Phosphorylation modification affects the gelation behavior of alkali-induced duck egg white gels

The gelling properties of fish gelatin as improved by ultrasound-assisted phosphorylation

This study investigated the effects of ultrasound-assisted phosphorylation on gelling properties of fish gelatin (FG). Ultrasound-assisted phosphorylation (UP) for 60, 90, and 120 min resulted in >6.54% increase of phosphorylation degree and decreased zeta potential of FG. Atomic force microscopy revealed that UP-FGs showed larger aggregates than P-FGs (normal phosphorylation FGs). Low frequent-NMR and microstructure analysis revealed that phosphorylation enhanced water-binding capability of FG and improved the gel networks. However, UP60 had the highest gel strength (340 g), gelling (17.96 °C) and melting (26.54 °C) temperature while UP90 and UP120 showed slightly lower of them. FTIR analysis indicated thatβ-sheet and triple helix content increased but random coil content decreased in phosphorylated FGs. Mass spectrometry demonstrated phosphate groups mainly bound to serine, threonine and tyrosine residues of FG and UP-FG exhibited more phosphorylation sites. The study showed that mild phosphorylation (UP60) could be applied to improve FG gel properties.

Moderation-excess interactions of epigallocatechin gallate and CaCl2 modulate the gelation performance of egg white transparent gels

In this study, the moderation-excess interaction of epigallocatechin gallate (EGCG) and calcium ions (Ca2+) to the gelation performance of transparent egg white protein (EWP) gel (EWG) was explored. The oxidation of EGCG introduced a yellowish-brown EWG, whereas the weakening of Ca2+ ionic bonds caused a notable reduction in the hardness of EWG, from 120.67 g to 73.57 g. Achieving the optimal EGCG-to-Ca2+ ratio in EWG conferred enhanced water-holding capacity to 86.98%, while an excess of EGCG attributed to the creation of a three-dimensional structure within the void "walls". The elevated presence of EGCG influenced the ionic bonds and hydrophobic interactions, thereby presenting a moderate-excess relationship with sulfhydryl and disulfide bonds, β-sheet, and α-helical structures. Notably, EGCG reduced the digestibility of EWG to 50.06%, while concurrently fostering the creation of smaller particle sizes. This study provides a scientific basis for the controllable preparation and quality regulation of transparent EWG.

Phosphate type dependent phosphorylation on the interfacial and emulsion stabilizing behaviors of goose liver protein: Perspective of protein charging

Elucidation on the emulsifying behaviors of goose liver protein (GLP) from interfacial perspective was scarce when protein charging was altered. This work aimed to elucidate the role of phosphorylation on the interfacial associative interaction and then emulsion stabilizing properties of GLP using three structurally relevant phosphates of sodium trimetaphosphate (STMP), sodium tripolyphosphate (STPP) and sodium pyrophosphate (TSPP). A monotonic increment of protein charging treated from STMP, STPP to TSPP caused progressively increased particle de-aggregation, surface hydrophobicity and structural flexibility of GLP. Compared with STMP and TSPP, STPP phosphorylation rendered the most strengthened interfacial equilibrium pressure (11.98 ± 0.24 mN/m) due to sufficient unfolding but moderated charging character conveyed. Desorption curve and interfacial protein microstructure indicated that STPP phosphorylation caused the highest interfacial connectivity between proteins adsorbed onto the same droplet, as was also verified by interfacial elastic modulus (10.3 ± 0.21 mN/m). STPP treated GLP also yielded lowest droplet size (8.16 ± 0.10 μm), flocculation (8.18%) and Turbiscan stability index (8.78 ± 0.36) of emulsion but most improved microrheological properties. Overall, phosphorylation functioned itself in fortifying the intradroplet protein-protein interaction but restraining the interdroplet aggregation, and STPP phosphorylation endowed the protein with most enhanced interfacial stabilization and emulsifying efficiency.

Effects of emerging food pretreatment and drying techniques on protein structures, functional and nutritional properties: An updated review

Protein is one of the most important components of food which significantly contributes to the structure, functionality, and sensory properties which may affect consumer acceptability of processed products. Conventional thermal processing affects protein structure and induce undesirable degradation of food quality. This review provides an overview of emerging pretreatment and drying technologies (plasma treatment, ultrasound treatment, electrohydrodynamic, radio frequency, microwave, and superheated steam drying) in food processing by assessing protein structural changes to enhance functional and nutritional properties. In addition, mechanisms and principles of these modern technologies are described while challenges and opportunities for the development of these techniques in the drying process are also critically analyzed. Plasma discharges can lead to oxidative reactions and cross-linking of proteins that can change the structure of proteins. Microwave heating contributes to the occurrence of isopeptide or disulfide bonds which promotes α-helix and β-turn formation. These emerging technologies can be adopted to improve protein surface by exposing more hydrophobic groups which restrict water interaction. It is expected that these innovative processing technologies should become a preferred choice in the food industry for better food quality. Moreover, there are some limitations for industrial scale application of these emerging technologies that need to be addressed.

Thermal gelation and digestion properties of hen egg white: Study on the effect of neutral and alkaline salts addition

In this study, the thermal gelation and digestion properties of hen egg white (hen EW) proteins with different salts were investigated. Results show that the addition of neutral salt - sodium chloride (NaCl) decreased the gel hardness/resilience, increased gel lightness, aggregated particle size and digestibility of hen EW proteins significantly. In contrast, alkaline salts - phosphate and carbonate addition increased the gel resilience and strain tolerance as well as reduced the aggregated particle size and gel lightness of hen EW proteins due to the increase of solution pH and negative charge. Correlation analysis shows that the digestibility of hen EW gels was affected by gel viscoelasticity, molecule forces and texture. In conclusion, thermal gelation properties of hen EW proteins could be modulated by salts with different pH/ionic strength, and thus affected the protein digestion and peptide released.

Effects of tetrasodium pyrophosphate coupled with soy protein isolate on the emulsion gel properties of oxidative myofibrillar protein

The effects of protein oxidation on the emulsion gel properties of myofibrillar protein (MP) in the presence of tetrasodium pyrophosphate (TSPP) and soybean protein isolate (SPI) were investigated from the perspective of interfacial protein interactions. The results showed that the emulsifying activity and emulsion stability of MP increased by 35.2 %-181.6 % with elevated H₂O₂ concentrations (1-20 mM), while the gel strength and water holding capacity of MP emulsions first increased to a maximum at 5 mM H₂O₂ and then decreased. TSPP and SPI further reinforced the effects caused by oxidation. The emulsifying properties of MP and its emulsion gel properties were closely related to surface hydrophobicity/hydrogen bonds/hydrophobic interactions and disulfide bonds among interfacial proteins, respectively. However, these correlations became difficult to define when TSPP and SPI were introduced. The study provides a theoretical basis for the strategy development to reduce protein oxidation damage on meat product quality.

Ultrasonic-assisted glycosylation with κ-carrageenan on the functional and structural properties of fish gelatin

BACKGROUND

Fish gelatin (FG) has multifunctional properties similar to mammalian gelatin (MG), and it has been recognized as the optimal alternative to MG. While its poor surface-active and gelling properties significantly limit its application values, glycosylation has been successfully used to increase surface-active properties of FG, but the influence of ultrasonic-associated glycosylation (UAG) on the gelling and structural characteristics of FG is still rarely reported. This article explores UAG (100-200 W, 0.5-1 h) with κ-carrageenan (κC) on the functional properties (emulsifying, gelling and rheological properties) and structural characteristics of FG.

RESULTS

The longer time and higher power of ultrasonics accelerated the glycosylation reaction with an increase in glycosylation degree and browning index values. Compared with original FG, FG-κC mixture and bovine gelatin, UAG-modified FG possessed higher emulsification activity index, emulsion stability index, gel strength, hardness and melting temperature values. Among them, gelatin modified by appropriate ultrasonic conditions (200 W, 0.5 h) had the highest emulsifying and gelling properties. Rheological results showed that UAG contributed to the gelation process of gelatin with advanced gelation time and endowed it with high viscosity. Structural analysis indicated that UAG promoted κC to link with FG by the formation of covalent and hydrogen bonds, restricting more bound and immobilized water in the gels, exhibiting higher gelling properties.

CONCLUSION

This work showed that UAG with κC is a promising method to produce high gelling and emulsifying properties of FG that could replace MG. © 2023 Society of Chemical Industry.

Study on the Structure, Function, and Interface Characteristics of Soybean Protein Isolate by Industrial Phosphorylation

The impacts of industrial phosphorylation on the structural changes, microstructure, functional, and rheological features of soybean protein isolate (SPI) were spotlighted. The findings implied that the spatial structure and functional features of the SPI changed significantly after treatment with the two phosphates. Sodium hexametaphosphate (SHMP) promoted aggregation of SPI with a larger particle size; sodium tripolyphosphate (STP) modified SPI with smaller particle size. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) results showed insignificant alterations in the structure of SPI subunits. Fourier transform infrared (FTIR) and endogenous fluorescence noted a decline in α-helix quantity, an amplification in β-fold quantity, and an increase in protein stretching and disorder, indicating that phosphorylation treatment fluctuated the spatial structure of the SPI. Functional characterization studies showed that the solubility and emulsion properties of the SPI increased to varying degrees after phosphorylation, with a maximum solubility of 94.64% for SHMP-SPI and 97.09% for STP-SPI. Emulsifying activity index (EAI) and emulsifying steadiness index (ESI) results for STP-SPI were better than those for SHMP-SPI. Rheological results showed that the modulus of G' and G″ increased and the emulsion exhibited significant elastic behavior. This affords a theoretical core for expanding the industrial production applications of soybean isolates in the food and various industries.

Effect of sodium trimetaphosphate on the physicochemical properties of modified soy protein isolates and its lutein-loaded emulsion

Due to people's pursuit of healthy and green life, soy protein isolate (SPI) is occupying a larger and larger market share. However, the low solubility of SPI affects its development in the field of food and medicine. This paper aimed to investigate the effects of sodium trimetaphosphate (STMP) on the functional properties and structures of phosphorylated SPI and its lutein-loaded emulsion. After modification by STMP, the phosphorus content of phosphorylated SPI reached 1.2-3.61 mg/g. Infrared spectrum and X-ray photoelectron spectrum analysis confirmed that PO₄ ^3- had phosphorylation with -OH in serine of SPI molecule. X-ray diffraction analysis showed that phosphorylation destroyed the crystal structure of protein molecules. Zeta potential value of phosphorylated SPI decreased significantly. When STMP addition was 100 g/kg, particle size of protein solution decreased to 203 nm, and solubility increased to 73.5%. Furthermore, emulsifying activity and emulsifying stability increased by 0.51 times and 8 times, respectively. At the same protein concentration (1%-3% [w/w]), lutein-loaded emulsion prepared by phosphorylated SPI had higher absolute potential and smaller particle size. The phosphorylated protein emulsion at 2% concentration had the best emulsion stability after storage for 17 days. PRACTICAL APPLICATION: Phosphorylation significantly improved the emulsifying properties and solubility of SPI. Phosphorylated SPI significantly improved the stability of lutein-loaded emulsion. It provides theoretical basis for the application of phosphorylated SPI as emulsifier in delivery system and broadens the development of lutein in food and medicine field.

Improving the gel properties of duck egg white by synergetic phosphorylation/ultrasound: Gel properties, crystalline structures, and protein structure

To improve the gel properties of duck egg white gel and increase the industrial value of duck egg white, the mechanisms of ultrasound and synergetic phosphorylation/ultrasound treatments were examined in this study. It was found that as the ultrasound power increased, the surface hydrophobicity, hardness, and cohesiveness of the gel system increased, and the ζ-potential and water mobility decreased. Of the two treatments, phosphorylation/ultrasound had the strongest impact on the conformation and crystallinity of the gel system and promoted the formation of high molecular polymers. Both gel systems displayed enhanced compactness, stability, and gel strength because of the enhanced protein-protein interactions via hydrogen bonds and protein aggregation, and increased the content of intramolecular β-sheets following ultrasound treatment, and synergetic phosphorylation/ultrasound further improved the stability, water binding and gel properties. This experiment showed that ultrasound and, particularly, phosphorylation/ultrasound are effective methods to improve the gel properties of duck egg white. This study enhanced our understanding of the interactions of sodium pyrophosphate and egg white under ultrasound treatment, and promote the potential application of sodium pyrophosphate and ultrasound treatment of novel food products.

Phosphorylation modification on functional and structural properties of fish gelatin: The effects of phosphate contents

The gel, rheological and structural properties of fish gelatin (FG) were investigated through phosphorylation with different ratios of sodium pyrophosphate (TSPP) (FG:TSPP = 40:0, 40:1, 40:2, 40:4, and 40:6). It showed that phosphorylation modification significantly increased gel strength, textural properties, emulsification, and emulsification stability of FG. The surface hydrophobicity and intrinsic fluorescence of phosphorylated FG were also significantly increased. Rheological results revealed that the apparent viscosity, melt/gel points, and gel strength of FG were increased by phosphorylation with TSPP, but shortened the gelation time. Low field nuclear magnetic resonance (LF-NMR) showed that phosphorylation reduced mobility of water in FG. FTIR results indicated that phosphorylation increased the β-sheet/β-turn contents but reduced the random coil contents. This study might provide a new guideline for the exploration of TSPP phosphorylation increased the functional properties of FG.

Modification methods and applications of egg protein gel properties: A review

Egg protein (EP) has a variety of functional properties, such as gelling, foaming, and emulsifying. The gel characteristics provide a foundation for applications in the food industry and research on EP. The proteins denature and aggregate to form a dense three-dimensional gel network structure, with a process influenced by protein concentration, pH, ion type, and strength. In addition, the gelation properties of EP can be altered to varying degrees by applying different treatment conditions to EP. Currently, modification methods for proteins include physical modification (heat-induced denaturation, freeze-thaw modification, high-pressure modification, and ultrasonic modification), chemical modification (glycosylation modification, phosphorylation modification, acylation modification, ethanol modification, polyphenol modification), and biological modification (enzyme modification). Pidan, salted eggs, egg tofu, and other egg products have unique sensory properties, due to the gel properties of EP. In accessions, EP has also been used as a new ingredient in food packaging and biopharmaceuticals due to its gel properties. This review will further promote EP gel research and provide guidance for its full application in many fields.

Mechanism of differences in characteristics of thick/thin egg whites during storage: Physicochemical, functional and molecular structure characteristics analysis

This study systematically analyzed and compared thechanges of physicochemical, functional and molecular structural characteristics between thick egg white (KEW) and thin egg white (NEW) during storage. Analysis of physicochemical properties showed that moisture content decreased significantly with the increase of pH during storage. KEW was gradually thinning, while NEW was closer to Newtonian fluid. Functional properties indicated that KEW thermal gel was gradually hard and brittle with the properties of NEW. KEW had better emulsifying property than NEW, and NEW had superior foaming ability. The α-helix and β-sheet in the FT-IR spectrum showed a downward trend, revealing secondary structure changed from order to disorder. Enhancement of fluorescence intensity indicated the structural unfolding and exposure of tryptophan residues. SDS-PAGE proved that OVO might be related to the difference between KEW and NEW characteristics. This study provided new idea and reference value for egg storage and diversified utilization of egg white.

Wheat gluten proteins phosphorylated with sodium tripolyphosphate: Changes in structure to improve functional properties for expanding applications

Poor solubility of wheat gluten proteins (WG) has negative impact on functional attributes such as gelation and emulsification, which limits it use in the food industry. In this study, WG underwent different degrees of phosphorylation using sodium tripolyphosphate (STP). Phosphoric acid groups were successfully incorporated in the WG via covalent bonding (C–N–P and C–O–P) involving hydroxyl and primary amino groups from WG. The introduction of phosphoric acid groups increased the negative charge of phosphorylation-WG, which caused the enhancement of electrostatic repulsion between proteins and reduced the droplet size in emulsions, thereby allowing proteins to be more efficiently dispersed in the solution system. The change of structure induced with phosphorylation improved hydration of protein, making the WG with higher solubility, thereby resulting in the improvement of its emulsification, foaming, thermal stability, and rheological properties. Therefore, WG can be modified by phosphorylation which caused an overall improvement of functional properties, thus facilitating the expansion of WG applications.

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Functional properties of WG were enhanced with phosphorylation (PP).

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The P2p at 133.1 eV and the bonds of C–O–P and C–N–P were found in PP-WG.

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Greater ζ-potential, solubility, viscosity, foaming in PP- WG.

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Phosphorylation increased WG thermal stability and gel properties.

The Effect of Salt on the Gelling Properties and Protein Phosphorylation of Surimi-Crabmeat Mixed Gels

The effects of different salt additions (1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 3.5%) on the gelling properties and protein phosphorylation of the mixed gels (MG) formed by silver carp (Hypophthalmichthys molitrix) surimi with 10% crabmeat were investigated. The MG's breaking force, deformation, gel strength, and water-holding capacity (WHC) increased as the salt concentration increased. The intrinsic fluorescence intensity of the samples initially decreased and then increased, reaching the lowest when the NaCl concentration was 2.5%. The result of SDS-polyacrylamide gel electrophoresis indicated that large aggregates were formed by protein-protein interaction in the MG containing 2.5% or 3.0% NaCl, decreasing the protein band intensity. It was also found that with the addition of NaCl, the phosphorus content initially increased and then decreased, reaching the maximum when the NaCl concentration was 2% or 2.5%, which was similar to the changing trend of actin band intensity reported in the results of Western blot. These results revealed that the amount of salt used had a significant effect on the degree of phosphorylation of the MG protein. The increase in phosphorylation was linked to improved gelling properties, which could lead to new ideas for manufacturing low-salt surimi products in the future.

Reversibility of the gel, rheological, and structural properties of alcohol pretreated fish gelatin: Effect of alcohol types

The reversibility of gel property of alcohol (methanol, ethanol)-pretreated fish gelatin (FG) were investigated through removing alcohol solutions by freeze drying. Results showed that the gel strength and the hardness of FG could be retained (1%, 40%) or even improved (1% methanol) using low or high concentration alcohol solutions, while decreased in medium concentration alcohol solutions. Compared with untreated FG, rheology results showed that, all alcohol solutions pretreated FG had lower apparent viscosity, while higher alcohol solutions pretreated ones decreased the gel and melt points and shorten the gelation time. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis showed that methanol pretreated FG had the higher α contents than those of ethanol pretreated. Circular dichroism spectra results indicated that β-sheet could be decreased after removing ethanol solutions, whereas the β-sheet increased after removing the methanol solutions. Moreover, low field nuclear magnetic resonance relaxation test showed that pretreated FG had lower transverse relaxation times of internal water (T₂₁ and T₂₂ ) compared to that of the untreated FG. Overall, FG still retains higher gel properties after removing the low or high alcohol concentrations.