Gel properties of heat-induced transparent hydrogels from ovalbumin by acylation modifications

Fabrication of CMC-PVA-EGDE hydrogels for maintaining overall postharvest quality of small-size packaged straw mushroom

The last-mile shipping or storage with a small-size and easy-carrying package from the distribution centers/retail markets to the customer's kitchens is a key issue to provide the fresh products for consumers. In the present study, a CMC-PVA-EGDE hydrogel with excellent transparency, highest swelling ratio value of 1011 % and complete shape recovery after dehydration was prepared by using 5 % of CMC, 1 % of PVA and 5 % of EGDE as a crosslinking agent. The prepared CMC-PVA-EGDE hydrogel with 80 % of water content maintained a high relative humidity of 92 % by absorbing and slowly-releasing the moisture in the small-size package and guaranteed the overall postharvest quality of the small-size packaged straw mushrooms to 4 d. Further results proved that the small-size packaged straw mushrooms retained a lower of 805-1060 mg CO2 mg -1 h-1, and activities/transcriptional levels of the respiration-associated vvPGI, vvSDH and vvCCO during 4-d storage.

Effects of the oleic acid-rich glycerolipids and thermal-mechanical treatment on the functionality of wheat gluten: Multi-spectroscopy and molecular simulation analysis

Lipids have been used to regulate dough's processing characteristics; however, how they affect gluten properties remains unclear. In this study, the effects of different acid-based glycerolipids and thermomechanical treatments on gluten functionalities were investigated. The results demonstrated that exogenous oleic acid-based lipids regulate gluten secondary structure. Oleic acid increased the α-helix content and improved the viscoelasticity of gluten, whereas triolein and rapeseed oil reduced the viscoelasticity and enhanced its tensile properties. Thermomechanical treatment promoted the aggregation and formation of more disulfide bonds in gluten, whereas clear fluorescence quenching was observed in gluten-containing exogenous lipids. Moreover, molecular simulation analysis indicated that hydrogen bond and hydrophobic interactions are key non-covalent forces that promoted the interaction of exogenous lipids and gluten. Compared with other oleic acid-based glycerolipids, monoolein-gliadin systems exhibited the highest binding energies (-20.6 kJ/mol). Our results deepen the understanding of why oils and fats regulate the processing characteristics of wheat-based foods.

Enhancement mechanism of ι-carrageenan on the network structure and gel-related properties of soy protein isolate/λ-carrageenan system

Enhancement mechanism of ι-carrageenan on the network structure and gel-related properties of soy protein isolate (SPI)/λ-carrageenan system was investigated. Adding ι-carrageenan decreased SPI particles' size in nano-scale, reduced hydrophobic interactions by suppressing exposure of hydrophobic groups, and increased the disulfide bonds in SPI. With rising ι-carrageenan content (< 0.55 %), the interaction between ι-carrageenan and SPI was enhanced mainly through electrostatic interaction and hydrogen bond. Meanwhile, SPI particles were reduced and their stacking compactness was increased as well. These contributed to the improvement of network structure and thus increased weakly bonded water from 97.7 to 98.5 %, water holding capacity from 55.29 % to 61.70 % and gel hardness from 0.53 to 1.30 N. Higher ι-carrageenan content (> 0.55 %) induced micro-phase separation as shown by CLSM images, and led to reduction of gel hardness. These results favor the rational design and application of SPI-based gel systems with desired practical properties.

Mechanism of CaCl2 modulation of the properties of acyl-modified ovalbumin-myofibrillar protein composite gel

Chicken breast products exhibit a rough texture and poor taste owing to the special fibrous tissue structure of chicken breast. Thus, adapting the taste of processed chicken breast products is pivotal to improving consumer satisfaction. Therefore, we used CaCl2 and acyl-modified ovalbumin (AOVA) in a concerted effort to improve the gelation properties of chicken breast myofibrillar protein (MP). The investigation of molecular interactions and microstructure revealed the mechanism behind the changes in the physicochemical properties of the prepared gel. Molecular docking showed that AOVA enhanced the gel structure of MP through hydrogen bonding and salt bridges. The investigation results indicated that 0.30 mol/L CaCl2 facilitated the unfolding of AOVA-MP molecules, increasing the number of disulphide bonds and hydrophobic interactions, as well as conferring better hardness, springiness, cohesiveness, and chewing properties to the AOVA-MP gel with a denser and more homogeneous gel network structure. This study provides new insights into the quality improvement in chicken breast mince products.

Ultrasound treatment on commercial pea protein isolates systems: Effect on structure, rheology and gelling properties

Pea protein has attracted great attention due to its capability to meet the growing requirements from consumers for desired nutrition and texture from plant protein. Hence, the current study aimed to investigate the effects of different ultrasonic treatment parameters (power and duration) on the gelling characteristics of commercial pea protein isolates (PPIc). The findings demonstrated that by manipulating the ultrasonic power and treatment duration, great enhancement of the solubility, adhesiveness and formation strength of PPIc gel can be realized. The reduction in particle size was positively correlated with higher power and longer treatment durations. Interestingly, no direct correlation between average particle size, solubility, turbidity, and ζ-potential was observed. Additionally, the ultrasound-modified PPIc in this study exhibited comparable characteristics to laboratory-prepared pea protein isolates, in terms of solubility, water-holding capacity, and gel strength. Overall, manipulating ultrasonic parameters presents a feasible method to customize the texture of pea-protein-based substitute.

Transparent mechanism of salted egg (white) hierarchically and synergistically driven by NaCl, NaOH and thermal treatment: Based on empirical data and molecular simulation

Currently, it is a challenge that the yolk in salted preserved egg tends to preserved egg yolk due to extreme NaOH treatment. Therefore, NaCl, NaOH and thermal were successfully used to prepare a new translucent salted quail egg (T-SQE), which combined advantages of preserved egg white with transparent appearance and salted egg yolk with unique texture and odour. Moreover, transparency of opaque gel (Transmittance: 0.09 %) subjected to NaCl and thermal was demonstrated to be improved under the synergistic effect of NaOH (8.55 %) via empirical data and molecular simulation. The disordered and dense network in opaque T-SQE induced by NaCl and thermal tended to form an ordered, porous and transparent structure in presence of NaOH, with more immobilized water that was poorly bonded to protein, larger radius of gyration and lower hydrophobic interaction. This research provides new insight into understanding the influence of hierarchy and synergism on transparency of egg products.

Highly ordered aggregation of soy protein isolate particles for enhanced gel-related properties through konjac glucomannan addition

This study assessed the effect of konjac glucomannan (KGM) on the aggregation of soy protein isolate (SPI) and its gel-related structure and properties. Raman results showed that KGM promoted the rearrangement of SPI to form more β-sheets, contributing to the formation of an ordered structure. Atomic force microscopy, confocal laser scanning microscopy, and small-angle X-ray scattering results indicated that KGM reduced the size of SPI particles, narrowed their size distribution, and loosened the large aggregates formed by the stacking of SPI particles, improving the uniformity of gel system. As the hydrogen bonding between the KGM and SPI molecules enhanced, a well-developed network structure was obtained, further reducing the immobilized water's content (T22) and increasing the water-holding capacity (WHC) of SPI gel. Furthermore, this gel structure showed improved gel hardness and resistance to both small and large deformations. These findings facilitate the design and production of SPI-based gels with desired performance.

The improvement of gel properties and volatiles for frozen egg white melted assisted with ultrasound

The variation in thawing time, deterioration behavior, secondary structure, surface hydrophobicity, and average particle size of frozen egg whites (EW) thawed with or without ultrasound were characterized to evaluate the effect of ultrasound on the gel properties and volatiles of egg white thermogel (EWG). The texture, water holding capacity, etc., gel properties and microstructure were well maintained in frozen EW thawed by ultrasound (UEW) resulted from the mitigation of deterioration behavior due to shorter melting time (reduced 91.3 %). Moreover, the deterioration of VOCs in fresh EWG due to freeze-thawing could be mitigated when thawed using ultrasound. Meanwhile, the formation of pleasant VOCs and reduction in unpleasant VOCs in EWG were also promoted by ultrasound-assisted thawing. The improvement mechanism of gel properties and volatiles for (frozen) egg white melted assisted with ultrasound were systematically elucidated and this study provided a new insight into improvement of VOCs in frozen food.

Effect of low degree succinylation on properties of enzyme-induced casein hydrogel

This study examines the impact of succinic anhydride (SA) modification (0-9 %) on the gel properties of casein. Upon succinylation, the surface hydrophobicity (H0) of casein initially increased before decreasing, achieving its peak at a degree of succinylation of 5.22 ± 0.16 %. The α-helix content rose to 14.13 ± 2.60 %, and the -OH peak shifted towards lower wavenumbers, suggesting enhanced hydrogen bonding within intra/intermolecular structures. The storage modulus in the rheological test escalated from 2160.11 Pa to 5047.60 Pa, and SEM analysis revealed that the optimally succinylated casein gel formed a denser and more stable gel network structure. Moreover, succinylated casein hydrogels demonstrated superior texture properties, swelling ability, and thermal stability. Molecular dynamics simulation (MD) results suggest that SA preferentially binds to LYS27 and LYS28 of β-casein via hydrogen bonds and amide bonds, respectively. The interaction between modified proteins is primarily governed by hydrogen bonds, aligning with FT-IR findings. PCA analysis identified a positive correlation between the ordered structure and gel performance. This research offers theoretical insights and reference data for modulating casein hydrogel properties through succinylation.

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.

Structural and functional optimization of egg white protein hydrogels by succinylation: Gel properties and mineral enrichment

The development of novel gel-mineral supplements is important for improving the health of patients with dysphagia. In this study, we used natural egg white protein (NEWP) and phosphorylated egg white protein (STEWP) as controls. We modified NEWP with succinic anhydride to produce varying degrees of succinylated egg white protein (SAEWP). The addition of 20 % (w/v) succinic anhydride increased the β-sheet content of SAEWP from 11.97 % to 50.60 %, which stabilized the gel structure and formed a uniformly ordered three-dimensional network, resulting in the average pore size of SAEWP could reach >80 μm. Compared to NEWP, SAEWP hydrogel with 20 % succinic anhydride showed a 22.27 % increase in water holding capacity, a 56.13 % increase in hardness, and a 173.01 % increase in elasticity. Immersion in a calcium chloride solution resulted in a 220 % increase in calcium content. This study provides new insights into the development of innovative gel mineral supplements.

Ultrasonic-microwave technique promotes the physicochemical structure of hydrogel and its release characterization of curcumin in vitro

In this study, soybean protein isolate and hawthorn pectin were mixed to prepare binary hydrogels using ultrasound and microwave techniques. Moderate treatment can not only significantly improve the mechanical strength of the hydrogel, but also increase the tightness of the internal cross-linking. The strengthening of interactions (hydrogen bonds, hydrophobic interactions, and disulfide bonds) was the main reason for this trend. Especially, the ultrasonic-microwave (80 s) treatment hydrogel possessed excellent hardness (33.426 N), water-holding capacity (98.26%), elasticity (G' = 1205 Pa), and a more homogeneous and denser microstructure. In addition, the hydrogel minimized the extent of curcumin loss (21.23%) after 5 weeks of storage. In general, the ultrasonic-microwave technique could significantly promote the physicochemical structure and curcumin bioaccessibility of hydrogels, which showed excellent market prospects in the food industry.

Carrier-free immobilized enzymatic reactor based on CipA-fused carbonyl reductase for efficient synthesis of chiral alcohol with cofactor self-sufficiency

In this study, based on the self-assembly strategy, we fused CipA with carbonyl reductase LXCARS154Y derived from Leifsonia xyli by gene coding, and successfully performed the carrier-free immobilization of LXCARS154Y. The immobilized enzyme was then characterized using scanning electron microscope (SEM), dynamic light scattering (DLS) and fourier transform infrared spectroscopy (FTIR). Compared with the free enzyme, the immobilized LXCARS154Y exhibited a 2.3-fold improvement in the catalytic efficiency kcat/km for the synthesis of a chiral pharmaceutical intermediate (R)-3,5-bis(trifluoromethyl)phenyl ethanol ((R)-BTPE) by reducing 3,5-bis(trifluoromethyl)acetophenone (BTAP). Moreover, the immobilized enzyme showed the enhanced stability while maintaining over 61 % relative activity after 18 cycles of batch reaction. Further, when CipA-fused carbonyl reductase was employed for (R)-BTPE production in a continuous flow reaction, almost complete yield (97.0 %) was achieved within 7 h at 2 M (512.3 g/L) of BTAP concentration, with a space-time yield of 1717.1 g·L-1·d-1. Notably, we observed the retention of cofactor NADH by CipA-based enzyme aggregates, resulting in a higher total turnover number (TTN) of 4815 to facilitate this bioreductive process. This research developed a concise strategy for efficient preparation of chiral intermediate with cofactor self-sufficiency via continuous flow biocatalysis, and the relevant mechanism was also explored.

Transglutaminase cross-linking ovalbumin-flaxseed oil emulsion gels: Properties, microstructure, and performance in oxidative stability

This study prepared emulsion gels by modifying ovalbumin (OVA)-flaxseed oil (FSO) emulsions with transglutaminase (TGase) and investigated their properties, structure and oxidative stability under different enzyme reaction times. Here, we found prolonged reaction times led to the transformation of α-helix and β-turn into β-sheet and random coil. The elasticity, hardness and water retention of the emulsion gels increased significantly, but the water-holding capacity decreased when the reaction time exceeded 4 h. Confocal laser scanning microscope (CLSM) indicated extended enzyme reaction time fostered oil droplet aggregation with proteins. Emulsion gel reduced FSO oxidation, especially after 4 h of the enzyme reaction, the peroxide value (PV) of the emulsion gel was reduced by 29.16% compared to the control. In summary, the enzyme reaction time of 4 h resulted in the formation of a dense gel structure and enhanced oxidative stability. This study provides the potential applications in functional foods and biomedical fields.

Formation mechanism, environmental sensitivity and functional characteristics of succinylated ovalbumin/ε-polylysine electrostatic complexes: The roles of succinylation modification and ε-polylysine combination

Biocomplex materials formed by oppositely charged biopolymers (proteins) tend to be sensitive to environmental conditions and may lose part functional properties of original proteins, and one of the approaches to address these weaknesses is protein modification. This study established an electrostatic composite system using succinylated ovalbumin (SOVA) and ε-polylysine (ε-PL) and investigated the impact of varying degrees of succinylation and ε-PL addition on microstructure, environmental responsiveness and functional properties. Molecular docking illustrated that the most favorable binding conformation was that ε-PL binds to OVA groove, which was contributed by the multi‑hydrogen bonding and hydrophobic interactions. Transmission electron microscopy observed that SOVA/ε-PL had a compact spherical structure with 100 nm. High-degree succinylation reduced complex sensitivity to heat, ionic strength, and pH changes. ε-PL improved the gel strength and antibacterial properties of SOVA. The study suggests possible uses of SOVA/ε-PL complex as multifunctional protein complex systems in the field of food additives.

Insight into the Stabilization Mechanism of Succinylation Modification on Black Bean Protein Gels: Molecular Conformation, Microstructure, and Gel Properties

The objective of this work was to investigate the effect of succinylation treatment on the physicochemical properties of black bean proteins (BBPI), and the relationship mechanism between BBPI structure and gel properties was further analyzed. The results demonstrated that the covalent formation of higher-molecular-weight complexes with BBPI could be achieved by succinic anhydride (SA). With the addition of SA at 10% (v/v), the acylation of proteins amounted to 92.53 ± 1.10%, at which point there was a minimized particle size of the system (300.90 ± 9.57 nm). Meanwhile, the protein structure was stretched with an irregular curl content of 34.30% and the greatest processable flexibility (0.381 ± 0.004). The dense three-dimensional mesh structure of the hydrogel as revealed by scanning electron microscopy was the fundamental prerequisite for the ability to resist external extrusion. The thermally induced hydrogels of acylated proteins with 10% (v/v) addition of SA showed excellent gel elastic behavior (1.44 ± 0.002 nm) and support capacity. Correlation analysis showed that the hydrogel strength and stability of hydrogels were closely related to the changes in protein conformation. This study provides theoretical guidance for the discovery of flexible proteins and their application in hydrogels.

Chicken Egg White Gels: Fabrication, Modification, and Applications in Foods and Oral Nutraceutical Delivery

Chicken egg white (EW) proteins possess various useful techno-functionalities, including foaming, gelling or coagulating, and emulsifying. The gelling property is one of the most important functionalities of EW proteins, affecting their versatile applications in the food and pharmaceutical industries. However, it is challenging to develop high-quality gelled foods and innovative nutraceutical supplements using native EW and its proteins. This review describes the gelling properties of EW proteins. It discusses the development and action mechanism of the physical, chemical, and biological methods and exogenous substances used in the modification of EW gels. Two main applications of EW gels, i.e., gelling agents in foods and gel-type carriers for nutraceutical delivery, are systematically summarized and discussed. In addition, the research and technological gaps between modified EW gels and their applications are highlighted. By reviewing the new modification strategies and application trends of EW gels, this paper provides insights into the development of EW gel-derived products with new and functional features.

Age Gelation in Direct Steam Infusion Ultra-High-Temperature Milk: Different Heat Treatments Produce Different Gels

To investigate the gelation process of direct ultra-high-temperature (UHT) milk, a pilot-scale steam infusion heat treatment was used to process milk samples over a wide temperature of 142-157 °C for 0.116-6 s, followed by storage at 4 °C, 25 °C, and 37 °C. The results of the physicochemical properties of milk showed that the particle sizes and plasmin activities of all milk samples increased during storage at 25 °C, but age gelation only occurred in three treated samples, 147 °C/6 s, 142 °C/6 s, and 142 °C/3 s, which all had lower plasmin activities. Furthermore, the properties of formed gels were further compared and analyzed by the measures of structure and intermolecular interaction. The results showed that the gel formed in the 147 °C/6 s-treated milk with a higher C* value had a denser network structure and higher gel strength, while the 142 °C/6 s-treated milk had the highest porosity. Furthermore, disulfide bonds were the largest contributor to the gel structure, and there were significant differences in disulfide bonds, hydrophobic interaction forces, hydrogen bonds, and electrostatic force among the gels. Our results showed that the occurrence of gel was not related to the thermal load, and the different direct UHT treatments produced different age gels in the milk.

Mechanically Tough and Conductive Hydrogels Based on Gelatin and Z-Gln-Gly Generated by Microbial Transglutaminase

Gelatin-based hydrogels with excellent mechanical properties and conductivities are desirable, but their fabrication is challenging. In this work, an innovative approach for the preparation of gelatin-based conductive hydrogels is presented that improves the mechanical and conductive properties of hydrogels by integrating Z-Gln-Gly into gelatin polymers via enzymatic crosslinking. In these hydrogels (Gel-TG-ZQG), dynamic π-π stacking interactions are created by the introduction of carbobenzoxy groups, which can increase the elasticity and toughness of the hydrogel and improve the conductivity sensitivity by forming effective electronic pathways. Moreover, the mechanical properties and conductivity of the obtained hydrogel can be controlled by tuning the molar ratio of Z-Gln-Gly to the primary amino groups in gelatin. The hydrogel with the optimal mechanical properties (Gel-TG-ZQG (0.25)) exhibits a high storage modulus, compressive strength, tensile strength, and elongation at break of 7.8 MPa at 10 °C, 0.15 MPa at 80% strain, 0.343 MPa, and 218.30%, respectively. The obtained Gel-TG-ZQG (0.25) strain sensor exhibits a short response/recovery time (260.37 ms/130.02 ms) and high sensitivity (0.138 kPa-1) in small pressure ranges (0-2.3 kPa). The Gel-TG-ZQG (0.25) hydrogel-based sensors can detect full-range human activities, such as swallowing, fist clenching, knee bending and finger pressing, with high sensitivity and stability, yielding highly reproducible and repeatable sensor responses. Additionally, the Gel-TG-ZQG hydrogels are noncytotoxic. All the results demonstrate that the Gel-TG-ZQG hydrogel has potential as a biosensor for wearable devices and health-monitoring systems.

Ultra-stable pickering emulsion stabilized by anisotropic pea protein isolate-fucoidan conjugate particles through Maillard reaction

Bio-based emulsifiers hold significant importance in various industries, particularly in food, cosmetics, pharmaceuticals and other related fields. In this study, pea protein isolate (PPI) and fucoidan (FUD) were conjugated via the Maillard reaction, which is considered safe and widely used in the preparation of food particle. The PPI-FUD conjugated particles exhibit an anisotropic non-spherical structure, thereby possessing a high detachment energy capable of preventing emulsion coalescence and Ostwald ripening. Compared to emulsions previously prepared in other studies (< 500 mM), the Pickering emulsion stabilized by PPI-FUD conjugate particles demonstrates outstanding ionic strength resistance (up to 5000 mM). Furthermore, when encapsulating curcumin, the Pickering emulsion protects the curcumin from oxidation. Additionally, the formulated emulsions demonstrated the capability to incorporate up to 60 % (v/v) oil phase, revealing remarkable performance in terms of storage stability, pH stability, and thermal stability.

Enhanced emulsification performance and interfacial properties of Janus-like rapeseed cruciferin through asymmetric acylation modification

Plant protein emulsifiers, particularly rapeseed protein isolate with its superior amino acid composition and predominantly globular protein, have captured significant interest in the food industry. Nonetheless, the application of these proteins has been stymied by their lackluster emulsification properties. Addressing this challenge, our study implements an innovative asymmetric acylation technique to modify the surface of rapeseed cruciferin (RC), morphing it into a structure resembling Janus nanoparticles. This alteration amplifies the emulsification prowess of RC by a remarkable 2.7 times compared to its natural form, and 1.43 times over its conventionally acylated counterpart. The asymmetrically acylated RC, marked by a distinctive three-phase contact angle of 90.4°, manifests an outstanding amphiphilic character. Moreover, it surpasses both the natural and conventionally acylated RC in terms of diffusion, penetration, and rearrangement rates, as well as protein concentration at the oil-water interface. Compared to commonly used emulsifiers in the food industry, such as lecithin and soy protein, the asymmetrically acylated RC stands out, stabilizing emulsions with the tiniest particle size and effectively staving off emulsion stratification over a longer duration. This study underscores that asymmetric acylation serves as a reliable methodology for producing efficient plant protein emulsifiers, considerably amplifying their utility in the food industry.

New insight into yolk sphere microgel structure impacted by lipid and protein distribution changing under heating processing

The gel structure of boiled, shelled egg yolk is formed by the accumulation of yolk spheres, which are rich in lipids and proteins, and investigating the properties of the lipid-protein complex gel structure of the yolk sphere under heating is important. In this study, we used SEM and CLSM to confirm lipid migration and protein aggregation. We observed that during the heating process, the thermal stability decreased, and there was an increase in the content of β-turns and the degrees of freedom of water and lipids. G' increased during the frequency sweep but decreased after heating for 120 min. The various yolk gel structures exhibited varying degrees of resistance to compression from external forces. Prolonged heating resulted in the presence of gaps and increased surface roughness of the spheres. In conclusion, heating induced lipid migration and protein aggregation in the sphere microgels, thereby altering the structural properties of the gels.

Translucency mechanism of heat-induced pigeon egg white gel

In this study, the properties of pigeon egg white (PEW) and chicken egg white (CEW) thermal gels were compared, with the aim of revealing the mechanisms involved in the high transparency of PEW thermal gels. Results demonstrated that PEW gels exhibited higher transparency than CEW gels. Scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis revealed that PEW gels formed a fine chain gel network structure with an average diameter of thermal aggregates (89.84 ± 7.13 nm). The molecular properties of PEW proteins, such as higher content of β-sheet structures (32.73 %), reactive groups (free sulfhydryl groups, hydrophobic groups), and absolute zeta potential (-3.563 mV), were found to contribute to the formation of smaller thermal aggregates during thermal denaturation. The microrheology measurements showed that these features allowed PEW proteins to interact less with each other and form smaller thermal aggregates during thermal denaturation, which facilitated the formation of fine chain gel networks and thus improved the transparency of the gels. The present study initially reveals the molecular basis of the high transparency of PEW thermal gels and provides a theoretical reference for the development of new highly transparent protein materials.

Designing future foods: Harnessing 3D food printing technology to encapsulate bioactive compounds

Bioactive compounds (BCs) provide numerous health benefits by interacting with one or more components of living tissues and systems. However, despite their potential health benefits, most of the BCs have low bioaccessibility and bioavailability, hindering their potential health-promoting activities. The conventional encapsulation techniques are time-consuming and have major limitations in their food applications, including the use of non-food grade chemicals, undesired sensory attributes, and storage stability issues. A cutting-edge, new technique based on 3D printing can assist in resolving the problems associated with conventional encapsulation technologies. 3D food printing can help protect BCs by incorporating them precisely into three-dimensional matrices, which can provide (i) protection during storage, (ii) enhanced bioavailability, and (iii) effective delivery and controlled release of BCs. Recently, various 3D printing techniques and inks have been investigated in order to create delivery systems with different compositions and geometries, as well as diverse release patterns. This review emphasizes the advances in 3D printing-based encapsulation approaches, leading to enhanced delivery systems and customized food formulations.

Rheological and physicochemical properties of heat-induced ovalbumin gels in presence of sodium carboxymethyl cellulose

In this study, the effect of sodium carboxymethylcellulose (CMC-Na) on the rheological and physicochemical properties of heat-induced ovalbumin (OVA) gels was evaluated. The OVA/CMC-Na composite gels were prepared by heat-induced (85 °C, pH 7.0) a mixture of CMC-Na (0, 0.2, 0.4, 0.8 and 1%) and OVA. The results revealed that the addition of CMC-Na dramatically reduced the springiness and hardness of the composite gels, while slightly enhancing the intermolecular hydrogen bonding interactions, which facilitated the improvement of the softness of the gels. It can be observed by SEM that the added CMC-Na was stacked on the surface of the OVA, resulting in visible "linear bumps". All gel samples exhibited shear-thinning behavior. The apparent viscosity of the composite gels increased with the addition of CMC-Na, and the OVA gel with 1% CMC-Na showed the highest apparent viscosity and the lowest storage modulus (G'). Additionally, low field nuclear magnetic resonance (LF-NMR) measurements indicated that the increasing CMC-Na boosted the water mobility of the composite gel. This study offers a novel approach to the development of ovalbumin-based soft gel foods, especially for certain populations with swallowing difficulties.

Protein-polysaccharide-based delivery systems for enhancing the bioavailability of curcumin: A review

In recent years, a wide attention has been paid to curcumin in medicine due to its excellent physiological activities, including anti-inflammatory, antioxidant, antibacterial, and nerve damage repair. However, the low solubility, poor stability, and rapid metabolism of curcumin make its bioavailability low, which affects its development and application. As a unique biopolymer structure, protein-polysaccharide (PRO-POL)-based delivery system has the advantages of low toxicity, biocompatibility, biodegradability, and delayed release. Many scholars have investigated PRO-POL -based delivery systems to improve the bioavailability of curcumin. In this paper, we focus on the interactions between different proteins (e.g. casein, whey protein, soybean protein isolate, pea protein, zein, etc.) and polysaccharides (chitosan, sodium alginate, hyaluronic acid, pectin, etc.) and their effects on complexes diameter, surface charge, encapsulation drive, and release characteristics. The mechanism of the PRO-POL-based delivery system to enhance the bioavailability of curcumin is highlighted. In addition, the application of PRO-POL complexes loaded with curcumin is summarized, aiming to provide a reference for the construction and application of PRO-POL delivery systems.

Structural and textural properties of walnut protein gels induced by ultrasound and transglutaminase: encapsulation and release of tea polyphenols

This study investigated the synergy of ultrasonic and transglutaminase (TGase) treatment on the structural, physicochemical, rheological, gelation properties and controlled release properties of dehulled walnut proteins (DWP). The results showed that after ultrasonic-TGase treatment, the surface hydrophobicity was decreased, indicating the involvement of disulfide bonds in gel formation. Scanning electron microscopy (SEM) showed that ultrasonic-TGase treatment resulted in a more uniform and denser microstructure of DWP gels. Ultrasonic-TGase treatment changed the secondary structure of the DWP gels as determined by Fourier transform infrared spectroscopy, with an increase in α-helix, β-turn and random coils and a decrease in β-sheets. In addition, in vitro drug release profiles showed that ultrasonic-TGase treatment promoted the cross-linking of protein molecules and formed a dense network to embed tea polyphenols (TP), thereby slowing down the digestion of TP in simulated gastric fluid and achieving the purpose of slow-release in simulated intestinal fluid. Thus, the synergy of ultrasonic and TGase treatment might be an effective method to improve gel properties and expand the application of protein gels in the food industries.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05756-6.

Allergenicity, assembly and applications of ovalbumin in egg white: a review

Ovalbumin (OVA), the most abundant protein in egg whites, has been widely used in various industries. Currently, the structure of OVA has been clearly established, and the extraction of high-purified OVA has become feasible. However, the allergenicity of OVA is still a serious problem because it can cause severe allergic reactions and may even be life-threatening. The structure and allergenicity of the OVA can be altered by many processing methods. In this article, a detailed description on the structure and a comprehensive overview on the extraction protocols and the allergenicity of OVA was documented. Additionally, the information on assembly and potential applications of OVA was summarized and discussed in detail. Physical treatment, chemical modification, and microbial processing can be applied to alter the IgE-binding capacity of OVA by changing its structure and linear/sequential epitopes. Furthermore, research indicated that OVA could assemble with itself or other biomolecules into various forms (particles, fibers, gels, and nanosheets), which expanded its application in the food field. OVA also shows excellent application prospects, including food preservation, functional food ingredients and nutrient delivery. Therefore, OVA demonstrates significant investigation value as a food grade ingredient.

Elastic and transparent ovalbumin hydrogels formed via succinylation combined with pH-shifting treatment

Ovalbumin (OVA) is a model protein with extensive research on structure and function, however, the application of OVA in food processing is limited due to its low gelation properties. In this study, thermally-induced highly transparent and elastic hydrogels from OVA pretreated by succinylation combined with pH-shifting method were reported. Transmission electron microscope (TEM) and free sulfhydryl groups determination revealed that the pretreatment induced the stretching of the protein structure and promoted the formation of preliminary aggregates. Further heating the pretreated OVA suspension resulted in a homogeneous and macroporous gel network with thin connecting walls. Such homogeneous gel network structures may be related to the effective modulation of the thermal aggregation efficiency of proteins by succinylation and the high level of protein unfolding by pH-shifting treatments, which synergistically allowed for more active sites to be created during heating to facilitate intermolecular interactions, including hydrogen bonding and hydrophobic interactions. Notably, the method resulted in a 507.14% increase in elasticity, a 60.74% increase in water holding capacity of the OVA hydrogels compared to the native OVA hydrogels without pretreatment. Also, the hydrogels were transparent with 73.11% light transmittance. In conclusion, succinylation and pH-shifting combined treatment could be an effective method for the preparation of OVA hydrogels with superior gelation properties.

Effects of dual succinylation and ultrasonication modification on the structural and functional properties of ovalbumin

In this study, the functional properties of ovalbumin (OVA) were improved through dual modification with succinylation (succinylation degrees of 32.1 % [S1], 74.2 % [S2], and 95.2 % [S3]) and ultrasonication (ultrasonication durations of 5 min [U1], 15 min [U2], and 25 min [U3]), and the changes in protein structures were explored. Results showed that as the succinylation degree was increased, the particle size and surface hydrophobicity of S-OVA decreased by the maximum values of 2.2 and 2.4 times, respectively, causing emulsibility and emulsifying stability to increase by 2.7 and 7.3 times, respectively. After ultrasonic treatment, the particle size of succinylated-ultrasonicated OVA (SU-OVA) had decreased by 3.0-5.1 times relative to that of S-OVA. Moreover, the net negative charge of S3U3-OVA had increased to the maximum value of - 35.6 mV. These changes contributed to the further enhancement in functional indicators. The unfolding of the protein structure and the conformational flexibility of SU-OVA were illustrated and compared with those of S-OVA via protein electrophoresis, circular dichroism spectroscopy, intrinsic fluorescence spectroscopy, and scanning electron microscopy. The dually modified OVA emulsion (S3U3-E) presented small droplets (243.33 nm), reduced viscosity, and weakened gelation behavior that were indicative of even distribution, which was visually proven by confocal laser scanning microscopy images. Furthermore, S3U3-E exhibited favorable stability, a particle size that was almost unchanged, and a low polydispersity index (<0.1) over 21 days of storage at 4 °C. The above results demonstrated that succinylation combined with ultrasonic treatment could be an effective dual modification method for enhancing the functional performance of OVA.

Research advance of non-thermal processing technologies on ovalbumin properties: The gelation, foaming, emulsification, allergenicity, immunoregulation and its delivery system application

Ovalbumin (OVA) is the most abundant protein in egg white, with excellent functional properties (e.g., gelling, foaming, emulsifying properties). Nevertheless, OVA has strong allergenicity, which is usually mediated by specific IgE thus results in gut microbiota dysbiosis and causes atopic dermatitis, asthma, and other inflammation actions. Processing technologies and the interactions with other active ingredients can influence the functional properties and allergic epitopes of OVA. This review focuses on the non-thermal processing technologies effects on the functional properties and allergenicity of OVA. Moreover, the research advance about immunomodulatory mechanisms of OVA-mediated food allergy and the role of gut microbiota in OVA allergy was summarized. Finally, the interactions between OVA and active ingredients (such as polyphenols and polysaccharides) and OVA-based delivery systems construction are summarized. Compared with traditional thermal processing technologies, novel non-thermal processing techniques have less damage to OVA nutritional value, which also improve OVA properties. OVA can interact with various active ingredients by covalent and non-covalent interactions during processing, which can alter the structure or allergic epitopes to affect OVA/active components properties. The interactions can promote OVA-based delivery systems construction, such as emulsions, hydrogels, microencapsulation, nanoparticles to encapsulate bioactive components and monitor freshness for improving foods quality and safety.

Design of glucono-δ-lactone-induced pinto bean protein isolate/κ-carrageenan mixed gels with various microstructures: fabrication, characterization, and release behavior

BACKGROUND

Protein gels are used for different purposes, such as providing good texture, serving as fat replacers, and enhancing the nutritional and functional characteristics of foods. They can also deliver controlled release agents for sensitive drugs. The objective of this study was to investigate the impact of κ-carrageenan (kcr) concentration (0, 1.5, 3, and 4.5 mg g^-1 ) on the morphological and physicochemical properties and release behavior of glucono-δ-lactone (GDL)-induced pinto bean protein aggregate (PBA) gels.

RESULTS

When κ-carrageenan concentration increased from 0 to 1.5 and 3 mg.g^-1 , the firmness of the samples increased significantly, by 2.04 and 3.7 fold, respectively (P < 0.05). A compact and homogenous network with considerable strength and maximum water-holding capacity (97.52 ± 1.17%) was obtained with the addition of 3 mg g^-1 κ-carrageenan to the gel system. Further increasing the κ-carrageenan concentration to 4.5 mg g^-1 produced a coarse gel structure with higher storage modulus (G'), firmness (6.30-fold), thermal stability, and entrapment efficiency (85.6%). Depending on the κ-carrageenan concentration, various microstructures from protein continuous phase to κ-carrageenan continuous phase were observed. The release test indicated that 70.25% of the loaded curcumin was released in the simulated gastrointestinal tract for pure PBA gels. In contrast, for binary gels containing 4.5 mg g^-1 κ-carrageenan, curcumin was protected in the upper gastrointestinal tract, and 64.45% of loaded curcumin was delivered to the colon.

CONCLUSION

Our study showed that κ-carrageenan/PBA gels had high entrapment efficiency and could protect curcumin in the upper gastrointestinal tract. The hydrogels are therefore very valuable for colon-targeting delivery purposes. © 2022 Society of Chemical Industry.

Spectroscopic Characterization of the Binding and Release of Hydrophilic, Hydrophobic and Amphiphilic Molecules from Ovalbumin Supramolecular Hydrogels

Protein-based hydrogels have attracted growing attention for pharmaceutical and biomedical applications. Ovalbumin (OVA), the hen egg white albumin, possessing good foaming and gelling properties and being widely used in the food industry, has recently been indicated as a potential pharmaceutical vehicle. In this study, the binding and release properties of pure OVA hydrogels were investigated by electron paramagnetic resonance (EPR) spin labeling. The comparative analysis between OVA and serum albumin (SA) hydrogels revealed the same release kinetics of hydrophilic 3-carbamoyl-proxyl and 3-carboxy-proxyl, suggesting the diffusion-dominated release of small probes from both hydrogel types. The results obtained with the amphiphilic 16-doxylstearate (16-DS) indicate that OVA, unlike SAs, does not possess a specific fatty acid binding site. However, the OVA hydrogels were able to accommodate a two-fold excess of 16-DS, resulting from protein thermally induced conformational changes, as confirmed by Raman spectroscopy. Similarly, the hydrophobic modified paullone ligand HL, which was initially free in the OVA solution, was bound in the hydrogel. The hydrogels were found to retain a significant amount of 16-DS and HL after 7-day dialysis in physiological saline. The observed facilitated binding of amphiphilic/hydrophobic molecules in OVA hydrogels compared to the solution, and their sustained release, demonstrate the applicability of OVA hydrogels in pharmaceutics.

Encapsulation and sustained release of curcumin by hawthorn pectin and Tenebrio Molitor protein composite hydrogel

In this study, the effects of pH value, mixing ratio and the Ca²⁺ concentration on the complex gelation of hawthorn pectin (HP) and Tenebrio Molitor protein (TMP) were investigated. The turbidity results showed that the composite gel had the maximum polymer concentration when the mixing ratio was 2:1 and the pH value was 3.35. The rheological measurement results showed that TMP/HP (15 mmol/L) hydrogel (THIH) had the highest storage modulus and loss modulus, indicating that the properties of the hydrogel at this Ca²⁺ concentration had been significantly improved. The results of scanning electron microscope and pore size also proved that the network structure prepared under this condition was compact and uniform, the pore size was small, which was beneficial to the entrapment of active components. Subsequently, in order to explore the storage stability and antioxidant activity of THIH-loaded curcumin in simulated gastrointestinal environment, in vitro simulated digestion experiment was carried out and satisfactory results were obtained. To sum up, THIH was a promising delivery system with broad application prospects, which was expected to provide a novel idea for the entrapment and delivery of active components.

Egg white protein-based delivery system for bioactive substances: a review

Some bioactive substances in food have problems such as poor solubility, unstable chemical properties and low bioavailability, which limits their application in functional food. Recently, many egg white protein-based delivery carriers have been developed to improve the chemical stability, biological activity and bioavailability of bioactive substances. This article reviewed the structure and properties of several major egg white proteins commonly used to construct bioactive substance delivery systems. Several common carrier types based on egg white proteins, including hydrogels, emulsions, micro/nanoparticles, aerogels and electrospinning were then introduced. The biological functions of common bioactive substances, the limitations, and the role of egg white protein-based delivery systems were also discussed. At present, whole egg white protein, ovalbumin and lysozyme are most widely used in delivery systems, while ovotransferrin, ovomucoid and ovomucin are less developed and applied. Egg white protein-based nanoparticles are currently the most commonly used delivery carriers. Egg white protein-based hydrogels, emulsions, and microparticles are also widely used. Future research on the application of various egg white proteins in developed new delivery systems will provide more choices for the delivery of various bioactive substances.

Formation mechanism of high-viscosity gelatinous egg white among "Fenghuang Egg": Phenomenon, structure, and substance composition

"Fenghuang Egg" is a special egg product incubated for 12 days by fertilized hen eggs. Its egg white contains high-viscosity and excellent thermal gel strength. A comparative study on the differences in gel properties, structure, and substance composition between fresh egg white (FEW) and "Fenghuang egg" gelatinous egg white (GEW) was carried out. Experimental results showed GEW had better apparent viscosity, as well as the hardness, cohesiveness and water holding capacity (WHC) of thermal gel; the content and size of aggregate structure increased significantly in GEW, and a fibrous dense network composed of numerous spherical nanoparticles connected in series was formed after heating. In addition, it also discovered that more water molecules in GEW existed in the form of bound water. A total of 41 proteins changed significantly in FEW and GEW, Mucin 6 might be the main reason for the enhanced viscosity of GEW, and OVA might be the dominant protein differentiating the thermal gel properties between FEW and GEW. This study revealed that the differences in gel properties and structures between FEW and GEW were closely related to the content of highly glycosylated globular proteins, laying a theoretical foundation for the application of high-viscosity egg whites.

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.