Reactive Sulfhydryl Content Research Articles

Role of ultrasonic freezing­treated pork dumpling filling during frozen storage: Insights from protein oxidation, aggregation, and functional properties

The effects of air freezing (AF), immersion freezing (IF), and ultrasonic freezing (UF) on the oxidation, aggregation, and functional properties of myofibrillar protein (MP) in pork dumpling filling during frozen storage were investigated. The findings demonstrated that, compared to AF and IF treatments, UF treatment had higher total and reactive sulfhydryl content, solubility, and absolute zeta potential. Conversely, it exhibited lower values in carbonyl content, dityrosine content, turbidity, and particle size within the same storage time (p < 0.05). SDS-PAGE revealed that UF treatment delayed the oxidation and excessive aggregation of MP during frozen storage. Moreover, samples treated with UF at 180 days (d) displayed similar functional and qualitative characteristics to those treated with IF at 90 d or AF at 60 d, as per the hierarchical cluster analysis findings. In conclusion, UF effectively delayed the oxidation, aggregation, and loss of functional properties of MP in pork dumpling filling during frozen storage.

Synergistic Effects of High-Intensity Ultrasound Combined with L-Lysine for the Treatment of Porcine Myofibrillar Protein Regarding Solubility and Flavour Adsorption Capacity.

This study aimed to investigate the synergistic effects of high-intensity ultrasound (0, 5, 10, 15, and 20 min) in combination with L-lysine (15 mM) on improving the solubility and flavour adsorption capacity of myofibrillar proteins (MPs) in low-ion-strength media. The results revealed that the ultrasound treatment for 20 min or the addition of L-lysine (15 mM) significantly improved protein solubility (p < 0.05), with L-lysine (15 mM) showing a more pronounced effect (p < 0.05). The combination of ultrasound treatment and L-lysine further increased solubility, and the MPs treated with ultrasound at 20 min exhibited the best dispersion stability in water, which corresponded to the lowest turbidity, highest absolute zeta potential value, and thermal stability (p < 0.05). Based on the reactive and total sulfhydryl contents, Fourier transform infrared spectroscopy, and fluorescence spectroscopy analysis, the ultrasound treatment combined with L-lysine (15 mM) promoted the unfolding and depolymerization of MPs, resulting in a larger exposure of SH groups on the surface, aromatic amino acids in a polar environment, and a transition of protein conformation from α-helix to β-turn. Moreover, the combined treatment also increased the hydrophobic bonding sites, hydrogen-bonding sites, and electrostatic effects, thereby enhancing the adsorption capacity of MPs to bind kenone compounds. The findings from this study provide a theoretical basis for the production and flavour improvement of low-salt MP beverages and the utilisation of meat protein.

Effect of protein structure changes during different power ultrasound thawing on emulsification properties of common carp (Cyprinus carpio) myofibrillar protein

The impact of ultrasound thawing (UT) at different power (0 W, 100 W/0.132 W·cm−2, 300 W/1.077 W·cm−2, and 500 W/1.997 W·cm−2, namely WT, UT-100, UT-300, and UT-500) on protein structure, aggregation, and emulsifying properties of common carp (Cyprinus carpio) myofibrillar protein were investigated in the present study. The result showed that the reactive sulfhydryl content, total sulfhydryl content, protein solubility, and absolute potential of UT-300 samples were obviously higher than those of other thawed samples, while the turbidity of UT-300 samples was lower (P < 0.05), which indicated that proper UT power was beneficial to inhibit protein aggregation caused by thawing, while too low (100 W) or too high (500 W) ultrasonic power had poor effect. The Ca2+-ATPase activity and thermal stability of UT-300 samples were much higher than those of other thawed samples (P < 0.05), indicating that UT-300 inhibited myosin denaturation and thermal stability reduction of thawed products. The α-helix content of UT-300 samples was higher than that of other thawed samples, while the β-sheet content was significantly lower than that of other thawed samples (P < 0.05). The fluorescence intensity of UT-300 samples was higher than that of other thawed samples, and the λmax of UT-300 samples and UT-100 samples were lower than that of other thawed samples, which indicated that UT-300 could effectively inhibit the alteration of protein secondary structure and tertiary structure during thawing. The emulsifying activity of UT-300 samples was significantly higher than that of WT samples, and the droplet diameter of UT-300 samples was also lower than that of WT samples (P < 0.05), which indicated that UT-300 inhibited the decrease of emulsifying property during thawing. Overall, moderate ultrasonic power (300 W) could effectively inhibit the protein aggregation and structural changes during thawing, led to the decrease of emulsifying activity.

RETRACTED: Characterization, antioxidant activity and potential application fractionalized Szechuan pepper on fresh beef meat as natural preservative

The pericarp of Szechuan pepper is rich in phenols and alkylamides, making it a potential source of antioxidant compounds. Despite being recognized as the primary antioxidants in Szechuan pepper, there is still limited knowledge about their application in real food systems. This study aims to identify, separate, and apply polyphenol and alkylamide fractions derived from Szechuan extracts to beef meat. Using HPLC-MS2, we identified 5 phenols and 11 alkylamides in Szechuan extracts. The quality of the minced meat was evaluated based on color, thiobarbituric acid reactive substances (TBARS), conjugated dienes, carbonyl content, Sulfhydryl content, microbiological content, and total volatile basic nitrogen content (TVB-N). Compared to the polyphenol fraction (1.25 mg/mL), alkylamide fraction (25 mg/mL), and control samples, beef samples incorporated with the polyphenol fraction (6.25 mg/mL) significantly reduced carbonyl content, TBARS, and TVB-N values at the end of storage. Furthermore, they exhibited a significant slowdown in microbial development, improved meat color stability, and preserved pH. Therefore, the use of Szechuan pepper fractions as natural preservatives in meat and meat products is an important area of research and has the potential to enhance the safety and quality of meat products.

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

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

Impact of Longkong Pericarp Extract on the Physicochemical Properties of Alginate-Based Edible Nanoparticle Coatings and Quality Maintenance of Shrimp (Penaeus monodon) during Refrigerated Storage.

The objective of this study was to evaluate the impact of varying concentrations of longkong pericarp extract (LPE) on the physicochemical properties of alginate-based edible nanoparticle coatings (NP-ALG) on shrimp. For developing the nanoparticles, the alginate coating emulsion with different LPE concentrations (0.5, 1.0, and 1.5%) was ultrasonicated at 210 W with a frequency of 20 kHz for 10 min and a pulse duration of 1s on and 4 off. After that, the coating emulsion was separated into four treatments (T): T1: Coating solution containing basic ALG composition and without the addition of LPE or ultrasonication treatment; T2: ALG coating solution converted into nano-sized particles with ultrasonication and containing 0.5% LPE; T3: ALG coating solution converted into nano-sized particles with ultrasonication and containing 1.0% LPE; T4: ALG coating solution converted into nano-sized particles with ultrasonication and containing 1.5% LPE. A control (C) was also used, where distilled water was used instead of ALG coating. Before coating the shrimp, all the coating materials were tested for pH, viscosity, turbidity, whiteness index, particle size, and polydispersity index. The control samples had the highest pH and whiteness index and was followed by the lowest viscosity and turbidity (p < 0.05). Among the T1-T4 coating materials, T4 coating had higher turbidity, particle size, polydispersity index, but lower pH, viscosity, and whiteness index (p < 0.05). To study the quality and shelf-life of the shrimp, all coated shrimp samples were refrigerated at 4 °C for a period of 14 days. At 2-day intervals, physiochemical and microbial analyses were performed. The coated shrimp also had a lower increase in pH and weight loss over the storage period (p < 0.05). Coatings containing 1.5% LPE significantly reduced the polyphenol oxidase activity in the shrimp (p > 0.05). The addition of LPE to NP-ALG coatings demonstrated dose-dependent antioxidant activity against protein and lipid oxidation. The highest LPE concentration (1.5%) led to increased total and reactive sulfhydryl content, along with a significant decrease in carbonyl content, peroxide value, thiobarbituric acid reactive substances, p-anisidine, and totox values at the end of the storage period (p < 0.05). Additionally, NP-ALG-LPE coated shrimp samples exhibited an excellent antimicrobial property and significantly inhibited the growth of total viable count, lactic acid bacteria, Enterobacteriaceae, and psychotropic bacteria during storage. These results suggested that NP-ALG-LPE 1.5% coatings effectively maintained the quality as well as extended the shelf-life of shrimp during 14 days of refrigerated storage. Therefore, the use of nanoparticle-based LPE edible coating could be a new and effective way to maintain the quality of shrimp during prolonged storage.

Ultrasonication Induced Alterations in Physicochemical and Functional Properties of Myosin.

Several reports have indicated that ultrasonication can change the solubility of muscle proteins and improves the functional properties of meat and isolated muscle proteins. Moreover, available literature suggests that ultrasonication can significantly improve the gelling properties of muscle proteins. The present study was carried out to investigate the effect of low-frequency ultrasonication on the secondary structure of myosin and the impact of these structural changes on solubility and gelling ability. Myosin from breast muscles (Pectoralis major) of broiler chicken was extracted and exposed to low-frequency ultrasonication for 30 min. Four aliquots collected at the interval of 5, 10, 20, and 30 min were analysed for change in ATPase activity, sulfhydryl content, surface hydrophobicity, alpha-helicity. The possible impact of these changes on heat-induced gelation was observed through electron micrographs. Ultrasonication reduced the enzymatic activity of myosin and increased the reactive sulfhydryl content. Decreased α-helicity and increased intrinsic fluorescence displayed significant structural changes at the secondary and tertiary levels. Myosin aggregation, as indicated by electron micrographs, showed a marked decrease. The microstructure of myosin gels displayed a distinct correlation with ultrasonication-induced structural changes. Furthermore, improved microstructure led to a significant increase in the water retention capacity of myosin gels. In conclusion, ultrasonication of myosin caused a marked change in structure at the tertiary and secondary levels. Structural changes apparently confined within the globular head region and rod portion of myosin were displayed by reduced enzymatic activity and improved gelation/solubility. Results of our study convincingly showed that ultrasonication improved the microstructure of myosin gels resulting in increased WHC.

Improved gelling and emulsifying properties of myofibrillar protein from frozen shrimp (Litopenaeus vannamei) by high-intensity ultrasound

The deterioration of shrimp protein functionality during chilling and frozen storage has recently attracted wide attention due to its adverse effects on shrimp quality. The high-intensity ultrasound (20 kHz, 400 W) was applied to improve the protein structure and functional properties of frozen shrimp ( Litopenaeus vannamei ) in this study. Fourier transform infrared (FTIR) spectroscopy showed that the cavitation effect of ultrasound could change the secondary structure of myofibrillar protein (MP) by turning the α-helix and random coil to β-sheet and β-turn. The unfolding of MP conformation increased the reactive sulfhydryl content and surface hydrophobicity accordingly. The structure changes eventually led to the significant improvement of protein functionality. Gel properties analysis showed after ultrasonic treatment, the gel strength and water holding capacity of protein gels were increased gradually. Scanning electron microscopy (SEM) images also demonstrated that ultrasound treatment contributed to the formation of stable network structures in protein gels. In addition, ultrasonic homogenization could increase the emulsifying ability (45.54 m 2 /g to 78.82 m 2 /g) and stability of protein in a short time, which might be related to the decrease of particle size. Confocal laser scanning microscope (CLSM) analysis further illustrated that ultrasound treatment made the emulsion distribution more uniform. The application of these findings will improve the deep processing ability and expand the commercialization of frozen shrimp products. • Ultrasonic treatment led to the unfolding of shrimp MP conformation. • Conformational change led to the increase of SH groups and surface hydrophobicity. • Ultrasound increased gel strength and water holding capacity of shrimp MP gel. • Ultrasound increased the emulsifying capacity and stability of frozen shrimp MP. • CLSM analysis illustrated ultrasound made emulsion distribution more uniform.

Changes in protein oxidation, structure, and thermal stability of chicken breast subjected to ultrasound-assisted immersion freezing during frozen storage

The influence of ultrasound-assisted immersion freezing (UF), immersion freezing (IF), and air freezing (AF) on the protein oxidation, structure, and thermal stability of chicken breast during frozen storage was evaluated in this study. Compared to IF and AF samples, the UF samples had a lower carbonyl content, dityrosine content, and surface hydrophobicity of myofibrillar protein (MP) (P < 0.05), as well as a higher free amino group content and total and reactive sulfhydryl content (P < 0.05). Moreover, UF significantly delayed the deterioration of protein secondary and tertiary structures and the decrease in protein thermal stability during frozen storage (P < 0.05). Additionally, the UF samples at 180 days had similar protein structures and quality characteristics to the IF samples at 90 days or the AF samples at 60 days. Overall, UF treatment can effectively retard protein oxidation, protein structure deterioration, and protein thermal stability loss caused by frozen storage.

Role of partial replacement of NaCl by KCl combined with other components on structure and gel properties of porcine myofibrillar protein

The effects of partial replacement of NaCl by KCl combined with other components on the structure and gel properties of porcine myofibrillar protein (MP) were investigated. Three salt substitute formulas were used: 100% NaCl (control, SF1), 70% NaCl +30% KCl (SF2), and 70% NaCl +20% KCl + 10% other components (SF3). The solubility, surface hydrophobicity, reactive sulfhydryl content, zeta potential, EAI and ESI of SF3 sample were significantly higher than those of SF1 sample (P < 0.05). SF3 reduced the α-helix content and increased the β-sheet content (P < 0.05). Low field nuclear magnetic resonance showed that T21 and T22 of SF3 sample were shorter than SF1 and SF2 samples (P < 0.05), implying that SF3 reduced the mobility of mobile water and free water. Additionally, SF3 had a better gel water holding capacity, gel strength, and gel microstructure. Overall, partial replacement of NaCl by KCl combined with other components improves the physicochemical and gel properties of MP.

Ultrasound-assisted alkaline pH-shift process effects on structural and interfacial properties of proteins isolated from shrimp by-products

This study investigated the effects of alkaline pH-shift processing (pH: 12, 12.5 and 13) combined with ultrasonication (300 W; 0, 10, 20, and 30 min) on the yield and functional characteristics of shrimp proteins. Ultrasound assistant pH-shift processing resulted in a significantly higher protein recovery than the alkaline pH-shifting as maximum protein recovery was obtained at pH 12.5 in combination with sonication for 30 min (25.12%). Applying ultrasonication during the alkaline solubilization remarkably (P < 0.05) decreased zeta potential and particle size of the recovered shrimp proteins while increasing their surface hydrophobicity, fluorescence intensity, and reactive sulfhydryl content. The combination led to the denaturation of the recovered proteins with a change in their α-helices, β-sheet, random coil and β-turn content. Foaming and emulsifying characteristics of the shrimp proteins were remarkably (P < 0.05) affected by using the combined treatment, however, the progress level was dependent on the ultrasonication time and the solubilization pH. The highest value in emulsifying activity and foaming capacity was obtained in the sample extracted at pH 12.5 in combination with ultrasound for 20 min (300 W). Altogether, applying ultrasonication during the pH-shift processing can help protein isolation from shrimp peeling by-products but the combination should be carefully tuned to achieve maximum protein functionality.

Insight into the effect of ultrasound treatment on the rheological properties of myofibrillar proteins based on the changes in their tertiary structure

This was the first study to perform correlation analysis to determine the relationships between tertiary structural and rheological properties of the myofibrillar proteins (MPs) under ultrasound treatment (UT, frequency 20 kHz, power 500 W, intensity 30 %) for 0, 2, 4, 6, 8, and 10 min. The objectives of this study were to 1) characterize the changes of the small and large deformation rheological properties of MPs based on the tertiary structural changes; 2) determine relationships of rheological property, tertiary structural changes, and UT time. The results showed that UT could enhance the structural rigidity and the resistance of the system to permanent deformation observed in rheological tests. Besides, UT could unfold MPs, expose more hydrophobic amino acid residues to increase the surface hydrophobicity (S0-BPB), destroy disulfide bonds to increase the content of reactive sulfhydryl content (R-SH). The correlation analysis showed that the rheological properties of MPs could be improved by UT with a longer treatment time (0–10 min), while inevitably and significantly changing the tertiary structure of MPs (p < 0.05). These findings suggested that UT might be effective in the food-processing industry to change the structure of proteins and improve rheological properties.

Potential application of DBD Plasma Technique for modifying structural and physicochemical properties of Soy Protein Isolate

The present study was designed and implemented to modify soy protein isolate (SPI) using dielectric barrier discharge (DBD) plasma and investigate the effects of this treatment on the protein's structural and physicochemical properties. For this purpose, SPI powder was treated with DBD plasma for 0, 5, 10, 15 min at 16, 18, 20 kV. Then, solubility, water holding capacity (WHC), emulsifying activity and emulsion stability, foaming capacity and foam stability, total and reactive sulfhydryl, free carbonyl, FTIR, electrophoretic patterns, as well as protein structures were evaluated. Results indicated that emulsifying properties, solubility, WHC, and foaming activity of SPI were enhanced, and the highest values were obtained after plasma treatment at 18 kV for 15 min. Free and reactive sulfhydryl and free carbonyl contents increased under prolonged exposure to DBD plasma at the applied voltage of 18 kV (p < 0.05). FTIR and circular dichroism (CD) results indicated partial denaturation and unfolding of the α-helix structure of SPI followed by the formation of protein aggregates resulting from 15 min plasma exposure; microscopic images also confirmed these results. The above changes indicate successful modification of the physicochemical and functional properties of SPI treated with DBD plasma.

The effect of gamma and electron beam irradiation on the structural and physicochemical properties of myofibrillar protein and myosin from grass carp.

Myofibrillar protein (MPS) and myosin (MS) from grass carp was irradiated by γ-ray and electron beam (EB) irradiation with different dose (2, 4, 6, 8, and 10kGy). The changes in the physicochemical properties (solubility, Ca2+ -ATPase activity, total and reactive sulfhydryl content, surface hydrophobicity [S0 -ANS]), and structure of MPS and MS were investigated in the present work. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that there were degradation and aggregation of MPS and MS caused by irradiation, and the disappearance of myosin heavy chains (MHC) irradiated by EB was earlier than that of irradiated by γ-ray. As compared with MPS, the extracted MS was more easily destroyed. With the increase of irradiation dose, the particle size, solubility, Ca2+ -ATPase activity, and SH content of MPS and MS decreased (p<.05), while the S0 -ANS first increased and then decreased. Two-way analysis of variance results suggested that the degree of protein denaturation depends on the irradiation mode and dose. Compared with γ-ray irradiation, the EB irradiation had a greater impact on the physicochemical properties of MPS and MS.

Effects of ultrasound-assisted vacuum tumbling on the oxidation and physicochemical properties of pork myofibrillar proteins

The present research aimed to investigate the effects of high-intensity ultrasound (HIU, 20 kHz, 0 W, 100 W, 300 W and 500 W)-assisted vacuum tumbling (UVT) for 60 min and 120 min on the oxidation and physicochemical properties of the pork myofibrillar proteins (MPs). Compared with the vacuum tumbling (VT) groups without the HIU assistance, the carbonyl content increased, while the total sulfhydryl (SH) content was reduced with the increase of HIU power and treatment time (P < 0.05). The reactive SH content was increased significantly after treated by UVT with 300 W compared with the VT group (P < 0.05) regardless of the treatment time. Similarly, the surface hydrophobicity (S0), the intrinsic tryptophan intensity, and the solubility in the UVT group (300 W) were remarkably higher than those of the VT group (P < 0.05). In contrast, the α-helix content and the particle size of MPs significantly decreased when the HIU power was at 100 W and 300 W (P < 0.05). The results suggest that UVT treatment could change the structure and physicochemical properties of MPs accompanied by protein oxidation.

Effects of ultra-high pressure treatment on the protein denaturation and water properties of red swamp crayfish (Procambarus clarkia)

This study aimed at understanding the effects of ultra-high pressure (UHP) treatment on the quality, protein structure and water distribution of red swamp crayfish. After pressurization (100–500 MPa, 5 min), shear force, sulfhydryl (total and reactive) and carbonyl content of myofibrillar protein extracted from crayfish muscle were significantly increased (P < 0.05) with the elevated pressure, while salt soluble protein content and Ca2+-ATPase activity decreased (P < 0.05), and the secondary structure was not affected by the pressure level. After pressurization at 300 MPa, the Ca2+-ATPase activity decreased by 0.65 fold comparing with the control (P < 0.05), while the shear force, drip loss, total and reactive sulfhydryl and carbonyl content increased by 0.34, 0.32, 0.36, 0.36 and 1.56 fold, respectively (P < 0.05). Besides, SDS-PAGE of percolate displayed the decrease of actin band (42 kDa) intensity and appearance of new bands (25–40 kDa) at 300 MPa. The increased T21 (immobilized water) and T22 (free water) of samples treated at high pressure (below 400 MPa) suggested the redistribution of water compartments, which was further confirmed with the images of proton compartments. Overall, moderate UHP treatments (less than 300 MPa) could be applied to modify the protein structure and water distribution of crayfish muscle.

Effects of inulin on the gel properties and molecular structure of porcine myosin: A underlying mechanisms study

The functional properties of myosin play a key role in the final quality characteristics of meat products. To explore the molecular mechanism of inulin in improving the properties of porcine myosin gel, different inulin concentrations (0%, 1%, 2%, 3%, 4%, and 5%) were added, and the gel water-holding capacity (WHC), microstructure, rheological properties, secondary structure, surface hydrophobicity and reactive sulfhydryl (R-SH) contents were determined. The results showed that the inulin concentration was in the range of 0%–5%, there was a positive correlation with the gel strength, the storage modulus (G′) and loss modulus (G″) of myosin also gradually increased with the increased of inulin concentration. The addition of inulin improved the WHC of myosin gel which was attributed to the formation of a fine microstructure, when the inulin concentration was 2%, the most significant improvement was observed. The improvement in the properties of heat-induced myosin gelation was due to the change in the molecular structure of myosin after the addition of inulin; the addition of inulin led to the transformation of the secondary structure of myosin, which resulted in the exposure of more hydrophobic groups and sulfhydryl groups than in the control and was conducive to the formation of a heat-induced dense myosin gel network. The principal component analysis results revealed the correlation between the gel properties and the molecular structure and provide a powerful tool for analysis. In conclusion, the addition of inulin can improve the functional properties of myosin and facilitate the heat-induced gelation of myosin.

Physicochemical and techno‐functional properties of acid‐aided pH‐shifted protein isolate from over‐salted duck egg (Anas platyrhucus) albumen

SummaryHere, potential physicochemical and techno‐functional properties of the albumen protein recovered from over‐salted albumen by an effective acid‐aided pH‐shift process (POA) were tested in comparison with the fresh albumen (FA) and albumen protein recovered from fresh albumen by acid‐aided pH‐shift process (PFA). POA contained 66.73% protein and 11.30% sodium (dry basis). Surface hydrophobicities of PFA and POA were higher than FA (P &lt; 0.05), whereas the reactive sulfhydryl content of FA was higher than PFA and POA (P &lt; 0.05). PFA had the highest whiteness followed by POA and FA, respectively. Single endothermic peak in DSC thermogram was found at 86.86, 89.67 and 98.96 °C for FA, PFA and POA, respectively. Long‐term salting impaired the solubility, viscosity, emulsifying activity and gelation but not for foaming of albumen protein isolate. FA can be softly gelled with continuously packed structure, whereas PFA and POA underwent agglutination to form white clot suspension with spongy network.

Effects of high pressure on biochemical properties and structure of myofibrillar protein from Tegillarca granosa

SummaryThe effects of high‐pressure (HP) treatment parameters (300 MPa for 5 min, 350 MPa for 3 or 5 min and 400 MPa for 1 min) on the biochemical properties and structure of myofibrillar protein (MP) from Tegillarca granosa were investigated. The results showed that HP significantly affected the biochemical properties of MP. Under the HP treatment at 400 MPa for 1 min, the MP extraction yield was reduced from 32.21 to 18.34 mg g−1, and its surface hydrophobicity was increased from 89.29 to 104.69 µg. Ca2+‐ATPase activity of MP decreased from 0.019 to 0.011 µmol (pi) mg−1 (pro) min−1, and both total and reactive sulfhydryl contents significantly declined. Furthermore, HP caused MP to undergo conformational changes. This study provides a reference data for the processing of T. granosa using HP treatment.

Glycation-induced structural modification of myofibrillar protein and its relation to emulsifying properties

In the present study, myofibrillar protein (MP) and dextran (DX) conjugates were prepared via glycation in a liquid solution. The effects of DX molecular weight on structural and emulsifying properties of conjugates compared with those of MP were investigated. The glycation was confirmed by evaluating modification degree of glycation (DG), electrophoresis and Fourier transform infrared spectroscopy. As DX molecular weight increased, the Ca2+-ATPase activity decreased markedly due to modification of MP, and the formation of MP-DX conjugates reduced surface hydrophobicity owing to the unfolding behaviour of MP and covalent attachment of DX. In addition, combined analysis of turbidity and reactive sulfhydryl contents indicated that MP may undergo a conformation unfolding and become looser and more flexible upon glycation. Glycation was able to increase the emulsifying activity and emulsion stability of MP, and MP-DX 70 showed the best emulsifying properties. A good correlation between reactive sulfhydryl contents and emulsifying properties was obtained, and the correlation coefficients were 0.930 for emulsifying activity and 0.961 for emulsion stability. Meanwhile, there was a negative correlation between surface hydrophobicity and emulsifying properties with correlation coefficients of −0.965 and −0.895, respectively. Overall, glycation could alter the structural characteristics and enhance the emulsifying properties of MP.