quality defects. Therefore, the biomarkers of these cellular processes (IRE1α, ATF6α, and p-eIF2α) are putative biomarkers of meat quality.

Deciphering the underlying mechanisms of the oxidative perturbations and impaired meat quality in Wooden breast myopathy by label-free quantitative MS-based proteomics

The study aimed to investigate biochemical mechanisms occurred in Wooden breast (WB) chicken meat, with attention to the impact on meat quality. Commercial chicken breasts were classified as Normal (N, n = 12), WB-M (moderate degree; focal hardness on cranial region, n = 12) and WB-S (severe degree; extreme and diffused hardness over the entire surface, n = 12). Samples were analyzed for physico-chemical properties, oxidative damage to lipids and proteins, and discriminating sarcoplasmic proteins by using a Q-Exactive mass spectrometer. WB meat presented impaired composition and functionality and higher levels of lipid and protein oxidation markers than N meat. The proteomic profile of WB-S presents a dynamic regulation of the relevant proteins involved in redox homeostasis, carbohydrate, protein and lipid metabolisms. Proteomics results demonstrate that the physiological and metabolic processes of muscles affected by WB myopathy are involved in combating the inflammatory process and in repairing the damaged tissue by oxidative stress.

Consolidating the gelling performance of myofibrillar protein using a novel OSA-modified-starch-stabilized Pickering emulsion filler: Effect of starches with distinct crystalline types

Starch-stabilized Pickering emulsions were employed as a novel particulate filler in myofibrillar protein (MP)-based gels for improving the gelling characteristics. The role of emulsions prepared by native starches (NS) with distinctive crystalline types (i.e., A-type waxy corn starch, B-type potato starch, and C-type pea starch) and their OSA-modified counterparts (A-OS, B-OS, C-OS) in the gelling performance was evaluated and compared with MP-stabilized-emulsion. Compared with MP-emulsion, starch-emulsion caused substantial increases in the gelling properties, notably for OSA-starch emulsions. Herein, A-OS exhibited up to 1.26-, 5.3-, and 2.9-fold increments in storage modulus, gel strength, and water holding capacity relative to pure MP gel, respectively, higher than B-OS and C-OS. Moreover, light microscopy evinced a more compact gel network filled with smaller and uniform oil droplets when A-OS emulsions were incorporated into the gels. The addition of OSA-starch emulsions, especially A-OS emulsion, facilitated the protein conformational conversion from α-helix to β-sheet and caused a marked reduction of free sulfhydryls in the gels; yet, the chemical forces that stabilized the gels altered, where remarkable reinforcements in hydrogen bond and hydrophobic interaction were detected, in support of the construction of splendid MP gels. Hence, OSA-starch emulsions show promise as functional components in meat products.

Principles, Application, and Gaps of High-Intensity Ultrasound and High-Pressure Processing to Improve Meat Texture

In this study, we evaluate the most recently applied emerging non-thermal technologies (NTT) to improve meat tenderization, high-intensity ultrasound (HIUS), and high-pressure processing (HPP), aiming to understand if individual effects are beneficial and how extrinsic and intrinsic factors influence meat toughness. We performed a systematic literature search and meta-analysis in four databases (Web of Science, Scopus, Embase, and PubMed). Among the recovered articles (n = 192), 59 studies were included. We found better sonication time in the range of 2-20 min. Muscle composition significantly influences HIUS effects, being type IIb fiber muscles more difficult to tenderize (p < 0.05). HPP effects are beneficial to tenderization at 200-250 MPa and 15-20 min, being lower and higher conditions considered inconclusive, tending to tenderization. Despite these results, undesirable physicochemical, microstructural, and sensory alterations are still unknown or represent barriers against applying NTT at the industrial level. Optimization studies and more robust analyses are suggested to enable its future implementation. Moreover, combining NTT with plant enzymes demonstrates an interesting alternative to improve the tenderization effect caused by NTT. Therefore, HIUS and HPP are promising technologies for tenderization and should be optimized considering time, intensity, pressure, muscle composition, undesirable changes, and combination with other methods.