Effect of dry heating on the aggregation behaviour and aggregate morphologies of ovalbumin

Temperature-orientation changes in ROS-oxidized egg white protein conformation modulate the thermal aggregation behavior

In this paper, the differences in thermal aggregation behavior of egg white protein (EWP) mediated by reactive oxygen species (ROS) at different heat temperatures were investigated. Results showed that an increase in EWP turbidity and the change in particle size during the heating process depended on the interactions after protein peptide chain unfolding. With the increase in heating temperature, the EWP aggregates changed from indeterminate fiber-like structure to regular network structure. The thermal stability results showed an increase in the thermal stability of EWP after oxidation. The formation of thermally induced aggregates was accompanied by a significant increase in the hydrophobicity of the protein surface from 249.93 to 2748.10. Raman spectroscopy indicated that oxidized EWP exposed hydrophobic groups to inhibit aggregation during heating, and EWP demonstrated significant anti-aggregation properties when heated at 72 °C. This study provides certain theoretical support for improving the thermal processing level of egg products.

Protein oxidation and its effect on functional properties of livestock products during the processing and storage: A review

Protein oxidation is a complex chemical process that pervades the entirety of the food domain. It is governed by two primary mechanisms: the direct oxidation by active entities and the indirect oxidation by secondary oxidation byproducts like lipid oxidation, influenced by many factors. The oxidation of proteins in livestock products readily occurs post-processing and storage through techniques such as freezing, cooking, ultrasonication, among others, leading to protein carbonylation and subsequent alterations in structure. Consequently, the purpose of this manuscript is to scrutinize the impacts of conventional processing and storage methodologies on protein oxidation in livestock products, delineating potential mechanisms, action sites, and influential factors implicated in this progression. Additionally, we delve into the ramifications of protein oxidation on the processing attributes of livestock products, while venturing into forthcoming trends and obstacles to set a groundwork for ensuring and regulating the caliber of these commodities.

Chain reactions of temperature-induced egg white protein amorphous aggregates: Formation, structure and material composition of thermal gels

Egg white protein is widely used in food, chemical, medical and other fields due to its excellent thermal gel properties. However, the regularity of egg white thermal gel (EWTG) by temperature influence is still unknown. In this study, we investigated the potential mechanism of temperature (75-95 °C, 15 min) gradient changes inducing thermal aggregation and gel formation of EWTG. The results showed that changes in textural characteristics and water holding capacity (WHC) of EWTGs depended on switching in protein aggregation morphology (spherical shape - chain shape - regiment shape) and gel network structure differences ("irregular bead-like" - "regular lamellar structure"). In addition, proteomics indicated that the generation of amorphous protein aggregates at 95 °C might be related to Mucin 5B as the aggregation core. The research revealed the EWTG formation from "whole egg white protein" to "single molecules", aiming to provide a reference for quality control in gel food processing.

Protein aggregation caused by pasteurization processing affects the foam performance of liquid egg white

Pasteurization is necessary during the production of liquid egg whites (LEW), but the thermal effects in pasteurization could cause an unavoidable loss of foaming properties of LEW. This study intended to investigate the mechanism of pasteurization processing affects the foam performance of LEW. The foaming capacity (FC) of LEW deteriorated significantly (ΔFCmax = 72.33 %) and foaming stability (FS) increased slightly (ΔFSmax = 3.64 %) under different temperature-time combinations of pasteurization conditions (P < 0.05). The increased turbidity and the decreased solubility together with the decreased absolute value of Zeta potential indicated the generation of thermally induced aggregates and the instability of the protein particles, Rheological characterization demonstrated improved viscoelasticity in pasteurization liquid egg whites (PLEW), explaining enhanced FS. The study revealed that loss in foaming properties of PLEW resulted from thermal-induced protein structural changes and aggregation, particularly affecting FC. This provided a theoretical reference for the production and processing of LEW products.

Biomacromolecular carriers based hydrophobic natural products for potential cancer therapy

Cancer is the second leading cause of death worldwide. It was estimated that 90 % of cancer-related deaths were attributable to the development of multi-drug resistance (MDR) during chemotherapy, which results in ineffective chemotherapy. Hydrophobic natural products plays a pivotal role in the field of cancer therapy, with the potential to reverse MDR in tumor cells, thereby enhancing the efficacy of tumor therapy. However, their targeted delivery is considered a major hurdle in their application. The advent of numerous approaches for encapsulating bioactive ingredients in the nanodelivery systems has improved the stability and targeted delivery of these biomolecules. The manuscript comprehensively analyses the nanodelivery systems of bioactive compounds with potential cancer therapy applications, including liposomes, emulsions, solid lipid nanoparticles (NPs), and polymeric NPs. Then, the advantages and disadvantages of various nanoagents in the treatment of various cancer types are critically discussed. Further, the application of multiple-compbine delivery methods to overcome the limitations of single-delivery have need critically analyzed, which thus could help in the designing nanodrug delivery systems for bioactive compounds in clinical settings. Therefore, the review is timely and important for development of efficient nanodelivery systems involving hydrophobic natural products to improve pharmacokinetic properties for effective cancer treatment.

Dry-heat-induced phosphoserine-specific fragmentation of ovalbumin

When subjected to dry-heating, egg white ovalbumin, a phosphoglycoprotein, undergoes fragmentation and forms soluble aggregates. We investigated the mechanisms of dry-heat-induced fragmentation of ovalbumin. SDS-PAGE analysis showed that ovalbumin fragmented into five polypeptides, and their amount increased over 6 h of dry-heat treatment at 120 °C. The fragments contained fewer or no phosphoserine, compared with that in crude ovalbumin. Liquid chromatography-tandem mass spectrometry analysis of tryptic digests revealed that the fragmentation sites were located on phosphoserine residues, S68 and S344. During fragmentation, the phosphoserine residues underwent conversion into dehydroalanine residues, which were subsequently hydrolyzed. The nitrogen from the dehydroalanine became a newly formed terminal amide group on the N-terminal fragment, while the remaining molecule predominantly formed a new terminal pyruvoyl group. Furthermore, the fragments were incorporated into monomers or soluble aggregates of ovalbumin via covalent and non-covalent bonds. This study demonstrated a novel mechanism for dry-heat-induced fragmentation of phosphoproteins.

Potassium Chloride as an Effective Alternative to Sodium Chloride in Delaying the Thermal Aggregation of Liquid Whole Egg

The potential of potassium chloride (KCl) to be used as a substitute for sodium chloride (NaCl) was studied by monitoring the effects of salt treatment on thermal behavior, aggregation kinetics, rheological properties, and protein conformational changes. The results show that the addition of KCl can improve solubility, reduce turbidity and particle size, and positively influence rheological parameters such as apparent viscosity, consistency coefficient (K value), and fluidity index (n). These changes indicate delayed thermal denaturation. In addition, KCl decreased the content of β-sheet and random coil structures and increased the content of α-helix and β-turn structures. The optimal results were obtained with 2% KCl addition, leading to an increase in Tp up to 85.09 °C. The correlation results showed that Tp was positively correlated with solubility, α-helix and β-turn but negatively correlated with ΔH, turbidity, β-sheet and random coil. Overall, compared to NaCl, 2% KCl is more effective in delaying the thermal aggregation of LWE, and these findings lay a solid theoretical foundation for the study of sodium substitutes in heat-resistant liquid egg products.

Magnesium ions regulated ovalbumin-lysozyme heteroprotein complex: Aggregation kinetics, thermodynamics and morphologic structure

This study aims to investigate the mechanism of magnesium ions regulated ovalbumin-lysozyme (OVA-LYS) heteroprotein aggregation behavior via aggregation kinetics model, exploring the relationship between differential aggregation behavior and protein molecular structure, intermolecular interactions and thermal stability. Results showed that the aggregation rate (kapp) and maximum absorbance (Amax) of the OVA-LYS heteroprotein complex were located between OVA and LYS. Meanwhile, the thermal denaturation temperature (Td) and denaturation enthalpy (ΔH) were between the values of OVA and LYS as well. Compared with OVA, the thermal stability of the OVA-LYS heteroprotein complex increased owing to the electrostatic interactions between OVA and LYS, resulting in slower aggregation rate and lower aggregation degree. Molecular dynamics simulations revealed the molecular conformational changes during OVA-LYS binary protein binding and the stability of the complex conformation. Moreover, MgCl2 weakened the OVA-LYS interactions through Debye shielding while increasing thermal stability, allowing the two proteins to aggregate into amorphous precipitates rather than spherical coacervates. Overall, this study provides information to further understand the regulation mechanism of proteins differential aggregation behavior by ions.

Changes in structural, rheological, and gel properties of egg white protein induced by preheating in the dry state

The knowledge of fundamental rheological concepts is essential to understand the gelling process of egg white proteins (EWP), which can be used to further manipulate the gel performance with desired sensorial attributes. In this study, the rheological and gel properties of EWP as influenced by heating in the dry state were investigated. The structural changes in dry heated EWP (DEWP) were also characterized in terms of morphology, protein stability, and protein microenvironment. The results showed that moderate dry heating induced linear aggregation of DEWP and decreased the denaturation temperature (Td) and enthalpy of denaturation (ΔH). Furthermore, the cross-linking on protein surface led to nonpolar microenvironment of hydrophobic groups, which lays the foundation of improved gel properties. The specific outcomes include the increase in the G'max and the G''max values, k'/k'' values of DEWP dispersions, gel hardness and gumminess of DEWP gels and a decrease in gelation temperature of DEWP dispersions. However, few changes were found in the springiness and cohesiveness of the DEWP gels with increasing dry heating time. Notably, gels prepared with DEWP also had better digestibility. Overall, these results can provide theoretical basis for quality control and sensory evaluation of DEWP in the food industry.

High intensity ultrasound-assisted quality enhancing of the marinated egg: Gel properties and in vitro digestion analysis

In this study, high intensity ultrasonication (HIU) was employed as an efficient tool to improve the gel property and in vitro digestibility of marinated egg (ME). The effects of HIU treatment at 100 W and 200 W for a series of time periods (0.5 h, 1 h, and 2 h) on the textural profiles, structural changes, and microstructures were also studied. After HIU treatment, the springiness and gumminess of ME white were enhanced. The water holding capacity reached the highest point (66.6%) when 0.5 h 200 W HIU was used. It was observed that 100 W HIU led to the highest zeta potential (-12.0 mV) and hydrophobicity (175.35 μg) of ME, indicating a high degree of electrostatic repulsion prevented agglomeration. HIU treatment at 100 W affected the dynamic rheological behaviors by boosting non-covalent bonds, which maintains the gel network's homogeneity. Meanwhile, the decreasing formation of α-helix, in contrast to β-turn, altered the aggregation behaviors of egg white gel. The microstructure of the 200 W HIU treated samples had porous colloidal network structures, and the in vitro digestibility (>75%) was increased after HIU. This work demonstrated that HIU could be a green and cost-effective tool for processing the egg product with high quality.

Quantitative N-glycoproteomic analyses provide insights into the effects of thermal processes on egg white functional properties

This study tries to elucidate the different mechanisms of functional properties among pasteurized egg white (P-EW), spray-dried egg white (SD-EW) and fresh egg white (F-EW) via quantitative N-glycoproteomic analyses. The results showed that spray-drying increased the surface hydrophobicity (181.4%) and zeta potential (25.6%) of egg white, which contributed to the enhancement of emulsifying activity index (20.1%) and foaming capacity (35.2%). Pasteurization caused the disintegration of natural protein aggregates in F-EW and resulted in a "block-like" P-EW gel and higher water holding capacity (6.2%). Spray-drying caused formation of thermal aggregates and led to a "mesh-like" SD-EW gel and better cohesiveness (3.6%). Quantitative N-glycoproteomic analysis showed that the abundance of 32 N-glycosites from 18 N-glycoproteins (such as Mucin 5B) of SD-EW was significantly reduced comparing to F-EW, indicated that the N-glycans of egg white protein are likely to be covalently cross-linked during spray-drying and are involved in thermal aggregation.

Natural protein-templated fluorescent gold nanoclusters: Syntheses and applications

For the past decades, the synthesis of metal nanoclusters has been a great interest for research, for their unique physicochemical properties and great contributions to the catalytic, electrical and biomedical applications. Protein-templated gold nanoclusters (AuNCs) is a kind of fluorescent nanomaterials with good solubility, excellent stability, biocompatibility, decent quantum yields and active groups (-COOH, -NH₂) for facilitating modifications. Natural proteins are easily available, commercially affordable, diverse and multitudinous in animals, plants and foods, which provide a template pool for the exploration of AuNCs. This is one of the few reviews of specifically focusing on the natural protein-templated fluorescent AuNCs. The syntheses, properties and applications of different AuNCs were enumerated. Prospects were given on utilizing structure-modified proteins, bioactive enzymes, antibodies which should endow the AuNCs more favourable fluorescence performances and functional characteristics. The applications of AuNCs in analytical, biomedical and food sciences would be further heightened.

Study on structural, rheological and foaming properties of ovalbumin by ultrasound-assisted glycation with xylose

This study was to evaluate the effect of ultrasound-assisted glycation with xylose on the foaming properties, physicochemical and structural characteristics of ovalbumin (OVA). The number of free amino groups in the glycated OVA (sOVA-X) significantly decreased with the increase of treatment time. The results obtained by circular dichroism (CD) and spectrofluorimetric measurements showed that there were slight changes on the subunits and secondary structure of OVA, indicating that the tertiary structure became more flexible and loose after the sonicated glycation treatment. The glycated OVA had higher solubility and foaming properties than the untreated samples. Therefore, ultrasound improved the glycation extent, and the changes in molecular structure were responsible for their different foaming ability and foaming stability. Our study also provided principle knowledge to understand how the viscosity and rheology were related to the foaming properties of OVA glycation by xylose. The results indicated that ultrasound-assisted glycation could be an excellent approach to improve the functional properties of OVA and promote its application in food industry.