Molecular structural modification of duck egg white protein conjugates with monosaccharides for improving emulsifying capacity

Impact of NaCl perturbation on physicochemical and structural properties of preheat-treated egg white protein modulating foaming property

This study aimed to investigate the mechanism of NaCl perturbed preheat-treated egg white proteins' (EWPs) physicochemical and structural properties to modulate the foaming property (FP). The results revealed that NaCl regulated the salinolysis (5 mM) - salt precipitation (50 mM) - gradual or complete coverage with hydrated Na+ of the hydration layer (100-300 mM) - enhanced Cl- hydration repulsion (500 mM) of EWP, showing a gradual decrease in aggregates particle size, and reversibility of structural freedom, including moleculer flexibility and surface hydrophobicity. Whereas preheating temperature affected the secondary structure rearrangement and tertiary conformation exposure, and excessive temperature reduced foaming capacity while enhanced foam stability, with a tight correlation between NaCl-mediated EWPs' FP and the extent of Na+ covering the hydration layer. The findings provide a theoretical basis for processing factors to modulate the protein hydration layer to influence the functional properties.

Glycosylated gelatin prepared based on electron beam irradiation and its physicochemical properties

The influence of electron beam irradiation (EBI) treatment on the modification of gelatin-galactose glycosylation was thoroughly examined. The results of the degree of grafting and browning revealed that EBI triggered the glycosylation reaction of gelatin. The degree of glycosylation exhibited a gradual increase with the rising irradiation dose, reaching a maximum of 25 kGy. Moreover, the irradiation process opened up gelatin's internal structure, exposing its hydrophobic groups. This exposure led to an enhancement in sample surface hydrophobicity. The fluorescence intensity at the maximum emission wavelength of the fluorescence spectra decreased; Fourier infrared spectroscopy demonstrated a new absorption peak at 1074 cm-1 for the glycosylation product. These findings substantiate that gelatin formed a new product through covalent bonding with galactose. Glycosylation boosted the emulsification stability of gelatin from 1.92 min to 10.42 min and improved its emulsification and rheological properties. These outcomes affirm that EBI can effectively induce the glycosylation reaction of gelatin, thereby enhancing its functional properties. In addition, EBI has the potential to supplant the conventional heating glycosylation method. This study lays a solid theoretical foundation for the future application of glycosylation and gelatin.

Structural modifications and augmented affinity for bile salts in enzymatically denatured egg white

Protein binding to bile salts (BSs) reduces cholesterol levels, but the exact mechanism is unclear. In this study, we performed simulated gastrointestinal digestion of egg white protein hydrolysate (EWPHs) and included an unenzyme digestion group (CK) to investigate the changes in BSs binding capacity before and after digestion, as well as the relationship between egg white protein (EWP) structure and BSs binding capacity. In addition, peptidomics and molecular docking were used to clarify EWP's binding mechanism. We found that the BSs binding ability of EWPHs was slightly decreased after digestion, but significantly higher than that of the CK group and the digested CK group (D-CK). Particle size analysis and electrophoresis demonstrated that smaller particles and lower molecular weights exhibited enhanced binding capacity to BSs. Fourier Transform infrared spectroscopy (FTIR) results revealed that a disordered structure favored BS binding ability enhancement. Peptides FVLPM and GGGVW displayed hypocholesterolemic efficacy.

Cyclic Continuous Glycation Enhanced Dispersibility of Myofibrillar Protein: Reaction Efficiency and Sites Modification

Reaction efficiency in glycation lacks sufficient attention, leading to the waste of process costs. Cyclic continuous glycation (CCG) is an effective approach to accelerate covalent binding between myofibrillar protein (MP) and glucose. This study elucidated that CCG promoted the exposure of reactive glycated sites in MP with full unfolding of secondary and tertiary structures. Notably, the glycation rate was significantly increased by 65.43%. Physicochemical properties indicated that MP-glucose conjugates with high graft degree exhibited favorable solubility, dispersibility, and thermal stability. Furthermore, proteomics was applied to reveal the glycated sites and products in glycoconjugates of MP. Glycation preferentially acted on the tails of the myosin heavy chain. The glucosylation modification on the head region was enhanced by CCG contributing to the inhibition of the head-head interaction. Overall, this study systematically clarifies the mechanism of CCG, providing a theoretical basis for the application of glycation in innovative meat products.

Emulsifying properties of egg proteins: Influencing factors, modification techniques, and applications

As an essential food ingredient with good nutritional and functional properties and health benefits, eggs are widely utilized in food formulations. In particular, egg proteins have good emulsification properties and can be commonly used in various food products, such as mayonnaise and baked goods. Egg protein particles can act as stabilizers for Pickering emulsions because they can effectively adsorb at the oil-water interface, reduce interfacial tension, and form a stable physical barrier. Due to their emulsifying properties, biocompatibility, controlled release capabilities, and ability to protect bioactive substances, egg proteins have become ideal carriers for encapsulating and delivering functional substances. The focus of this review is to summarize current advances in using egg proteins as emulsifiers. The effects of influencing factors (temperature, pH, and ionic strength) and various modification methods (physical, chemical, and biological modification) on the emulsifying properties of egg proteins are discussed. In addition, the application of egg proteins as emulsifiers in food products is presented. Through in-depth research on the emulsifying properties of egg proteins, the optimization of their applications in food, biomedical, and other fields can be achieved.

Effect of glycosylation modification on structure and properties of soy protein isolate: A review

Soybean protein isolate (SPI) is a highly functional protein source used in various food applications, such as emulsion, gelatin, and food packaging. However, its commercial application may be limited due to its poor mechanical properties, barrier properties, and high water sensitivity. Studies have shown that modifying SPI through glycosylation can enhance its functional properties and biological activities, resulting in better application performance. This paper reviews the recent studies on glycosylation modification of SPI, including its quantification method, structural improvements, and enhancement of its functional properties, such as solubility, gelation, emulsifying, and foaming. The review also discusses how glycosylation affects the bioactivity of SPI, such as its antioxidant and antibacterial activity. This review aims to provide a reference for further research on glycosylation modification and lay a foundation for applying SPI in various fields.

Reduction in the antigenicity of beta-lactoglobulin in whole milk powder via supercritical CO2 treatment

Cow milk allergy is a common phenomenon experienced in early childhood (<5 yr of age) with an average occurrence rate of roughly 2.5%. The most prevalent allergen in cow milk is believed to be β-LG. The objective of this study was to evaluate the use of hydrophobic supercritical CO2 (ScCO2) to modify the chemical structure β-LG, thus impairing its recognition by antibodies. Whole milk powder (WMP) was selected because of its closest compositional resemblance to bovine fluid milk and its applications in reconstitution and in the beverage (infant, toddler, and adult), confectionary, bakery, and meat industries. For this study, WMP was treated with food-grade CO2 at temperatures of 50, 63, and 75°C under operating pressures of 100, 150, 200, 250, and 300 bar. Proteins in WMP were examined using SDS-PAGE, western blot, and ELISA. Orbitrap Fusion liquid chromatography-tandem MS (LC-MS/MS) and periodic staining was performed to confirm post-translational modifications in β-LG. Functional properties of WMP before and after treatment were assessed by its solubility index, oil holding capacity, emulsion capacity and stability, zeta potential, particle size, and color analysis. SDS-PAGE of treated samples yielded fuzzy bands (variable mobility of molecules due to different molecular weights results in ill-defined bands) indicative of an increase in molecular weight, presumably due to chemical change in the protein, and demonstrated a maximum of 71.13 ± 0.29% decrease in the band intensity of β-LG under treatment conditions of 75°C/300 bar for 30 min. These changes were small with samples treated with heat only. Lighter, diffused bands were observed using western blot analysis. The ELISA tests proved that ScCO2 treatment specifically and significantly affected the antigenicity of β-LG with a reduction of 42.9 ± 2.83% and 54.75 ± 2.43% at 63°C/200 bar and 75°C/300 bar, respectively. Orbitrap fusion detected the presence of fatty acids and sugar moieties bound to β-LG and the latter was confirmed by periodic staining. Functional properties of ScCO2-treated milk powder yielded a decrease in solubility index and an increase in emulsion capacity of WMP was observed under ScCO2 treatment at 75°C/300 bar, with small and insignificant changes at other treatments producing a decrease in antigenicity. Color changes were small for most samples, except at 63°C/200 bar, where a significant increase in yellowness was observed. Zeta potential and particle size measurements indicated that most changes were temperature driven. This study demonstrates 2 approaches to mitigate β-LG antigenicity via fatty acid binding and lactosylation using hydrophobic ScCO2.

Characterization of aroma characteristics of silver carp mince glycated with different reducing sugars

The purpose of this study was to investigate the volatile flavor changes in silver carp mince (SCM) gel glycated with different reducing sugars (glucose, L-arabinose, and xylose) based on E-nose, GC-IMS, and sensory evaluation. These results showed that glycation reduced the fishy smell of SCM gel and increased the meaty, toasty, and burnt smell. A total of 10 volatile compounds were considered as characteristic flavor compounds and potential markers. Among them, the main contributors of fishy included hexanal, heptanal, n-nonanal, octanal, etc. Toasty and burnt were mainly related to the production of 3-methylbutanal and furfurol. These results heralded that glycation could be used to improve the volatile flavor of SCM. This research provided a theoretical basis and technical support for glycation in aquatic food flavor quality control, aquatic pre-made food development, and aquatic leisure food processing.

Polysaccharide- and protein-based edible films combined with microwave technology for meat preservation

To reduce food-borne bacterial infection caused by food spoilage, developing highly efficient food packing film is still an urgent need for food preservation. Herein, microwave-assisted antibacterial nanocomposite films CaO2@PVP/EA/CMC-Na (CP/EC) were synthesized using waste eggshell as precursor, egg albumen (EA) and sodium carboxymethylcellulose (CMCNa) as matrix by casting method. The size of CaO2@PVP (CP) nanoparticles with monodisperse spherical structures was 100-240 nm. When microwave and CP nanoparticles (0.05 mg/mL) were treated for 5 min, the mortality of E. coli and S. aureus could reach >97 %. Under microwave irradiation (6 min), the bactericidal rate of 2.5 % CP/EC film against E. coli and S. aureus reached 98.6 % and 97.2 %, respectively. After adding CP nanoparticles, the highest tensile strength (TS) and elongation at break (EB) of CP/EC film reached 19.59 MPa and 583.43 %, respectively. At 18 °C, the proliferation of bacterial colonies on meat can be significantly inhibited by 2.5 % CP/EC film. Detailed characterization showed that the excellent meat preservation activity was due to the synergistic effect of dynamic effect generated by ROS and thermal effect of microwave. This study provides a promising approach for the packaging application of polysaccharide- and protein-based biomass nanocomposite antibacterial edible films.

Allergenicity Modulation of Casein with the Modifications of Linearization, Cross-Linking, and Glycation via the Regulation of Th1/Th2 Homeostasis

Casein (CN) is the primary allergenic protein in cow's milk, contributing to the worldwide escalating prevalence of food allergies. However, there remains limited knowledge regarding the effect of structural modifications on CN allergenicity. Herein, we prepared three modified CNs (mCN), including sodium dodecyl sulfate and dithiothreitol-induced linear CN (LCN), transglutaminase-cross-linked CN (TCN), and glucose-glycated CN (GCN). The electrophoresis results indicated widespread protein aggregation among mCN, causing variations in their molecular weights. The unique internal and external structural characteristics of mCN were substantiated by disparities in surface microstructure, alterations in the secondary structure, variations in free amino acid contents, and modifications in functional molecular groups. Despite the lower digestibility of TCN and GCN compared to LCN, they significantly suppressed IL-8 production in Caco-2 cells without significantly promoting their proliferation. Moreover, GCN showed the weakest capacity to induce LAD2 cell degranulation. Despite the therapeutic effect of TCN, GCN-treated mice displayed the most prominent attenuation of allergic reactions and a remarkably restored Th1/Th2 imbalance, while LCN administration resulted in severe allergic phenotypes and endotypes in both cellular and murine models. This study highlighted the detrimental effect of linear modifications and underscored the significance of glycation in relation to CN allergenicity.

Soybean isolate protein complexes with different concentrations of inulin by ultrasound treatment: Structural and functional properties

The effects of ultrasound and different inulin (INU) concentrations (0, 10, 20, 30, and 40 mg/mL) on the structural and functional properties of soybean isolate protein (SPI)-INU complexes were hereby investigated. Fourier transform infrared spectroscopy showed that SPI was bound to INU via hydrogen bonding. All samples showed a decreasing and then increasing trend of α-helix content with increasing INU concentration. SPI-INU complexes by ultrasound with an INU concentration of 20 mg/mL (U-2) had the lowest content of α-helix, the highest content of random coils and the greatest flexibility, indicating the proteins were most tightly bound to INU in U-2. Both UV spectroscopy and intrinsic fluorescence spectroscopy indicated that it was hydrophobic interactions between INU and SPI. The addition of INU prevented the exposure of tryptophan and tyrosine residues to form a more compact tertiary structure compared to SPI alone, and ultrasound caused further unfolding of the structure of SPI. This indicated that the combined effect of ultrasound and INU concentration significantly altered the tertiary structure of SPI. SDS-PAGE and Native-PAGE displayed the formation of complexes through non-covalent interactions between SPI and INU. The ζ-potential and particle size of U-2 were minimized to as low as -34.94 mV and 110 nm, respectively. Additionally, the flexibility, free sulfhydryl groups, solubility, emulsifying and foaming properties of the samples were improved, with the best results for U-2, respectively 0.25, 3.51 μmoL/g, 55.51 %, 269.91 %, 25.90 %, 137.66 % and 136.33 %. Overall, this work provides a theoretical basis for improving the functional properties of plant proteins.

Impact of cod skin peptide-ι-carrageenan conjugates prepared via the Maillard reaction on the physical and oxidative stability of Antarctic krill oil emulsions

This research aimed to construct an emulsifier by the Maillard reaction at various times using cod fish skin collagen peptide (CSCP) and ι-carrageenan (ι-car) to stabilize an Antarctic krill oil (AKO) emulsion. This emulsion was then investigated for physicochemical stability, oxidative stability, and gastrointestinal digestibility. The emulsion stability index and emulsifying activity index of Maillard reaction products (MRPs) were increased by 36.32 % and 66.30 %, respectively, at the appropriate graft degree (25.58 %) compared with the mixture of ι-car and CSCP. In vitro digestibility suggested the higher release of free fatty acids (FFAs) of 10d-MRPs-AKO-emulsion, and the highest bioavailability of AST in 10d-MRPs-AKO was found to be 28.48 %. The findings of this study showed the potential of MRPs to improve peptide function, serve as delivery vehicles for bioactive chemicals, and possibly serve as a valuable emulsifier to be used in the food industry.

Conjugation of Soybean Proteins 7S/11S Isolate with Glucose/Fructose in Gels through Wet-Heating Maillard Reaction

Conjugation with glucose (G) and fructose (F) via the Maillard reaction under the wet-heating condition is a natural and non-toxic method of improving the technological functions of 7S/11S proteins in different kinds of gels. It may be used as an affordable supply of emulsifiers and an excellent encapsulating matrix for gels. This study aimed to create a glucose/fructose-conjugated 7S/11S soy protein via the Maillard reaction. The conjugation was confirmed by determining the SDS-PAGE profile and circular dichroism spectra. In addition, these conjugates were comprehensively characterized in terms of grafting degree, browning degree, sulfhydryl content, surface hydrophobicity (H0), and differential scanning calorimetry (DSC) through various reaction times (0, 24, 48, and 72 h) to evaluate their ability to be used in food gels. The functional characteristics of the 7S/11S isolate-G/F conjugate formed at 70 °C, with a high degree of glycosylation and browning, were superior to those obtained at other reaction times. The SDS-PAGE profile indicated that the conjugation between the 7S and 11S proteins and carbohydrate sources of G and F through the Maillard reaction occurred. Secondary structural results revealed that covalent interactions with G and F affected the secondary structural components of 7S/11S proteins, leading to increased random coils. When exposed to moist heating conditions, G and F have significant potential for protein alteration through the Maillard reaction. The results of this study may provide new insights into protein modification and establish the theoretical basis for the therapeutic application of both G and F conjugation with soy proteins in different food matrixes and gels.

Effects of glycation method on the emulsifying performance and interfacial behavior of coconut globulins-fucoidan complexes

Coconut globulins (CG) possesses potential as an emulsifier but has not been utilized well. In this study, the emulsifying performance of glycated CG-fucoidan (CGF) complexes, and the relationship between emulsifying stability and interfacial behavior were investigated. The results showed that the grafting of fucoidan increased the molecular weight of CG, and decreased the zeta potential and fluorescence intensity. With the higher glycosylation degree, the fucoidan modified CG exhibited better emulsifying stability and higher viscosity. Moreover, the result of adsorption kinetics revealed that elasticity was the main property of the interface layer. Compared to CG, CGF complexes with high degree of glycosylation had thicker interfacial layer on the oil-water interface. A thicker elastic interfacial layer may be beneficial to the emulsion stability, owing to the strong interaction of electrostatic repulsion and steric hindrance between oil droplets. These findings may provide useful information for glycated CGF complexes as emulsifiers in functional food.

High-temperature glycosylation of saccharides to modify molecular conformation of egg white protein and its effect on the stability of high internal phase emulsions

This paper investigates the freeze-thaw stability of oil-in-water emulsions stabilized by high-temperature wet heating glycosylation products. Glucose (Glu), D-fructose (Fru), xylose (Xyl), maltodextrin (MD), oligofructose (FO), and oligomeric isomaltulose (IMO) were chosen as sugar sources for the glycosylation reaction with egg white proteins (EWPs) at 120 °C to prepare the GEWPs. The study reveals that the type of sugar significantly influences the Maillard reactions with EWPs. The degree of glycosylation was highest in the Xyl group with the greatest reducing capacity and lowest in the MD, FO, and IMO groups. High-temperature wet glycosylation treatment induced changes in the secondary and tertiary structures of EWP. Elevated temperature exposed hydrophobic groups within the protein, while covalent binding of hydrophilic carbohydrates via the Maillard reaction decreased the protein's H0 value. Improved foaming and emulsifying properties were attributed to the increase in α-helix content, disulfide bond formation, and reduced surface tension. Emulsions prepared from GEWPs exhibited higher apparent viscosity and G' compared to those from natural EWPs, with the GEWP/Xyl group showing the highest values. After freeze-thaw treatment, the GEWP/Fru and GEWP/FO groups demonstrated superior stability and reduced freezing point, along with minimal microstructural alterations. These findings underscore the importance of sugar type in the stability of high internal phase emulsions (HIPEs) stabilized by GEWPs, indicating that a tailored Maillard reaction can yield stabilizers with exceptional freeze-thaw stability for emulsions.

Modified Structural and Functional Properties of Fish Gelatin by Glycosylation with Galacto-Oligosaccharides

This study aimed to investigate the effects of galacto-oligogalactose (GOS) glycosylation on the structural and functional properties of fish gelatin (FG). Results showed that with the increase of glycosylation time, grafting degree and browning increased, and new protein bands with increased molecular weight were observed by SDS-PAGE. Structural analysis showed that glycosylation reduced intrinsic fluorescence intensity and increased surface hydrophobicity of FG. FTIR analysis showed α-helix content decreased while random coil content increased in glycosylated FG. Emulsion activity index and emulsion stability index along with foam activity and foam stability were significantly elevated in GOS-4 and GOS-8, but FG glycosylated longer than 12 h exhibited less pronounced improvement. Glycosylated FG showed lower gel strength than control. The results indicate that moderate glycosylation could be applied to improve interfacial properties of FG.

Ultrasound-assisted free radical modification on the structural and functional properties of ovalbumin-epigallocatechin gallate (EGCG) conjugates

The influence of ultrasound-assisted free radical modification on the structure and functional properties of ovalbumin-epigallocatechin gallate (OVA-EGCG) conjugates was investigated by experimental measurements and computer simulations. Compared with the traditional free radical condition, the ultrasonic-assisted processing significantly increased the conjugating efficiency of OVA and EGCG and shortened the conjugating from 24 h to 1 h without affecting the equivalent amount of EGCG conjugating. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis and multi-spectroscopy analysis (Fourier transform infrared spectroscopy, intrinsic fluorescence spectroscopy, and UV spectroscopy) indicated that the covalent conjugates could be formed between OVA and EGCG. And modification in the conformation of OVA was induced by EGCG. Furthermore, molecular docking results demonstrated the possession of high-affinity EGCG binding location on OVA, supporting and clarifying the experimental results. In addition, the functional properties of OVA including emulsification (emulsifying activity and emulsion stability) and antioxidant properties (DPPH scavenging capacity and ABTS scavenging capacity) were significantly improved after conjugation with EGCG, especially in ultrasound-assisted conditions. Overall, OVA-EGCG conjugates produced by ultrasound-assisted free radical treatment could be applied as a potential emulsifier and antioxidant, thereby expanding the application of OVA as a dual-functional ingredient.

W/O/W emulsions stabilized with whey protein concentrate and pectin: Effects on storage, pasteurization, and gastrointestinal viability of Lacticaseibacillus rhamnosus

Probiotics have demonstrated various bioactive functions but poor storage and application stability, and encapsulation a promising method of increasing its viability. In this study, whey protein concentrate (WPC) and pectin (PEC) formed non-covalent complexes through electrostatic interaction at pH 3.0. The formed WPC-PEC complexes showed superior particle size, absolute potential, emulsification properties, and structural changes when PEC concentration was >0.8 % (w/v). This made them appropriate as a hydrophilic emulsifier to stabilize W/O/W emulsions. Then, Lacticaseibacillus rhamnosus, one representative of probiotics, was encapsulated in the internal aqueous phase of W/O/W emulsions. We obtained higher encapsulation efficiency (78.49 %) and smaller D_4,3 (9.72 μm) with 0.8 % (w/v) PEC concentration. Encapsulation of Lacticaseibacillus rhamnosus in W/O/W emulsions improved its viability under harsh conditions, including 28 days storage at 4 °C, simulated pasteurization, and simulated gastrointestinal digestion. W/O/W emulsions stabilized by WPC-PEC non-covalent complexes further improved the survival of Lacticaseibacillus rhamnosus against various adverse conditions as compared to WPC. These findings suggest that the studied W/O/W emulsions systems have the potential to deliver probiotics in food substrates to enhance their viability during production processing, storage transportation, and digestion.

Enhancing the foaming properties of brewer's spent grain protein by ultrasound treatment and glycation reaction

The denaturation state and relatively poor solubility of brewer's spent grain protein (BSGP) have limited its industrial application. Ultrasound treatment and glycation reaction were applied to improve the structural and foaming properties of BSGP. The results showed that all ultrasound, glycation, and ultrasound-assisted glycation treatments increased the solubility and surface hydrophobicity of BSGP while decreasing its zeta potential, surface tension and particle size. Meanwhile, all these treatments resulted in a more disordered and flexible conformation of BSGP, as observed by CD spectroscopy and SEM. After grafting, the result of FTIR spectroscopy confirmed the covalent binding of -OH between maltose and BSGP. Ultrasound-assisted glycation treatment further improved the free SH and S-S content, which might be due to -OH oxidation, indicating that ultrasound promoted the glycation reaction. Furthermore, all these treatments significantly increased the foaming capacity (FC) and foam stability (FS) of BSGP. Notably, BSGP treated with ultrasound showed the best foaming properties, increasing the FC from 82.22% to 165.10% and the FS from 10.60% to 131.20%, respectively. In particular, the foam collapse rate of BSGP treated with ultrasound-assisted glycation was lower than that of ultrasound or traditional wet-heating glycation treatment. The enhanced hydrogen bonding ability and hydrophobic interaction between protein molecules caused by ultrasound and glycation might be responsible for the improved foaming properties of BSGP. Thus, ultrasound and glycation reactions were efficient methods for producing BSGP-maltose conjugates with superior foaming properties.

Understanding interactions among flavor compounds from spices and myofibrillar proteins by multi-spectroscopy and molecular docking simulation

Influence of the constant heating treatment on structural and adsorption properties of myofibrillar proteins (MPs) of chicken was investigated. The results showed that heat treatment enhanced the exposure of sulfhydryl groups and improved hydrophobicity of MPs surface. Particle size distribution of MPs significantly varied depending on heat treatment duration. Also, heat treatments resulted in significant changes in the α-helix and β-sheet structures of MPs. Besides, the MPs formed larger, irregular, and cluster-like aggregates after heat treatments. Moreover, heat treatments increased viscosity and surface roughness of MPs, while zeta potential value was reduced after heat treatments. Furhthermore, binding interactions between the MPs and spices flavors signifcanlty varied relying on nature of MPs and flavor compounds, as well as heat treatments duration. Amino acid residues were interacted with flavor compounds of spices via a variety of bonds and a stable MPs-flavors complex was performed. The obtained results provide a basis for understanding structural and physicochemical changes that occur in MPs during cooking and the interactions between MPs and flavors of spices.

Changes in partial properties of glycosylated egg white powder during storage

BACKGROUND

Glycosylation is an effective method to modify protein. However, there is a lack of research on the property changes of glycosylated protein during storage. In the present study, the changes in the physicochemical, functional, and structural properties of xylo-oligosaccharide (XOS) glycosylated egg white powder (EWP) (XOS-EWP conjugates) prepared with different glycosylation conditions (XOS/EWP ratio and reaction time) were investigated when stored at 25 °C and 60% relative humidity.

RESULTS

In the 12 weeks of storage, the degree of grafting, browning, and the formation of Maillard reaction products of XOS-EWP conjugates increased. The increase in XOS/EWP ratio and reaction time led to an increase in protein aggregation, though a decrease in solubility, due to increased degree of glycosylation and structural changes. Furthermore, improved gel hardness of XOS-EWP conjugates deteriorated, while improved emulsification ability was kept stable during storage. For the sample with a lower XOS/EWP ratio and reaction time, the gel hardness and emulsifying properties underwent little or no deterioration even improving during storage. The results could be attributed to the limited degree of glycosylation, further unfolding of the protein structure, increased surface hydrophobicity of protein, and improved thermal characteristics.

CONCLUSION

During storage, the Maillard reaction would continue to occur in the glycosylated EWP, further affecting the performance of modified EWP. Modified EWP prepared under different glycosylation conditions performed differently during storage. Modified EWP with a larger XOS/EWP ratio and reaction time meant it was harder to maintain good performance. Modified EWP with a smaller XOS/EWP ratio and reaction time changed significantly to better performances. © 2022 Society of Chemical Industry.

Relationship between flexibility and interfacial functional properties of soy protein isolate: succinylation modification

BACKGROUND

In this paper, the effects of different succinic anhydride (SA) additions on the flexibility of soy protein isolate (SPI) were investigated, and changes in protein conformation and interfacial functional properties were measured. The structure-effect relationship between conformation, flexibility, and interfacial functional properties was established.

RESULTS

SPI was bound to SA through disulfide bonds, and the zeta potential was reduced. The β-sheet content decreased, the disordered structure increased, and there were changes in tertiary structure and microstructure. The surface hydrophobicity, disulfide bond content, and solution turbidity were reduced to 5063, 1.0967 μmol g-1 , and 0.0036 μmol g-1 respectively. The best flexibility of SPI (0.3977) and interfacial functional properties were obtained when the mass ratio of SA/SPI was 15%. Correlation analysis showed a highly significant positive correlation (P < 0.01) between flexibility and emulsification and foaming properties, with correlation coefficients of 0.960 and 0.942 for flexibility with emulsifying activity and emulsion stability respectively, and 0.972 and 0.929 for flexibility with foaming capacity and foaming stability respectively.

CONCLUSION

The results suggest that succinylation-induced conformational changes of SPI improved its interfacial functional properties by changing its flexibility. These results provide theoretical guidelines for the development and application of highly emulsifiable and stable soy protein products utilizing succinylation. © 2022 Society of Chemical Industry.

Molecular structural modification of β-conglycinin using pH-shifting with ultrasound to improve emulsifying properties and stability

This present work underlines the effect of pH-shifting at pH 2 and pH 12 individually or combined with ultrasound treatment to modify the molecular structure of β-conglycinin (7S) on its emulsifying properties and stability. Fourier transform infrared (FTIR) spectroscopy and intrinsic fluorescence spectroscopy showed that pH-shifting improves the molecular structure of 7S, while ultrasound further promotes structural changes. In particular, the pH-shifting at pH 12 combined with ultrasound treatment (U-7S-12) resulted in more significant changes than the pH-shifting at pH 2 combined with ultrasound (U-7S-2). U-7S-12 showed a significant reduction in protein particle size from 152 to 34.77 nm and a relatively smooth protein surface compared to 7S. The protein had the highest surface hydrophobicity and flexibility at 81,560.0 and 0.45, respectively, and the free sulfhydryl content from 1.57 to 2.02 μmol/g. In addition, we characterized the emulsions prepared after 7S treatment. The single or combined treatment increased the interfacial protein adsorption of the samples, which showed lower viscosity and shear stress compared to 7S. The U-7S-12 emulsion exhibited the highest emulsifying properties and was more stable than other emulsions under creaming, heating, and freeze-thaw conditions. In summary, the concerted action of pH-shifting and ultrasound can modify the structure, and combined alkaline pH-shifting and ultrasound treatment can further improve the emulsifying properties and stability of 7S.

Preparation and characterization of W1 /O/W2 emulsions stabilized by glycated and heat-modified egg white proteins

BACKGROUND

Water-in-oil-in-water (W₁ /O/W₂ ) emulsions stabilized by protein-carbohydrate complexes were prepared from an inner water phase (W₁ ), an oil phase (O) and an outer water phase (W₂ ). The complexes consisted of heat-induced aggregates (HIAs) of isomalto-oligosaccharide/egg white protein Maillard conjugates. The effects of polyglycerol ester of polyricinoleic acid (PGPR) concentration, HIA concentration, W₁ -to-O volume ratio and W₁ /O-to-W₂ volume ratio on the properties of the W₁ /O/W₂ emulsions were systematically investigated.

RESULTS

At sufficiently high PGPR concentrations (>2%), the emulsions possess a high negative charge (≈-44 mV). The encapsulation efficiency of the emulsions, which was determined by incorporating a hydrophilic yellow dye in the inner water phase prior to homogenization, was relatively high (up to 93%) and did not change significantly during 14-day storage at 4 °C. All emulsions were fluids that exhibited shear thinning behavior.

CONCLUSION

Overall, this study shows that nature-derived emulsifiers can be used to create W₁ /O/W₂ emulsions suitable for application in the food industry. In addition, we provided a viable strategy to encapsulate water-soluble nutrients. © 2022 Society of Chemical Industry.

Effects of Glucose and Homogenization Treatment on the Quality of Liquid Whole Eggs

To investigate the effect of glucose on the protein structure, physicochemical and processing properties of liquid whole eggs (LWE) under homogenization, different concentrations of glucose (0.01, 0.02, 0.04, 0.08 g/mL) were added into LWE, followed by homogenizing at different pressures (5, 10, 20, 40 MPa), respectively. It was shown that the particle size and turbidity of LWE increased with the increase in glucose concentration while decreasing with the increase in homogenization pressure. The protein unfolding was increased at a low concentration of glucose combined with homogenization, indicating a 40.33 ± 5.57% and 165.72 ± 33.57% increase in the fluorescence intensity and surface hydrophobicity under the condition of 0.02 g/mL glucose at 20 MPa, respectively. Moreover, the remarkable increments in foaming capacity, emulsifying capacity, and gel hardness of 47.57 ± 5.1%, 66.79 ± 9.55%, and 52.11 ± 9.83% were recorded under the condition of 0.02 g/mL glucose at 20 MPa, 0.04 g/mL glucose at 20 MPa, and 0.02 g/mL glucose at 40 MPa, respectively. Reasonably, glucose could improve the processing properties of LWE under homogenization, and 0.02 g/mL-0.04 g/mL and 20-40 MPa were the optimal glucose concentration and homogenization pressure. This study could contribute to the production of high-performance and stable quality of LWE.

Effect of carbon numbers and structures of monosaccharides on the glycosylation and emulsion stabilization ability of gelatin

Herein, the effect of saccharide glycosylation by nine monosaccharides on bovine bone gelatin for the stabilization of fish oil-loaded emulsions was explored. The gelatin modification was analyzed and then the emulsifying properties of monosaccharide-modified gelatins were analyzed at pH 9.0 and 3.0. The results demonstrated that glycosylated gelatin structure, droplet stability, creaming stability, and liquid-gel transition time were dependent on monosaccharide carbon numbers, monosaccharide structures, and solution pH. Glycosylation modification of gelatins did not obviously change the emulsion droplet stability at pH 9.0, whereas it increased the emulsion droplet stability at pH 3.0. Glycosylation modification of gelatins did not obviously change the emulsion creaming index values (5.1%-8.4% at pH 9.0 and 25.8%-33.1% at pH 3.0). Three-carbon and four-carbon monosaccharides glycosylation significantly increased emulsion liquid-gel transition times. This work provided useful information to understand the effects of carbon numbers and structures of monosaccharides on the protein modification.

Sources, chemical synthesis, functional improvement and applications of food-derived protein/peptide-saccharide covalent conjugates: a review

Proteins/peptides and saccharides are two kinds of bioactive substances in nature. Recently, increasing attention has been paid in understanding and utilizing covalent interactions between proteins/peptides and saccharides. The products obtained through covalent conjugation of proteins/peptides to saccharides are shown to have enhanced functional attributes, such as better gelling property, thermostability, and water-holding capacity. Additionally, food-derived protein/peptide-saccharide covalent conjugates (PSCCs) also have biological activities, such as antibacterial, antidiabetic, anti-osteoporosis, anti-inflammatory, anti-cancer, immune regulatory, and other activities that are widely used in the functional food industry. Moreover, PSCCs can be used as packaging or delivery materials to improve the bioavailability of bioactive substances, which expands the development of food-derived protein and saccharide resources. Thus, this review was aimed to first summarize the current status of sources, classification structures of natural PSCCs. Second, the methods of chemical synthesis, reaction conditions, characterization and reagent formulations that improve the desired functional characteristics of food-derived PSCCs were introduced. Third, functional properties such as emulsion, edible films/coatings, and delivery of active substance, bio-activities such as antioxidant, anti-osteoporosis, antidiabetic, antimicrobial of food-derived PSCCs were extensively discussed.

The Effect of Batter Characteristics on Protein-Aided Control of Fat Absorption in Deep-Fried Breaded Fish Nuggets

Soy protein (SP), egg white protein (EP), and whey protein (WP) at 6% w/w were individually incorporated into the batter of a wheat starch (WS) and wheat gluten (WG) blend (11:1 w/w ratio). Moisture adsorption isotherms of WS and proteins and the viscosity, rheological behavior, and calorimetric properties of the batters were measured. Batter-breaded fish nuggets (BBFNs) were fried at 170 °C for 40 s followed by 190 °C for 30 s, and pick-up of BBFNs, thermogravimetric properties of crust, and fat absorption were determined. The moisture absorption capacity was the greatest for WS, followed by WG, SP, EP, and WP. The addition of SP significantly increased the viscosity and shear moduli (G″, G') of batter and pick-up of BBFNs, while EP and WP exerted the opposite effect (p < 0.05). SP, EP, and WP raised WS gelatinization and protein denaturation temperatures and crust thermogravimetry temperature, but decreased enthalpy change (ΔH) and oily characteristics of fried BBFNs. These results indicate that hydrophilicity and hydration activity of the added proteins and their interactions with batter matrix starch and gluten reinforced the batter and the thermal stability of crust, thereby inhibiting fat absorption of the BBFNs during deep-fat frying.

Molecular structure modification of ovalbumin through controlled glycosylation with dextran for its emulsibility improvement

Ovalbumin (OVA) is a high nutritious protein, but the poor emulsibility limited its application. The present study glycosylated OVA with dextran (Dex) by controlled wetheating (60-90 °C for 3 h). Temperature was an inductive factor for glycosylation degree (DG and browning intensity), and higher temperature could accelerate the reaction. Variations in molecular structure of OVA were analyzed by SDS-PAGE, FTIR, fluorescence spectroscopy and UV spectroscopy, which verified successes in the generation of glycoconjugate with more flexible structure. Emulsifying activity index (EAI) and emulsion stability index (ESI) for the emulsion of OVA-Dex glycoconjugates were significantly enhanced with the increasing of glycosylation temperature. Moreover, confocal laser scanning results revealed that the emulsion exhibited smaller size and more uniform distribution, and slower transmission profiles were checked by LUMiSizer centrifugal analysis as well, confirming the emulsibility improvement of OVA. Thus, controlled glycosylation reaction is an available method to improve the emulsifying properties of OVA.

Stabilization and operational selectivity alteration of Lipozyme 435 by its coating with polyethyleneimine: Comparison of the biocatalyst performance in the synthesis of xylose fatty esters

Differently modified Lipozyme 435 (L435) (immobilized lipase B from Candida antarctica) preparations were used as biocatalysts in the esterification reaction to synthesize sugar fatty acid esters (SFAEs) from xylose (acyl acceptor) and lauric/palmitic acids (acyl donors) in methyl ethyl ketone (MEK) solvent. The L435 treatment with polyethyleneimine (PEI) (2; 25; and 750 KDa) prevented the enzyme leakage in the crude sugar ester reaction product. The 2 KDa PEI coating of this enzyme preparation produced the highest enzyme stability in MEK, buffer solutions (pHs 5 and 7), and methanol aqueous phosphate buffer at pH 7. Using an excess of the acyl donor (1:5 xylose: fatty acid molar ratio), high xylose conversions (70-84%) were obtained after 24 h-reaction using both, non-modified and PEI (2 KDa) coated L435, but the PEI treated biocatalyst afforded a higher xylose modification degree. After 5 reuse cycles with the L435 coated with PEI 2 KDa, the xylose conversions only decreased 10%, while with the non-treated biocatalyst they decreased by 37%. The formation of SFAEs was confirmed by mass spectrometry, which showed the presence of xylose mono-, di-, and triesters. They exhibited emulsion capacities close to that of a commercial sucrose monolaurate.

Study on preparation of acylated soy protein and stability of emulsion

BACKGROUND

Protein can be used as an emulsifier to improve emulsion stability at the interface of water-in-oil emulsion. However, natural soybean protein isolate (SPI) does not meet the high demands as an emulsifier in the food industry. The effect of acylation modification by ethylenediaminetetraacetic dianhydride (EDTAD; 0-300 g kg-1 ) on the physicochemical properties of SPI was studied.

RESULTS

The results of the Fourier transform infrared spectra analyses showed that carboxyl groups were introduced into the SPI structure by the EDTAD treatment. The carboxyl concentration of SPI was increased by 30-74.07% with an increase in EDTAD addition from 50 to 300 g kg-1 . When 150 g kg-1 EDTAD was added, the surface hydrophobicity, the emulsifying activity, and the absolute value of the zeta potential were increased by 213%, 120%, and 68% respectively, and the particle size decreased to 247 nm. The droplet size of emulsion decreased to 10 μm when pH was 6. At the same concentration of SPI and pH, the absolute value of zeta potential of the emulsion was biggest. A comparison of the emulsions during storage showed the improvement of emulsion stability was related to the increase in the zeta potential and the decrease in the average particle size. The experimental group showed no destabilization on day 21, and no obvious aggregation phenomenon was observed.

CONCLUSION

Acylation modification by EDTAD changed the emulsifying properties of SPI and enhanced the stability of the SPI emulsion. © 2021 Society of Chemical Industry.

Lipozyme 435-Mediated Synthesis of Xylose Oleate in Methyl Ethyl Ketone

In this paper, we have performed the Lipozyme 435-catalyzed synthesis of xylose oleate in methyl ethyl ketone (MEK) from xylose and oleic acid. The effects of substrates’ molar ratios, reaction temperature, reaction time on esterification rates, and Lipozyme 435 reuse were studied. Results showed that an excess of oleic acid (xylose: oleic acid molar ratio of 1:5) significantly favored the reaction, yielding 98% of xylose conversion and 31% oleic acid conversion after 24 h-reaction (mainly to xylose mono- and dioleate, as confirmed by mass spectrometry). The highest Lipozyme 435 activities occurred between 55 and 70 °C. The predicted Ping Pong Bi Bi kinetic model fitted very well to the experimental data and there was no evidence of inhibitions in the range assessed. The reaction product was purified and presented an emulsion capacity close to that of a commercial sugar ester detergent. Finally, the repeated use of Lipozyme 435 showed a reduction in the reaction yields (by 48 and 19% in the xylose and oleic acid conversions, respectively), after ten 12 h-cycles.