Protein-based Emulsions Research Articles

Improving emulsion stability: The role of flaxseed gum in stabilizing bovine bone protein hydrolysates emulsions

The use of natural proteins as emulsifiers in stable emulsion systems has gained attention due to the increasing demand for healthy food products. However, the limited thermal stability and ionic tolerance of BBPH restrict its application in emulsions. This study explores the effects of FG on enhancing the stability of BBPH-based emulsions. FTIR and SEM confirmed that BBPH and FG form complexes through hydrophobic and electrostatic interactions, with increasing FG concentrations leading to higher turbidity and particle size. At 0.4 % FG, emulsions showed the smallest particle size (9.12 μm) and the highest zeta potential (-28.73 mV), indicating optimal interaction. Raman spectroscopy further supported these findings, showing enhanced oil-complex interactions and favorable rheological properties. The emulsions exhibited excellent stability during storage, with a creaming index of 1.786 % after 7 days. Oxidation tests showed low POV (0.596 mg/L) and TBARS (6.24 mg/L) after 15 days. FG also improved resistance to environmental stress, providing theoretical support for the broader use of BBPH in the food industry and highlighting FG's potential in stabilizing protein-based emulsions.

Improving plant-based protein drinks: The potential of flavors for cross-modal enhancement of fat perception

Fat perception is a complex phenomenon that influences the sensory experience of beverages. In this study, we explored the role of olfaction and flavor to modulate the fat perception and physical-chemical characteristics of protein-based emulsions with different fat contents. The emulsions consisted of pea protein isolate, canola oil and tap water. Two milky-creamy flavors were used, each with different composition and volatile profile. Our results showed that all fat contents (0, 1.5 and 3.5%) could be differentiated by the panelists. The fat-related creamy, milky, fatty, thickness and mouthcoating attributes had higher scores at higher fat contents, which positively correlated with the lubrication factor. Interestingly, adding flavor or blocking olfaction did not change the discrimination capacity, but the addition of flavor did cause a cross-modal effect on the fat perception. With olfaction, both flavors increased the fat descriptive aroma and mouthfeel attributes. Without olfaction, the taste and mouthfeel attributes were uninfluenced. Moreover, the flavors did not influence the physical-chemical characteristics at these low concentrations. Congruency of the flavor with fat increases the fat perception of the emulsions. Overall, this study suggests that fat congruent flavor can be utilized to modulate the fat perception in protein-lipid drinks, such as plant-based milks.

Development of non-animal chicken fat using faba bean protein-based emulsion gels

Increasing awareness of the risks associated with overconsumption of saturated fats has focused attention on healthier fat replacers that can be incorporated into alternative protein foods as non-animal fat. A key technological challenge is in developing non-animal fats that are: (1) relatively high in melting point, (2) low in saturated fat, and (3) able to combine with proteins in a food matrix. In our study, protein-based emulsion gels (PEGs) consisting of faba bean protein concentrate, olive oil and water at different protein (7-10% w/w) and oil (40-60% w/w) concentrations, were created using high-pressure processing (HPP) technology. The PEGs were characterized and compared to chicken fatty deposits based on their appearance, color, oil-holding capacities, freeze-thaw stability, and rheological properties. We found that PEGs with lower protein concentrations, particularly 7% protein, 40% oil (7%P,40%O) exhibited the closest rheological properties and gel strength G’ (4465.07 ± 76.12 Pa) to chicken fatty deposits (2933.60 ± 763.21 Pa). PEGs with 10% protein had better long-term oil-holding capacities after the second freeze-thaw (for 10%P,60%O: 42.062 ± 0.530%), in comparison to chicken fat (45.362 ± 5.928%). Freeze-thaw treatments disrupted the stability of the PEG, signifying the importance of temperature control during gel storage and transportation. These results provide valuable insight into the effect of protein and oil concentrations on measured attributes in the PEGs. This will enable us to utilize PEGs to create and mimic animal fats such as chicken fat.

Construction and characteristics of EGCG-porcine serum albumin pickering emulsion: Based on noncovalent interactions mechanism

Pickering emulsion prepared by the interaction between polyphenols and protein can improve the stability of protein-based emulsion. The purpose of this study was to explore the complex formation mechanism of epigallocatechin gallate (EGCG)-porcine serum albumin (PSA) complex and the preparation of food-grade Pickering emulsion. By the UV and fluorescence spectral analysis, it was found that EGCG has an obvious fluorescence quenching effect on PSA, mainly static quenching. The results of synchronous, three-dimensional fluorescence and FT-IR spectroscopy showed that the hydrophobic microenvironment of aromatic amino acids and the secondary structure of PSA changed after EGCG was added. The results of molecular docking examined that EGCG and PSA form more stable complexes due to hydrogen bonds, and the binding energy was −4.43 kcal /mol. Compared with the PSA emulsion, the successfully prepared EGCG-PSA Pickering emulsion had smaller droplets and no obvious color in CLMS. The Pickering emulsion of EGCG-PSA had strong emulsification and high viscosity, which belonged to pseudoplastic non-Newtonian fluid. In addition, the free fatty acids release rate of EGCG-PSA Pickering emulsion was decreased by 9.9 %. The antioxidant performance of the EGCG-PSA Pickering emulsion was improved, and the DPPH radical scavenging rate and the ABTS+ radical scavenging rate reached the highest, which were 93.72 % and 57.16 % respectively. This study provides important insights into the interaction between EGCG and PSA, and a reference for the development of polyphenol-protein complex Pickering emulsion in food, medicine, cosmetics, and other fields.

Impact of κ-Carrageenan on the Freshwater Mussel (Solenaia oleivora) Protein Emulsion Gels: Gel Formation, Stability, and Curcumin Delivery.

Protein-based emulsion gels are an ideal delivery system due to their unique structure, remarkable encapsulation efficiency, and tunable digestive behavior. Freshwater mussel (Solenaia oleivora) protein isolate (SoPI), an emerging sustainable protein with high nutritional value, possesses unique value in the development of functional foods. Herein, composite emulsion gels were fabricated with SoPI and κ-carrageenan (κ-CG) for the delivery of curcumin. SoPI/κ-CG stabilized emulsions possessed a high encapsulation efficiency of curcumin with a value of around 95%. The addition of κ-CG above 0.50% facilitated the emulsion gel formation and significantly improved the gel strength with 1326 g. Furthermore, the storage and digestive stability of curcumin were significantly improved as the κ-CG concentration increased. At 1.50% κ-CG, around 80% and 90% curcumin remained after 21-day storage at 45 °C and the 6 h in vitro gastrointestinal digestion, respectively. The addition of 0.50% κ-CG obtained the highest bioaccessibility of curcumin (~60%). This study illustrated the potential of SoPI emulsion gels as a carrier for stabilizing and delivering hydrophobic polyphenols.

Spirulina platensis protein-based emulsion gel as fat substitute in meat analogs: Evaluation performance across post-processing

In this paper, Spirulina platensis protein-based emulsion gels were investigated as fat substitutes in meat analogs and compared with conventional fat sources like palm oil, oleogel, and soybean oil. Evaluating parameters such as cooking loss, shrinkage, texture, appearance, and moisture distribution across various cooking methods. Emulsion gels imparted superior juiciness to meat analogs whereas palm oil and oleogel led to drier meat textures. Besides they also resulted in comparable cooking loss and shrinkage to traditional fats, indicating preferred fat options for incorporation of emulsion gels. The novel emulsion gel-filled meat analogs exhibited robust tolerance across three distinct cooking methods, boiling, steaming, and deep-frying. Steamed meat analogs exhibited brighter MRI signals, while fried counterparts displayed peripheral hollowing, attributed to steam's energy transfer and humidity-induced water migration, respectively. Overall, the study underscores the efficacy of these fat analogs in meat analogs, offering insights into their potential as viable alternatives in food formulations.

Composite starch/fermented protein emulsion gels for plant-based cheese applications

This work investigated the effect of incorporating lipids and proteins on the properties of starch-based gels relevant for plant-based cheese analogues. Gels were prepared by first fermenting protein-based emulsions to create primary gels, and subsequently using the water of these primary gels as starch hydration media to produce secondary, starch-based, pea protein-rich composite emulsion gels. Fermentation appeared to increase gel hardness compared to non-fermented protein addition. Compared to natural and crosslinked/acetylated starches, the acid-hydrolysed/acetylated starch produced firmer gels and was selected for further experimentation. Gels were macroscopically homogeneous but microscopically showed lipid coalescence at increasing lipid content (>8%), which was reduced by ultrasonicating the emulsion prior to fermentation. Dry matter content was key in determining textural and rheological properties of the gels, with starch/protein gels of 36% dry matter showing hardness and viscoelastic properties similar to those of the dairy cheese Danbo. However, the composite gels did not melt on increasing temperature up to 80 °C (delta below 20°). Proton dynamics were found to depend on gel properties and lipid addition. Overall, this work contributes towards the development of plant-based cheeses with desired characteristics by increasing their protein content and modulating their properties through fermentation and syneresis.

Enhancing soy protein isolate flexibility through non-covalent ferulic acid modification: Implications for interfacial characteristics and protein-based emulsion performance

This study aims to enhance the flexibility of soy protein isolate (SPI) to improve its functional properties, focusing on the investigated the effects of ferulic acid (FA) on the structure, interfacial behaviour and emulsification performance of SPI. Our study showed that FA induces SPI structures to depolymerization and unfolding primarily through hydrogen bonding and hydrophobic interactions, thereby increasing the flexible structures (random coils and β-turns) of protein. These changes enhanced the interfacial functional properties of SPI, with 150 μmol/g of FA-modified SPI exhibiting the best molecular flexibility, and its emulsification and emulsification stability were improved by 21.26 % and 39.86 %, respectively, compared to unmodified SPI. In addition, non-covalently modified FA significantly improved emulsions stability. Emulsions stabilized by SPI-FA150 complexes exhibited better storage, heat, and freeze-thaw stability than SPI, with a significant reduction in oxidation products. This relationship between flexibility and function reveals the importance of structural modification in enhancing protein functionality. These discoveries shed new light on flexible protein processing technologies and the application of FA in protein functional modification.

Fabrication of pea protein isolate-stabilized oil-in-water emulsions with high freeze-thaw stability: Effect of high intensity ultrasonic on emulsions and interfacial protein structure

The poor freeze-thaw stability of plant protein-based emulsions posed a major challenge for their application in the cold chain foods. The present study successfully prepared oil-in-water emulsions stabilized solely with pea protein isolate (PPI) with excellent freeze-thaw stability using a facile high intensity ultrasonic (HIU)-assisted method. The optimized emulsion can endure three freeze-thaw cycles without stratification or oil leakage, maintaining oil droplet sizes at the nanometer scale. Furthermore, changes of interfacial protein structure induced by HIU were systematically investigated to reveal the stabilizing mechanism. The freeze-thaw stability of emulsions treated under varying intensities was evaluated based on changes in the appearance and oil drop size distribution. The results showed that the oil drop size of emulsions decreased from micron to nanometer and the freeze-thaw stability was significantly enhanced with the increase of HIU intensity. The emulsion exhibited optimized freeze-thaw stability under 800W. Subsequently, the effect of HIU on the structure of interfacial protein was analyzed through SDS-PAGE, –SH/S–S contents, UV spectrum, surface hydrophobicity, protein adsorption percentage, emulsifying activity and interfacial dilatational rheology. It was found that HIU triggered crosslinking of disulfide bonds among interfacial PPI molecules and enhanced the strength of the interface layer. Additionally, HIU promoted the unfolding of interfacial PPI structure, resulting in the improvement of surface hydrophobicity, emulsifying activity, and interfacial adsorption percentage of PPI. The study demonstrated the feasibility of using HIU to improve the freeze-thaw stability of oil-in-water emulsions stabilized with PPI and provided references for the fabricating of plant protein-based frozen emulsion foods.

Improving physical stability of microalgae protein-based emulsions under acidic and neutral conditions via carboxymethyl chitosan complexation

The emulsification stability of microalgae protein (MP) is limited to strongly alkaline conditions, restricting its applications in food processing. This study aims to investigate the capability of carboxymethyl chitosan (CMCS) to improve MP's emulsification stability over a wider pH range. Results indicated soluble MP-CMCS complexes formed at pH 2, 4, and 7, while aggregation of the complexes occurred at pH 8. The complexes stabilized emulsions exhibited smaller droplet sizes and higher absolute zeta potential at pH 2, 4, and 7 compared to pH 8. After 2 weeks of storage, emulsions remained stable at pH 2, 4, and 7, with significant delamination at pH 8. Laser confocal microscopy confirmed uniform droplet distribution at pH 2 and 7, with slight fusion at pH 4. The complexes stabilized emulsions exhibited higher viscosity and shear stress than MP stabilized emulsions at pH 2, 4, and 7. The stronger viscoelastic properties and higher storage moduli (G') values of MP-CMCS complexes under acidic and neutral conditions indicated stronger intermolecular interactions compared to alkaline conditions. The increase in G' and loss moduli (G") values for emulsions at pH 8 under stress highlighted the significant impact on network structure strength and viscosity in these emulsions. This study elucidated the binding interactions between MP and CMCS under various pH conditions, and demonstrated a feasible approach to improving MP's emulsification stability over a wider pH range.

Preparation of Transglutaminase-Catalyzed Rice Bran Protein Emulsion Gels as a Curcumin Vehicle.

Protein-based emulsion gels have tunable viscoelasticity that can be applied to improve the stability of bioactive ingredients. As the by-product of rice processing, rice bran protein (RBP) has high nutritional value and good digestibility, exhibiting unique value in the development of hypoallergenic formula. In this study, the effect of transglutaminase (TGase) cross-linking on the physicochemical properties of RBP emulsion gels was investigated. To improve the stability of curcumin against environmental stress, the entrapment efficiency and stability of curcumin in the emulsion gel systems were also evaluated. The results indicated that TGase increased the viscoelastic modulus of RBP emulsion gels, resulting in a solid-like structure. Moreover, the entrapment efficiency of curcumin was increased to 93.73% after adding TGase. The thermal stability and photo-stability of curcumin were enhanced to 79.54% and 85.87%, respectively, compared with the sample without TGase addition. The FTIR results showed that TGase induced the cross-linking of protein molecules and the secondary structure change in RBP. Additionally, SEM observation confirmed that the incorporation of TGase promoted the formation of a compact network structure. This study demonstrated the potential of RBP emulsion gels in protecting curcumin and might provide an alternative strategy to stabilize functional ingredients.

Type of pectin affects the functionality of potato protein-pectin conjugates in emulsions

This study investigated the effect of the molecular structure of pectin on conjugate formation and its functionality in plant protein-based emulsions. For this purpose, high-methoxylated, low-methoxylated, amidated citrus pectin and their mixtures with potato protein were vacuum-dried at defined process conditions. The change in free amino groups, colour and molecular weight distribution assessed conjugation. The side reaction, such as pectin degradation, was monitored by the degree of methoxylation, galacturonic acid content and intrinsic viscosity. In addition, FT-IR and hydrophobicity measurements were performed to determine the changes in chemical structure due to the occurring reactions. The ζ-potential, solubility and oil droplet size reflected the functionality of the conjugated samples.The results confirm that, apart from the conjugation of protein and pectin, where the most significant decrease in free amino groups was obtained with an increasing degree of methoxylation or presence of amide groups, undesirable degradation of pectin occurring, resulting in a broad molecular weight distribution of the conjugate samples. The conjugate formation was the highest with amidated pectin. The FT-IR measurements confirmed the formation of Maillard conjugates. The FT-IR spectra showed a decrease in the intensity signals of amide I and amide II and the formation of new C–N bond maxima. In addition, the conjugation caused the shift of the protein's isoelectric point to the acidic environment, resulting in higher solubility and improved emulsion stability at the isoelectric point of the protein.Regarding emulsion stability, the conjugates with amidated pectin performed best and achieved the narrowest oil droplet size distribution over a wider pH range. Emulsion-stabilising properties of conjugates with high- and low-methoxylated pectin differed only slightly. To better understand the underlying mechanisms for emulsion stabilisation, future research will focus on the interfacial properties of the conjugates as determined by interfacial shear rheology and pendant drop analysis.

Formation conditions of soy protein isolate-carrageenan complex particles and their stabilization effect on the relationship between structure and rheology of emulsions

This study investigated the formation conditions of the soy protein isolate (SPI)/κ-carrageenan (κCG) complex particles (SCP) and their stabilization effect on the structure and rheology of emulsions over the range of SCP concentration (Cp, 0.5%–2.5%, w/v) and oil phase content (φ, 10%–60%, v/v). By conducting turbidity titration of SPI/κCG mixtures with different ratios and ionic strengths, we observed the formation of soluble complexes in all samples at pH 6.0. The saturation complex ratio of SPI/κCG at pH 6.0 was 1:0.2 using isothermal titration calorimetry, and thermal complex with saturation ratio to form SCP as stabilizers could prepare emulsions with smaller droplet size in comparison of other ratios. Microstructure showed that SCP provided stabilization at the interface, and excess SCP formed network in the bulk phase to give solid-like emulsions. Furthermore, the power-law relationships of G′ with particle concentration (G' ∼ Cpn) and oil content (G' ∼ φm) was established. The exponent n and m decreased with increase of Cp and φ, indicating structure of SCPEs depends on Cp and φ. The G'/G″ crossover strain (γco) is indicator of breakdown of emulsion structure. For φ ≤ 20%, γco slightly decreased with increasing Cp; For 30%<φ<50%, γco increased with increasing Cp; For φ = 60%, γco significantly decreased with increasing Cp. In summary, these findings indicate the structure and rheology of soy protein-based emulsion can be regulated by controlling the formation condition of SCP and altering the SCP concentration and oil content.

Chitooligosaccharide assisted in the construction of pickering high internal phase emulsion near the isoelectric point of porcine plasma protein

Protein-based emulsion products always be challenged due to destabilize the emulsification at the pH range near isoelectric point (pI) of the protein. Herein, chitooligosaccharide (COS) was successfully used to assist porcine plasma proteins (PPP) to construct the high internal phase emulsions (HIPEs) near pI of PPP, and the characteristics and mechanism of the HIPEs was investigated. Particle size of oil droplets in the HIPEs reduced significantly by adding only 0.25% COS, and the PPP-COS composite HIPEs exhibited excellent performance characteristics near pI of PPP, i.e., pH 5.0, including appearance, particle size, apparent viscosity, modulus, 3D printing and stability. PPP and COS combined to form micro-size particles with many positive charges at pH 5.0, and a strong adsorption between PPP and COS was observed at the pH by quartz crystal microbalance with dissipation (QCMD). The pI of PPP shifted increasingly by about 0.5 along with addition of COS, and so no precipitates were formed at pH 5.0 according to the optical density. Hydrophobic interaction and hydrogen bond could be the main forces between PPP and COS based on interaction analysis. The work provided an excellent compound emulsifier with some bioactivities to stabilize the HIPEs near pI of the protein.

Comparison of the physical stability, microstructure and protein-lipid co-oxidation of O/W emulsions stabilized by l-arginine/l-lysine-modified soy protein hydrolysate

This work investigated the physical stability, microstructure, and oxidative stability of the emulsions prepared by soy protein hydrolysate (SPH) after modification with different concentrations of l-arginine and l-lysine. l-Arginine and l-lysine significantly increased the absolute zeta potential values, and decreased droplet sizes of the emulsions, thereby improving the physical stability of the emulsions. Meanwhile, l-arginine and l-lysine markedly decreased the apparent viscosity of the emulsions. The measurement of interfacial protein adsorption percentage showed that l-arginine (≤0.5 %) promoted the adsorption of SPH at the oil–water interface, whereas l-lysine (≤1%) reduced the adsorption of SPH at the oil–water interface. In addition, l-arginine and l-lysine (≤0.5 %) could retard lipid and protein oxidation. Correlation analysis indicated that the improvement in the physical stability of the emulsions by l-arginine and l-lysine also enhanced the oxidative stability of the emulsions. In summary, l-arginine and l-lysine could be effective modifiers for the protein-based emulsion systems.

Effect of cellulose nanofibrils on stability and digestive properties of legume protein-based emulsions

The global sustainability and health consciousness awakening have contributed to the rise of legume proteins, but the poor emulsion stability of legume proteins limits their application. Herein, cellulose nanofibrils (CNFs) isolated from citrus peels were used to improve the stability of pea isolate protein, chickpea isolate protein, and soybean isolate protein emulsions. Results showed that CNFs extracted from citrus peels could improve the interfacial properties of legume proteins via non-covalent interaction. The addition of CNFs could increase interfacial tension and contact angle compared to the legume protein alone. CNFs resulted in the formation of homogeneous emulsions with smaller particle sizes as well as an increase in the viscosity of the emulsions. Meanwhile, the stability of legume protein/CNFs complex emulsions showed significant advantages over single legume protein emulsions in terms of long-term storage, centrifugation, salt ions, and high temperature. Furthermore, legume protein/CNFs emulsions have a lower rate of lipid digestion. These results revealed that CNFs have promising potential for improving legume protein emulsion stability and retarding lipolysis, which provides a theoretical basis for advancing the use of legume proteins.

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.

Stability and gastrointestinal behavior of curcumin-loaded emulsion stabilized by multi-conformation soy proteins: Influence of oil volume fraction

The aim of this work was to assess the potential of nanoemulsions stabilized by mixed soy protein with multi-conformation as curcumin carrier, and the influence of oil volume fraction on stability and gastrointestinal behavior of curcumin-loaded emulsion was investigated. Loading efficiency showed a slight increase with higher oil content, though the difference was not statistically significant. With the increase of oil, the viscosity (Pa‧s), thixotropy (area of hysteresis loop) and particle size of the emulsion increased, which facilitated the physical and chemical stability of curcumin-loaded emulsion. However, the free fatty acid release rate and bioaccessibility of curcumin was negatively correlated with the oil volume fraction and the particle size of emulsion after gastric digestion. Notably, the digestion in stomach did not affect the structure of interfacial protein, demonstrating that protein-based nanoemulsions exhibited resistance to gastric digestion. This study provides theoretical guidance for the application of protein-based emulsion in curcumin delivery.

Interaction between Chinese quince fruit proanthocyanidins and soy protein isolate: Effects on physical and oxidative stability of oil-in-water emulsions

Protein-based emulsions are extremely sensitive to droplet aggregation. The interaction between the proanthocyanidins (PAs) and protein can affect the efficacy of protein on the stability of emulsions. In this study, PAs with different molecular weights of ethyl acetate (EA) and retained aqueous (RA) phase were prepared from Chinese quince fruit and mixed with soy protein isolate (SPI) to form complexes, and their effects on the physical and oxidative stability of oil-in-water (O/W) emulsions were assessed. The results confirmed that SPI had fewer α-helices and more random coils when bound to EA and RA. The main forces between PAs and SPI were hydrogen bonds and hydrophobic interactions. Furthermore, RA-SPI, particularly EA-SPI, showed better foaming, emulsifying and antioxidant properties than SPI. The emulsifying activity index values of EA-SPI and RA-SPI were 39.7% and 33.4% higher than that of SPI, respectively. The physical and oxidative stability of O/W emulsions stabilized by SPI were lower than those stabilized by EA-SPI and RA-SPI. At day 15, the lipid hydroperoxide content of EA-SPI and RA-SPI emulsions was 30.5% and 10.3% lower than that of SPI emulsion, respectively. This study provides a basis for PAs as natural antioxidants to improve the stability of O/W emulsions.

Structural properties and emulsification of myofibrillar proteins from hairtail (Trichiurus haumela) at different salt ions

The structural properties and emulsification of myofibrillar proteins (MPs) are susceptibly affected by salt ions. The effect of different salt ions on the structural properties and emulsification of MPs from hairtail (Trichiurus haumela) remains unclear. Hairtail MPs were analyzed under different ion treatments of Na+, K+, Ca2+ and Mg2+. MPs at K+ and Na+ treatment showed a similar trend on salt effect due to the unfolding of proteins under salt ions. However, the excessive electrostatic effect of divalent ions could enhance protein aggregation, especially at Ca2+ and Mg2+. The β-sheet of MPs at different salt ions interconverted with α-helix and random coil at ionic strengths from 0.1 mol/L to 1.0 mol/L. The surface hydrophobicity and active sulfhydryl content of MPs increased with the improvement of ionic strengths at 0–0.8 mol/L. Under Ca2+ and Mg2+ treatments, the turbidity of MPs was low compared to that under the treatment of Na+ and K+. Additionally, the emulsification of hairtail MPs treated with different ions was improved at an ionic strength of 0.6 mol/L. This study can contribute to using salts in constructing fish protein-based emulsions for manufacturing emulsified surimi products and promoting the development and utilization of hairtail proteins.