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The purpose of this study was to prepare and characterize inclusion complexes between tea polyphenol (TP) and hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD), and to evaluate their antioxidant properties. Freeze‐drying was used to prepare the inclusion complex of TP/HP‐β‐CD at different component ratios (1:0.5, 1:1, and 1:2). The supermolecular structure of the TP/HP‐β‐CD complex was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Molecular docking was used to simulate the positions and interactions of the binding sites of TP/HP‐β‐CD inclusion complexes and target protein receptors. In addition, the effects of TP/HP‐β‐CD inclusion complexes on myofibrillar protein (MP) from lamb tripe were observed under oxidative conditions. Results showed that TP was encapsulated in the cavity of HP‐β‐CD to form an optimal complex with 1:2 molar ratio of stoichiometry, while the FTIR, TGA, and SEM studies also support the inclusion process. Molecular modeling results were systematically analyzed to determine the stability of inclusion complexes and protein. Furthermore, the addition of an appropriate concentration (5 to 105 µmol/g) of TP/HP‐β‐CD inclusion complex decreased the carbonyl content, hydrophobicity, and protein aggregation of MP from lamb tripe, whereas it increased the sulfhydryl content. This improved antioxidant activity and bioavailability of the inclusion complexes will be beneficial for its potential applications in food. Practical Application: Tea polyphenol was an antioxidant with potential for the field of food. In this study, the unstable properties of tea polyphenols were evaluated and were improved by inclusion of HP‐β‐cyclodextrin. The binding mode of the inclusion complex with protein was revealed via the molecular docking method, and the application of inclusion complex to control protein oxidation was studied. Results showed that the inclusion complex could effectively inhibit protein oxidation, which can provide a reference for the application of polyphenols in meat products and the improvement of protein properties. [ABSTRACT FROM AUTHOR]

Covalent complexes of bovine bone proteins (BBP) with four polyphenols (chlorogenic acid (CA), quercetin (Q), rutin (R), epigallocatechin gallate (EGCG)) with were prepared to increase the high-value utilization degree of bovine bone. The differences in coupling effect and structural and functional properties between the conjugates were also investigated. The results showed that EGCG-BBP had the highest polyphenolic equivalent at 88.05 mg/g protein and the lowest sulfhydryl group content. EGCG-BBP also had the best covalent effect. The SDS-PAGE and fluorescence spectra results revealed that the molecular weight of the conjugates increased significantly as different polyphenols conjugated with the aromatic amino acids in BBP, resulting in significant changes in the structure of EGCG-BBP. Fourier Transform infrared spectroscopy (FTIR) analysis demonstrated that the amide I band of conjugates was slightly shifted, indicating that the polyphenols were covalently bonded with BBP. Based on the results of this study and well-established mechanisms, it could be speculated that the best covalent effect of EGCG may be not only due to the eight phenolic hydroxyl groups but also to its two benzene rings, which are greatly increased in its reaction site. In terms of functional characteristics, EGCG-BBP had the highest 1-diphenyl-2-picryl-hydrazyl radical (DPPH·) scavenging capacity, while Q-BBP had the best solubility. Thus, this study provides a theoretical basis for different polyphenols' structural and functional effects on covalently modified proteins. [Display omitted] • Bovine bone protein (BBP) was conjugated with four polyphenols. • EGCG has the strongest covalent capacity, followed by CA, R, and Q. • The structural and functional properties of different polyphenol-protein conjugates have changed significantly. • Covalent difference between polyphenols and BBP may be related to the number of phenolic hydroxyl and benzene rings. [ABSTRACT FROM AUTHOR]

To enhance the functional properties of bovine bone proteins (BBP) for food-related applications, their quercetin conjugates (BBP-QC), with antioxidant and emulsifying properties, were prepared by alkaline induction. The structural changes of BBP-QC conjugates were investigated, and their different concentrations were examined for the physical and oxidative stability of oil-in-water (O/W) emulsions. Structural characterization using Fourier transform infrared spectroscopy (FT-IR) and fluorescence spectroscopy confirmed the covalent binding of QC with BBP resulting in a conformational change in BBP. Particle size and ζ-potential measurements showed that 0.6% BBP-QC effectively improved the physical stability, increased the net charge of the O/W emulsion. Fluorescence microscopy observation of emulsion microstructure showed that the distribution of oil droplets in the BBP-QC stabilized emulsion was smaller and more uniform than that without the conjugates and effectively alleviated the phase separation in the emulsion. The 0.6% BBP-QC emulsion had a peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) value of only 1.45 mmol/kg and 3.32 μmol/kg after 12 days. Additionally, BBP-QC stabilized emulsions exhibited excellent antioxidant capacity in vitro antioxidant experiments. This study highlights the excellent properties of BBP-QC conjugates as novel emulsifiers with high antioxidant activity and potential applications in the food industry. [Display omitted] • Preparation of a novel antioxidant emulsifier based on bovine bone protein-quercetin conjugates. • The effect of BBP-QC conjugates on the physical and oxidative stability of emulsion was determined. • Further revealed the possible intrinsic mechanism of BBP-QC covalent stabilized emulsion. • Improved thermodynamic instability of oil-in-water emulsions. [ABSTRACT FROM AUTHOR]

In this study, the mechanism of the interactions between sesamol and myosin was explored to confirm the potential application of sesamol in a meat protein system. A series of sesamol and myosin solutions were prepared for spectroscopic studies. UV–vis spectroscopy revealed that sesamol formed a complex with myosin and affected the myosin microenvironment. Fourier transform infrared spectroscopy showed that hydrogen bonding was involved in the formation of the complex. Static quenching (Kq = 1.044 × 1012 m−1s−1) of sesamol on myosin and the good binding effect (Ka = 1.44 × 105 L/mol, n = 1.33) between sesamol and myosin were verified by the fluorescence quenching mechanism. Circular dichroism spectroscopy confirmed that the interactions resulted in a decrease of myosin α-helix content. Furthermore, the best pose for successfully docking sesamol with myosin (lowest binding affinity of −6.2 kcal/mol) was shown by molecular docking. The molecular dynamics simulation and small-angle X-ray scattering results determined that hydrophobic interactions and hydrogen bonding allowed the protein structure to be more compact and stabilized. Several key residues (Glu-477, Cys-480, Ile-481, Glu-272, Leu-271, and Leu-270) and a protein residue (Lys-273) formed a structurally stable complex with sesamol through hydrophobic interactions and hydrogen bonding (3.28 Å). The surface hydrophobicity of the sesamol-myosin complex was reduced, solubility and emulsification properties were improved, and a smaller particle size was produced. [Display omitted] • Sesamol formed complex with myosin and affected the myosin microenvironment. • The binding of sesamol to myosin changed the secondary structure of myosin. • Sesamol reduced the fluorescence of myosin by static quenching. • Hydrophobic interactions and hydrogen bond stabilized the structure of complex. • Better solubility and emulsification properties of the complex. [ABSTRACT FROM AUTHOR]

[Display omitted] • The inclusion complexes (ICs) improved the antioxidation ability of apple polyphenols. • ICs decreased susceptibility of myofibrillar proteins (MPs) to frozen oxidation. • The MPs degradation were inhibited by ICs with concentration on 0.2–1.6 mg/mL. • 1.6 mg/mL ICs most effectively improved the tissue structure of frozen muscle. This study aimed to evaluate the effect of inclusion complexes (ICs) on the oxidative stability of myofibrillar proteins (MPs) and microstructures in lamb during frozen storage. The inclusion process between apple polyphenols (APs) and hydroxypropyl-β-cyclodextrin (HP-β-CD) was verified using Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and the antioxidant activity of APs. Results showed that the sensitivity of MPs to oxidation improved after 40 weeks. The ICs (0.2–1.6 mg/mL) significantly reduced the carbonyl content, particle size aggregation, protein degradation, fluorescence quenching effect, and decreased the α-helix contents loss of MPs. Additionally, the changes in protein oxidation showed a correlation with the microstructure of muscles, and the addition of 1.6 mg/mL IC remarkably improved the structure of muscle tissues while that of 3.2 mg/mL IC was detrimental to the structural properties. Overall, the exertion of antioxidant activity significantly influenced the cryoprotective effect of ICs on frozen lamb meat. [ABSTRACT FROM AUTHOR]

[Display omitted] • 200 W, and 9 min induced the highest emulsification of MPs from C. peled. • HIU induced structural modification of MPs, which strengthened the emulsification. • HIU improved the oxidative modification of MPs and the degradation of MHC. • Oxidation and MHC degradation partial contribute to the emulsification improvement. This study evaluated the effects of high intensity ultrasonication (HIU, 100, 150, 200, and 250 W) and treatment time (0, 3, 6, 9, and 12 min) on the structure and emulsification properties of myofibrillar proteins (MPs) from Coregonus peled. These investigations were conducted using an ultrasonic generator at a frequency of 20 kHz (ultrasonic probe). Analysis of the carbonyl content and total number of sulfhydryl groups showed that HIU significantly improved the oxidative modification of MPs (P < 0.05). SDS-PAGE profiling showed significant degradation of the myosin heavy chain (P < 0.05). In addition, Fourier transformed infrared spectroscopy (FTIR) revealed that HIU altered these treated MP secondary structures, this was due to molecular unfolding and stretching, exposing interior hydrophobic groups. Particle size analysis showed that HIU treatment reduced particle sizes. Solubility, emulsification capacity, and emulsion stability were improved significantly, and each decreased with an increase in treatment time (up to 12 min), indicating aggregation with prolonged sonication. These results indicate that HIU could improve the emulsification properties of MPs from C. peled, demonstrating a promising method for fish protein processing. [ABSTRACT FROM AUTHOR]