Stabilization of Pickering emulsions via synergistic interfacial interactions between cellulose nanofibrils and nanocrystals

Oleanolic acid nanoparticles-stabilized W/O Pickering emulsions: Fabrication, characterization, and delivery application

Water-in-oil (W/O) Pickering emulsions have wide applications in the food industries. However, the existing W/O Pickering particles have disadvantages such as lack of bioactivity and poor stability. In this study, naturally occurring bioactive oleanolic acid (OA) was used as a novel emulsifier for W/O emulsions. Results revealed that rod-like OA could formulate into spherical nanoparticles by self-assembly, and then be anchored onto the oil-water interface to stabilize the emulsions. Besides, both OA concentration and internal water fraction (φ) had significant effect on the properties of emulsions. Furthermore, the resulted emulsions exhibited potential application as carriers for epigallocatechin-3-gallate (EGCG), which significantly improved its UV and thermal stability. Meanwhile, it could effectively protect EGCG from gastric digestion, and controlled release in the intestine. This work demonstrated the successful application of OA as a stabilizer for W/O emulsions, and provided valuable insight into its potential as delivery system for hydrophilic instable compounds.

Hydration effects of insoluble soybean fiber (ISF) on rheological properties and freeze-thaw stability of ISF concentrated emulsions

BACKGROUND

Concentrated emulsions have been formulated in many foods. The insoluble soybean fiber (ISF) can be utilized as a particle to stabilize concentrated emulsions. However, the approach to control the rheological properties and stability of the ISF concentrated emulsions is still worth investigating.

RESULTS

In this study, alkali-extracted ISF was hydrated by adding sodium chloride or heating and the prepared concentrated emulsions were subjected to freeze-thawing. Compared with the original hydration method, salinization reduced the absolute ζ-potential of the ISF dispersions to 6 mV, resulting in a lower absolute ζ-potential of the concentrated emulsions, which led to a decreased electrostatic repulsion and the largest droplet size, but to the lowest apparent viscosity, viscoelastic modulus, and stability. By contrast, hydration by heating promoted the interparticle interactions, and then a decreased droplet size (54.5 μm) but with a more densely distributed droplets was observed, together with enhanced viscosity and viscoelasticity properties. The fortified network structure improved the stability of the concentrated emulsions both against high-speed centrifugation and long-term storage. Additionally, secondary emulsification after freeze-thaw further improved the performance of the concentrated emulsions.

CONCLUSION

The results suggest that the formation and stability of the concentrated emulsion could be regulated by different hydration methods of particles, which could be adjusted according to the practical applications. © 2023 Society of Chemical Industry.

Stabilization of ginger essential oil Pickering emulsions by pineapple cellulose nanocrystals

Pickering emulsions (PE) are systems made up of two incompatible fluids, these are stabilized by solid organic or inorganic particles located on their interface. Cellulose nanocrystals (CNCs) are sustainable and biocompatible value-added naturally occurring biomolecules which are being investigated as PE stabilizers in the cosmetic, food, and pharmaceutical industries. The objective of this research was to investigate the efficacy of pineapple cellulose nanocrystals as stabilizers for a ginger essential oil-in-water Pickering emulsion. Anionic pineapple cellulose nanocrystals were prepared by acid hydrolysis. Ginger essential oil-in-water emulsions were prepared by ultrasonication. Pineapple CNC produced stable Pickering emulsions with surface average droplet size of 4.3 μm-6.2 μm, high negative zeta potential, high viscosity, and high adsorption at the interface. Pickering emulsions by ultrasonication were stable against droplet coalescence, phase separation, and droplet flocculation for at least 8 weeks at 25 °C or 40 °C at various droplet sizes. The emulsion droplet size and volume density (droplet size distribution) were evaluated by varying the particle concentration (CNC 0.25 g/100 ml or 0.50 g/100 ml) and/or oil fraction (10-20 g/100 ml). At constant oil fraction, the emulsion viscosity increased as the nanocrystal concentration increased. The cellulose nanocrystal-stabilized ginger oil-Pickering emulsions exhibited shear-thinning characteristics of a pseudo-plastic fluid. Pineapple nanocellulose crystal -stabilized ginger oil-Pickering emulsions exhibited high stability with a creaming index of zero. CNC was found to be an effective Pickering stabilizer for oil-in-water emulsions in various food applications.

Properties of Pickering emulsions stabilized by cellulose nanocrystals extracted from litchi peels

The development of Pickering emulsions which are applicable to the food industry still remains challenges due to the limited availability for biocompatible, edible and natural emulsifiers. The purpose of this study was to extract cellulose nanocrystals from litchi peels (LP-CNCs), and evaluate their emulsifying properties. The results showed that the LP-CNCs were needle-like and they possessed high crystallinity (72.34 %) and aspect ratio. When the concentrations of LP-CNCs were >0.7 wt% or the contents of oil were no >0.5, stable Pickering emulsions were obtained. The microstructures of emulsions confirmed that LP-CNCs formed dense interfacial layers on the surface of oil droplets, which functioned as barriers to prevent aggregation and flocculation among droplets. Rheological results showed that the emulsions exhibited typical shear thinning behavior. The elastic of emulsions was dominant, and their gel strength could be enhanced by regulating the contents of emulsifiers or oil. Additionally, the Pickering emulsions stabilized by LP-CNCs showed extremely high pH, ionic strength, and temperature tolerance. This strategy provides an innovative alternative to tackle the dilemma of preparing highly stable Pickering emulsions using natural particles in food products.

Impact of interactions between peanut protein isolate and cellulose nanocrystals on the properties of Pickering emulsions: Rheological properties and physical stabilities

The interactions between cellulose nanocrystals and proteins can regulate the interfacial properties of Pickering emulsions, which plays a leading role in the stabilities of Pickering emulsions. In this work, oil-in-water (O/W) Pickering emulsions with different oil-water ratios were prepared using peanut protein isolate modified by cellulose nanocrystals (PPI/CL-CNCs). The distributions of PPI/CL-CNCs at the oil-water interfaces and the microstructures of Pickering emulsions were observed by CLSM and cryo-SEM. The results showed that stable complexes PPI/CL-CNCs formed thick and dense interface layers on the surface of oil droplets. The results of rheological tests clarified that the Pickering emulsions showed an elastic and gel texture, and their gel strength could be enhanced by regulating the oil-water ratios from 3:7 to 7:3. In addition, after one month of storage, the EI of all emulsions remained above 92 % with no obvious phase separation or demulsification. These results suggested that the PPI/CL-CNCs-stabilized Pickering emulsions showed good physical stabilities. The study on the rheological properties and physical stabilities of PPI/CL-CNCs-based Pickering emulsions provided novel insights on developing highly stable Pickering emulsions.