Binding affinity, antioxidative capacity and in vitro digestion of complexes of grape seed procyanidins and pork, chicken and fish protein

Improved emulsifying and foaming properties of ovalbumin and antioxidant activity of (-)-gallocatechin gallate: Effects of ultrasound-assisted glycation based on natural deep eutectic solvents and noncovalent binding

In this study, ultrasound-assisted glycated ovalbumin (G-UOVA) based on natural deep eutectic solvents (NADES) was prepared using response surface optimization. The binding affinity of (-)-gallocatechin gallate (GCG) to native OVA (NOVA), ultrasound treated OVA (UOVA), glycated OVA (GOVA), and G-UOVA followed G-UOVA > GOVA > UOVA > NOVA. The effects of various modifications and GCG binding on the secondary structure, particle size, and thermal stability of NOVA were investigated. After ultrasound-assisted glycation, the emulsifying activity, emulsifying stability, foaming activity, and foaming stability of NOVA increased by 61.9 %, 119.0 %, 36.0 %, and 47.1 %, respectively, and further increased due to GCG binding. The encapsulation of native and modified OVA, particularly G-UOVA, significantly enhanced the antioxidant activity and bioaccessibility of GCG. The degradation of GCG encapsulated by G-UOVA decreased from 100 % to 20.9 % within 10 h. This study can lay the foundation for further applications of NADES in related fields.

Protein-Tannin Organic Polymer-Based Oxygen-Enriched Graded Porous Carbon as a Cathode for Metal-Ion Hybrid Capacitors

Metal-ion hybrid capacitors represent an innovative class of electrochemical energy storage systems. However, hybrid capacitors made from traditional carbon-based materials struggle to simultaneously achieve both high specific capacity and long-cycle stability. A hierarchical porous carbon material with an optimized pore structure was synthesized using pig kidney proteins and tannic acid as precursors, employing cross-linking polymerization and carbonization activation strategies. The as-synthesized sample features an exceptionally high specific surface area and abundant porosity, which efficiently accommodate the adsorption and transport of solvated zinc and magnesium ions. The zinc-ion hybrid capacitor (ZHC) achieved a reversible capacity of 221 mA h g-1 at 0.2 A g-1, while the magnesium-ion hybrid capacitor (MHC) delivered 132 mA h g-1 under the same conditions. Additionally, DFT calculations revealed the critical influence of pore size on metal ion storage. In a 2 M ZnSO4 aqueous electrolyte solution, when the pore size of the carbon material was 1.13 nm, solvated zinc ions exhibited the highest adsorption energy. In contrast, in a 0.4 M (MgPhCl)2-AlCl3 organic electrolyte, a pore size of 2.29 nm optimized the storage capacity of solvated magnesium ions. This study provides important theoretical insights into designing ZHCs and MHCs.

Effects of Extraction Temperature of Protein from Date Palm Pollen on the Astringency Taste of Tea

The astringency of tea, predominantly attributed to epigallocatechin gallate (EGCG), plays a crucial role in shaping its overall quality, and plant-based proteins are gaining popularity as a preferred alternative to milk-based proteins for enhancing the flavor profile of tea. This study investigated the impact of extraction temperature on date palm pollen (DPP) protein quality and tea astringency, comparing temperatures of 30 °C and 80 °C. Results indicated that higher extraction temperatures yield more protein and improve the thermal and surface properties of DPP. The molecular interaction between DPP and EGCG was investigated in an aqueous solution, and spectroscopic analyses (FTIR, UV, and CD) revealed that EGCG interactions at a 1:1 molar ratio induced structural changes in α-helix and β-sheet content in secondary structures in DPP, particularly at 80 °C, which strengthened and enhanced the hydrophobic interactions and hydrogen bonds between DPP molecules as EGCG concentration increased. A sensory evaluation using quantitative descriptive analysis (QDA) confirmed a significant reduction in astringency in DPP-tea polyphenol solutions extracted at 80 °C. This research highlights the potential of DPP as a functional ingredient in the food industry, creating a protein-polyphenol complex that reduces tea's astringency while maintaining its unique flavor profile, thus offering a novel approach to enhance tea beverages.

Utilization of egg white powders to mitigate the astringency of Aronia berry juice and produce protein-Proanthocyanidin aggregates with enhanced stability during digestion

Aronia berry has a strong unpleasant astringency, however, few approaches have been developed to modify it. This study aims to screen out the suitable proteins to mitigate astringency in aronia juice, elucidate the interaction mechanism, and evaluate the digestive stability of formed complexes. Among proteins tested, two egg white powders (original P-110 and modified M-200) were the optimal ones with 0.5 % (w/w) addition to effectively reduce astringency. At room temperature (25 °C), the interaction of proanthocyanidins (PAs) with both P-110 and M-200 was spontaneous, endothermic, and majorly driven by hydrophobic interaction. The binding affinity of PAs with M-200 is stronger than that with P-110. On the other hand, the egg white protein-PA aggregates enhanced the stability of PAs during digestion, allowing more PAs to reach gut microbiota to exert their bioactivities. This study improves fundamental understanding of egg white protein-PAs interaction and provides a practical processing approach for aronia industry.

The Effect of Lipids on the Structure and Function of Egg Proteins in Response to Pasteurization

In recent years, the consumption of liquid eggs has failed to meet the expectations of the public due to growing concerns regarding food safety and health. It is well known that there are interactions between the components in liquid eggs, and the interaction effect on the structure and functional properties of the proteins and antigenicity remains unclear. To investigate egg component interactions, we focused on four major egg lipids, namely phosphatidylcholine, palmitic acid, oleic acid, and linoleic acid, as well as four major egg proteins, including ovalbumin, ovotransferrin, ovomucoid, and lysozyme. The protein structural changes were analyzed using polypropylene gel electrophoresis, circular dichroism, ultraviolet absorption spectra, and exogenous fluorescence spectra, and the functional properties were assessed through solubility measurements and particle size analysis, while protein antigenicity was evaluated using an enzyme-linked immunosorbent assay. All the results revealed that oleic acid had the most significant effect on proteins' secondary and tertiary structures, particularly affecting ovalbumin and ovotransferrin. Linoleic acid substantially increased the solubility of ovalbumin and ovomucoid, while palmitic acid significantly influenced the particle size of ovalbumin and lysozyme. Thus, we found that different lipids exhibit distinct effects on egg protein properties during pasteurization conditions, with oleic acid showing the most substantial impact on protein structure and antigenicity.

Epigallocatechin Gallate Combine with Ice Glazing: A Promising Way to Preserve the Quality of Frozen Eriocheir sinensis

The quality of frozen Eriocheir sinensis plays an important role in influencing consumer preference. Polyphenol oxidase (PPO) activity changes are commonly used to evaluate melanosis in aquatic products. In this study, we examined the interactions between epigallocatechin gallate (EGCG) and PPO. Further, we investigated whether treatment with EGCG in combination with ice glazing could restrict melanosis in E. sinensis during frozen storage and maintain its quality. The results demonstrated that EGCG inhibited PPO activity in a dose-dependent manner and firmly binds to the active pocket of PPO, thereby altering its tertiary structure. The melanosis and oxidation of E. sinensis in frozen storage were significantly reduced by adding 0.1 g/L EGCG combined with ice-glazing treatment (EGCG + IG). EGCG + IG improved the melanosis score of E. sinensis after six-week storage by 77.17%, and reduced protein and lipid oxidation by 10.80% and 62.46%, respectively, compared with untreated specimens. Moreover, the umami and sweet amino acids were better retained. Among the combined treatments, ice glazing effectively inhibited oxidation, whereas EGCG significantly inhibited melanosis. In summary, EGCG combine with ice glazing, is an effective way to maintain the quality of frozen E. sinensis and could also be studied to store other aquatic products.

The synergistic effects of rice bran rancidity and dephenolization on digestive properties of rice bran protein

Both rice bran (RB) rancidity and dephenolization could affect the structural characteristics and phenolics composition of rice bran protein (RBP), thereby affecting RBP digestibility. The synergistic effects of RB rancidity and dephenolization on RBP digestibility were investigated. Excessive RB rancidity (RB stored for 10 d) and non-dephenolization reduced RBP digestibility, while moderate RB rancidity (RB stored for 1 d) combined with dephenolization improved RBP digestibility to a maximum of 74.19%. Dephenolization reduced the antioxidant capacities of RBP digestive products. The digestibility of non-dephenolized RBP (NDRBP) was significantly (P < 0.05) related with its carbonyl content, surface hydrophobicity, and ζ-potential. The digestibility of dephenolized RBP (DRBP) was significantly related with its β-sheet structure content, surface hydrophobicity, ζ-potential, and average particle size. Overall, moderate RB rancidity combined with dephenolization enhanced RBP digestibility by reducing the non-competitive inhibition of endogenous phenolics on protease and regulating the spatial structural characteristics of RBP.

Comparative study of dietary phenols with Tartary buckwheat protein (2S/13S): impact on structure, binding sites and functionality of protein

BACKGROUND

This research was to investigate the interaction mechanism between 2S albumin and 13S globulin (2S and 13S, the most important storage proteins in Tartary buckwheat seeds) and three phenols (rutin, quercetin and myricetin) regarding the structural and antioxidant properties of their complexes.

RESULTS

There are differences in the binding affinity of phenols for 2S and 13S. Rutin had a higher binding affinity for 2S, myricetin had a higher binding affinity for 13S, and 13S exhibited a higher affinity toward phenols than did 2S. Binding with phenols significantly changed the secondary and tertiary structures of 2S and 13S, decreased the surface hydrophobic value and enhanced the antioxidant capacity. Molecular docking and isothermal titration calorimetry showed that the binding processes were spontaneous and that there were hydrogen bonds, hydrophobic bonds and van der Waals force interactions between phenols and proteins.

CONCLUSION

These findings could provide meaningful guidance for the further application of buckwheat protein complex. © 2023 Society of Chemical Industry.

Study on the interaction and functional properties of Dolichos lablab L. protein-tea polyphenols complexes

Tea polyphenols (TP) and plant proteins are significant materials in the food industry, the interactions between them are beneficial for their stability, functional properties, and biological activity. In this study, the mechanism and interaction between Dolichos lablab L. protein (DLP) obtained from nine treatments and three tea polyphenol monomers (EGCG, ECG, and EGC) were investigated. The results showed that the fluorescence of DLP was noticeably quenched and exhibited static quenching after the addition of polyphenols. DLP exhibited 1-2 binding sites for EGCG and ECG, but weakly binding to EGC (<1). The binding sites of DLP-TP were found to be in close proximity to the tyrosine residues, primarily interacting through hydrophobic interactions, van der Waals forces, and hydrogen bonds. The antioxidant capacity of DLP-TP compound was significantly improved after digestion. ECG showed a strong resistance to intestinal digestion. Compared with ECG (653.456 μg/mL), the content of free tea polyphenols of 20/40 kHz-ECG after digestion was 732.42 μg/mL. DLP-TP complexes significantly improved the storage stability, thermal stability, and bioaccessibility of tea polyphenols. The interaction between TP and DLP, as a protein-polyphenol complex, has great potential for application in preparing emulsion delivery systems due to their antioxidant activity and improved stability.

Preparation, Characterization and Antioxidant Activity of Glycosylated Whey Protein Isolate/Proanthocyanidin Compounds

A glycosylated protein/procyanidin complex was prepared by self-assembly of glycosylated whey protein isolate and proanthocyanidins (PCs). The complex was characterized through endogenous fluorescence spectroscopy, polyacrylamide gel electrophoresis, Fourier infrared spectroscopy, oil-water interfacial tension, and transmission electron microscopy. The results showed that the degree of protein aggregation could be regulated by controlling the added amount of procyanidin, and the main interaction force between glycosylated protein and PCs was hydrogen bonding or hydrophobic interaction. The optimal binding ratio of protein:PCs was 1:1 (w/w), and the solution pH was 6.0. The resulting glycosylated protein/PC compounds had a particle size of about 119 nm. They exhibited excellent antioxidant and free radical-scavenging abilities. Moreover, the thermal denaturation temperature rose to 113.33 °C. Confocal laser scanning microscopy (CLSM) images show that the emulsion maintains a thick interface layer and improves oxidation resistance with the addition of PCs, increasing the application potential in the functional food industry.

Alginate/Pectin Film Containing Extracts Isolated from Cranberry Pomace and Grape Seeds for the Preservation of Herring

Alginate/pectin films supplemented with extracts from cranberry pomace (CE) or grape seeds (GE) were developed and applied to herring fillets that were stored for 18 days at 4 °C. Herring coated with films containing GE and CE inhibited the growth of Listeria monocytogenes and Pseudomonas aeruginosa during the storage period, whereas pure alginate/pectin films did not show an antimicrobial effect against the tested pathogens. The application of alginate/pectin films with CE and GE minimised pH changes and inhibited total volatile basic nitrogen (TVN) and the formation of thiobarbituric acid-reactive substances (TBARS) in the herring fillets. The coating of herring fillets with films with CE or GE resulted in three- and six-fold lower histamine formation and one-and-a-half- and two-fold lower cadaverine formation, respectively, when compared to unwrapped herring samples after 18 days of storage. The incorporation of 5% extracts isolated from cranberry pomace or grape seeds into the alginate/pectin film hindered herring spoilage due to the antimicrobial and antioxidant activity of the extracts.

Physicochemical and functional properties of capsaicin loaded cricket protein isolate and alginate complexes

As people become more aware of the health benefits of foods and their nutritional benefits for preventing diseases and promoting health, the demand for functional foods rich in proteins, fiber, and bioactives like capsaicin (CAP) is constantly rising. This study hypothesized that the electrostatic complexes developed by cricket protein isolate (CPI) and alginate (AL) could be utilized to encapsulate CAP, making it more water-soluble and protecting it at acidic pHs. Quantitative analysis revealed that CAP was efficiently encapsulated into the CPI-AL complexes with a maximum encapsulation efficiency of 91%, improving its aqueous solubility 45-fold. In vitro release tests showed that CAP was retained at acidic pHs (3.0 and 5.0) in CPI-AL complexes but released steadily at neutral pH (7.4), which will protect CAP in the stomach while enabling its release in the small intestine. Moreover, the antioxidant activity of CAP-CPI-AL complexes was superior to that of their individual bare equivalents. The complexes also demonstrated enhanced emulsifying capabilities and stability at acidic pHs (2.0-5.0) as the CPI fraction in the complexes increased. Our findings thus contribute to the growing body of knowledge that validates protein-polysaccharide complexation as a promising strategy for developing edible delivery systems.

Interaction between Chinese quince fruit proanthocyanidins and bovine serum albumin: Antioxidant activity, thermal stability and heterocyclic amine inhibition

Heterocyclic amines (HCAs) are carcinogenic and mutagenic substances produced in fried meat. Adding natural antioxidants (e.g., proanthocyanidins (PAs)) is a common method to reduce HCAs; however, the interaction between the PAs and protein can affect the inhibitory efficacy of PAs on the formation of HCAs. In this study, two PAs (F1 and F2) with different degrees of polymerization (DP) were extracted from Chinese quince fruits. These were combined with bovine serum albumin (BSA). The thermal stability, antioxidant capacity and HCAs inhibition of all four (F1, F2, F1-BSA, F2-BSA) were compared. The results showed that F1 and F2 interact with BSA to form complexes. Circular dichroism spectra indicate that complexes had fewer α-helices and more β-sheets, β-turns and random coils than BSA. Molecular docking studies indicated that hydrogen bonds and hydrophobic interactions are the forces holding the complexes together. The thermal stabilities of F1 and, particularly, F2 were stronger than those of F1-BSA and F2-BSA. Interestingly, F1-BSA and F2-BSA showed increased antioxidant activity with increasing temperature. F1-BSA's and F2-BSA's HCAs inhibition was stronger than F1 and F2, reaching 72.06 % and 76.3 %, respectively, for norharman. This suggests that PAs can be used as natural antioxidants for reducing the HCAs in fried foods.

Characterization of proteases from Irpex lacteus grown on minimally denatured soybean meal

BACKGROUND

Acid and thermal stabilities are important properties for the preparation of acidic protein beverage. It is an important method for enzymatic modification to improve the functional properties of protein. Irpex lacteus protease showed a selective hydrolysis to soy proteins. The purpose of this study was to investigate the mechanism of enzymatic hydrolysis and its effects on acid and thermal stabilities of soy proteins.

RESULTS

The I. lacteus protease selectively hydrolyzed the α and α' subunits of the native soybean β-conglycinin (7S globulin) to produce products that presented as the 55 kDa band upon sodium dodecyl sulfate polyacrylamide gel electrophoresis. The amino acid sequences of 55 kDa polypeptides were analyzed in gel multi-enzyme digestion followed by liquid chromatography-mass spectrometry. By matching the multi-enzyme digestion peptides with the published polypeptide chain sequences of the α and α' subunits, it was confirmed that the 55 kDa polypeptides were formed by eliminating amino acid residues on both sides of the N- and C-terminals. From the published protein structure database (https://www.uniprot.org/), it is known that the cleaved peptide bonds were in extension regions. Non-selective enzyme hydrolysis of both β-conglycinin (7S globulin) and glycinin (11S globulin), with corresponding drastic increases in the degree of hydrolysis, was observed when the substrates were preheated to the denaturation degree of 40% and above. However, 55 kDa hydrolyzed products and B polypeptides showed some extent of resistance to the proteolysis by I. lacteus protease even if denaturation degree was 100%. Both selective and non-selective hydrolysis of soy proteins by I. lacteus protease improved the acid and heat stabilities under the same hydrolysis conditions (enzyme/substrate ratio, time, and temperature).

CONCLUSION

Enzymatic hydrolysis of soybean proteins by the I. lacteus protease can effectively improve the acid and thermal stabilities of proteins. This discovery is significant to avoid aggregation during processing in the beverage industry. In the near future, the protease has potential application value for modification of other proteins. © 2022 Society of Chemical Industry.

Antioxidant activity, stability, in vitro digestion and cytotoxicity of two dietary polyphenols co-loaded by β-lactoglobulin

The combination of multiple dietary polyphenols may have synergistic beneficial effects. And the beneficial effects can be further improved by the encapsulation of proteins. The interactions of procyanidin B2 (PB2) and/or dihydromyricetin (DMY) with β-lactoglobulin (β-LG) were investigated using multi-spectroscopic techniques and molecular docking. The structural change of β-LG in the presence of PB2 and/or DMY was demonstrated by dynamic light scattering, Fourier transform infrared spectroscopy and circular dichroism spectroscopy. Response surface analysis was used to optimize the synergistic antioxidant activity between PB2 and DMY. Besides, the antioxidant activity, stability, in vitro digestion and cytotoxicity of PB2 and DMY in the binary and ternary systems were investigated. These studies will elucidate the interaction mechanism of PB2 and/or DMY with β-LG. The research results can provide theoretical support for the development of functional foods and beverages with synergistic activity, improved stability and bioaccessibility, thereby promoting human health and preventing diseases.

Microencapsulated procyanidins by extruding starch improved physicochemical properties, inhibited the protein and lipid oxidant of chicken sausages

Microencapsulated procyanidins by extruding starch (MPS) were used in meat and meat products as an antioxidant for their simple production process and high stability. This study investigated the controlled released properties of MPS and their effect on antioxidant capacity, physicochemical properties, and sensory qualities of chicken sausages during 4°C storage within 28 days. Antioxidant capacity, particle size analysis, and simulated digestion in vitro demonstrated that microencapsulation by extruding starch delayed the procyanidins release. The reduced crystal structure of MPS was determined by the morphology observation (SEM) and the decrease of the typical diffraction peak at 2θ of 20.9° (XRD). The MPS-added sausage had a higher (p < 0.05) ABTS and DPPH radical scavenging ratio (97.6% and 67.3%) and sulfhydryl contents (114.69 nmol/g protein) than other groups. Moreover, lower (p < 0.05) thiobarbituric acid reactive substances (TBARS) (0.67 mg MDA/kg sausage) and carbonyl values (3.24 nmol/mg protein) were detected in MPS-added sausages than others at the end of storage. The MPS addition increased redness (a* value) and decreased the lightness (L* value). The sensory analysis suggested that the sausage with the increased redness was favorable. These results denominated that MPS was an alternative antioxidant in chicken sausages. Practical Application: In this study, microencapsulated procyanidins were prepared by extrusion technology, and the effect on the quality of chicken sausages was investigated, which provides an alternative natural antioxidant for meat and meat products.

In vitro gastric bioaccessibility of avocado peel extract in beef and soy-based burgers and its impact on Helicobacter pylori risk factors

The objective of the present study was to investigate the impact of phenolic-rich avocado peel extract (APE) as an ingredient in beef and soy-based burgers to increase their antioxidant activity, reduce lipid and protein oxidation during gastric digestion, and inhibit urease and anhydrase carbonic activity, which are considered as key factors in the main steps of Helicobacter pylori adhesion in the stomach. The gastric bioaccessible fraction of soy and beef burgers with added 0.5% APE obtained by in vitro digestion exhibited a higher content of phenolic compounds, including monomeric and oligomeric (epi)catechin forms and quercetin, and reduced levels of thiobarbituric acid-reactive substances (TBARS) and carbonyls (49% to 73% and 57% to 60%, respectively) when compared with control burgers. Moreover, the burgers with APE inhibited urease and carbonic anhydrase activity. Results generally showed that including APE reduces the primary risk factors associated with H. pylori infection.