Effect Of Interfacial Composition Research Articles

Effect of interfacial composition on the physical stability and co-oxidation of proteins and lipids in a soy protein isolate-(−)-epigallocatechin gallate conjugate emulsion

In this study, oil-in-water emulsions were co-stabilized by a soy protein isolate-(−)-epigallocatechin gallate (SPI-EGCG) conjugate, tea saponin (TS), and hexadecyltrimethylammonium bromide (CTAB) (0.01–1.00%, w/v), and the influence of the mixed SPI-EGCG-conjugate–surfactant interface on the physical stability and protein–lipid co-oxidation properties of each emulsions was investigated. Our results demonstrated that TS exhibits a better emulsifying ability than CTAB by significantly reducing interfacial tension; this emulsion contained the smallest particles at a TS concentration of 1.0% (w/v). In addition, the interfacial protein content revealed the existence of synergistic (CTAB) and competitive (TS) adsorption between the protein and surfactant. The presence of TS displaced protein molecules at the interface and inhibited protein oxidation, which reveals that proteins adsorbed at the oil–water interface are more sensitive to oxidation than unadsorbed proteins. The degrees of protein and lipid oxidation were enhanced in the presence of CTAB. Furthermore, the addition of TS delayed lipid oxidation; this phenomenon was most pronounced at a TS concentration of 1.0% (w/v). Our results indicate that combining SPI-EGCG conjugates with TS provides an optimal design for the development of nutritionally fortified products with longer shelf lives. • Effects of the surfactant concentration and type on the emulsions were investigated. • TS gave the best emulsification ability and effective interfacial tension reduction. • The co-oxidation of proteins and lipids occurred depending on the protein location.

Influence of Blending of Nonionic Emulsifiers Having Various Hydrophilic Head Sizes on Lipid Oxidation: Investigation of Antioxidant Polarity Interfacial Characteristics Relationship.

The purpose of this study was to deliver insights into the effect of interfacial composition and antioxidant polarity on the lipid oxidation of emulsions. Emulsions were created using blends of nonionic ethoxylated fatty acid alcohol surfactants with different hydrophilic head sizes, and lipophilic (TBHQ) and amphiphilic (lauryl gallate) antioxidants were incorporated into the emulsions. At the same surfactant concentration, emulsion stabilized with surfactant with a smaller hydrophilic head was more susceptible to lipid oxidation than that stabilized with surfactant with a larger hydrophilic head. When surfactants with a similar hydrophilic head size were used, lipid oxidation in emulsion containing more surfactant was slightly faster than that containing less surfactant. When emulsions were created with a 1:1 molar ratio mixture of surfactants with small and large hydrophilic heads, surfactant concentration (1.00 and 2.932 mM) had little effect on lipid peroxide generation rate. However, the concentration of thiobarbituric acid-reactive substances (TBARSs) in the emulsion prepared at 1.00 mM increased faster than that prepared at 2.93 mM. Alteration of interfacial composition and surfactant concentration did not affect antioxidant ability, regardless of antioxidant polarity, to inhibit lipid peroxide generation. However, the ability of lauryl gallate and TBHQ to prevent TBARS generation was elevated by mixing surfactants with small and large hydrophilic heads and by decreasing surfactant concentration. In most emulsions, lauryl gallate showed a more effective antioxidant ability than TBHQ.

Zein/carboxymethyl dextrin nanoparticles stabilized pickering emulsions as delivery vehicles: Effect of interfacial composition on lipid oxidation and in vitro digestion

In this study, zein/carboxymethyl dextrin nanoparticles (ZCPs) were used as stabilizers to prepare Pickering emulsions. The contact angle (θ) of ZCPs with a mass ratio of 2:1 (zein:CMD) was 89.1°, which was suitable for stabilizing Pickering emulsions. The droplet sizes of ZCPs stabilized Pickering emulsions were dependent on particle concentration and oil volume fraction. The droplet sizes of emulsions decreased with increasing particle concentration at a constant oil volume fraction, and increased as the oil volume fraction increased fixing particle concentration. Visual observation indicated that ZCPs stabilized Pickering emulsions at various particle concentrations and oil fractions were stable during long-term storage. The rheological measurements indicated that all emulsions exhibited shear thinning behavior and the elastic gel-like structure. Furthermore, the viscosity and gel-like structure were relied on ZCPs concentrations and oil volume fractions. Confocal laser scanning microscope showed that ZCPs formed the densely packed layer around the oil droplets. ZCPs stabilized Pickering emulsions significantly inhibited lipid oxidation compared to zein nanoparticles stabilized emulsions. In vitro digestion study suggested that the free fatty acids (FFA) released, bioaccessibility and stability of curcumin in ZCPs stabilized Pickering emulsions were higher than those in bulk oil and zein nanoparticles stabilized emulsions. These researches might facilitate the preparation of Pickering emulsions with excellent stability for nutraceutical delivery in food and pharmaceutical applications.

Development and Characterization of Lipid-Based Nanosystems: Effect of Interfacial Composition on Nanoemulsion Behavior

Nanoemulsions were successfully developed through high-pressure homogenization. The layer-by-layer electrostatic technique was used for the subsequent deposition of a chitosan and alginate polyelectrolyte layers, thus leading to the development of a multilayer nanoemulsion. The effect of polyelectrolytes concentration in the development of multilayer nanoemulsions was evaluated in terms of hydrodynamic diameter (Hd), polydispersity index (PdI), zeta potential (Zp), and curcumin encapsulation efficiency. The interactions between polyelectrolytes and nanoemulsion were further analyzed using Fourier transform infrared (FTIR) spectroscopy and quartz crystal microbalance (QCM), while curcumin degradation was determined through the evaluation of the antioxidant capacity of the nanosystems. Results showed an encapsulation efficiency of 99.8 ± 0.8% and a loading capacity of 0.53 ± 0.03% (w/w). The presence of the multilayers leads to an increase of the Hd of the nanosystems, from 80.0 ± 0.9 nm (nanoemulsion) to 130.1 ± 1.5 nm (multilayer nanoemulsion). Release profiles were evaluated at different conditions, fitting a linear superposition model to experimental data suggests an anomalous behavior, being the relaxation of the surfactant and polyelectrolytes the rate-determining phenomena in curcumin release. The developed nanosystems showed great potential for the incorporation of lipophilic bioactive compounds, in view of their application in food and pharmaceutical products.

Hybrid Bionanoparticle-Stabilized Pickering Emulsions for Quercetin Delivery: Effect of Interfacial Composition on Release, Lipolysis, and Bioaccessibility

Pickering emulsions stabilized by gliadin/phospholipid nanoparticles were assembled employing a two-stage method: (i) coarse emulsions containing large oil droplets (d = 4.0 to 40 μm) were formed b...

Effects of interfacial composition on the stability of emulsion and encapsulated bioactives after thermal and high pressure processing

The composition of the oil-in-water (O/W) interface of emulsion droplets plays a critical role in their physicochemical stability as well as that of encapsulated bioactives during processing. This study evaluates three emulsifiers, whey protein isolate (WPI), Tween 20 and Ludox HS-30 silica (Pickering), which stabilize O/W emulsions containing either all-trans retinol or curcumin, and determines the physicochemical stability of the emulsion and encapsulated bioactives post processing. In addition to thermal methods, this study utilizes high hydrostatic pressure processing (HPP) (600 MPa for 5 min). Physical stability of emulsions was characterized using particle size and ζ-potential measurements. Recovery of bioactives was determined using UV-vis spectrophotometry. WPI emulsions maintained a constant particle size across all processing parameters compared to other formulations. Tween 20 provided the most protective effect to encapsulated bioactives during processing. HPP had no significant effect on the physicochemical stability for any emulsion and had minimum effect on bioactive recovery.

Effect of interfacial composition on Ag-based Ohmic contact of GaN-based vertical light emitting diodes

By investigating the effect of a defective interface structure on Ag-based Ohmic contact of GaN-based vertical light-emitting diodes, we found a direct relationship between the interfacial composition and the Schottky barrier height of the Ag(111)/GaN(0001) interface. It was demonstrated that the Schottky barrier height of a defect-free Ag(111)/GaN(0001) interface was 2.221 eV, and it would be dramatically decreased to 0.375 eV with the introduction of one Ni atom and one Ga vacancy at the interface structure. It was found that the tunability of the Schottky barrier height can be attributed to charge accumulations around the interfacial defective regions and an unpinning of the Fermi level, which explains the experimental phenomenon of Ni-assisted annealing improving the p-type Ohmic contact characteristic. Lastly, we propose a new method of using Cu as an assisted metal to realize a novel Ag-based Ohmic contact. These results provide a guideline for the fabrication of high-quality Ag-based Ohmic contact of GaN-based vertical light-emitting diodes.

Insights into the photocatalytic mechanism of mediator-free direct Z-scheme g-C3N4/Bi2MoO6(010) and g-C3N4/Bi2WO6(010) heterostructures: A hybrid density functional theory study

Abstract Graphite-like carbon nitride (g-C3N4)-based heterostructures have received much attention due to their prominent photocatalytic activity. The g-C3N4/Bi2WO6 and g-C3N4/Bi2MoO6 heterostructures, which follow a typical hetero-junction charge transfer mechanisms show a weak potential for hydrogen evolution and reactive radical generation under visible light irradiation. A mediator-free Z-scheme g-C3N4/Bi2MoO6(010) and g-C3N4/Bi2WO6(010) heterostructures photocatalyst are designed for the first time using first-principles studies. Moreover, theoretical understanding of the underlying mechanism, the effects of interfacial composition and the role the interface play in the overall photoactivity is still unexplained. The calculated band gap of the heterostructures is reduced compared to the bulk Bi2WO6 and Bi2MoO6. In this study, we systematically calculated energy band structure, optical properties and charge transfer of the g-C3N4/Bi2MoO6(010) and g-C3N4/Bi2WO6(010) heterostructures using the hybrid density functional theory approach. The results show that the charge transfer at the interface of the heterostructures induces a built-in potential, which benefits the separation of photogenerated charge carriers. The g-C3N4/Bi2MoO6(010) heterostructure with more negative adhesion energy (−1.10 eVA−2) is predicted to have a better adsorptive ability and can form more easily compared to the g-C3N4/Bi2WO6(010) interface (−1.16 eVA−2). Therefore, our results show that the g-C3N4 interaction with Bi2MoO6 is stronger than Bi2WO6, which is also verified by the smaller vertical separation (3.25 A) between Bi2MoO6 and g-C3N4 compared to the g-C3N4/Bi2WO6(010) interface (3.36 A). The optical absorption verifies that these proposed Z-scheme heterostructures are excellent visible light harvesting semiconductor photocatalyst materials. This enhancement is ascribed to the role of g-C3N4 monolayer as an electron acceptor and the direct Z-scheme charge carrier transfer at the interface of the heterostructures. This work is useful for designing new types of Z-scheme photocatalyst and offers new insight into Z-scheme charge transfer mechanism for applications in the field of solar energy conversion.

In vitro behaviour of curcumin nanoemulsions stabilized by biopolymer emulsifiers – Effect of interfacial composition

Nanoemulsions present a high potential to be used in food products due to their advantages over conventional emulsions (e.g. higher stability to gravitational separation and droplet aggregation and enhanced bioavailability of encapsulated compounds), however their application to foods is hindered by some concerns about potential risks associated with their ingestion. The knowledge of the behaviour of nanoemulsions as well as the fate of bioactive compounds encapsulated within them in the gastrointestinal (GI) tract is of utmost importance to assess their safety for human consumption and to produce delivery systems that provide an optimized bioactivity of the encapsulated compound. In this work, a dynamic gastrointestinal model, comprising the simulation of stomach, duodenum, jejunum and ileum, was used to evaluate the behaviour of curcumin nanoemulsions stabilized by biopolymer emulsifiers (lactoferrin and lactoferrin/alginate multilayer structure) under GI conditions. The interfacial characteristics of curcumin nanoemulsions had a significant impact on their physicochemical stability within the simulated GI tract. Also, results suggested that alginate coating may be able to control the rate of lipid digestion and free fatty acids adsorption within the GI tract, but the encapsulated lipid is digested at the same extent, releasing the lipophilic bioactive compound. This work contributes to an improved understanding of how multilayer nanoemulsions behave within the GI tract and this knowledge will be useful for the optimization of delivery systems that improve the physicochemical stability of emulsions in food products, while still releasing encapsulated lipophilic bioactive compounds.

Spray dried double emulsions containing procyanidin-rich extracts produced by premix membrane emulsification: Effect of interfacial composition

Spray drying of procyanidin-loaded W1/O/W2 emulsions produced by premix membrane emulsification (ME) enabled to produce microcapsules containing procyanidins. The interface of the emulsion droplets prior to spray drying was stabilized with several hydrophilic emulsifiers (whey protein (WPI), WPI–carboxylmethyl cellulose, WPI–gum Arabic, and WPI–chitosan). Their effect on procyanidin encapsulation efficiency, water activity, moisture and oil content, and microcapsule size distribution was investigated. Furthermore, the microstructure and droplet size distribution of redispersed microcapsules were analyzed. Although premix ME produced W1/O/W2 emulsions with a narrow droplet size distribution regardless the hydrophilic emulsifier (main peak of droplet size distribution around 9μm), microcapsules after spray drying and double emulsions after redispersion showed profound differences in sizes depending on the interfacial composition. WPI–CMC stabilized microcapsules not only showed the highest procyanidin content (5.3gkg−1) but also gave the narrowest particle size distribution with the lowest particle size for both microcapsules and the corresponding emulsions after rehydration (7.7 and 9.9μm respectively).