Comparison of interaction mechanism between chlorogenic acid/luteolin and glutenin/gliadin by multi-spectroscopic and thermodynamic methods

Production, characterization, and application of zein-polyphenol complexes and conjugates: A comprehensive review

The corn protein zein has several advantages, such as low production cost, excellent biodegradability, good biocompatibility, and low allergenicity. However, the application of zein in the food industry is limited by its high hydrophobicity. To increase the functionality of zein and meet the diverse requirements of food systems, researchers have explored several methods to form complexes or conjugates through noncovalent or covalent interactions, respectively, with polyphenols. This paper comprehensively reviews the formation mechanisms, preparation methods, and influencing factors of zein-polyphenol complexes and conjugates. In addition, the paper presents the techniques used to characterize zein-polyphenol complexes and conjugates and their various new functional properties and bioactivities including water solubility, emulsification activity, in vitro antioxidant activity and antibacterial activity, as well as factors that affect these properties. Furthermore, the potential uses of these compounds in the food sector and future research areas are discussed.

Study on protein hydrolysis and microbial community changes during the fermentation of pork loin ham mediated by electrical stimulation

This study explored the effect of electrical stimulation (ES) and Pediococcus pentosaceus LL-07 (P. pentosaceus LL-07) and Staphylococcus simulans QB7 (S. simulans QB7) on the quality and microbial community of loin ham during the ripening. After the ES and starter culture treatments, the Aw and pH were decreased. Surface hydrophobicity, myogenic fiber fragmentation index (MFI), TCA-soluble peptide, amino nitrogen and free amino acids (FAAs) were also significantly higher than the control group (CK) (P < 0.05). This increase was more significant in the E-S group (electrical stimulation followed by inoculation with P. pentosaceus LL-07 and S. simulans QB7) than the rest of the experimental group (E、S、S-E group). Furthermore, the CK and E-S groups were subjected to a bacterial community comparison experiment. The microbial diversity of these two groups was increased. Pediococcus spp. and Staphylococcus spp. became the dominant bacteria in E-S groups during the ripening. Correlation analyses show a strong correlation between protein hydrolysis, microorganisms and FAAs. In conclusion, the combination of ES and starter culture could promote protein hydrolysis, the accumulation of FAAS, and improves the bacterial community of loin ham.

Preparation, structural changes and functional properties of the covalent complexes of almond protein and phloretin

Proteins and polyphenols exhibit distinct biological activities and functional properties. A comprehensive investigation into the formation mechanisms, structures, and functional properties of protein-polyphenol complexes will deepen our understanding of their interactions and establish a theoretical foundation and technical support for development of novel functional foods and pharmaceutical products. The almond protein-phloretin (AP-PHL) covalent complex was synthesized through the covalent binding of hydroxyl radicals to phloretin (PHL), utilizing almond protein (AP) as the raw material. Ultraviolet absorption spectroscopy (UV), fluorescence spectroscopy (FS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (RS), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were employed to characterize the AP-PHL complex. Additionally, its properties, including emulsification characteristics and antioxidant activity, were analyzed. The results indicated that the hydrophobic groups in hydroxyl radical-treated AP relocated to a hydrophilic environment and interacted with PHL, thereby forming a stable complex. TEM results indicated that AP formed clusters within the central region of PHL. Additionally, UV and FS analyses revealed that the maximum absorption wavelength of AP-PHL shifted from 287.5 nm to 258 nm and 280 nm, respectively. As the PHL concentration increased, the fluorescence intensity gradually decreased, accompanied by a slight redshift. FTIR and RS analyses revealed that modifications in functional groups (e.g., -CH3, =CH2, CO, CC, CO) were implicated in the interaction between AP and PHL. Such structural modifications, along with other changes, enhanced the functional properties of AP-PHL, including thermal stability, water solubility, and emulsification, thereby indicating its substantial potential for applications in food and pharmaceuticals.

Effects of black soybean peel anthocyanins on the structural and functional properties of wheat gluten

BACKGROUND

Wheat gluten (WG) is a crucial cereal protein commonly utilized in the food, biological and pharmaceutical industries. However, WG is poorly soluble in water, resulting in poor functional properties, which restrict its application in the food industry. As a result, there is an urgent need for improving the properties of WG.

RESULTS

This study was conducted to examine the functional properties of WG after binding with black soybean peel anthocyanin extract (BAE). Results showed that BAE enhanced the solubility, water-holding and antioxidant capacity, foaming properties and emulsifying activity of WG, while decreasing the emulsion stability. The degree of hydrolysis of WG and retention rate of BAE became higher in the digested WG-BAE complex than in the control groups. Additionally, an analysis was conducted on the mechanism of interaction between cyanidin-3-O-glucoside (C3G) and WG/gliadin (Gli)/glutenin (Glu). The secondary structure of WG/Gli/Glu was altered after adding C3G. C3G had high affinity for WG/Gli/Glu since their binding constants were greater than 104 L mol-1. The primary binding forces between C3G and WG/Gli were hydrophobic interactions, whereas the main interaction forces between C3G and Glu were hydrogen bonding and van der Waals forces. Moreover, C3G increased the thermal stability and changed the network structure of WG/Gli/Glu.

CONCLUSION

This study revealed that BAE effectively enhanced a range of functional properties of WG. The interaction between WG and BAE also improved the bioavailability and nutritional value of them. Furthermore, the interaction mode between BAE and WG was investigated. These findings lay a foundation for utilizing gluten-anthocyanins in the food sector. © 2024 Society of Chemical Industry.

Regulation of catechins with different structure characteristics on the physicochemical properties of casein and the structure-activity relationship

Regulation of catechins with different structure characteristics on the physicochemical properties of casein were investigated, and the structure-activity relationship was further explored. All testing catechins effectively modulated the physicochemical properties of casein, and esterified catechins showed the stronger binding affinity to casein than non-esterified catechins. Catechins significantly altered the secondary and tertiary structures of casein. Fluorescence spectroscopy and thermodynamic analyses indicated that the fluorescence quenching mechanism of casein by the four catechins was static. The Gibbs free energies (ΔG) for the interactions between EC, ECG, EGC, and EGCG with α-casein were - 14.16, -25.41, -22.23, and - 24.48 kJ/mol, respectively. For β-casein, ΔG were - 17.91, -29.85, -17.34, and - 19.33 kJ/mol, respectively. All negative ΔG values suggested that the interactions between catechins and casein occurred spontaneously. At 297 K, the binding constants for catechins with α-casein followed the order: ECG (29.51 × 103 L/mol) > EGCG (20.23 × 103 L/mol) > EGC (8.13 × 103 L/mol) > EC (0.31 × 103 L/mol). For β-casein, the order was: ECG (177.83 × 103 L/mol) > EGCG (2.51 × 103 L/mol) > EC (1.41 × 103 L/mol) > EGC (1.12 × 103 L/mol). Molecular docking combined with multispectral analysis further demonstrated that hydrogen bonds, van der Waals forces, and hydrophobic interactions governed the interactions between catechins and casein, and hydrogen bonds were the predominant force. All results indicate that the amount of hydroxyl groups and the presence of galloyl group significantly affect the capability of catechins to interact with casein.

Study on the effects of endogenous polyphenols on the structure, physicochemical properties and in vitro digestive characteristics of Euryales Semen starch based on multi-spectroscopies, enzyme kinetics, molecular docking and molecular dynamics simulation

Euryales Semen (ES) is a highly nutritious food with low digestibility, which is closely associated with its endogenous phenolic compounds. In this study, five phenolic compounds (naringenin, isoquercitrin, gallic acid, epicatechin and quercetin) with high concentrations in ES were selected to prepare starch-polyphenol complexes. Subsequently, the effects of endogenous polyphenols on the structure, physicochemical properties and digestion characteristics of ES starch were studied using multiple techniques. The addition of phenolic compounds markedly reduced the in vitro digestibility, swelling power, gelatinization enthalpy, while increased the solubility of ES starch. Fourier-transform infrared spectroscopy and X-ray diffraction analysis showed that phenolic compounds interacted with the starch through non-covalent bonds. Five phenolic compounds inhibited α-amylase activity through a mixed competitive inhibition mechanism, with the inhibition potency ranked as follows: quercetin > epicatechin > gallic acid > isoquercitrin > naringenin. The spectroscopic analysis and molecular dynamics simulations confirmed that five phenolic compounds interacted with the amino acid residues of α-amylase through hydrogen bonding and hydrophobic interactions, caused α-amylase static fluorescence quenching, and altered its conformation and microenvironment. This study provides a better understanding of the interaction mechanisms between ES starch and polyphenols, and supports the development of ES as a food that lowers sugar levels.

Intermolecular interactions between malvidin-3-O-glucoside and caffeic acid: Structural and thermodynamic characterization and its effect on real wine color quality

The copigmentation effect between malvidin-3-O-glucoside and caffeic acid was comprehensive inquiry on the model wine solution, theoretical simulation and real wine. Thermodynamic parameters were determined by UV/Visible spectroscopy and Isothermal titration calorimetry (ITC). Theoretical data were obtained employing a dispersion-corrected density functional approach. The effects in real wines were investigated by adding the caffeic acid during different fermentation periods. Results shown that the copigmentation reaction between caffeic acid and malvidin-3-O-glucoside is a spontaneous exothermic reaction driven by hydrogen bonding and dispersions forces. Computations show that the polyhydroxyl sugar moiety and phenolic hydroxyl groups are the key active sites. The addition of caffeic acid in post-alcohol fermentation samples evidences an improving color characteristics in the wine.

Protein-Chlorogenic Acid Interactions: Mechanisms, Characteristics, and Potential Food Applications

The interactions between proteins and chlorogenic acid (CGA) have gained significant attention in recent years, not only as a promising approach to modify the structural and techno-functional properties of proteins but also to enhance their bioactive potential in food systems. These interactions can be divided into covalent (chemical or irreversible) and non-covalent (physical or reversible) linkages. Mechanistically, CGA forms covalent bonds with nucleophilic amino acid residues of proteins by alkaline, free radical, and enzymatic approaches, leading to changes in protein structure and functionality, such as solubility, emulsification properties, and antioxidant activity. In addition, the protein-CGA complexes can be obtained by hydrogen bonds, hydrophobic and electrostatic interactions, and van der Waals forces, each offering unique advantages and outcomes. This review highlights the mechanism of these interactions and their importance in modifying the structural, functional, nutritional, and physiological attributes of animal- and plant-based proteins. Moreover, the potential applications of these protein-CGA conjugates/complexes are explored in various food systems, such as beverages, films and coatings, emulsion-based delivery systems, and so on. Overall, this literature review provides an in-depth overview of protein-CGA interactions, offering valuable insights for future research to develop novel protein-based food and non-food products with improved nutritional and functional characteristics.

Inhibition of α-amylase digestion by a Lonicera caerulea berry polyphenol starch complex revealed via multi-spectroscopic and molecular dynamics analyses

Polyphenol-starch complexes exhibit synergistic and beneficial effects on both polyphenols and resistant starches. This study evaluates the inhibitory effects and mechanisms of α-amylase on a Lonicera caerulea berry polyphenol-wheat starch (LPWS) complex following high hydrostatic pressure treatments of 400 MPa for 30 min and 600 MPa for 30 min. The IC50 values for α-amylase inhibition by the complex were 3.61 ± 0.10 mg/mL and 3.42 ± 0.08 mg/mL at a 10 % (w/w) polyphenol content. This interaction was further supported by Fourier-transform infrared spectroscopy and circular dichroism, which confirmed that the alpha helix component of the secondary structure of α-amylase was reduced due to the complex. Multifluorescence spectroscopy revealed that the complex induces changes in the microenvironment of fluorophores surrounding the α-amylase active site. Molecular dynamics simulations and molecular docking revealed that the active site of amylose within the complex becomes enveloped in polyphenol clusters. This wrapping effect reduced the hydrogen bonds between amylose and α-amylase, decreasing from 16 groups to just one group. In summary, the LPWS complex represents a low-digestible carbohydrate food source, thus laying the groundwork for the research and development of functional foods aimed at postprandial hypoglycemic effects.

Functional and structural properties of gliadin as influenced by pH, extraction protocols, and wheat cultivars

Gliadin, owing to its low cost, ease to extract, high foaming capacity, easily available and high surface hydrophobicity, has found a wide range of applications both in the food and pharmaceutical sectors. The functional and structural characteristics of gliadin extracted with four extraction protocols from six wheat cultivars were investigated in this study. The surface-active properties of gliadin protein as a function of pH, extraction protocols, and wheat cultivars were compared, including solubility, zeta-potential, foaming properties, emulsion properties, surface hydrophobicity and secondary structure. Overall gliadin extracted using different extraction protocols and from different wheat cultivars was found to be higher in β-turns (24.88-37.91 %), followed by β-sheet (12.81-22.37 %), α-helix (15.13-20.70 %) and lower in random coil (6.53-9.08 %). Varied pH ranges, wheat cultivars, and different extraction protocols were found to have a substantial impact on solubility, zeta potential, foaming stability, emulsion capacity and surface hydrophobicity. The foaming capacity was observed to be more influenced by extraction protocols than wheat cultivars. Emulsion stability showed statistically significant (p ≤ 0.05) influence between the wheat cultivars, and a non-significant (p ≥ 0.05) difference among extraction protocols. The functional properties of freeze-dried gliadin extracted using different protocols were found to be pH-dependent. A comprehensive understanding of how the structural, surface active and functional properties of gliadin are influenced by the extraction protocols and wheat cultivars will enable us to understand the gliadin better and broaden its use for both food and non-food applications.

Mechanistic understanding of the effect of zein–chlorogenic acid interaction on the properties of electrospun nanofiber films

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The quenching of zein by chlorogenic acid is mainly static quenching.

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Hydrogen bonding and electrostatic interaction are main driving forces.

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The tensile strength of zein film with 2.0% chlorogenic acid increased by 132.44%.

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The addition of chlorogenic acid to zein films has potential as an active packaging.

The interaction mechanism between zein and chlorogenic acid (CA) and the effect of interaction on the performance of coaxial nanofiber films were investigated. The interactions between zein and CA were characterized by multiple spectroscopic methods. Ultraviolet spectrum analysis revealed the formation of a zein–CA complex. Fluorescence analysis pointed out that the quenching of zein by CA was static. FTIR and thermodynamic analyses showed that hydrogen bonds and electrostatic interactions dominated the interaction between zein and CA. Zein-based nanofiber films were successfully prepared by coaxial electrospinning. The interaction between zein and CA enhanced the mechanical properties but reduced the thermal stability of nanofiber films. The presence of CA endowed nanofiber films with antioxidant and antibacterial properties. This research provides significant insight into the effect of protein–polyphenol interactions on the properties of electrospun nanofiber films, which can be applied in the field of active packaging to improve food safety.