Shabbar Abbas

An Overview of Ultrasound-Assisted Food-Grade Nanoemulsions

Nanoemulsions are considered a very important tool for the delivery of bioactive compounds to the human body through food systems. Application of low-frequency ultrasound, a high-energy method, facilitates the homogenization and dispersion process under the influence of cavitation phenomena. Frequency, time, power, oil phase and aqueous phase are major parameters governing the cavitation process, concomitantly influencing the size and polydispersity index of nanoemulsion droplet. Additionally, hydrostatic pressure, gas content and temperature may also have profound effects on the process. Present review highlights the principles and production technology of high-intensity ultrasound and discusses the role of acoustic cavitation in the preparation of food-grade O/W nanoemulsions. Finally, it indicates technical hurdles, issues and future prospects of the technology.

Process optimization of ultrasound-assisted curcumin nanoemulsions stabilized by OSA-modified starch.

This study reports on the process optimization of ultrasound-assisted, food-grade oil-water nanoemulsions stabilized by modified starches. In this work, effects of major emulsification process variables including applied power in terms of power density and sonication time, and formulation parameters, that is, surfactant type and concentration, bioactive concentration and dispersed-phase volume fraction were investigated on the mean droplet diameter, polydispersity index and charge on the emulsion droplets. Emulsifying properties of octenyl succinic anhydride modified starches, that is, Purity Gum 2000, Hi-Cap 100 and Purity Gum Ultra, and the size stability of corresponding emulsion droplets during the 1 month storage period were also investigated. Results revealed that the smallest and more stable nanoemulsion droplets were obtained when coarse emulsions treated at 40% of applied power (power density: 1.36 W/mL) for 7 min, stabilized by 1.5% (w/v) Purity Gum Ultra. Optimum volume fraction of oil (medium chain triglycerides) and the concentration of bioactive compound (curcumin) dispersed were 0.05 and 6 mg/mL oil, respectively. These results indicated that the ultrasound-assisted emulsification could be successfully used for the preparation of starch-stabilized nanoemulsions at lower temperatures (40-45 °C) and reduced energy consumption.

Liposome as a Delivery System for Carotenoids: Comparative Antioxidant Activity of Carotenoids As Measured by Ferric Reducing Antioxidant Power, DPPH Assay and Lipid Peroxidation

This study was conducted to understand how carotenoids exerted antioxidant activity after encapsulation in a liposome delivery system, for food application. Three assays were selected to achieve a wide range of technical principles, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging, ferric reducing antioxidant powder (FRAP), and lipid peroxidation inhibition capacity (LPIC) during liposome preparation, auto-oxidation, or when induced by ferric iron/ascorbate. The antioxidant activity of carotenoids was measured either after they were mixed with preformed liposomes or after their incorporation into the liposomal system. Whatever the antioxidant model was, carotenoids displayed different antioxidant activities in suspension and in liposomes. The encapsulation could enhance the DPPH scavenging and FRAP activities of carotenoids. The strongest antioxidant activity was observed with lutein, followed by β-carotene, lycopene, and canthaxanthin. Furthermore, lipid peroxidation assay revealed a mutually protective relationship: the incorporation of either lutein or β-carotene not only exerts strong LPIC, but also protects them against pro-oxidation elements; however, the LPIC of lycopene and canthaxanthin on liposomes was weak or a pro-oxidation effect even appeared, concomitantly leading to the considerable depletion of these encapsulated carotenoids. The antioxidant activity of carotenoids after liposome encapsulation was not only related to their chemical reactivity, but also to their incorporation efficiencies into liposomal membrane and modulating effects on the membrane properties.

Liposomes as delivery systems for carotenoids: comparative studies of loading ability, storage stability and in vitro release

This study compared the loading ability of various carotenoids into liposomal membrane, lipid peroxidation inhibition capacity, storage stability and in vitro release behavior in simulated gastrointestinal (GI) media. It was found that carotenoids exhibited various incorporating abilities into liposomes ranging from the strongest to the weakest: lutein > β-carotene > lycopene > canthaxanthin. A similar trend was also observed in their antioxidant activities against lipid peroxidation during preparation. Storage measurements demonstrated that a liposomal membrane can strongly retain β-carotene and lutein, whereas this effect was not pronounced for lycopene and canthaxanthin. In vitro release experiments showed that lutein and β-carotene were hardly released in a simulated gastric fluid, while displaying a slow and sustained release in a simulated intestinal fluid. By contrast, lycopene and canthaxanthin underwent fast and considerable release in GI media. Dynamic light scattering indicated that carotenoid incorporation strongly affected the particle stability and dispersion during preparation and GI incubation. The differences in molecular release may be attributed to the different modulating effects of carotenoids. Our results may guide the potential application of liposomes as carriers for the controlled delivery of carotenoids in nutraceutical and functional foods.

Ascorbic Acid: Microencapsulation Techniques and Trends—A Review

Developments in nutritional sciences have increased the functional significance of ascorbic acid (vitamin C) as a food component in the human diet for health promotion and disease prevention. This has motivated food researchers to develop ascorbic acid–fortified food products to deliver appropriate levels of this vital food ingredient. Unfortunately, the highly unstable nature of ascorbic acid has posed technological challenges for its incorporation into different food systems. Microencapsulation is a promising approach to ensure the stability of ascorbic acid and to improve consumer acceptability towards the carrier food. The most commonly used techniques for ascorbic acid (water soluble) encapsulation, including spray drying, spray cooling, spray chilling, fluidized bed coating, liposomes, and extrusion, are reviewed and discussed with respect to technical hurdles and potential benefits.

Fabrication of polymeric nanocapsules from curcumin-loaded nanoemulsion templates by self-assembly.

In this study, biodegradable polymeric nanocapsules were prepared by sequential deposition of food-grade polyelectrolytes through the self-assembling process onto the oil (medium chain triglycerides) droplets enriched with curcumin (lipophilic bioactive compound). Optimum conditions were used to prepare ultrasound-assisted nanoemulsions stabilized by octenyl-succinic-anhydride (OSA)-modified starch. Negatively charged droplets (-39.4 ± 1.84 mV) of these nanoemulsions, having a diameter of 142.7 ± 0.85 nm were used as templates for the fabrication of nanocapsules. Concentrations of layer-forming cationic (chitosan) and anionic (carboxymethylcellulose) biopolymers were optimized based on the mean droplet/particle diameter (MDD/MPD), polydispersity index (PDI) and net charge on the droplets/capsules. Prepared core-shell structures or nanocapsules, having MPD of 159.85 ± 0.92 nm, were characterized by laser diffraction (DLS), ζ-potential (ZP), atomic force microscopy (AFM), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). Furthermore, physical stability of curcumin-loaded nanocapsules in suspension was determined and compared at different storage temperatures. This study may provide information regarding the formation of ultrasound-assisted polymeric nanocapsules from the nanoemulsion templates which could be helpful in the development of delivery systems for lipophilic food bioactives.

Modulation of the carotenoid bioaccessibility through liposomal encapsulation.

The low bioaccessibility of carotenoids is currently a challenge to their incorporation in pharmaceutics, nutraceuticals and functional foods. The aim of this study was to evaluate the modulating effects of liposome encapsulation on the bioaccessibility, and its relationship with carotenoid structure and incorporated concentration. The physical stability of liposomes, lipid digestibility, carotenoids release and bioaccessibility were investigated during incubation in a simulated gastrointestinal tract. Analysis on the liposome size and morphology showed that after digestion, the majority of particles maintained spherical shape with only an increase of size in liposomes loading β-carotene or lutein. However, a large proportion of heterogeneous particles were visible in the micelle phase of liposomes loading lycopene or canthaxanthin. It was also found that the release of lutein and β-carotene from liposomes was inhibited in a simulated gastric fluid, while was slow and sustained in a simulated intestinal fluid. By contrast, lycopene and canthaxanthin exhibited fast and considerable release in the gastrointestinal media. Both carotenoid bioaccessibility and micellization content decreased with the increase of incorporated concentration. Anyway, the bioaccessibility of carotenoids after encapsulated in liposomes was in the following order: lutein>β-carotene>lycopene>canthaxanthin. Bivariate correlation analysis revealed that carotenoid bioaccessibility depended strongly on the incorporating ability of carotenoids into a lipid bilayer, loading content, and nature of the system.

Modulating effect of lipid bilayer–carotenoid interactions on the property of liposome encapsulation

Liposomes have become an attractive alternative to encapsulate carotenoids to improve their solubility, stability and bioavailability. The interaction mechanism of carotenoid with lipid bilayer is one of the major concerns in improving the delivery efficiency of liposomes. In this study, the microstructure and carotenoid encapsulation efficiency of liposomes composed of native phospholipid (egg yolk phosphatidylcholine, EYPC) and nonionic surfactant Tween 80 were investigated by atomic force microscopy, dynamic light scattering, and Raman spectroscopy, respectively. Subsequently, the effects of carotenoid incorporation on the physical properties of liposomal membrane were performed by Raman spectroscopy, fluorescence polarization, and electron paramagnetic resonance. Results showed that the incorporation of carotenoids affected the liposomes morphology, size and size distribution to various extents. Analysis on the Raman characteristic peaks of carotenoids revealed that lutein exhibited the strongest incorporating ability into liposomes, followed by β-carotene, lycopene, and canthaxanthin. Furthermore, it was demonstrated that carotenoids modulated the dynamics, structure and hydrophobicity of liposomal membrane, highly depending on their molecular structures and incorporated concentration. These modulations were closely correlated with the stabilization of liposomes, including mediating particle aggregation and fusion. These findings should guide the rationale designing for liposomal encapsulation technology to efficiently deliver carotenoids in pharmaceutics, nutraceuticals and functional foods.

Stable nanoparticles prepared by heating electrostatic complexes of whey protein isolate-dextran conjugate and chondroitin sulfate.

A simple and green method was developed for preparing the stable biopolymer nanoparticles with pH and salt resistance. The method involved the macromolecular crowding Maillard process and heat-induced gelation process. The conjugates of whey protein isolate (WPI) and dextran were produced by Maillard reaction. The nanoparticles were fabricated by heating electrostatic complexes of WPI-dextran conjugate and chondroitin sulfate (ChS) above the denaturation temperature and near the isoelectric point of WPI. Then, the nanoparticles were characterized by spectrophotometry, dynamic laser scattering, zeta potential, transmission electron microscopy, atomic force microscopy, and scanning electron microscopy. Results showed that the nanoparticles were stable in the pH range from 1.0 to 8.0 and in the presence of high salt concentration of 200 mM NaCl. WPI-dextran conjugate, WPI, and ChS were assembled into the nanoparticles with dextran conjugated to WPI/ChS shell and WPI/ChS core. The repulsive steric interactions, from both dextran covalently conjugated to WPI and ChS electrostatically interacted with WPI, were the major formation mechanism of the stable nanoparticles. As a nutrient model, lutein could be effectively encapsulated into the nanoparticles. Additionally, the nanoparticles exhibited a spherical shape and homogeneous size distribution regardless of lutein loading. The results suggested that the stable nanoparticles from proteins and strong polyelectrolyte polysaccharides would be used as a promising target delivery system for hydrophobic nutrients and drugs at physiological pH and salt conditions.

The effect of soy protein structural modification on emulsion properties and oxidative stability of fish oil microcapsules

Hydrolysates of soy protein isolate-maltodextrin (SPI-Md) conjugate were used as wall material to prepare fish oil microcapsules by freeze-drying method. Effects of the protein structural modifications on the physicochemical properties of the emulsion and the oxidative stability of the microcapsules were characterized. Compared with emulsions of SPI-Md conjugates or soy protein isolate/maltodextrin (SPI/Md) mixture, lower droplet size (212.5-329.3nm) and polydispersity index (PDI) (0.091-0.193) were obtained in the fish oil emulsions prepared by SPI-Md conjugate hydrolysates. The improved amphiphilic property of SPI-Md conjugate hydrolysates was supported by the results of surface and interfacial tension, and further confirmed by the improved emulsion stability during the storage period. Although the microencapsulation efficiency (MEE) of SPI-Md conjugate hydrolysates slightly decreased from 97.84% to 91.47% with the increasing degree of hydrolysis (DH), their oxidative stabilities (peroxide value and headspace propanal) were apparently improved compared with native SPI/Md mixture or SPI-Md conjugates system. Moreover, favorable thermal stability as well as a porous and uniform surface structure of the microcapsules coated by SPI-Md conjugate hydrolysates (DH 2.9%) was observed via the thermal analysis and scanning electron microscope (SEM) micrographs, respectively.