Development of antioxidant Pickering high internal phase emulsions (HIPEs) stabilized by protein/polysaccharide hybrid particles as potential alternative for PHOs

Preparation and antimicrobial activity of thyme essential oil microcapsules prepared with gum arabic

Thyme essential oils (TEO) exhibit antimicrobial activities against a wide range of pathogenic microorganisms. Microcapsulation technology can be used to improve the stability, water solubility and antibacterial performance of TEO. In this paper, TEO was selected as the core material, and β-cyclodextrin (β-CD) was the wall material for microcapsulation; gum arabic (GA) was used as an emulsifier to prepare microcapsules by coprecipitation. The effects of gum arabic on the encapsulation rate, particle size and release rate of microcapsules were investigated. The optimal condition was found to be TEO : GA by 1 : 3 (w/w) ratio. In this condition, the embedding rate, release rate, and average size of the microcapsules were 87.61%, 53.00%, and 8.20 μm, respectively. Scanning electron microscopy (SEM) revealed that, under the action of gum arabic, the surface of microcapsules was more complete, and the size apparently decreased. Fourier-transform infrared spectroscopy (FTIR) indicated that there was no significant chemical interaction between gum arabic and β-CD. Gum arabic acted only as an emulsifier and remained in the mixed solution. For microcapsules with gum arabic as an emulsifier, the cumulative release rate of essential oils were slower at the initial time compared to microcapsules without added gum arabic. Antimicrobial activity assay exhibited TEO, which showed an inhibitory effect against Botryodiplodia theobromae Pat., and the inhibitory effect was especially strong against Colletotrichum gloeosporioides Penz. Finally, the obtained microcapsules showed the same antibacterial effect.

The gum arabic was, for the first time, used as an emulsifier for microcapsulation of essential oil.

Fabrication of Zein/Pectin Hybrid Particle-Stabilized Pickering High Internal Phase Emulsions with Robust and Ordered Interface Architecture

Diets containing partially hydrogenated oils (PHOs) expose the human body to trans fatty acids, thus endangering cardiovascular health. Pickering high internal phase emulsions (HIPEs) is a promising alternative of PHOs. This work attempted to construct stable Pickering HIPEs by engineering interface architecture through manipulating the interfacial, self-assembly, and packing behavior of zein particles using the interaction between protein and pectin. Partially wettable zein/pectin hybrid particles (ZPHPs) with three-phase contact angles ranging from 84° to 87° were developed successfully. ZPHPs were irreversibly anchored at the oil-water interface, resulting in robust and ordered interfacial structure, evidenced by the combination of LB-SEM and CLSM. This situation helped to hold a percolating 3D oil droplet network, which facilitated the formation of Pickering HIPEs with viscoelasticity, excellent thixotropy (>91.0%), and storage stability. Curcumin in HIPEs was well protected from UV-induced degradation and endowed HIPEs with ideal oxidant stability. Fabricated Pickering HIPEs possess a charming application prospect in foods and the pharmaceutical industry.

Synergistic Effect of Laccase and Sugar Beet Pectin on the Properties of Concentrated Protein Emulsions and Its Application in Concentrated Coconut Milk

Concentrated coconut milk (CCM), a raw material from coconut products, is extremely unstable because of its high oil content (>30%). In this study, three model emulsions-primary emulsions stabilized by coconut proteins only, secondary emulsions stabilized by the conjugation of sugar beet pectin (SBP) and coconut protein, and laccase-treated secondary emulsions-were prepared to investigate the effects of different factors (coconut proteins, coconut proteins + SBP, laccase-treated emulsions) on the stability of model emulsions and the application of this method to real CCM. The stability of the emulsions was evaluated based on their interfacial tension, zeta potential, particle size distribution, rheological properties, and the assembly formation of SBP and coconut protein at the oil⁻water interface. Results showed that addition of SBP or laccase can increase the viscosity and reduce the interfacial tension of the emulsion, and the effect was concentration dependent. Zeta potential of the emulsion decreased with the increase of protein (from -16 to -32 mV) and addition of SBP (from -32 to -46 mV), and it was reduced when laccase was added (from -9.5 to -6.0 mV). The secondary emulsion exhibited the narrowest particle size distribution (from 0.1 to 20 μm); however, laccase-catalyzed secondary emulsions showed the best storage stability and no layering when the laccase content reached 10 U/100 g. Confocal laser scanning microscopy (CLSM) revealed that protein was adsorbed on the oil⁻water interface and SBP distributed in the continuous phase could undergo oxidative crosslinking by laccase. These results show that the stability of the concentrated emulsion can be effectively improved by adding SBP and laccase.

Development of stable high internal phase emulsions by pickering stabilization: Utilization of zein-propylene glycol alginate-rhamnolipid complex particles as colloidal emulsifiers

In this study, zein-propylene glycol alginate-rhamnolipid complex particles were prepared with suitable three-phase contact angles (θ) for stabilizing oil-in-water Pickering high internal phase emulsions (HIPEs). At a fixed oil phase volume (φ = 0.75), particle concentration influenced the stability, physical properties, and rheology of HIPEs. Confocal laser scanning microscopy showed that complex particles formed a densely packed particle layer around the oil droplets and a three-dimensional network in the continuous phase, highlighting the potential for the complex particles to act as effective HIPE stabilizers. The storage modulus (G') was higher than loss modulus (G″) over the entire angular frequency range, suggesting HIPEs had an elastic gel-like structure. The HIPEs had good stability across a range of environmental conditions (pH, temperatures and salt concentrations). These findings may extend the application of zein in foods and the HIPEs formed may be used as novel delivery system for bioactives.

High-Internal-Phase Pickering Emulsions Stabilized Solely by Peanut-Protein-Isolate Microgel Particles with Multiple Potential Applications

High-internal-phase Pickering emulsions have various applications in materials science. However, the biocompatibility and biodegradability of inorganic or synthetic stabilizers limit their applications. Herein, we describe high-internal-phase Pickering emulsions with 87 % edible oil or 88 % n-hexane in water stabilized by peanut-protein-isolate microgel particles. These dispersed phase fractions are the highest in all known food-grade Pickering emulsions. The protein-based microgel particles are in different aggregate states depending on the pH value. The emulsions can be utilized for multiple potential applications simply by changing the internal-phase composition. A substitute for partially hydrogenated vegetable oils is obtained when the internal phase is an edible oil. If the internal phase is n-hexane, the emulsion can be used as a template to produce porous materials, which are advantageous for tissue engineering.

Stabilization and Rheology of Concentrated Emulsions Using the Natural Emulsifiers Quillaja Saponins and Rhamnolipids

Concentrated emulsions are widely used in the cosmetic, personal-care, and food industries to reduce storage and transportation costs and to provide desirable characteristics. The current study aimed to produce concentrated emulsions (50 wt % oil) using two natural emulsifiers, quillaja saponins and rhamnolipids. The impacts of emulsifier concentrations on the particle sizes, rheological properties, and stabilities of concentrated emulsions were evaluated. Emulsion particle sizes were negatively correlated with the concentrations of both quillaja saponins and rhamnolipids, and rhamnolipids were more effective in producing smaller droplets. Both emulsifiers formed stable concentrated emulsions against a series of environmental stresses, including various temperatures (30-90 °C), salt concentrations (≤200 mM NaCl), and pHs (pH 5-8). The rheology tests suggested that concentrated emulsions stabilized by quillaja saponins or rhamnolipids presented shear-thinning behaviors and had relatively low consistency coefficients.

Development of Pickering Emulsions Stabilized by Gliadin/Proanthocyanidins Hybrid Particles (GPHPs) and the Fate of Lipid Oxidation and Digestion

This work attempted to engineer emulsions' interface using the special affinity between proline-rich gliadin and proanthocyanidins (PA), to develop surfactant-free antioxidant Pickering emulsions with digestive-resistant properties. This binding interaction between gliadin and PA benefited the interfacial adsorption of the particles to corn oil droplets. Pickering droplets as building units assembled into an interconnected three-dimensional network structure, giving the emulsions viscoelasticity and ultrastability. Oxidative markers in Pickering emulsions were periodically monitored under thermally accelerated storage. Lipid digestion and oxidation fates were characterized using in vitro gastrointestinal (GI) models. The interfacial membrane constructed by antioxidant particles served as a valid barrier against lipid oxidation and digestion, in a PA dose-dependent manner. Briefly, lipid oxidation under storage and simulated GI tract was retarded. Free fatty acid (FFA) fraction released decreased by 55% from 87.9% (bulk oil) to 39.5% (Pickering emulsion), implying engineering interfacial architecture potentially benefited to fight obesity. This study opens a facile strategy to tune lipid oxidation and digestion profiles through the cooperation of the Pickering principle and the interfacial delivery of antioxidants.

Development of antioxidant gliadin particle stabilized Pickering high internal phase emulsions (HIPEs) as oral delivery systems and the in vitro digestion fate

In this paper, we demonstrate for the first time the use of gliadin particles to structure algal oil (rich in DHA) and to exert chemical stability against lipid oxidation via the Pickering high internal phase emulsion (HIPE) strategy.