Adsorption and dilatational rheology of heat-treated soy protein at the oil-water interface: relationship to structural properties

Effect of cross-linking density on the rheological behavior of ultra-soft chitosan microgels at the oil-water interface

In this paper, microgels with uniform particle size were prepared by physically cross-linking the hydrophobically modified chitosan (h-CS) with sodium phytate (SP). The effects of cross-linking density on the interfacial adsorption kinetics, viscoelasticity, stress relaxation, and micorheological properties of the hydrophobically modified chitosan microgels (h-CSMs) at the oil-water interface were extensively investigated by the dilatational rheology, compressional rheology, and particle tracing microrheology. The results were correlated with the particle size, morphology, and elasticity of the microgels characterized by dynamic light scattering and atomic force microscopy. It was found that with the increase of cross-linking density, the h-CSMs changed from a polymer-like state to ultra-soft fussy spheres with higher elastic modulus. The compression isotherms demonstrated multi-stage increase caused by the interaction between the shells and that between the cores of the microgels successively. As the increase of cross-linking density, the h-CSMs diffused slower to the oil-water interface, but demonstrating faster permeation adsorption and rearrangement at the oil-water interface, finally forming interfacial layers of higher viscoelastic modulus due to the core-core interaction. Both the initial tension relaxation and the microgel rearrangement after interface expansion became faster as the microgel elasticity increased. The interfacial microrheology demonstrated dynamic caging effect caused by neighboring microgels. This article provides a more comprehensive understanding of the behaviors of polysaccharide microgels at the oil-water interface.

Enhanced stability of Pickering emulsions through co-stabilization with nanoliposomes and thermally denatured ovalbumin

Pickering emulsions were co-stabilized by nanoliposome (NL) and thermally denatured ovalbumin (DOVA) based on the induction of OVA with strong particle characteristics through thermal denaturation. DOVA-NL particles were spherical and their sizes were mainly distributed between 50 and 100 nm. The surface tension and interfacial tension of DOVA-NL were significantly reduced, and the surface hydrophobicity, amphiphilicity and free -SH content of DOVA were enhanced after complexation with NL. The content of α-helix and β-sheet in DOVA decreased, whereas the content of β-turn and random coil increased after complexation with NL. Hydrophobic interactions, hydrogen bonding and electrostatic forces played a vital role in the interactions between NL and DOVA, leading to conformational changes in DOVA. The number of binding sites between NL and DOVA was more than one, and the interaction between NL and DOVA was exothermic and spontaneous. The emulsification index showed that DOVA-NL-stabilized Pickering emulsions (DNPE) were significantly more stable than DOVA-stabilized emulsions. DOVA-NL particles adsorbed at the oil-water interface and the droplet size of DNPE was smaller than that of DOVA-stabilized emulsions. This study suggests that it may be an effective strategy to improve the stability of Pickering emulsions through co-stabilization with NL and DOVA.

Toward Diverse Plant Proteins for Food Innovation

This review highlights the development of plant proteins from a wide variety of sources, as most of the research and development efforts to date have been limited to a few sources including soy, chickpea, wheat, and pea. The native structure of plant proteins during production and their impact on food colloids including emulsions, foams, and gels are considered in relation to their fundamental properties, while highlighting the recent developments in the production and processing technologies with regard to their impacts on the molecular properties and aggregation of the proteins. The ability to quantify structural, morphological, and rheological properties can provide a better understanding of the roles of plant proteins in food systems. The applications of plant proteins as dairy and meat alternatives are discussed from the perspective of food structure formation. Future directions on the processing of plant proteins and potential applications are outlined to encourage the generation of more diverse plant-based products.

Effect of ultrasonic pretreatment on the emulsion rheological properties and interface protein structure of epigallocatechin-3-gallate and rice bran protein complex

The effect of ultrasonic pretreatment on the emulsion rheological properties and the structural characteristics of interface-adsorbed protein (IAP) and interface-unabsorbed protein (IUP) of rice bran protein and epigallocatechin-3-gallate complex (RBP-EGCG) were studied. Compared to RBP-EGCG without ultrasonic pretreatment, appropriate ultrasonic pretreatment (ultrasonic power was 425 W) enhanced the IAP trypsin sensitivity (from 3.20 to 3.73), increased the IUP surface hydrophobicity (from 12.59 to 20.87), and decreased the ζ-potential (from -24.93 mV to -36.88 mV) and particle size (from 567.30 nm to 273.13 nm) of IUP, thereby increasing the viscosity and viscoelasticity of emulsion. Compared to appropriate ultrasonic pretreatment, high-power ultrasonic pretreatment (ultrasonic power was 500 W) attenuated the IAP trypsin sensitivity, and increased the ζ-potential and particle size of IUP, thereby decreasing the viscosity and viscoelasticity of emulsion. Overall, ultrasonic pretreatment changed the EGCG-RBP emulsion viscoelasticity by regulating spatial structural characteristics and flexibility of interface protein.

Almond protein as Pickering emulsion stabilizer: Impact of microgel fabrication method and pH on emulsion stability

We evaluated the ability of almond proteins to produce Pickering emulsions (EM) stabilized by microgels (MG) fabricated by three different methods (heat treatment-HT, crosslinking with transglutaminase-TG or calcium-CA), at two pH levels (pH 3 or 7). Compared to pH 7, acidic pH significantly denatured almond proteins (ellipticity ∼0 mdeg), decreased absolute zeta potential values (10.5 to 18.6 mV at pH 3 and - 24.6 to -32.6 mV at pH 7), and free thiol content (114.64-131.60 μmol SH/g protein at pH 3 and 129.46-148.17 μmol SH/g protein at pH 7 - except in CA-crosslinked microgels, p > 0.05). These changes led to larger microgel sizes (D3,2pH3: 26.3-39.5 μm vs. D3,2pH7: 5.9-9.0 μm) with lower polydispersity (SpanpH3: ∼ 1.94 vs. SpanpH7: 2.32, excluding CA-based samples). Consequently, the Turbiscan Stability Index (TSI) was higher in acidic conditions for all emulsions, except for the calcium-containing formulation (EM_CApH3), emphasizing the critical role of calcium binding in maintaining emulsion stability in acidic environments. Microgels prepared via the traditional heat treatment method produced emulsions with intermediate stability (TSI ranging from 3.4 % to 5.1 % at 28 days of storage). Conversely, TG-crosslinked microgels led to unstable emulsions at pH 3, likely due to the lowest zeta potential (+4.2 mV), whereas at pH 7, the greatest stability was attributed to bridging flocculation that created a stable gel-like structure. Indeed, emulsions with lower TSI (EM_CApH3 = 1.8 %, EM_CApH7 = 2.3 % and EM_TGpH7 = 1.0 %, at 28 days of storage) also exhibited higher elastic modulus (G') over frequency sweep, indicating that the strong elastic network was relevant for emulsion stability (up to 28 days). This study, for the first time, demonstrated the production of stable almond-based Pickering emulsions, with properties modulated by the pH and method used to fabricate the microgels.

Dynamic interfacial adsorption and emulsifying performance of self-assembled coconut protein and fucoidan mixtures

The functional properties of protein are affected by their aggregation behavior and morphology. In this study, the self-assembled coconut protein aggregates with specific morphology, including small amorphous aggregates (WLA), spherical-like aggregates (SLA) and rod-like aggregates (RLA), were regulated to form. The self-assembled process resulted in a decrease in fluorescence intensity and an increase in the surface hydrophobicity of coconut protein. Fucoidan was added to improve the stability of protein solutions, and the interfacial adsorption behavior was evaluated by dilatational rheology analysis. The results showed that the aggregation state of coconut protein affected its ability to reduce surface tension, and the interfacial layers mainly exhibited elastic property at oil-water interface (tanφ < 0.5). For macroscale analysis, the emulsions based on self-assembled coconut protein exhibited smaller droplet size, better rheological properties and centrifugal stability, especially WLA and RLA. This study may provide a reference to inspire the utilization of self-assembled coconut protein in the food industry.

The emulsifying capacity and stability of potato proteins and peptides: A comprehensive review

The potato has recently attracted more attention as a promising protein source. Potato proteins are commonly extracted from potato fruit juice, a byproduct of starch production. Potato proteins are characterized by superior techno-functional properties, such as water solubility, gel-forming, emulsifying, and foaming properties. However, commercially isolated potato proteins are often denatured, leading to a loss of these functionalities. Extensive research has explored the influence of different conditions and techniques on the emulsifying capacity and stability of potato proteins. However, there has been no comprehensive review of this topic yet. This paper aims to provide an in-depth overview of current research progress on the emulsifying capacity and stability of potato proteins and peptides, discussing research challenges and future perspectives. This paper discusses genetic diversity in potato proteins and various methods for extracting proteins from potatoes, including thermal and acid precipitation, salt precipitation, organic solvent precipitation, carboxymethyl cellulose complexation, chromatography, and membrane technology. It also covers enzymatic hydrolysis for producing potato-derived peptides and methods for identifying potato protein-derived emulsifying peptides. Furthermore, it reviews the influence of factors, such as physicochemical properties, environmental conditions, and food-processing techniques on the emulsifying capacity and stability of potato proteins and their derived peptides. Finally, it highlights chemical modifications, such as acylation, succinylation, phosphorylation, and glycation to enhance emulsifying capacity and stability. This review provides insight into future research directions for utilizing potato proteins as sustainable protein sources and high-value food emulsifiers, thereby contributing to adding value to the potato processing industry.

Effect of thermal and non-thermal processing methods on the Structural and Functional Properties of Whey Protein from Donkey Milk

This study evaluated the impact of thermal, ultrasonication, and UV treatment on the structural and functional properties of whey proteins from donkey milk (DWP). Whey proteins exhibited notable stability in non-heat-treated environments, while their structural and functional characteristics were notably impacted by excessive heat treatment. The application of high-temperature long-time thermal treatment (HTLT) resulted in a decrease in fluorescence intensity, foaming and emulsification stability, and considerable damage to the active components of the proteins. Specifically, the preservation of lysozyme activity was only 23%, and lactoferrin and immunoglobulin G exhibited a significant loss of 70% and 77%, respectively. Non-thermal treatment methods showed superior efficacy in preserving the active components in whey proteins compared with heat treatment. Ultrasonic treatment has demonstrated a notable capability in diminishing protein particle size and turbidity, and UV treatment has been observed to have the ability to oxidize internal disulfide bonds within proteins, consequently augmenting the presence of free sulfhydryl groups, which were beneficial to foaming and emulsification stability. This study not only offers a scientific basis for the processing and application of DWP but also serves as a guide to produce dairy products, aiding in the development of dairy products tailored to specific health functions.

The zinc absorption of the novel peptide-Zn complex in Caco-2 cells: effects of soybean peptides charge and hydrophobicity

BACKGROUND

The supplemental effect of zinc depends not only on adequate intake, but also on how efficiently it is absorbed in the small intestine. In the present study, weak hydrophobic peptides (WHP), strong hydrophobic peptides (SHP), positively charged peptides (PCP) and negatively charged peptides (NCP) were isolated from soybean peptides (SP). The peptide-Zn complexes (PCP-Zn, NCP-Zn, WHP-Zn, SHP-Zn and SP-Zn) were prepared to compare their promotion zinc absorption capacity in the Caco-2 cells monolayers model.

RESULTS

We found that the carboxyl, carbonyl and amino groups in peptide were the primary binding sites of Zn. Compared with zinc sulfate, the peptide-Zn complexes with different charge and hydrophobic peptides could improve zinc solubility at different pH. NCP-Zn had a lower Zn-binding capacity but a higher zinc absorption capacity compared to that of PCP-Zn in Caco-2 cells. In addition, the capacity of PCP-Zn to promote zinc absorption was lower than the control group (SP-Zn). There were no significant differences in transport rates, retention rates and uptake rates of WHP-Zn, SHP-Zn and SP-Zn. NCP-Zn could improve the activity of Zn-related enzymes, and the expression levels of PepT1 and ZnT1 were higher than other peptide-Zn complexes.

CONCLUSION

The promotion zinc absorption capacity of peptide-Zn complexes was not completely dependent on the Zn-binding capacity, but also depended on the charge and hydrophobicity of peptides. © 2024 Society of Chemical Industry.

Exploring changes in aggregation and gel network morphology of soybean protein isolate induced by pH, NaCl, and temperature in view of interactions

The texture of soybean protein-based products is primarily influenced by the aggregation and gel morphology of the protein, which is modulated by manufacturing factors. Interactions involved in protein morphology changes include disulfide bonds, hydrophobic interactions, electrostatic interactions, and hydrogen bonds. Notably, an interaction perspective probably provides a new way to explaining the aggregation and gel morphology, which could help overcome the hurdle of developing a textured product. Based on the interaction perspective, this review provides detailed information and evidence on aggregation, conformational stability, and gel network morphology of soybean protein and its components induced by pH, NaCl, and temperature. pH-induced electrostatic interactions and hydrogen bonds, NaCl-induced electrostatic interactions, and temperature-induced hydrophobic interactions and disulfide linkages are the main motivations responsible for changes in soybean aggregation and gel morphology. By reducing the proportion of strong-interactions, such as disulfide linkages and hydrophobic interactions, and increasing the proportion of weak-interactions, such as electrostatic interactions and hydrogen bonds, the protein total surface area expands, indicating increased conformational stretching and decreased cohesion. This possibly results in reduced hardness and increased toughness of textured proteins. The opposite effect can be observed when the proportion of strong interactions is increased and that of weak interactions is decreased.

Inhibitory effects of nobiletin-mediated interfacial instability of bile salt emulsified oil droplets on lipid digestion

Previous lipase inhibitors studies mainly focus on the binding between inhibitors and lipase, ignoring the impact of inhibitors on the oil-water interface of lipid droplets. This study aimed to investigate the effect of nobiletin (NBT) from Citri Reticulatae Pericarpium on the oil-water interface properties and lipid digestion. Here, we found that NBT could destroy bile salt (BS)-stabilized lipid droplets and thus inhibited free fatty acid release, owing to the interaction between NBT and BS at the oil-water interface, and reducing the stability of the oil-water interface (the stability index decreased from 91.15 ± 2.6 % to 66.5 ± 3.6 %). Further, the molecular dynamics simulation and isothermal titration calorimetry revealed that NBT could combine with BS at oil-water interface through intermolecular interactions, including hydrogen bonds, Van der Waals force, and steric hindrance. These results suggest that the interfacial instability of NBT mediated BS emulsified oil droplets may be another pathway to inhibit lipid digestion.

Aggregation structure induced by heat treatments mediated the gastric digestion behavior of soybean protein

The common belief that heat treatment enhances the gastric digestion of proteins is largely based on findings from animal proteins and may not apply to all proteins, particularly plant proteins. Here, we compared the digestion characteristics of soybean protein isolates (SPI) in an in vitro semi-dynamic digestion model and found distinct effects of heat treatment on the digestion properties of plant proteins. The results revealed that heat-treated SPIs formed clots during the early stages of digestion, although the clots gradually became smaller and looser as digestion progressed, the systems remained turbid at the end of gastric digestion, indicating the lag in their emptying. Furthermore, heat treatment altered the rheological properties of SPI, resulting in increased viscosity and slower gastric emptying. These effects became more pronounced with increasing heat treatment temperatures. The fluorescence spectrum analysis indicated that heat treatment altered its conformation. This led to protein unfolding and exposure of hydrophobic groups, facilitating the formation of larger aggregates during digestion. Additionally, heat treatment exposed more cleavage sites for gastric proteases, increasing the extent of hydrolysis. Elevated levels of free amino acids and a smaller molecular weight distribution further corroborated these findings. These findings contribute to a deeper understanding of the gastric digestion characteristics of plant proteins and the relationship between protein aggregation structure and the digestion process.

Extracting bioactive compounds and proteins from Bacopa monnieri using natural deep eutectic solvents

This study employed novel extraction methods with natural deep eutectic solvents (NADES) to extract bioactive compounds and proteins from Bacopa monnieri leaves. The conditional influence of ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE), and enzymatic-assisted extraction (EAE) on the recovery efficiency of phenolics, proteins, flavonoids, and terpenoids was evaluated. The conditions of UAE were 50 mL/g LSR, 600W of ultrasonic power, and 30% water content with 40°C for 1 min to obtain the highest bioactive compounds and protein contents. The conditions of MAE were 40 mL/g LSR, 400W of microwave power with 30% water content for 3 min to reach the highest contents of biological compounds. The conditions of EAE were 30 mL/g of LSR, 20 U/g of enzyme concentration with L-Gly-Na molar ratio at 2:4:1, and 40% water content for 60 min to acquire the highest bioactive compound contents. Scanning electron microscopy (SEM) is employed to analyze the surface of Bacopa monnieri leaves before and after extraction. Comparing seven extraction methods was conducted to find the most favorable ones. The result showed that the UMEAE method was the most effective way to exploit the compounds. The study suggested that UMEAE effectively extracts phenolics, flavonoids, terpenoids, and protein from DBMP.

Heat-induced agglomeration of water-soluble cod proteins toward gelled structures

Cod proteins (CPs) have potential applications in designing desirable gel-based products, and this study aimed to unravel their heat-induced aggregation pattern and further probe the roles in protein gels. SDS-PAGE analysis indicated that high-precipitation-coefficient aggregates (HPCAs) of CPs aggregates were composed of considerable polymers of myosin heavy chains and actin, and their low-precipitation-coefficient aggregates (LPCAs) contained myosin light chains and tropomyosin. Studies from correlation analysis between the structure and aggregation kinetics revealed that the generation of β-sheet and SS bonds were responsible for their spontaneous thermal aggregation induced by heating temperature and protein concentration, respectively. Additionally, as protein denaturation ratio increased, more and larger HPCAs were formed, which was evidenced driving the network formation of protein gels and resulting in higher storage modulus (G') values. These novel findings may be applicable to other animal proteins for better tailoring the manufacturing of muscle gel-based products.

Physicochemical Quantitative Analysis of the Oil-Water Interface as Affected by the Mutual Interactions between Pea Protein Isolate and Mono- and Diglycerides

As a commercially available ingredient, the mono- and diglycerides (MDG) were widely used in a plant protein-based emulsion to provide effective, functional, emulsifying properties. The simultaneous addition of the MDG and pea protein isolate (PPI) was investigated by the methods of interfacial rheology and quantitative protein proteomics. The physicochemical quantitative analysis of the oil-water interface revealed an interfacial stability mechanism for the protein adsorption layer. For a low MDG concentration, the interfacial quantities of vicilin and albumin were increased, which could be attributed to the adsorption rate. For a high MDG concentration, both vicilin and albumin were displaced by MDG and desorbed from the interface, while legumin was more difficult to displace due to its slow adsorption and the complex structure of protein molecules. The protein molecules with the structural rearrangement interacted with MDG, exhibiting potential effects on the interfacial film structure. Combined with some nanotechnologies, the new comprehension of protein-emulsifier interactions may promote food delivery systems. The research aims to develop an in-depth analysis of interfacial proteins, and provide more innovative and tailored functionalities for the application of the plant protein emulsion.

Thermo-induced changes in the structure of lentil protein isolate (Lens culinaris) to stabilize high internal phase emulsions

This study aims to assess the impact of heat treatment on the emulsifying properties of lentil protein isolate (LPI) dispersion to produce high internal phase emulsions (HIPEs). The heat-treated LPI dispersion was characterized by size, turbidity, solubility, zeta potential, free sulfhydryl group, electrophoresis, differential scanning calorimetry, circular dichroism, Fourier transforms infrared spectroscopy and intrinsic fluorescence. HIPEs were produced with 25% of LPI dispersion (2%, w/w) and soybean oil (75%) using a rotor-stator (15,500 rpm/1 min). HIPEs were evaluated for their droplet size, zeta potential, centrifugal stability, microscopy, appearance, Turbiscan stability, and rheology over 60 days (25 °C). Heat treatment reduced the size of LPI, resulting in increased turbidity, solubility, and exposure of hydrophobic groups. HIPEs produced with heat-treated LPI at 70 °C (HIPE70) and 80 °C (HIPE80) for 20 min exhibited lower droplet sizes, increased stability, reduced oil loss, and a homogeneous appearance compared to HIPE produced with untreated LPI (HIPEc). In addition, HIPE70 and HIPE80 displayed resistance to shear stress, higher apparent viscosity, and increased storage modulus than HIPEc. HIPEs produced with heat-treated LPI were stable, suggesting that the treatment was efficient for improving the functional properties of the protein and the possibility of future research focusing on fat substitutes in food applications.

Effects of protein concentration, ionic strength, and heat treatment on the interfacial and emulsifying properties of coconut (Cocos nucifera L.) globulins

This research aimed to investigate the effects of protein concentration (0.2 %-1.0 %), ionic strength (100-500 mM NaCl), and heat treatment (temperature: 80 and 90℃; time: 15 and 30 min) on the interfacial and emulsifying properties of coconut globulins (CG). When protein concentration was set at 0.2-0.6 %, the interfacial adsorption increased with the increasing of protein concentration. However, the lowest interfacial viscoelasticity was found when CG concentration was 0.6 %. When the protein concentration was higher than 0.6 %, the dilatational viscoelasticity increased with the increasing of protein concentration. The protein concentration showed positive effect on the emulsion stability of CG. The ionic strength showed positive effect on the interfacial adsorption but negative effects on the interfacial viscoelasticity and emulsion stability. Higher temperature and longer heating time brought worse interface behavior. The heated CG (90℃, 30 min) had the worst interfacial behavior but the best emulsion stability.

Aggregate Size Modulates the Oil/Water Interfacial Behavior of Myofibrillar Proteins: Toward the Thicker Interface Film and Disulfide Bond

Myofibrillar protein (MP) aggregate models have been established to elucidate the correlation between their aggregate sizes and interfacial properties. The interfacial layer thickness was measured by the polystyrene latex method and quartz crystal microbalance with dissipation measurement. Interfacial conformations were then characterized in situ (front-surface fluorescence spectroscopy) and ex situ (reactive sulfhydryl group and secondary structure measurement following MP displacement). The viscoelasticity of the interfacial film and its resistance to surfactant-induced competitive displacement were reflected by the dilatational rheology and dynamic interfacial tension with the bulk phase exchange. Finally, we compared the findings of competitive displacement before/after adding a sulfhydryl-blocking agent, N-ethylmaleimide, to highlight the role of S-S linkage on interfacial film formation and stability. We substantiated that the aggregate size of the MP governed their interfacial properties. Small-sized aggregates exhibited more ordered secondary structures on the oil-water interface, which was conducive to the adsorption ratio of the protein and the adsorption dynamics. Although larger aggregates lowered the diffusion rate during interfacial film formation, they allowed the thicker and more viscoelastic interfacial film to be constructed afterward through more disulfide bond formation, resulting in greater resistance to surfactant-induced competitive displacement.

Investigating the physicochemical properties and air-water interface adsorption behavior of transglutaminase-crosslinking rapeseed protein isolate

Improving the technical functionality to adapt to the application of complex food systems is an important challenge for the development of plant protein ingredients. Herein, the correlation between the physicochemical properties and interfacial adsorption behavior of rapeseed protein isolate (RPI) at the air-water interface after transglutaminase (TG) treatment was investigated. The results of cross-linking degree, Fourier transform infrared spectroscopy (FTIR) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the TG enzyme was able to catalyse cross-linking between lysine and glutamine residues of RPI. The foaming capacity of RPI was enhanced from 120 % to 150 % after TG cross-linking 5 h, whereas the average size (210-219 nm) of the RPI determined by dynamic light scattering did not change significantly. Besides, the hydrophobicity tended to increase overall under the enzyme treatment, while the surface electrostatic potential decreased. The former indicates the unfolding of the protein and reduces the kinetic barriers to protein adsorption at the air-water interface, with a consequent increase in disulfide bonding and surface pressure. Furthermore, as the enzyme treatment time increased, a significant increase in protein content of foam by 33.86 %. These findings provide novel insight into the foaming mechanism of TG cross-linking RPI.

Covalent modification of (+)-catechin to improve the physicochemical, rheological, and oxidative stability properties of rice bran protein emulsion

The aim of this study is the effects of (+)-catechin (CC) covalent cross-linking (CCCI) (0.05-0.25 %, w/v) on the physicochemical properties, rheological properties, and oxidative stability of rice bran protein (RBP) emulsion. Analysis of particle size, ζ-potential, circular dichroism, fluorescence spectroscopy, surface hydrophobicity, and emulsifying properties demonstrated that a concentration of 0.15 % (w/v) CCCI facilitated protein structure unfolding, resulting in reduced particle size, enhanced electrostatic repulsion, and improved emulsion stability. Moreover, the covalent complexes of RBP-0.15 %CC (w/v) exhibited increased viscosity and shear stress, reflected by the highest G' and G″ values, ultimately enhancing the oxidative stability. Furthermore, analysis using atomic force microscopy and confocal laser scanning microscopy revealed that the RBP-0.15 %CC complexes exhibited the smallest particle size (164 nm) and displayed greater homogeneity. An increase in CC concentration to 0.25 % (w/v) resulted in a higher emulsion aggregation. The emulsions stabilized by CCCI exhibited superior rheological properties and enhanced oxidation stability compared to the control. In conclusion, an appropriate amount of CC can enhance the rheology and oxidation stability of the RBP emulsion, while CCCI treatment holds potential for expanding the utility of RBP in various applications.

Effects of electric field intensity regulation on protein aggregation behaviour and foaming property of soybean 7S globulin

In this study, the aggregation behaviour of soybean 7S globulin after moderate electric field (MEF) treatment was investigated, and the influence of the electric field and temperature field on the structure and foaming property of the aggregates were analysed and compared with conventional water bath (COV). The results showed that MEF treatment enhanced the properties of the aggregates. The properties of the treated aggregates were significantly better than those of native 7S globulin. At an electric field strength of 8 V/cm, the solubility, turbidity, and particle size increased from 95.81 % to 99.37 %, 0.097 to 0.189 and 61.97 nm to 113.21 nm, respectively, and the absolute value of potential decreased from 23.56 mV to 22.12 mV. The SDS-PAGE and size exclusion chromatography (SEC) results showed that the electric field had a positive effect on the aggregate formation of the Fourier-transform infrared spectroscopy (FTIR), fluorescence spectroscopy, surface hydrophobicity (H0) and total sulfhydryl (SHT) results indicated that the spatial structure of the protein was changed by MEF treatment. The protein β-sheet content was reduced, and the Try that was originally buried inside the molecule was exposed, resulting in an increase in H0 and a decrease in SHT. The foaming property of the 7S globulin aggregates was improved by MEF treatment.

Low oil Pickering emulsion gels stabilized by bacterial cellulose nanofiber/soybean protein isolate: An excellent fat replacer for ice cream

Food-grade Pickering emulsion gels with different oil phase fractions stabilized by Bacterial cellulose nanofibers/Soy protein isolate complex colloidal particles were prepared by one-step method. The properties of Pickering emulsion gels with different oil phase fractions (5 %, 10 %, 20 %, 40 %, 60 %, 75 %, v/v) and their applications in ice cream were investigated in the present study. The microstructural results showed that Pickering emulsion gels with the low oil phase fractions (5 %-20 %) were an emulsion droplet-filled gel, where the oil droplets were embedded in the network structure of cross-linked polymer, while Pickering emulsion gels with higher oil phase fractions (40 %-75 %) were an emulsion droplet-aggregated gel, which formed a network structure by flocculated oil droplets. The rheology result showed that the low oil Pickering emulsion gels had the same excellent performance as the high oil Pickering emulsion gels. Furthermore, the low oil Pickering emulsion gels showed good environmental stability under harsh conditions. Consequently, Pickering emulsion gels with 5 % oil phase fraction were used as fat replacers in ice cream and ice cream with different fat replacement rates (30 %, 60 % and 90 %, w/w) was prepared in this work. The results showed the appearance and texture of the ice cream with low oil Pickering emulsion gels as fat replacers was similar to that of the ice cream with no fat replacers, and the melting rate of the ice cream with low oil Pickering emulsion gels as fat replacers showed the lowest value of 21.08 % during the 45 min of melting experiment, as the fat replacer rate in the ice cream reached to 90 %. Therefore, this study demonstrated that low oil Pickering emulsion gels were excellent fat replacers and had great potential application in low calorie food production.

L-lysine moderates thermal aggregation of coconut proteins induced by thermal treatment

This work attempts to investigate the inhibitory effect of L-lysine (Lys) on the thermal aggregation of coconut protein (CP). The results showed that under neutral conditions (pH = 7), temperature reduced the solubility and enhanced the thermally induced gel formation of CP. In addition, Lys reduced the fluorescence properties, particle size and increased the turbidity of CP, which had an inhibitory effect on heat induced gels. The results indicate that Lys plays an important role in inhibiting protein thermal aggregation by interacting with CP to create steric hindrance and increase protein electrostatic repulsion.

Soy protein particles with enhanced anti-aggregation behaviors under various heating temperatures, pH, and ionic strengths

Protein-containing food products are frequently heated during processing to passivate anti-nutritional components. However, heating also contributes to protein aggregation and gelation, which limits its application in protein-based aqueous systems. In this study, heat-stable soy protein particles (SPPs) were fabricated by preheating at 120 °C for 30 min and at 0.5% (w/v) protein concentration. Compared to untreated soy proteins (SPs), SPPs exhibited a higher denaturation ratio, stronger conformational rigidity, compacter colloidal structure, and higher surface charge. The aggregation state of SPs and SPPs at various heating conditions (temperatures, pH, ionic strength, and types) was analyzed by dynamic light scattering, atomic force microscopy, and cryo-scanning electron microscopy. SPPs showed less increase in particle size and greater anti-aggregation ability than SPs. When heated in the presence of salt ions (Na⁺, Ca²⁺) or at acidic conditions, both SPs and SPPs formed larger spherical particles, but the size increase rate of SPPs was significantly lower than SPs. These findings provide theoretical information for preparing heat-stable SPPs. Furthermore, the development of SPPs is conducive to designing protein-enriched ingredients for producing innovative foods.

Effect of Stir-Frying on Physicochemical and Functional Properties of Oat Protein Isolates

The heat treatment required for the deactivation of enzymes was carried out on crop species such as oats. Stir-frying, a frequently employed method for enzyme inactivation to preserve their desirable shelf life, can result in diminished nutritional value and protein degeneration. The mechanism by which stir-frying affects the oat protein remains largely unknown. Therefore, this study aimed to investigate the physicochemical and functional properties of the extracted oat protein isolates (OPI) at different stir-frying durations (0, 10, 20, and 30 min) at a temperature of 230 °C. The findings of this study demonstrated that stir-frying led to a decrease in the content of amino acids (AA), potentially attributed to the involvement of certain amino acids in the Maillard reaction. As the time of stir-frying increased, the secondary structure of OPI underwent changes: specifically, β-turns transformed into β-sheets. The process of protein denaturation and redistribution of chemical bonds resulted in an increase in the disulfide bond content of OPI, leading to aggregation, large particle size, and reduced digestibility. However, the water retention properties, foaming properties, and emulsification properties of OPI showed improvement. These findings provide valuable insights for the controlled and precise processing of oats and highlight the potential of OPI as a functional food.

Controlling the assembly of soy β-conglycinin to fabricate heat-stable particles for high protein liquid systems

BACKGROUND

Recently, there is a growing interest in developing protein-fortified liquid systems, which are formulated to provide special nutrient combinations to those with special dietary needs. The fabrication of heat-stable protein for protein-fortified liquid systems relies heavily on precise control of the edible protein-building process.

RESULTS

Results suggested that heat-stable 7S protein particles (7SPPs) could be obtained by preheating at 100 °C for an extended time, whereas 7S proteins with better gelling properties were discovered after preheating at lower temperatures. According to the findings of the protein conformational and morphological characterization, the 7SPPs showed rather stable tertiary and secondary structures as well as size distributions, which might be responsible for their heat stability. Additionally, during the reheating test, suspensions of 7SPPs showed no signs of gelation and had a low viscosity even though the protein content was as high as 120 mg mL^-1 . However, 7S proteins with improved gelling properties were found to show rising aggregate size, higher susceptibility and larger conformational structure changing rates upon reheating treatment.

CONCLUSION

Soy β-conglycinin (7S) proteins with tunable heat stability were successfully prepared by preheating 10 mg mL^-1 protein dispersions at various temperatures (80-120 °C) and durations (15-120 min). These findings provide fundamental insights for developing 7S-based protein-fortified systems. © 2023 Society of Chemical Industry.

Quantitative analysis and interfacial properties of mixed pea protein isolate-phospholipid adsorption layer

Proteins and low-molecular-weight (LMW) surfactants are widely used for the physical stabilization of many emulsion-based food products. This study investigated the oil-water interfacial behavior between pea protein isolate (PPI) and phospholipid (PL). The emulsions prepared with different concentrations of PPI and PL were stabilized by their synergetic or competitive adsorption at the oil-water interface. In addition, the quantitative proteomics results could illustrate the displacements of proteins by PL. The result showed that the vicilin (7S) could be preferentially displaced by PL. Meanwhile, the results of quartz crystal microbalance with dissipation (QCM-D) indicated the high affinity of legumin (11S) with PL, suggesting that the legumin possessed higher interfacial affinity to prevent interfacial displacement. This research could help us to understand the interaction and competitive adsorption between plant proteins and LMW surfactants profoundly, which could promote the development of plant protein-based emulsion beverage with improved stability.

Aggregation and Growth Mechanism of Ovalbumin and Sodium Carboxymethylcellulose Colloidal Particles under Thermal Induction

Ovalbumin (OVA)/sodium carboxymethylcellulose (CMC) colloidal particles were prepared with different compactness and morphologies by regulating the interaction between proteins and polysaccharides during heating. Electrostatic interactions between the amine groups of OVA (-NH₃⁺) and carboxyl groups of CMC (-COO^-) enhanced complex formation. The protein conformation change benefited the hydrophobic interaction between the particles. Proteins in colloidal particles were unfolded/folded under thermal induction to form aggregates having more β-sheet structures. When the OVA/CMC ratio was 1:2, the initially loosely connected OVA/CMC aggregation changed into a uniform sphere between 25 and 90 °C. The mass ratio of OVA to CMC within the final colloidal particle (90 °C) was about 1:1.4. The OVA/CMC particle stability was maintained with hydrogen bonding, hydrophobicity, and disulfide bond. When OVA levels were predominant, OVA and CMC developed an approximately hollow sphere. Moreover, the final colloidal particle composition showed the OVA-to-CMC ratio as 3:1 (w/w). OVA bound into colloidal particle pores to increase compactness. Moreover, OVA and CMC bound to the colloidal particle while the particle shrank, thereby increasing the compactness of colloidal particles. There was a significant decrease in ABTS^•+ scavenging activity of curcumin compared with that of the particles with a ratio of 1:2. Thus, the rational adjustment of the structure of colloidal particles could effectively enhance their functional characteristics, providing a new way for the controlled release of the active ingredients.

Soy Protein Isolate Interacted with Acrylamide to Reduce the Release of Acrylamide in the In Vitro Digestion Model

Acrylamide (AA), a common carcinogen, has been found in many dietary products.. This study aimed to explore the interaction of soybean protein isolate (SPI) with AA and further research the different effects of SPI on the AA release due to interactions in the in vitro digestion model. Analysis of variance was used to analyze the data. The results suggested that AA could bind with SPI in vitro, leading to the variation in SPI structure. The intrinsic fluorescence of SPI was quenched by AA via static quenching. The non-covalent (van der Waals forces and hydrogen bonding) and covalent bonds were the main interaction forces between SPI and AA. Furthermore, the release of AA significantly decreased due to its interaction with SPI under simulated gastrointestinal conditions. SPI had different effects on the AA release rate after different treatments. The thermal (80, 85, 90, and 95 °C for either 10 or 20 min) and ultrasound (200, 300, and 400 W for either 15, 30, or 60 min) treatments of SPI were useful in reducing the release of AA. However, the high pressure-homogenized (30, 60, 90, and 120 MPa once, twice, or thrice) treatments of SPI were unfavorable for reducing the release of AA.

Pickering emulsion stabilized by modified pea protein-chitosan composite particles as a new fat substitute improves the quality of pork sausages

Pickering emulsion is a potential substitute for animal fat due to high stability and solid-like properties. Therefore, the effect of replacing 25%-100% pork backfat with Pickering emulsion (75% corn oil volume fraction) stabilized by modified pea protein-chitosan composite particles on the quality of sausages was studied. All meat pastes exhibited a strong gel-like rheological character (G' > G"). The incorporation of Pickering emulsion in sausages enhanced the textural properties (hardness, springiness, chewiness, cohesiveness and resilience) and the uniformity and compactness of micromorphology, as well as suppressed the cooking loss and TBARS content. In particular, the sausages with a backfat substitution ratio of 100%, showing a similar overall sensory acceptability to the backfat sausage, revealed the best rheological properties, texture properties and micromorphology and the lowest cooking loss and fat oxidation (P < 0.05). The results showed that Pickering emulsion stabilized by modified pea protein-chitosan composite particles is a potential fat substitute for meat products with the desirable characteristics.

Correlation between interfacial layer properties and physical stability of food emulsions: current trends, challenges, strategies, and further perspectives

Emulsions are thermodynamically unstable systems that tend to separate into two immiscible phases over time. The interfacial layer formed by the emulsifiers adsorbed at the oil-water interface plays an important role in the emulsion stability. The interfacial layer properties of emulsion droplets have been considered the cutting-in points that influence emulsion stability, a traditional motif of physical chemistry and colloid chemistry of particular significance in relation to the food science and technology sector. Although many attempts have shown that high interfacial viscoelasticity may contribute to long-term emulsion stability, a universal relationship for all cases between the interfacial layer features at the microscopic scale and the bulk physical stability of the emulsion at the macroscopic scale remains to be established. Not only that, but integrating the cognition from different scales of emulsions and establishing a unified single model to fill the gap in awareness between scales also remain challenging. In this review, we present a comprehensive overview of recent progress in the general science of emulsion stability with a peculiar focus on interfacial layer characteristics in relation to the formation and stabilization of food emulsions, where the natural origin and edible safety of emulsifiers and stabilizers are highly requested. This review begins with a general overview of the construction and destruction of interfacial layers in emulsions to highlight the most important physicochemical characteristics of interfacial layers (formation kinetics, surface load, interactions among adsorbed emulsifiers, thickness and structure, and shear and dilatational rheology), and their roles in controlling emulsion stability. Subsequently, the structural effects of a series of typically dietary emulsifiers (small-molecule surfactants,proteins, polysaccharides, protein-polysaccharide complexes, and particles) on oil-water interfaces in food emulsions are emphasized. Finally, the main protocols developed for modifying the structural characteristics of adsorbed emulsifiers at multiple scales and improving the stability of emulsions are highlighted. Overall, this paper aims to comprehensively study the literature findings in the past decade and find out the commonality of multi-scale structures of emulsifiers, so as to deeply understand the common characteristics and emulsification stability behaviour of adsorption emulsifiers with different interfacial layer structures. It is difficult to say that there has been significant progress in the underlying principles and technologies in the general science of emulsion stability over the last decade or two. However, the correlation between interfacial layer properties and physical stability of food emulsions promotes revealing the role of interfacial rheological properties in emulsion stability, providing guidance on controlling the bulk properties by tuning the interfacial layer functionality.

High pressure homogenization to boost the technological functionality of native pea proteins

Pea proteins are being increasingly used for the formulation of plant-based products, but their globular structure and the presence of aggregates can affect their technological properties. In this study, the effect of high pressure homogenization (HPH) at different intensities (60 and 100 MPa) was investigated as a pre-treatment to modulate the techno-functional properties of a pea protein isolate (IP) extracted through an alkaline extraction/isoelectric precipitation process. SDS-PAGE, circular dichroism, thermal properties, total free sulfhydryl groups, antioxidant capacity and reducing properties were evaluated along with technological indices as solubility, WHC and OHC, interfacial tension and emulsifying capacity. HPH treatments were able to unfold and modify proteins structure, leading also to a change of the relative abundance of pea protein globulins (SDS-PAGE) and of the vicilin to legumin ratio. Solubility, WHC and OHC were improved, while interfacial tension and emulsifying capacity were weakly affected. However, an enhanced physical stability over time of the emulsions prepared with the 60 MPa-treated protein was found, likely as an effect of the decreased ratio between vicilin and legumin after treatment. Results of this study will contribute to deepen the effect of the HPH technology used as pre-treatment, adding useful results and expanding knowledge about the structure and techno-functional properties of native and modified pea proteins.

Impact of Cavitation Jet on the Structural, Emulsifying Features and Interfacial Features of Soluble Soybean Protein Oxidized Aggregates

A cavitation jet can enhance food proteins' functionalities by regulating solvable oxidized soybean protein accumulates (SOSPI). We investigated the impacts of cavitation jet treatment on the emulsifying, structural and interfacial features of soluble soybean protein oxidation accumulate. Findings have shown that radicals in an oxidative environment not only induce proteins to form insoluble oxidative aggregates with a large particle size and high molecular weight, but also attack the protein side chains to form soluble small molecular weight protein aggregates. Emulsion prepared by SOSPI shows worse interface properties than OSPI. A cavitation jet at a short treating time (<6 min) has been shown to break the core aggregation skeleton of soybean protein insoluble aggregates, and insoluble aggregates into soluble aggregates resulting in an increase of emulsion activity (EAI) and constancy (ESI), and a decrease of interfacial tension from 25.15 to 20.19 mN/m. However, a cavitation jet at a long treating time (>6 min) would cause soluble oxidized aggregates to reaggregate through an anti-parallel intermolecular β-sheet, which resulted in lower EAI and ESI, and a higher interfacial tension (22.44 mN/m). The results showed that suitable cavitation jet treatment could adjust the structural and functional features of SOSPI by targeted regulated transformation between the soluble and insoluble components.

Heat-induced amorphous aggregates assembly of soy protein modulate in vitro digestibility of potato starch

This research focused on the characteristics of amorphous aggregates derived from soy protein (SPAA), and their effects on the structural, physicochemical, and digestive properties of potato starch (PS). The SPAA induced by different heating temperatures at pH 7.0 formed an inhomogeneous spherical structure. The presence of SPAA could improve the degree of short-range order of starch, increase thermal stability, reduce pasting viscosity and breakdown, and setback viscosity values of PS. For the PS complexed with SPAAs under simulated cooking conditions, the fraction of digested starch at 300 min (C₃₀₀) decreased by 6-14 %, and rapid digestible starch content (RDS) decreased by 18-25 %, while the slowly digestible starch (SDS) and resistant starch (RS) increased by 0.4-3 % and 15-23 %, respectively. The SPAA at higher temperature treatment (SPAA₁₃₀) reduced digestive rate coefficient (k) values more significantly than SPAA at a lower temperature (SPAA₇₀, SPAA₉₀, SPAA₁₁₀). And the SPAA had no inhibitory effect on α-amylase. The results of this study would significantly contribute to expanding the theoretical information about protein regulation in starch digestion and promoting the development of healthy foods with digestion-resistant properties.