Droplet clustering in cyclodextrin-based emulsions mediated by methylcellulose

Pickering emulsion stabilized by quercetin-β-cyclodextrin-diglyceride particles: Effect of diglyceride content on interfacial behavior and emulsifying property of complex particles

This research develops diacylglycerol (DAG) based Pickering emulsions with enhanced oxidative stability stabilized by self-assembled quercetin/DAG/β-cyclodextrin (β-CD) complexes (QDCCs) using a one-step agitation method. Influence of DAG content (5%, 15%, 40%, and 80%, w/w) on the self-assembly behavior, interfacial properties, and emulsifying ability of complex particles was investigated. SEM, XRD and ATR-FTIR studies confirmed the formation of ternary composite particles. QDCCs in 80% DAG oil had the highest quercetin encapsulation efficiency (6.09 ± 0.01%), highest DPPH radical scavenging rate and ferric reducing antioxidant property (FRAP). β-CD and quercetin adsorption rates in emulsion with 80% DAG oil were 88.4 ± 2.53% and 98.34 ± 0.15%, respectively. Pickering emulsions with 80% DAG had the smallest droplet size (8.90 ± 1.87 μm) and excellent oxidation stability. This research develops a novel approach to regulate the physicochemical stability of DAG-based emulsions by anchoring natural antioxidants at the oil-water interface through a one-pot self-assembly method.

Ejected microcrystals probe jammed states of droplets in cyclodextrin-based emulsions

The cyclodextrin (CD)-based emulsions exhibit complex instability behaviors such as rapid flocculation and creaming, and how to capture droplet dispersion states of the emulsions remains a great challenge. Here we prepare the CD-based emulsions with different oil-water volume ratios and CD concentrations by using high-pressure homogenization, and characterize the emulsion droplets by using optical microscopy and confocal laser scanning microscopy. We evaluate the effects of homogenization pressure on the stability of the emulsions, identify armored droplets with different surface features, measure interfacial concentrations of adsorbed ICs microcrystals, and observe ejection of the oil/CD inclusion complexes (ICs) microcrystals from the droplet surface. The droplet dispersion states are sensitive to the dynamic buildup and evolving morphologies of the interfacial microcrystals, and there are clear correlations between the properties of the ejected microcrystals and the characteristics of the emulsions. We ascribe the subsequent ejection of ICs microcrystals from the droplet surface to consolidation and deformation of the films formed between neighboring droplets. The ejection of the ICs microcrystals affords a simple method to detect the droplet-droplet interactions and phase transitions in the CD-based emulsions, which might be a generic feature in the broader context of the creaming processes of emulsions.

Jamming to unjamming: Phase transition in cyclodextrin-based emulsions mediated by sodium casein

HYPOTHESIS

Cyclodextrin (CD) can spontaneously build up the solid particle membrane with CD-oil inclusion complexes (ICs) by a self-assembly process. Sodium casein (SC) is expected to preferentially adsorb at the interface to transform the type of interfacial film. The high-pressure homogenization can increase interfacial contact opportunities of the components, which promote the phase transition of the interfacial film.

EXPERIMENTS

We added SC by sequential and simultaneous orders to mediate the assembly model of the CD-based films, examined the patterns in which the films adopt phase transitions to retard emulsion flocculation, and studied the physic-chemical properties of the emulsions and films from the structural arrest, interface tension, interfacial rheology, linear rheology, and nonlinear viscoelasticities through Fourier transform (FT)-rheology and Lissajous-Bowditch plots.

FINDINGS

The interfacial and large amplitude oscillatory shear (LAOS) rheological results showed that the films changed from jammed to unjammed. We divide the unjammed films into two types: one is SC dominated liquid-like film, which is fragile and related to droplet coalescence; the other is cohesive SC-CD film, which helps droplet rearrangement and retards droplet flocculation. Our results highlight the potential of mediating phase transformation of interfacial films to improve emulsion stability.

Synergistic effects of psyllium husk powder and different levels of methylcellulose on the storage stability of sodium caseinate emulsion

The study investigated the effects of compound fibers composed of psyllium husk powder (PHP, 0.3%) and methylcellulose (MC, 0, 0.3, 0.6, 0.9, and 1.2%) on the storage stability, rheology, and microstructure of sodium caseinate emulsions. Results showed that the emulsion stability was enhanced with the increased concentrations of MC, especially at the concentration of 1.2%. The oil droplet size in the emulsions was decreased as the concentrations of compound fibers increased, which was further confirmed by the optical microscope analysis. The rheological measurements and cryo-scanning electron microscopy results indicated that compound fibers improved the viscosity of the emulsions, and formed a strong three-dimensional network structure. The results of confocal laser scanning microscope and surface protein concentration measurements showed that compound fibers were evenly distributed into the oil droplet surface. The above results demonstrate that compound fibers are an effective thickener and emulsifier in enhancing the stability properties of oil-in-water (O/W) emulsions stabilized by sodium caseinate.

Droplet Dispersion States of Cyclodextrin-Based Emulsions from Nonlinear Rheological Properties

Polymers are desirable to improve emulsion stability by stuffing them into the continuous phase. How to get information on the droplet dispersion states of the emulsions remains a challenge, as the emulsion characteristics are dictated by two intertwining components, the polymer matrix and the droplets. Herein, we use an amphiphilic polymer, gum arabic (GA), to mediate the droplet flocculation of cyclodextrin (CD)-based emulsions and compare them with our previous studies on the stabilization of CD-based emulsions by a nonamphiphilic polymer, methylcellulose (MC). We characterize the emulsions by using optical microscopy, confocal laser scanning microscopy, and laser particle analysis, explore their rheological behavior through large-amplitude oscillatory shear experiments, and analyze the nonlinear viscoelasticities through Fourier transform (FT)-rheology and Lissajous-Bowditch plots. There is a great difference between GA and MC in the viscosity effect and the arrangement around emulsion droplets. GA is not an effective flocculation inhibitor due to a bridging flocculation mechanism rather than a direct viscosity effect. Our analysis highlights the role of the intrinsic nonlinearity parameter (Q₀) extracted by FT analysis in reflecting the droplet dispersion states of the emulsions by decoupling structural contributions from the polymers and the emulsion droplets.

Effect and Mechanism of Acid-Induced Soy Protein Isolate Gels as Influenced by Cellulose Nanocrystals and Microcrystalline Cellulose

The effects of cellulose nanocrystals (CNC) and microcrystalline cellulose (MCC) on the gel properties and microstructure of glucono-δ-lactone-induced soy protein isolate (SPI) gels were investigated. The water-holding capacity, gel strength, and viscoelastic modulus of CNC-SPI gels were positively associated with CNC concentration from 0 to 0.75% (w/v). In contrast, MCC-SPI gels exhibited decreased water-holding capacity, gel strength, and viscoelastic modulus. All composite gels displayed high frequency dependence and the typical type I (strain thinning) network behavior. Changes in viscoelasticity under large strain were correlated with differences in the microstructure of SPI composite gels. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) showed that CNC were more evenly and steadily distributed in the protein matrix and formed a compact network structure. In contrast, MCC-SPI gels exhibited a discontinued and rough gel network with some large aggregates and pores, in which MCC was randomly entrapped. Fourier transform infrared spectroscopy (FTIR) and molecular forces results revealed that no new chemical bonds were formed in the gelation process and that the disulfide bond was of crucial importance in the gel system. With the addition of CNC, electrostatic interactions, hydrophobic interactions, and hydrogen bonds in the SPI gel network were significantly strengthened. However, the incorporation of MCC might obstruct the connection of the protein network. It is concluded that both cellulose type and concentration affect gelling properties.

Bulk and Interfacial Contributions to Stabilization of Cyclodextrin-Based Emulsions Mediated by Bacterial Cellulose

Cyclodextrin (CD)-based emulsions have a characteristic of rapid droplet flocculation, which limits their application as functional material templates, so it is very important to improve the stability of CD-based emulsions. In this study, we select bacterial cellulose (BC) as a nonadsorbing inhibitor to prevent flocculation of CD-based emulsions. We map a phase diagram of the aqueous dispersions of CD inclusion complexes (ICs) and BC from morphological observations and investigate the effects of BC on properties of the IC-laden films. We further explore the effects of BC concentration on the stability of the CD-based emulsions and investigate rheological behavior of the emulsions through large-amplitude oscillatory shear experiments. It shows that BC can effectively suppress the flocculation of CD-based emulsion droplets even at a concentration as low as 0.01 wt %. We propose that BC has dual effects from bulk and interfacial contributions on increasing emulsion stability. At low concentrations, BC mainly results in higher packing density of ICs on the emulsion droplet surface through excluded volume repulsion, and at high concentrations, BC creates a network structure that confines the motion of emulsion droplets and retards flocculation.