Modulating interfacial dilatational properties by electrostatic sodium caseinate and carboxymethylcellulose interactions

Physical stability, microstructure and interfacial properties of solid-oil-in-water (S/O/W) emulsions stabilized by sodium caseinate/xanthan gum complexes

Calcium carbonate (CaCO₃) has poor suspension stability, which severely limits its application in food processing and products. In this study, sodium caseinate (NaCas) and sodium caseinate (NaCas)-xanthan gum (XG) mixtures were compared for the stable preparation of solid/oil/water (S/O/W) emulsions for the delivery of calcium carbonate (CaCO₃) to solve the problem of poor suspension stability. The physical stability, particle size distribution, and microstructure of S/O/W emulsions were investigated to prove the successful construction of the system. The dynamic surface pressure and surface swelling properties of 2.0 wt% NaCas with different concentrations of XG were investigated to clarify the effect of interfacial properties of NaCas-XG mixtures on the emulsion stability of S/O/W emulsions. The results showed that the addition of XG resulted in enhanced physical stability, reduced particle size distribution, and enhanced encapsulation effect of the emulsion, forming a more three-dimensional core-shell structure via dendritic links. XG had a significant effect on the dynamic properties of the NaCas adsorption membrane: NaCas interacted with XG and the diffusion (k_diff) of NaCas to the interface decreased in short adsorption time, thus limiting the protein adsorption effectiveness; the presence of XG reduced the penetration (k_P) and rearrangement (k_R) rates at the interface during long adsorption times. Meanwhile, the NaCas-XG mixture has a high swelling elasticity. The results of this study can be used to improve the quality of related emulsion products or to prepare delivery systems for bioactive compounds.

Emulsification characteristics of soy hull polysaccharides obtained by membrane separation

Membrane separation technology was used to separate and purify the microwave-assisted oxalic acid extraction of soy hull polysaccharides (MOSP) in order to obtain samples of different molecular weights. The emulsification characteristics of the MOSP were investigated including protein adsorption, polysaccharide adsorption, interfacial tension, emulsion index, and particle size; optical microscopy and Phenom electron microscopy were used to elucidate the emulsion structures. In addition, Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and high-performance gel-filtration chromatography (HPGFC) were used to study the differences in the components and structures of MOSP in different molecular weights. The molecular weight had several important effects on the emulsifying properties of MOSP. The adsorption capacities of the emulsion droplets containing low molecular weight MOSP (L-MOSP), middle molecular weight MOSP (M-MOSP), and high molecular weight MOSP (H-MOSP) were relatively low, and those of H-MOSP were slightly higher than those of L-MOSP. With extended storage time, the particle sizes of the emulsions rich in L-MOSP, M-MOSP, and H-MOSP increased. L-MOSP, M-MOSP, and H-MOSP were mainly composed of furans. The conformation of the molecular chain was spherical. The emulsions formed with H-MOSP were the most stable.

Formation and stability of Pickering emulsion gels by insoluble soy peptide aggregates through hydrophobic modification

In this work, a highly stable food-grade Pickering emulsion gels was successfully prepared by hydrophobically modified insoluble soybean peptide aggregates. The relationships between the surface properties of insoluble soybean peptide aggregates and Pickering emulsion gels characteristics were clarified. After modification, the insoluble soybean peptide aggregates with high surface hydrophobicity had small particle size (377 nm), near-neutral wettability (θo/w = 92°) and strong interfacial adsorption capability. These allowed the modified insoluble soybean peptide aggregates to stabilize the oil-water interface and form continuous network surrounding oil droplets, leading to the formation of stable Pickering emulsion gels. Besides, Pickering emulsion gels prepared by insoluble soybean peptide aggregates with higher surface hydrophobicity had smaller droplet size and higher gel strength, and remained stable even after 60 days of storage. The findings suggest a preferable plant protein particle for the preparation of stable Pickering emulsion gels in food industry.

Protein-polysaccharide interactions for the fabrication of bioactive-loaded nanocarriers: Chemical conjugates and physical complexes

As unique biopolymeric architectures, covalently and electrostatically protein-polysaccharide (PRO-POL) systems can be utilized for bioactive delivery by virtue of their featured structures and unique physicochemical attributes. PRO-POL systems (i. e, microscopic /nano-dimensional multipolymer particles, molecularly conjugated vehicles, hydrogels/nanogels/oleogels/emulgels, biofunctional films, multilayer emulsion-based delivery systems, particles for Pickering emulsions, and multilayer coated liposomal nanocarriers) possess a number of outstanding attributes, like biocompatibility, biodegradability, and bioavailability with low toxicity that qualify them as powerful agents for the delivery of different bioactive ingredients. To take benefits from these systems, an in-depth understanding of the chemical conjugates and physical complexes of the PRO-POL systems is crucial. In this review, we offer a comprehensive study concerning the unique properties of covalently/electrostatically PRO-POL systems and introduce emerging platforms to fabricate relevant nanocarriers for encapsulation of bioactive components along with a subsequent sustained/controlled release.

pH-Dependent Binding Behavior of the α-Lactalbumin/Glycyrrhizic Acid Complex in Relation to Their Foaming Characteristics in Bulk

This work aimed to understand the relationships of the interaction mechanism and foaming characteristics of α-lactalbumin (α-La) and glycyrrhizic acid (GA) after acidic (pH 2.5) and neutral (pH 7.0) treatment. The critical aggregation concentration (CAC) of GA in the presence of α-La was 0.6 mM at pH 7.0, while it was 1.0 mM at pH 2.5. Also, in the presence of a GA concentration of 0-15.00 mM, more GA molecules combined onto the α-La surface at pH 2.5 than at pH 7.0, as evident from the binding isotherms. The turbidity and particle size of α-La/GA were greater in acidic solution than those under neutral conditions. This result could be interpreted by the formation of aggregates under higher GA concentration at pH 2.5. Meanwhile, the viscosity of the complex was higher at pH 2.5 than at pH 7.0 in the presence of 3.00-15.00 mM GA, as analyzed from the rheological properties. The foaming ability (FA) of α-La was significantly enhanced in the presence of 10.00 mM GA. Simultaneously, acidic solution could generate a more stable foaming system with a thicker film layer stabilized by the complex compared with neutral solution. These findings could be beneficial for developing a kind of acidic food-grade foaming agent.

Interfacial rheology of sodium caseinate/high acyl gellan gum complexes: Stabilizing oil-in-water emulsions

In this work, the effects of pH and high acyl gellan gum concentration on the adsorption kinetics and interfacial dilatational rheology of sodium caseinate/high acyl gellan gum (CN/HG) complexes were investigated using a pendant drop tensiometer. In addition, stability related properties including interfacial protein concentration, droplet charge, size, microstructure and creaming index of emulsions were studied at different HG concentration (0–0.2 wt%) and pH values (4, 5.5 and 7). The results showed that HG adsorbed onto the CN mainly through electrostatic interactions which could lead to increase the interfacial pressure (π), rates of protein diffusion (k_diff), and molecular penetration (k_p). The CN/HG complexes formed thick adsorption layers around the oil droplets which significantly increased the surface dilatational modulus with the increasing HG concentration. The CN/HG complexes appeared to form more elastic interfacial films after a long-term adsorption time compared with CN alone, which could reduce the droplet coalescence and thus prevented the growth of emulsion droplets. All four phosphorylated proteins of CN (α_s1-, α_s2-, β-, and κ-casein) were adsorbed at the oil-water (O/W) interface as confirmed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), and surface protein coverage increased progressively with increasing HG concentration at pH 5.5, but decreased at pH 7. The CN/HG stabilized emulsions at pH 5.5 revealed the higher net charges and smaller z-average diameters than those at pH 4 and pH 7. This study provides valuable information on the use of CN/HG complexes to improve the stability and texture of food emulsions.

•Interactions between sodium caseinate (CN) and high acyl gellan gum (HG) studied.

•At pH 5.5, CN/HG interaction was mainly driven by electrostatic attractions.

•CN/HG complex improved the adsorption of CN at the oil-water interface.

•CN/HG complex could form stronger interfacial films than protein alone.

•Cooperative adsorption onto oil-water interface improved emulsion stability.

The emulsifying stability of soy hull polysaccharides with different molecular weight obtained from membrane-separation technology

Polysaccharides are macromolecules used for food development, and their further separation into different molecular weights allows their broader application in the food industry. Here, we performed microwave-assisted ammonium oxalate extraction of soy hull polysaccharide (SHP; MASP), followed by their separation and purification using membrane-separation technology and analyses of the emulsifying stability and MASP mechanism at different molecular weights. Additionally, we compared the composition and structural differences in SHP components and evaluated the separation and grading-emulsification stability properties of the membrane-emulsified components. The results showed improved emulsification stability properties of high molecular weight SHPs that had been separated and purified by membrane separation, with the formed emulsion exhibiting a high degree of viscosity, uniform particle-size distribution, smaller particle size, less interfacial tension, and a high Zeta potential. Moreover, the chemical composition, monosaccharide composition, and molecular weight of SHP were different.

Effect of glycosylation with sugar beet pectin on the interfacial behaviour and emulsifying ability of coconut protein

The aim of the present study was to investigate the effect of glycosylation with sugar beet pectin (SBP) on the interfacial behaviour and emulsifying ability of coconut protein (CP). The physical stabilities of the emulsions were predicted by transmission variation, droplet distribution and zeta potentials. The results showed that SBP-CP-stabilized emulsions showed better stability during centrifugation than those stabilized by CP because SBP-CP reduced the degree of variation in the CP transmission profile. The adsorption kinetics of all emulsifiers at the oil-water interface were determined to investigate the relationship between the interfacial behaviour and emulsion stability. The presence of SBP considerably reduced the adsorption rate of CP (0.698 mN/m/s^1/2) and hampered the development of a highly viscoelastic network at the oil-water interface. The values of the dilatational elastic modulus (E_d = 19.477 mN/m) and dilatational viscous modulus (E = 19.719 mN/m) were approximately equal, indicating that the adsorption process was mainly dominated by elastic behaviour. Additionally, the SBP-CP interaction enhanced the dilatational property of the CP-absorbed layer.

Emulsion stability and dilatational viscoelasticity of ovalbumin/chitosan complexes at the oil-in-water interface

The contribution of the emulsion rheological properties and the viscoelastic of the interface adsorbed layer to the emulsification mechanism of ovalbumin (OVA)-chitosan (CS) mixtures were investigated. In comparison to the treatment with OVA alone and OVA/CS mixtures at pH 4.0, the addition of CS at pH 5.5 increased the size distribution of emulsion droplets with significant flocculation through polyelectrolyte bridging, remarkably enhancing the emulsions stability against gravity creaming after storage at 25 °C for 14 days. The dynamic rheological properties indicated that the formation of the complex at pH 5.5 increased the elastic modulus (G') and apparent viscosity (η^∗) of the emulsions, which is useful for inhibiting creaming. Moreover, the complexation of OVA and CS at pH 5.5 increased the dilatational modulus (E), especially the elastic modulus (E_d), of the oil/water interfacial absorbed layer, which could reduce the droplet coalescence and therefore inhibit the growth of emulsion droplets.