Effect of Proteolytic Modification on Texture and Mastication of Heat-Treated Egg White Gels

Unraveling the impact of protease hydrolysis on the gelation properties of whole egg liquid: physicochemical, textural and structural characteristics

BACKGROUND

Egg proteins are of high quality with excellent gelation properties. This study explored how neutral protease hydrolysis (400, 800, 1200 U g-1) and heating time (10, 20 min) affect whole egg liquid (WEL) gelation, focusing on protein solubility, intermolecular interactions and gel structure changes for food applications.

RESULTS

Enzymatic hydrolysis significantly increased the degree of hydrolysis, with higher enzyme dosage (up to 1200 U g-1) leading to enhanced protein solubility (from 81.09% to 93.21%) and reduced average particle size (from 476 to 80 nm). Texture analysis showed that higher enzyme levels reduced the breaking force and distance to rupture, while prolonged heating time (20 min) could increase breaking force, such as increasing the 1200 U g-1 sample from 17.4 to 23.27 g. Fourier transform infrared spectroscopy showed that enzymatic hydrolysis raised β-sheet content (from 43.62% to 43.98%) but reduced β-turn, whereas prolonged heating shifted β-sheet to β-turn. Intermolecular force analysis indicated dominant hydrophobic interactions in control gels, while enzymatically treated gels exhibited increased ionic bonds and hydrogen bonds. Scanning electron microscopy demonstrated that enzymatic hydrolysis and longer heating produced denser, more uniform gel networks.

CONCLUSION

Protease hydrolysis and heating time greatly modulate WEL gel properties. Enzymatic treatment makes gels softer, while longer heating improves hardness and microstructure. These findings can guide tailoring of WEL gel properties for industrial uses like custards by optimizing conditions. © 2025 Society of Chemical Industry.

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.

Physicochemical and functional properties of egg white peptide powders under different storage conditions

This study aims to evaluate the effects of different storage conditions (temperature and relative humidity) on the physicochemical and functional properties of egg white peptide powders (EWPPs). The samples (EWPPs) were stored for 28 d under four conditions (4 °C, 50% RH; 4 °C, 75% RH; 25 °C, 50% RH; 25 °C, 75% RH). Results showed that storage temperature and relative humidity had a significant effect on the physicochemical and functional properties of EWPPs. The contents of antioxidant amino acids such as histidine, tyrosine, tryptophan, and lysine were reduced significantly under different storage conditions, which resulted in the decrease of the antioxidant activity of EWPPs. Circular dichroism spectroscopy analysis indicated that the secondary structure of EWPPs changed from the regular structure to the irregular coiled structure during the storage. Additionally, the hydrophobic groups of the EWPPs originally embedded inside the molecules were exposed to the surface of the molecules during the storage, which led to an aggregation of EWPPs molecule and a decrease in solubility of EWPPs. The aggregation of EWPPs molecules resulted in a decrease in emulsification, emulsification stability, foaming ability and foaming stability of the EWPPs. Therefore, different storage conditions do have an impact on the physicochemical and functional properties of EWPPs. Lower temperature and humidity storing conditions were beneficial to retain the functional property of the EWPPs.

Preparation and Characterization of Beads of Sodium Alginate/Carboxymethyl Chitosan/Cellulose Nanofiber Containing Porous Starch Embedded with Gallic Acid: An In Vitro Simulation Delivery Study

In this study, a system was designed that can encapsulate and deliver gallic acid (GA), which was composed of polysaccharide polymers based on sodium alginate (SA), carboxymethyl chitosan (CCT), and cellulose nanofibers (CN) and was assisted by porous starch. The compositions were characterized by rheology and zeta potentials, and the results showed that the materials used in this study could effectively guarantee the stability of the system. The morphology and chemical structure of the beads were characterized by SEM and FT-IR, the results indicated that the addition of CCT could effectively reduce the cracks and pores on the surface of the beads, which was beneficial to the encapsulation and delivery of GA. Moreover, the results of the swelling rate, release tests, and antioxidant tests also proved the effectiveness of the system. The pH response effect of SA/CN/CCT (SCC) beads and the protection of GA were superior, and the release rate of GA in simulated gastric fluid (SGF) was only 6.95%, while SA and SA/CN (SCN) beads reached 57.94% and 78.49%, respectively. In conclusion, the interpenetrating network polymers constructed by SA, CCT, and CN, which, combined with porous starch as a coating layer, can achieve the embedding and the delivery of GA.