New insights into the NaCl impact on emulsifying properties of globular proteins

Improving the emulsifying properties and oil-water interfacial behaviors of chickpea protein isolates through Maillard reaction with citrus pectin

The limited adsorption capability of chickpea protein isolates (CPI) at the oil-water interface restricts its application in emulsions. This study aimed to improve the emulsifying properties and interfacial behaviors of CPI through Maillard reaction with citrus pectin (CP). The research findings showed that the covalent linking of CP with CPI caused the unfolding of the molecular structure of CPI, exposing more hydrophobic groups. Consequently, the CPI-CP conjugates exhibited improved emulsifying properties. Emulsions stabilized by CPI-CP conjugates after 12 h of glycosylation demonstrated the smallest droplet sizes (1.73 μm) and the highest negative zeta potentials (-54.7 mV). Glycosylation also improved the storage and environmental stability of these emulsions. Interfacial adsorption kinetics analysis revealed the lower interfacial tension (13.94 mN/m) and faster diffusion rates of the CPI-CP conjugates. Furthermore, interfacial dilatational rheology analysis indicated that the CPI-CP conjugates formed an interfacial layer with a higher viscoelastic modulus (33.214 mN/m) and predominant elastic behavior. The interfacial film of CPI-CP conjugates showed excellent resistance to amplitude and frequency variations, enhancing emulsion stability. Thus, this study demonstrates that moderate glycosylation enhances interfacial performances and improves emulsion stability of CPI, providing new insights into the mechanisms by which CPI stabilizes emulsions.

Conformational changes induced by cellulose nanocrystals in collaboration with calcium ion improve solubility of pea protein isolate

The low solubility of pea protein isolate (PPI) greatly limits its functional properties and its wide application in food field. Thus, this study investigated the effects and mechanisms of cellulose nanocrystals (CNC) (0.1-0.4 %) and CaCl2 (0.4-1.6 mM) on the solubility of PPI. The results showed that the synergistic effect of CNC (0.3 %) and Ca2+ (1.2 mM) increased the solubility of PPI by 242.31 %. CNC and Ca2+ changed the molecular conformation of PPI, enhanced intermolecular forces, and thus induced changes in the molecular morphology of PPI. Meanwhile, the turbidity of PPI decreased, while surface hydrophobicity, the absolute zeta potential value, viscoelasticity, β-sheet ratio, and thermal properties increased. CNC bound to PPI molecules through van der Waals force and hydrogen bond. Ca2+ could strengthen the crosslinking between CNC and PPI. In summary, it is proposed a valuable combination method to improve the solubility of PPI, and it is believed that this research is of great significance for expanding the application fields of PPI and modifying plant proteins.

Freeze-thaw stability of high-internal-phase emulsion stabilized by chickpea protein microgel particles and its application in surimi

BACKGROUND

Future applications of high-internal-phase emulsions (HIPEs) are highly regarded, but poor freeze-thaw stability limits their utilization in frozen products. This study aimed to characterize the structure of chickpea protein microgel particles (HCPI) induced by NaCl and to assess its impact on the freeze-thaw stability of HIPEs.

RESULTS

The results showed that NaCl induction (0-400 mmol L-1) increased the surface hydrophobicity (175.9-278.9) and interfacial adsorbed protein content (84.9%-91.3%) of HCPI. HIPEs prepared with HCPI induced by high concentration of NaCl exhibited superior flocculation index and centrifugal stability, and their freeze-thaw stability was better than that of natural chickpea protein. The increase in NaCl concentration reduced the droplet aggregation and coalescence index of the freeze-thaw emulsions, diminishing the precipitation of oil from the emulsion. Linear and nonlinear rheology showed that the strengthened gel structure (higher G' values) restricted water flow and counteracted the damage to the interfacial film by ice crystals at 100-400 mmol L-1 NaCl, thus improving the viscoelasticity of the freeze-thaw emulsions. Finally, the thawing loss of surimi gel with HCPI-200 HIPE was reduced by 2.04% compared to directly adding oil.

CONCLUSION

This study provided a promising strategy to improve the freeze-thaw stability of HIPEs and reduce the thawing loss of frozen products. © 2024 Society of Chemical Industry.

Insight into the mechanisms of combining direct current magnetic field with phosphate in promoting emulsifying properties of myofibrillar protein

This study investigated the combined effects of direct-current magnetic field (DC-MF, 9.5 mT) and tetrasodium-pyrophosphate (TSPP, 1-5 g/L) on emulsified gel properties of porcine myofibrillar protein (MP). Results showed that MP at DC-MF and 3 g/L TSPP had decreased spectrum intensity of UV and fluorescence compared to that without DC-MF, owing to the changes of MP tertiary structure caused by DC-MF, especially tryptophan and tyrosine. The emulsion treated with DC-MF behaved better emulsifying activity and stability than that without DC-MF under such condition. And emulsion had lower creaming index and better storage stability. Gels prepared by this MP emulsion had low porosity and stable structure, accompanying with smaller size and more uniform distribution of oil droplets. Microstructure images showed that gels were covered with microporous structure, which was conducive to the good WHC of the emulsified gels (97.12%). These results showed the feasibility of DC-MF and TSPP in improving MP emulsion/emulsified gel.

Improved encapsulation effect and structural properties of whey protein isolate by dielectric barrier discharge cold plasma

The whey protein isolate (WPI) was modified by dielectric barrier discharge cold plasma (DBD) in order to improve its encapsulation efficiency of rutin. In this work, the effect of DBD treatment on structure and physicochemical properties of WPI and the interaction between DBD-treated WPI and rutin were investigated. The results showed that the structural change of WPI leaded to the exposure of internal hydrophobic groups, increasing the interaction site with rutin. The encapsulation efficiency of DBD-treated WPI (30 kV, 30 s) on rutin was improved by 12.42 % compared with control group. The results of multispectral analysis showed that static quenching occurred in the process of interaction between DBD-treated and rutin, hydrogen bond and van der Waals force were the main forces between them. Therefore, DBD treatment can be used as a method to improve the encapsulation efficiency of WPI on hydrophobic active substances.

The Effect of Ionic Strength on the Formation and Stability of Ovalbumin-Xanthan Gum Complex Emulsions

Protein-polysaccharide complexes have been widely used to stabilize emulsions, but the effect of NaCl on ovalbumin-xanthan gum (OVA-XG) complex emulsions is unclear. Therefore, OVA-XG complex emulsions with different XG concentrations at pH 5.5 were prepared, and the effects of NaCl on them were explored. The results indicated that the NaCl significantly affected the interaction force between OVA-XG complexes. The NaCl improved the adsorption of proteins at the oil-water interface and significantly enhanced emulsion stability, and the droplet size and zeta potential of the emulsion gradually decreased with increasing NaCl concentrations (0-0.08 M). In particular, 0.08 M NaCl was added to the OVA-0.2% XG emulsion, which had a minimum droplet size of 18.3 μm. Additionally, XG as a stabilizer could improve the stability of the emulsions, and the OVA-0.3% XG emulsion also exhibited good stability, even without NaCl. This study further revealed the effects of NaCl on emulsions, which has positive implications for the application of egg white proteins in food processing.

Hemp seed globulin-alginate nanoparticles for encapsulation of Cannabisin A with enhanced colloidal stability and antioxidant activity

This study develops hemp seed globulin (GLB)-alginate (ALG) nanoparticles (GANPs) for Cannabisin A (CA) stabilization under environmental stress and during pepsin digestion. The optimal GLB: ALG mass ratio of 1: 1.5 was determined for GANPs formation at pH 3.5, resulting in a high yield of 95.13 ± 0.91 %, a ζ-potential of -35.73 ± 1.04 mV, a hydrodynamic diameter of 470.67 ± 11.36 nm, and a PDI of 0.298 ± 0.016. GANPs were employed to encapsulate CA, achieving a high loading capacity of 13.48 ± 0.04 μg mg-1. FTIR analysis demonstrated that the formation of CA-GLB-ALG nanoparticles (CGANPs) involves electrostatic interactions, hydrogen bonding, and hydrophobic interactions. XRD and DSC analyses revealed that CA is amorphous within the CGANPs. CGANPs demonstrated remarkable dispersion stability as well as resistance to high ionic strength and high-temperature treatments, indicating their potential as efficient hydrophobic drug-delivery vehicles. When compared to free CA, CA coated within CGANPs displayed greater DPPH/ABTS scavenging activity. Furthermore, the ALG-shelled nanoparticles protected GLB from pepsin digestion and slowed the release of CA throughout the release process, extending their stay on the intestinal wall mucosa. These findings imply that CGANPs is an ideal delivery vehicle for CA as they may expand the application of CA in food items.

Non-covalent interaction between hemp seed globulin and two hemp seed phenolic compounds: Mechanism and effects on protein structure, bioactivity, and in vitro simulated digestion

This study focused on elucidating the non-covalent interactions between hemp seed globulin (GLB) and two hemp seed phenolic compounds, Cannabisin A (CA) and Cannabisin B (CB), and to explore these interactions on the protein's structure, conformation, and functionality. Fluorescence quenching and thermodynamic analysis revealed that static quenching governed non-covalent interaction processes, with hydrogen bonds and van der Waals forces functioning as major forces. This was further substantiated by molecular docking studies. The binding affinity order was CA > CB, indicating that the specific phenolic compound had a notable impact on the binding affinity. Furthermore, when complexed with CA, Tyr and Trp residues were exposed to a more hydrophilic environment than when complexed with CB. It was noted that the complexation with either CA or CB consistently affects GLB's secondary structure, particle size, and ζ-potential. GLB treated with the phenolic compounds exhibited enhanced ABTS and DPPH scavenging activities and improved digestibility compared to untreated GLB. Furthermore, the non-covalent interactions significantly increased CA's water solubility, highlighting GLB as a promising natural carrier for hydrophobic bioactive components. These findings hold potential implications for enhancing hemp seed protein applications within the food industry by positively influencing its functional properties and bioactivity.

Effects of high-pressure homogenization on the physicochemical, foaming, and emulsifying properties of chickpea protein

In order to expand the utilization of chickpeas in various food products, this study investigated the effects of different homogenization pressures (0-150 MPa) and cycles (1-3) on the physicochemical, and functional properties of chickpea protein. After high-pressure homogenization (HPH) treatment, hydrophobic groups and sulfhydryl groups of chickpea protein was exposed which increased its surface hydrophobicity and decreased its total sulfhydryl content. SDS-PAGE analysis showed that the molecular weight of modified chickpea protein remained unchanged. The particle size and turbidity of chickpea protein significantly decreased with an increase in homogenization pressure and cycles. Furthermore, the solubility, foaming, and emulsifying properties of chickpea protein were all enhanced by HPH treatment. In addition, the emulsions prepared by modified chickpea protein showed better stability capacity due to its smaller particle size and higher zeta potential. Therefore, HPH might be an effective technique to improve the functional properties of chickpea protein.

Effect of salt treatment on the stabilization of Pickering emulsions prepared with rice bran protein

In this study, salt addition (NaCl and CaCl₂) was utilized to improve the stability of emulsions formed by rice bran protein (RBP). The result showed that salt addition improved the adsorption of protein on the oil-water interface and enhanced the physical stability of emulsions. Compared to NaCl condition, emulsions with CaCl₂ (especially 200 mM) addition exhibited more significant storage stability, as microscopy images showed emulsion structure unchanged and droplet size increasing slightly from 12.02 µm to 16.04 µm in 7 days. It was attributed to the strengthened particle complexation with CaCl₂ and the increased hydrophobic interactions, which is explained by the improved particle size (260.93 nm), surface hydrophobicity (1890.10) and fluorescence intensity, thus inducing dense and hardly destroyed interfacial layers. Rheological behavior analyses suggested that salt-induced emulsions had higher viscoelasticity and maintained a stable gel-like structure. The result of study explored the mechanism of salt treated protein particles, developed a further understanding of Pickering emulsion, and was beneficial to the application of RBP.

Effects of pH-shifting treatments on the emulsifying properties of rice protein isolates: Quantitative analysis of interfacial protein layer

For the limitation of poor solubility and interfacial adsorption capacity of rice protein isolates (RPI), in this work the effects of pH-shifting treatments on the emulsifying properties of RPI were investigated. The results showed that the particle size of the emulsion stabilized by alkaline pH-shifting treated RPI was smaller than that stabilized by acid pH-shifting treated RPI. In addition, the RPI-10 stabilized emulsion showed a more uniform particle size distribution, which was explained by its high emulsifying activity and stability (EAI: 49.5 m²/g, ESI: 59.5 min). The interface rheology results showed that the alkaline pH-shifting treatment could promote the protein rearrangement and subsequently formed interface film with higher rate of protein penetration and rearrangement. The quantitative analysis of adsorbed proteins in the RPI-10 stabilized emulsion showed that glutelin-type isoforms as major proteins in RPI were increased at the oil-water interface for their balanced distribution of the hydrophilic and hydrophobic amino acid group. These quantitative and interfacial rheology analysis could improve deep understanding of the interfacial properties of pH-shifting treated RPI, and promote the development of application in grain protein stabilized emulsion.

Effect of Ionic Strength on Heat-Induced Gelation Behavior of Soy Protein Isolates with Ultrasound Treatment

This study investigated the effect of ultrasound on gel properties of soy protein isolates (SPIs) at different salt concentrations. The results showed that ultrasound could significantly improve the gel hardness and the water holding capacity (WHC) of the salt-containing gel (p < 0.05). The gel presents a uniform and compact three-dimensional network structure. The combination of 200 mM NaCl with 20 min of ultrasound could significantly increase the gel hardness (four times) and the WHC (p < 0.05) compared with the SPI gel without treatment. With the increase in NaCl concentration, the ζ potential and surface hydrophobicity increased, and the solubility decreased. Ultrasound could improve the protein solubility, compensate for the loss of solubility caused by the addition of NaCl, and further increase the surface hydrophobicity. Ultrasound combined with NaCl allowed proteins to form aggregates of different sizes. In addition, the combined treatment increased the hydrophobic interactions and disulfide bond interactions in the gel. Overall, ultrasound could improve the thermal gel properties of SPI gels with salt addition.

Chitosan-regulated biomimetic hybrid nanoflower for efficiently immobilizing enzymes to enhance stability and by-product tolerance

Organic-inorganic hybrid nano-materials have been considered to be promising immobilization matrixes for enzymes due to their significantly enhanced reusability and stability of enzymes. Herein, we constructed a novel organic-inorganic hybrid nanoflower via biomacromolecule-regulated biomimetic mineralization to immobilize sucrose phosphorylase (SPase). It was found that chitosan (CS) effectively regulated the biomimetic mineralization of calcium phosphate (CaP), leading to the formation of flower-like hybrid materials for the entrapment of SPase via self-assembly to establish a nano-biocatalyst (CS-CaP@SPase). Upon immobilization, the obtained CS-CaP@SPase exhibited excellent pH, by-product and organic solvents tolerance, and storage stability. Specifically, at acidic condition (pH 4), CS-CaP@SPase performed over 80 % of initial activity, which was 2.42-folds higher than that of free SPase. The catalytic activity of free SPase was severely inhibited about 30 % in the presence of fructose (1.2 M), but CS-CaP@SPase only lost 5 % relative activity. The CS-CaP@SPase retained over 80 % of its relative activity, while the free SPase maintained <20 % of its relative activity in acetonitrile. The relative activity of CS-CaP@SPase was still retained about 80 % after 10 cycles and maintained 75 % after 15 days. Based on Raman spectra analysis, it was also found that the increased β-folding component of SPase in the secondary structure after immobilization was the main factor for its enhanced stability. It is reasonable to believe that biomacromolecule-regulated biomimetic mineralization could be potentially used as a promising method to immobilize enzymes with excellent stability and recyclability, thereby facilitating the preparation of highly efficient catalysts for industrial biocatalysts, biosensing, and biomedicine.