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

Guest-guided anchoring patterns of cyclodextrin supramolecular microcrystals on droplet surfaces

The growth of cyclodextrin inclusion complexes (ICs) on oil/water interfaces represents a beautiful example of spontaneous pattern formation in nature. How the supramolecules evolve remains a challenge because surface confinement can frustrate microcrystal growth and give rise to unusual phase transitions. Here we investigate the self-assembly of ICs on droplet surfaces using microfluidics, which allows directly visualizing packing, wetting and ordering of the microcrystals anchored on the surface. The oil guests of distinct molecular structures can direct the assembly of the ICs and largely affect anchoring dynamics of the ICs microcrystals, leading to a range of behaviors including orientating, slipping, buckling, jamming, or merging. We discuss the behaviors observed in terms of the flexibility of the building blocks, which offers a new degree of freedom through which to tailor their properties and gives rise to a striking feature of anchoring patterns that have no counterpart in normal colloidal crystals.

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.

Fabrication of Pickering emulsions stabilized by citrus pectin modified with β-cyclodextrin and its application in 3D printing

Pickering emulsions stabilized by polysaccharide particles have received increasing attention because of their potential applications in three-dimensional (3D) printing. In this study, the citrus pectins (citrus tachibana, shaddock, lemon, orange) modified with β-cyclodextrin (β-CD) were used to stabilize Pickering emulsions reaching the requirements of 3D printing. In terms of pectin chemical structure, the steric hindrance provided by the RG I regions was more conducive to the stability of the complex particles. The modification of pectin by β-CD provided the complexes a better double wettability (91.14 ± 0.14°-109.43 ± 0.22°) and a more negative ζ-potential, which was more beneficial for complexes to anchor at oil-water interface. In addition, the rheological properties, texture properties and stability of the emulsions were more responsive to the ratios of pectin/β-CD (R_β/C). The results showed that the emulsions stabilized at a φ = 65 % and a R_β/C = 2:2 achieved the requirements (shear thinning behavior, self-supporting ability, and stability) of 3D printing. Furthermore, the application in 3D printing demonstrated that the emulsions under the optimal condition (φ = 65 % and R_β/C = 2:2) displayed excellent printing appearance, especially for the emulsions stabilized by β-CD/LP particles. This study provides a basis for the selection of polysaccharide-based particles to prepare 3D printing inks which may be utilized in food manufacturing.

The preparation of Diacylglycerol-rich soybean oil by acetylated modification of arachin nanoparticles for W/O Pickering emulsion system

Pickering emulsion catalytic system (PEC) stabilized by nanoparticles is an efficient catalytic platform. Herein, a high-performance PEC was constructed by acetylated modification of arachin nanoparticles (AAPs). The results showed the pI of arachin was decreased from pH 5.5 to pH 3.5. The surface hydrophobicity index was significantly increased (from 56.28 ± 4.23 to 120.77 ± 0.79) after acetylated modification. The three-phase contact angle of AAPs was 91.20 ± 0.98°. AAPs were used as lipase immobilization carriers to increase the activity of free lipase fabricating lipase-AAPs. The immobilization efficiency and activity of lipase-AAPs were 12.95 ± 0.03% and 1.74 ± 0.07 U/mg, respectively. Enzymatic reaction kinetics showed that V_m of lipase-AAPs was twice of free lipase. K_m was 1/5 of free lipase. The catalytic efficiency of PEC to prepare DAG was 2.36 times of biphasic catalytic system (BCS). This work provided a promising way to promote the efficiency of DAG preparation.

Effect of hydroxypropyl-β-cyclodextrin and lecithin co-stabilized nanoemulsions on the konjac glucomannan/pullulan film

In this study, the various ratio of hydroxypropyl-β-cyclodextrin (HPCD) to lecithin (LEC) was 0:1, 0.5:1, 1:1, 1.5:1 and 2:1 (w/w) co-stabilized cinnamon essential oil (CEO) nanoemulsions were prepared. These nanoemulsions were successfully incorporated in the konjac glucomannan/pullulan polysaccharides-based film matrix. The composition of nanoemulsions and the effect of various nanoemulsions on rheological, mechanical, Water vapor permeability, optical, color, morphology properties, and CEO retention rate of the composite films were characterized. The results demonstrated that HPCD and LEC nanoemulsions had small particle size under 120 nm and high stability during 21 days storage, the incorporation of nanoemulsions reduced the viscosity of film-solution, transmittance, Water vapor permeability and mechanical properties of films, but an appropriate HPCD content 1:1 w/w of nanoemulsions could restored the mechanical properties of the films. Otherwise, 1:1 w/w of nanoemulsion film also exhibited a more compact and uniform structure, Furthermore, 2:1 w/w of nanoemulsion films with high retention rate of CEO, and the antioxidant and better antibacterial activities against E. coli and S. aureus. The nanoemulsion films utilized in this study also prolonged the shelf life of Agaricus bisporus mushrooms and cherries while maintaining their commercial value.

Pickering emulsions stabilized by β-CD microcrystals: Construction and interfacial assembly mechanism

β-Cyclodextrin (β-CD) can combine with oil and other guest molecules to form amphiphilic inclusion complexes (ICs), which can be adsorbed on the oil-water interface to reduce the interfacial tension and stabilize Pickering emulsions. However, the subtle change of β-CD in the process of emulsion preparation is easily ignored. In this study, β-CD and ginger oil (GO) were used to prepare the Pickering emulsion by high-speed shearing homogenization without an exogenous emulsifier. The stability of the emulsion was characterized by microscopic observation, staining analysis, and creaming index (CI). Results showed that the flocculation of the obtained Pickering emulsion was serious, and the surface of the droplets was rough with lamellar particles. In order to elucidate the formation process of the layered particles, the GO/β-CD ICs were further prepared by ball milling method, and the X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and interfacial tension analyses found that β-CD and GO first formed amphiphilic nanoscale small particles (ICs) through the host-guest interaction, and the formed small particles were further self-assembled into lamellar micron-scale amphiphilic ICs microcrystals. These amphiphilic ICs and microcrystals aggregated at the oil-water interface and finally formed the Pickering emulsion. In this study, by exploring the formation process and evolution of GO/β-CD self-assembly, the formation process and stabilization mechanism of the β-CD-stabilized GO Pickering emulsion were clarified preliminarily, with the aim of providing a theoretical basis for the development of high-performance CD-stabilized Pickering emulsions.

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.